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OBJECT                            = INSTRUMENT                                
 INSTRUMENT_HOST_ID               = GO                                        
 INSTRUMENT_ID                    = RSS                                       
                                                                              
 OBJECT                           = INSTRUMENT_INFORMATION                    
                                                                              
  INSTRUMENT_NAME                 = "RADIO SCIENCE SUBSYSTEM"                 
  INSTRUMENT_TYPE                 = "RADIO SCIENCE"                           
  INSTRUMENT_DESC                 = "                                         
                                                                              
    Instrument Overview                                                       
    ===================                                                       
      Galileo Radio Science investigations utilized instrumentation with      
      elements on the spacecraft and at the Deep Space Network (DSN).  Much   
      of this was shared equipment, being used for routine                    
      telecommunications as well as for Radio Science.  The performance       
      and calibration of both the spacecraft and tracking stations directly   
      affected the radio science data accuracy, and they played a major role  
      in determining the quality of the results.  The spacecraft part of the  
      radio science instrument is described immediately below; that is        
      followed by a description of the DSN (ground) part of the instrument.   
                                                                              
      Radio Science investigations were carried out by two teams.  The        
      Celestial Mechanics Team, under Team Leader John Anderson, conducted    
      experimental tests of general relativity (including searching for       
      gravitational waves), made measurements to improve solar system         
      ephemerides, and sought to improve gravitational models for Jupiter     
      and its satellites [ANDERSONETAL1992].  The Radio Propagation Team,     
      under Team Leader Tay Howard, investigated the solar corona and         
      carried out various studies in the Jovian system primarily concerning   
      atmospheres and ionospheres [HOWARDETAL1992].                           
                                                                              
                                                                              
    Instrument Specifications - Spacecraft                                    
    ======================================                                    
      The Galileo spacecraft telecommunications subsystem served as part of   
      a radio science subsystem for investigations primarily of Jupiter and   
      its satellites, but also including Venus, the Earth-Moon system, and    
      the Sun.  Many details of the subsystem are unknown; its 'build date'   
      is taken to be 1989-01-01, which was during the prelaunch phase of      
      the Galileo mission.                                                    
                                                                              
      Instrument Id                  : RSS                                    
      Instrument Host Id             : GO                                     
      Pi Pds User Id                 : UNK                                    
      Instrument Name                : RADIO SCIENCE SUBSYSTEM                
      Instrument Type                : RADIO SCIENCE                          
      Build Date                     : 1989-01-01                             
      Instrument Mass                : UNK                                    
      Instrument Length              : UNK                                    
      Instrument Width               : UNK                                    
      Instrument Height              : UNK                                    
      Instrument Manufacturer Name   : UNK                                    
                                                                              
                                                                              
    Instrument Overview - Spacecraft                                          
    ================================                                          
      The spacecraft radio system was constructed around a redundant pair     
      of transponders which received and transmitted at both S-band           
      (2.3 GHz, 13 cm wavelength) and X-band (8.4 GHz, 3.6 cm wavelength)     
      frequencies; the following combinations of uplink/downlink were         
      supported by the design: S/S, X/X, S/X and S.                           
                                                                              
      The exact frequency transmitted from the spacecraft was controlled      
      by the signal received from a ground station ('two-way' or 'coherent'   
      mode) or by an on-board oscillator ('one-way' or 'non-coherent' mode).  
      In some circumstances an uplink signal was transmitted from one         
      ground station while two ground stations participated in reception;     
      this was known as the 'three-way' mode.  In the absence of an uplink    
      signal, the spacecraft system switched automatically to the one-way     
      mode.  The on-board frequency reference could be either of two          
      redundant 'auxiliary' crystal oscillators or a single ultra-stable      
      oscillator (USO) provided specifically to support radio science         
      observations.                                                           
                                                                              
      Each transponder included a receiver, command detector, exciter, and    
      low-power amplifier.  The transponders provided the usual uplink        
      command and downlink data transmission capabilities.  The following     
      modulation states could be commanded: telemetry alone, ranging alone,   
      telemetry and ranging, or carrier only.                                 
                                                                              
      Each transponder could be operated through one of two low-gain          
      antennas at S-band only; a furlable high-gain antenna (HGA) never       
      deployed properly during Cruise, resulting in a serious degradation     
      of radio science measurements, including loss of X-band capability.     
      The HGA was aligned with the spin axis of the rotor part of the         
      spacecraft.  Low-Gain Antenna 1 (LGA-1) was located at the end of       
      the HGA feed, so it is also aligned with the spin axis.  LGA-2 was      
      at the end of a boom, 3.52 m from the spin axis.                        
                                                                              
      When operating in the coherent mode, the transponder downlink           
      frequency was related to the uplink frequency by the 'turn-around       
      ratio' of 240/221 at S-band.  At X-band it would have been 880/749.     
      An X-band downlink controlled by an S-band uplink would have had a      
      turn-around ratio of (240/221)*(11/3).                                  
                                                                              
                                                                              
    Science Objectives                                                        
    ==================                                                        
      Two different types of radio science measurements were conducted with   
      the Galileo Orbiter: radio tracking in which the magnitude and          
      direction of gravitational forces could be derived from 'closed-loop'   
      Doppler (and, sometimes, ranging) measurements, and radio propagation   
      experiments in which modulation on the signal received at Earth stations
      could be attributed to properties of the intervening medium.  The       
      radio science measurements were analyzed by two investigation teams;    
      the Celestial Mechanics Team was primarily interested in characterizing 
      variations in gravitational forces, and the Radio Propagation Team was  
      primarily interested in the atmospheres of the Sun, Jupiter, and        
      Jupiter's satellites.                                                   
                                                                              
      Gravity Measurements                                                    
      --------------------                                                    
        Measurement of the gravity field provides significant constraints     
        on inferences about interior structure of Jupiter and its satellites. 
        Precise, detailed study of spacecraft motion in Jupiter orbit and     
        during satellite flybys can yield a mass distribution of each body    
        and higher-order field terms if the measurements are sensitive enough.
        Compared with determinations from previous missions, improvements in  
        the gravity field of Jupiter itself were not expected from            
        tracking the Galileo Orbiter, but second-order gravity harmonics were 
        expected from flyby encounters with satellites.  One equatorial and   
        one polar flyby at Ganymede were sought to determine independently    
        the rotational and tidal response of the body assuming hydrostatic    
        equilibrium.  Departures from hydrostatic equilibrium were expected   
        to confuse that issue at Europa, though the measurements were         
        expected to be useful, while the relatively weak response             
        to rotation and tides at Callisto made the experiment most marginal   
        there [HUBBARD&ANDERSON1978].  Differences in principal moments of    
        inertia to an accuracy of one percent or better were sought at Io     
        [ANDERSONETAL1996].                                                   
                                                                              
      Tests of General Relativity                                             
      ---------------------------                                             
        There has been continuing interest in testing the theory of general   
        relativity by bouncing radar signals from hard planetary surfaces     
        and using two-way ranging data from spacecraft anchored to other      
        planetary bodies.  No hard surface exists at Jupiter and no previous  
        spacecraft had orbited the planet, so Galileo represented a unique    
        opportunity to investigate this question.  Two years of ranging to    
        Galileo were expected to fix the range to Jupiter to an accuracy      
        of about 150 m, with the limit set by orbit determination error       
        along the Earth-Jupiter line and not by limitations of the            
        radio 'instrument'.  In combination with results from the Pioneer     
        and Voyager spacecraft, these measurements were expected to lead      
        to an improved ephemeris for Jupiter.                                 
                                                                              
        As Jupiter (and Galileo) appear to pass behind the Sun when viewed    
        from Earth, solar gravity should retard the radio signal propagating  
        between the spacecraft and Earth.  One set of time delay measurements 
        to/from the Viking Orbiters and Landers agreed to within 0.1 percent  
        of the General Relativity prediction.  Measurements with Galileo      
        were expected to be a factor of 5 worse, but the next best            
        measurements were only to 2 percent of the General Relativity         
        prediction.  Not only would another set of measurements at the        
        sub-one percent level be good experimental practice, but Galileo      
        measurements could also verify the agreement over a range of          
        directions in inertial space [WILL1981].                              
                                                                              
        The red shift of the signal in Jupiter's gravitational field could    
        be measured to an accuracy of about +/-1 percent after radiation      
        hardening of the USO crystal in Jupiter's charged particle            
        environment.                                                          
                                                                              
      Search for Gravitational Radiation                                      
      ----------------------------------                                      
        Matter undergoing asymmetrical motion (theoretically) radiates        
        gravitational waves which propagate at the velocity of light.         
        Observed acceleration of the mean orbital motion of binary pulsar     
        PSR 1913+16 is consistent with predictions [TAYLOR&WEISBERG1989];     
        other evidence is more ambiguous, and gravity waves themselves had    
        not been detected with certainty before Galileo.  For several         
        extended periods during Galileo's cruise to Jupiter, when other       
        spacecraft activity was at a minimum and when the spacecraft was      
        near opposition, its radio link with Earth was monitored carefully    
        for signs of passing, cosmicly generated, long period gravitational   
        waves.  Similar observations were conducted simultaneously with the   
        Mars Observer and Ulysses spacecraft so that detections could be      
        confirmed and direction of propagation of the gravitational waves     
        inferred from time differences along other paths.  Previous searches  
        have been conducted using Viking, Voyager, and Pioneers 10 and 11     
        [ARMSTRONG1989].                                                      
                                                                              
      Solar Corona Observations                                               
      -------------------------                                               
        For several weeks around each of four superior conjunctions           
        Galileo's radio link passed through the solar corona.  Signals        
        were scattered and refracted as they propagated through the           
        turbulent plasma; the resulting modulation could be analyzed to       
        obtain estimates of coronal structure and dynamics [WOO1993].         
        Specific objectives of the Galileo solar corona experiments           
        included better understanding of:                                     
          (1) three-dimensional electron density distribution and its         
              relation to the photospheric magnetic field configuration,      
              solar cycle, distance from the surface, and solar latitude;     
          (2) structural differences among coronal 'holes', active            
              regions, and the 'quiet' Sun;                                   
          (3) characteristics of the acceleration regions of the solar        
              wind in coronal holes, streamers, and other parts of the        
              corona;                                                         
          (4) energy sources responsible for creation of coronal materials    
              with temperatures over 1000000K;                                
          (5) resonant solar oscillations on the dynamical characteristics    
              of the tenuous solar atmosphere;                                
          (6) excitation and propagation conditions for magnetoacoustic,      
              Alfven, and other waves; and                                    
          (7) form and evolution of disturbances near the Sun and their       
              relationship to white light coronal mass ejections.             
                                                                              
      Jupiter Occultations                                                    
      --------------------                                                    
        Radio occultation measurements can contribute to an improved          
        understanding of structure, circulation, dynamics, and transport      
        in the atmosphere of Jupiter.  Results from Galileo were based        
        on detailed analysis of the radio signal as it entered and exited     
        occultation by the planet.  Three phases of the atmospheric           
        investigation may be defined.  The first is to obtain vertical        
        profiles of electron content in the ionosphere; second is to          
        extract large scale structure in the neutral atmosphere; third        
        is to detect and interpret fine scale structure in both the           
        ionospheric and neutral atmosphere profiles and to measure            
        absorption in the neutral atmosphere.                                 
                                                                              
        The Galileo tour permitted radio occultations on approximately        
        half of the planned orbits at a number of latitudes.  Pioneers        
        10 and 11 had earlier shown sharp, multiple, dense, low-lying         
        ionospheric layers [FJELDBOETAL1976].  The vertical extent of         
        the ionized layers, their time histories, and detailed                
        structure were sought as keys to both the composition and             
        chemistry of the upper atmosphere.                                    
                                                                              
        With precise pointing of the HGA, Galileo was expected to             
        penetrate below the condensation level for ammonia in the             
        neutral atmosphere, providing global measures of ammonia              
        concentration in well-mixed regions where Voyager had produced        
        only one [LINDALETAL1981].  Measurements between 15N and 15S          
        latitudes were expected to provide snapshots of vertical structure    
        of waves propagating in the atmosphere; ingress and egress            
        measurements from the same occultation could provide strong           
        constraints on zonal wavenumber and meridional structure              
        [HINSON&MAGALHAES1991].                                               
                                                                              
      Satellite Occultations                                                  
      ----------------------                                                  
        Radio data acquired during occultation by a satellite could be        
        used to determine its diameter to accuracies on the order of 1 km     
        and, possibly, properties of any satellite atmosphere or              
        ionosphere.  In the case of Io a substantial ionosphere had been      
        detected by Pioneer 10 [KLIOREETAL1975]; repeated occultations        
        by Io were intended to improve understanding of spatial and temporal  
        variability of the charged particles and their interaction with       
        Jupiter's magnetic field.  Occultations by the Io torus would         
        provide a measure of the total number of free electrons along the     
        propagation path, a useful constraint of the spatial structure        
        of the torus.                                                         
                                                                              
      Jupiter's Magnetic Field                                                
      ------------------------                                                
        Galileo was the first spacecraft equipped to measure both Faraday     
        rotation of propagating waves and differential phase retardation      
        between S- and X-band.  Faraday rotation measurements were planned    
        during each occultation by Jupiter and were to be used to             
        investigate the characteristics of the magnetic field in the          
        planet's ionosphere.  Different models of the magnetic field yield    
        differences in the predicted Faraday rotation on the order of 0.3     
        radians; the Faraday rotation experiment designed for Galileo         
        exceeded this threshold by a factor of 10.                            
                                                                              
      Bistatic Scattering from Icy Galilean Moons                             
      -------------------------------------------                             
        Monostatic radar echoes from Europa, Ganymede, and Callisto were      
        found to be anomalously diffuse, strong, and polarized                
        [CAMPBELLETAL1978].  By using the Galileo spacecraft as a             
        microwave signal source during encounters with each of these          
        bodies, the bistatic scattering as a function of angle could be       
        determined, providing constraints on both the models for the          
        anomalous scattering process and also the properties of the ice       
        that presumably is responsible.                                       
                                                                              
                                                                              
    Operational Considerations - Spacecraft                                   
    =======================================                                   
                                                                              
      Because the HGA never deployed and only right-circularly polarized      
      signals at S-band were available from LGA-1, the Faraday and dual-      
      frequency measurements were never realized.  For the Celestial          
      Mechanics Team, the single frequency meant that signal dispersion       
      resulting from passage through the solar wind, Earth's ionosphere,      
      and other media could not be removed easily from data.  For the         
      Radio Propagation Team, the loss of antenna gain meant that only        
      observations with the strongest signals could be made.  Penetration     
      below the ionosphere during Jupiter occultations and sensing            
      charged and neutral particle environments of satellites became          
      very difficult, and the bistatic surface experiments were dropped.      
      Because Faraday Rotation experiments required linearly transmitted      
      polarizations (available only from the HGA), those were also dropped.   
                                                                              
    Calibration Description - Spacecraft                                      
    ====================================                                      
      No information available.                                               
                                                                              
                                                                              
    Platform Mounting Descriptions - Spacecraft                               
    ===========================================                               
      The HGA and LGA-1 antennas were mounted facing in the negative          
      Zr direction; see the INSTHOST.CAT file for more information.           
                                                                              
                                                                              
    Principal Investigators                                                   
    =======================                                                   
      The Team Leader for the Celestial Mechanics Team was John D.            
      Anderson of the Jet Propulsion Laboratory.  Team members                
      were (all from JPL):                                                    
        J.W. Armstrong                                                        
        J.K. Campbell                                                         
        F.B. Estabrook                                                        
        T.P. Krisher                                                          
        E.L. Lau                                                              
      The Team Leader for the Radio Propagation Team was H. Taylor            
      Howard of Stanford University.  Team members and affiliations           
      were:                                                                   
        V.R. Eshleman             Stanford University                         
        D.P. Hinson               Stanford University                         
        A.J. Kliore               Jet Propulsion Laboratory                   
        G.F. Lindal               Jet Propulsion Laboratory                   
        R.   Woo                  Jet Propulsion Laboratory                   
        M.K. Bird                 University of Bonn, Germany                 
        H.   Volland              University of Bonn, Germany                 
        P.   Edenhofer            University of Bochum, Germany               
        M.   Paetzold             DFLR, Germany                               
        H.   Porsche              DFLR, Germany                               
      Experiment Representative at JPL for both teams was Randy Herrera.      
                                                                              
                                                                              
    Instrument Section / Operating Mode Descriptions - Spacecraft             
    =============================================================             
      The Galileo radio system consisted of two sections, which               
      could be operated in the following modes:                               
                                                                              
      Section      Mode                                                       
      -------------------------------------------                             
      Oscillator   two-way (coherent)                                         
                   one-way (non-coherent)                                     
      RF output    low-gain antenna (choice from two)                         
                   high-gain antenna (failed to deploy properly)              
                                                                              
      Details for the radio system, as designed, are given in the table       
      below:                                                                  
                                                                              
       Transmitting Parameters:                                               
        Frequency (MHz)                    8415       2295                    
        Transmit Power (w)               12 or 21    9 or 27                  
        HGA Gain (dBi)                      50         38                     
        HGA Half-Power Beamwidth (deg)      0.6        1.5                    
        Polarization                    LCP or RCP   Linear                   
        Axial Ratio (dB)                     2         32                     
                                                                              
       Receiving Parameters:                                                  
        Frequency (MHz)                    7167       2115                    
        HGA Gain (dBi)                      46         36                     
        Polarization                    LCP or RCP   Linear                   
        Noise Temperature (K)               270       1000                    
                                                                              
                                                                              
    Instrument Overview - DSN                                                 
    =========================                                                 
      Three Deep Space Communications Complexes (DSCCs) (near                 
      Barstow, CA; Canberra, Australia; and Madrid, Spain) comprise           
      the DSN tracking network.  Each complex is equipped with                
      several antennas [including at least one each 70-m, 34-m High           
      Efficiency (HEF), and 34-m standard (STD)], associated                  
      electronics, and operational systems.  Primary activity at each         
      complex is radiation of commands to and reception of telemetry          
      data from active spacecraft.  Transmission and reception is             
      possible in several radio-frequency bands, the most common              
      being S-band (nominally a frequency of 2100-2300 MHz or a               
      wavelength of 14.2-13.0 cm) and X-band (7100-8500 MHz or 4.2-           
      3.5 cm).  Transmitter output powers of up to 400 kw are                 
      available.                                                              
                                                                              
      Ground stations have the ability to transmit coded and uncoded          
      waveforms which can be echoed by distant spacecraft.  Analysis          
      of the received coding allows navigators to determine the               
      distance to the spacecraft; analysis of Doppler shift on the            
      carrier signal allows estimation of the line-of-sight                   
      spacecraft velocity.  Range and Doppler measurements are used           
      to calculate the spacecraft trajectory and to infer gravity             
      fields of objects near the spacecraft.                                  
                                                                              
      Ground stations can record spacecraft signals that have                 
      propagated through or been scattered from target media.                 
      Measurements of signal parameters after wave interactions with          
      surfaces, atmospheres, rings, and plasmas are used to infer             
      physical and electrical properties of the target.                       
                                                                              
      Principal investigators vary from experiment to experiment.             
      See the corresponding section of the spacecraft instrument              
      description or the data set description for specifics.                  
                                                                              
      The Deep Space Network is managed by the Jet Propulsion                 
      Laboratory of the California Institute of Technology for the            
      U.S.  National Aeronautics and Space Administration.                    
      Specifications include:                                                 
                                                                              
      Instrument Id                  : RSS                                    
      Instrument Host Id             : DSN                                    
      Pi Pds User Id                 : N/A                                    
      Instrument Name                : RADIO SCIENCE SUBSYSTEM                
      Instrument Type                : RADIO SCIENCE                          
      Build Date                     : N/A                                    
      Instrument Mass                : N/A                                    
      Instrument Length              : N/A                                    
      Instrument Width               : N/A                                    
      Instrument Height              : N/A                                    
      Instrument Manufacturer Name   : N/A                                    
                                                                              
      For more information on the Deep Space Network and its use in           
      radio science investigations see the reports by                         
      [ASMAR&RENZETTI1993] and [ASMAR&HERRERA1993].  For design               
      specifications on DSN subsystems see [DSN810-5].  For an                
      example of use of the DSN for Radio Science see [TYLERETAL1992].        
                                                                              
                                                                              
    Subsystems - DSN                                                          
    ================                                                          
      The Deep Space Communications Complexes (DSCCs) are an integral         
      part of the Radio Science instrument, along with other                  
      receiving stations and the spacecraft Radio Frequency                   
      Subsystem.  Their system performance directly determines the            
      degree of success of Radio Science investigations, and their            
      system calibration determines the degree of accuracy in the             
      results of the experiments.  The following paragraphs describe          
      the functions performed by the individual subsystems of a DSCC.         
      This material has been adapted from [ASMAR&HERRERA1993]; for            
      additional information, consult [DSN810-5].                             
                                                                              
      Each DSCC includes a set of antennas, a Signal Processing               
      Center (SPC), and communication links to the Jet Propulsion             
      Laboratory (JPL).  The general configuration is illustrated             
      below; antennas (Deep Space Stations, or DSS -- a term carried          
      over from earlier times when antennas were individually                 
      instrumented) are listed in the table.                                  
                                                                              
          --------   --------   --------   --------   --------                
         | DSS 12 | | DSS 18 | | DSS 14 | | DSS 15 | | DSS 16 |               
         |34-m STD| |34-m STD| |  70-m  | |34-m HEF| |  26-m  |               
          --------   --------   --------   --------   --------                
              |            |     |             |          |                   
              |            v     v             |          v                   
              |           ---------            |     ---------                
               ---------❯|GOLDSTONE|❮----------     |EARTH/ORB|               
                         | SPC  10 |❮--------------❯|   LINK  |               
                          ---------                  ---------                
                         |   SPC   |❮--------------❯|   26-M  |               
                         |  COMM   |         ------❯|   COMM  |               
                          ---------         |        ---------                
                              |             |            |                    
                              v             |            v                    
             ------       ---------         |        ---------                
            | NOCC |❮---❯|   JPL   |❮-------        |         |               
             ------      | CENTRAL |                |   GSFC  |               
             ------      |   COMM  |                |  NASCOM |               
            | MCCC |❮---❯| TERMINAL|❮--------------❯|         |               
             ------       ---------                  ---------                
                                                      ^     ^                 
                                                      |     |                 
                   CANBERRA (SPC 40) ❮----------------      |                 
                                                            |                 
                     MADRID (SPC 60) ❮----------------------                  
                                                                              
                          GOLDSTONE     CANBERRA      MADRID                  
             Antenna        SPC 10       SPC 40       SPC 60                  
            --------      ---------     --------     --------                 
            26-m            DSS 16       DSS 46       DSS 66                  
            34-m STD        DSS 12       DSS 42       DSS 61                  
                            DSS 18       DSS 48       DSS 68                  
            34-m HEF        DSS 15       DSS 45       DSS 65                  
            70-m            DSS 14       DSS 43       DSS 63                  
            Developmental   DSS 13                                            
                                                                              
                                                                              
      Subsystem interconnections at each DSCC are shown in the                
      diagram below, and they are described in the sections that              
      follow.  The Monitor and Control Subsystem is connected to all          
      other subsystems; the Test Support Subsystem can be.                    
                                                                              
       -----------   ------------------   ---------   ---------               
      |TRANSMITTER| |                  | | TRACKING| | COMMAND |              
      | SUBSYSTEM |-| RECEIVER/EXCITER |-|SUBSYSTEM|-|SUBSYSTEM|-             
       -----------  |                  |  ---------   ---------  |            
             |      |     SUBSYSTEM    |       |           |     |            
       -----------  |                  |  ---------------------  |            
      | MICROWAVE | |                  | |      TELEMETRY      | |            
      | SUBSYSTEM |-|                  |-|      SUBSYSTEM      |-             
       -----------   ------------------   ---------------------  |            
             |                                                   |            
       -----------    -----------    ---------   --------------  |            
      |  ANTENNA  |  |  MONITOR  |  |   TEST  | |    DIGITAL   | |            
      | SUBSYSTEM |  |AND CONTROL|  | SUPPORT | |COMMUNICATIONS|-             
       -----------   | SUBSYSTEM |  |SUBSYSTEM| |   SUBSYSTEM  |              
                      -----------    ---------   --------------               
                                                                              
                                                                              
      DSCC Monitor and Control Subsystem                                      
      ----------------------------------                                      
        The DSCC Monitor and Control Subsystem (DMC) is part of the           
        Monitor and Control System (MON) which also includes the              
        ground communications Central Communications Terminal and the         
        Network Operations Control Center (NOCC) Monitor and Control          
        Subsystem.  The DMC is the center of activity at a DSCC.  The         
        DMC receives and archives most of the information from the            
        NOCC needed by the various DSCC subsystems during their               
        operation.  Control of most of the DSCC subsystems, as well           
        as the handling and displaying of any responses to control            
        directives and configuration and status information received          
        from each of the subsystems, is done through the DMC.  The            
        effect of this is to centralize the control, display, and             
        archiving functions necessary to operate a DSCC.                      
        Communication between the various subsystems is done using a          
        Local Area Network (LAN) hooked up to each subsystem via a            
        network interface unit (NIU).                                         
                                                                              
        DMC operations are divided into two separate areas: the               
        Complex Monitor and Control (CMC) and the Link Monitor and            
        Control (LMC).  The primary purpose of the CMC processor for          
        Radio Science support is to receive and store all predict             
        sets transmitted from NOCC such as Radio Science, antenna             
        pointing, tracking, receiver, and uplink predict sets and             
        then, at a later time, to distribute them to the appropriate          
        subsystems via the LAN.  Those predict sets can be stored in          
        the CMC for a maximum of three days under normal conditions.          
        The CMC also receives, processes, and displays event/alarm            
        messages; maintains an operator log; and produces tape labels         
        for the DSP.  Assignment and configuration of the LMCs is             
        done through the CMC; to a limited degree the CMC can perform         
        some of the functions performed by the LMC.  There are two            
        CMCs (one on-line and one backup) and three LMCs at each DSCC         
        The backup CMC can function as an additional LMC if                   
        necessary.                                                            
                                                                              
        The LMC processor provides the operator interface for monitor         
        and control of a link -- a group of equipment required to             
        support a spacecraft pass.  For Radio Science, a link might           
        include the DSCC Spectrum Processing Subsystem (DSP) (which,          
        in turn, can control the SSI), or the Tracking Subsystem.             
        The LMC also maintains an operator log which includes                 
        operator directives and subsystem responses.  One important           
        Radio Science specific function that the LMC performs is              
        receipt and transmission of the system temperature and signal         
        level data from the PPM for display at the LMC console and            
        for inclusion in Monitor blocks.  These blocks are recorded           
        on magnetic tape as well as appearing in the Mission Control          
        and Computing Center (MCCC) displays.  The LMC is required to         
        operate without interruption for the duration of the Radio            
        Science data acquisition period.                                      
                                                                              
        The Area Routing Assembly (ARA), which is part of the Digital         
        Communications Subsystem, controls all data communication             
        between the stations and JPL.  The ARA receives all required          
        data and status messages from the LMC/CMC and can record them         
        to tape as well as transmit them to JPL via data lines.  The          
        ARA also receives predicts and other data from JPL and passes         
        them on to the CMC.                                                   
                                                                              
                                                                              
      DSCC Antenna Mechanical Subsystem                                       
      ---------------------------------                                       
        Multi-mission Radio Science activities require support from           
        the 70-m, 34-m HEF, and 34-m STD antenna subnets.  The                
        antennas at each DSCC function as large-aperture collectors           
        which, by double reflection, cause the incoming radio                 
        frequency (RF) energy to enter the feed horns.  The large             
        collecting surface of the antenna focuses the incoming energy         
        onto a subreflector, which is adjustable in both axial and            
        angular position.  These adjustments are made to correct for          
        gravitational deformation of the antenna as it moves between          
        zenith and the horizon; the deformation can be as large as            
        5 cm.  The subreflector adjustments optimize the channeling           
        of energy from the primary reflector to the subreflector              
        and then to the feed horns.  The 70-m and 34-m HEF antennas           
        have 'shaped' primary and secondary reflectors, with forms            
        that are modified paraboloids.  This customization allows             
        more uniform illumination of one reflector by another.  The           
        34-m STD primary reflectors are classical paraboloids, while          
        the subreflectors are standard hyperboloids.                          
                                                                              
        On the 70-m and 34-m STD antennas, the subreflector directs           
        received energy from the antenna onto a dichroic plate, a             
        device which reflects S-band energy to the S-band feed horn           
        and passes X-band energy through to the X-band feed horn.  In         
        the 34-m HEF, there is one 'common aperture feed,' which              
        accepts both frequencies without requiring a dichroic plate.          
        RF energy to be transmitted into space by the horns is                
        focused by the reflectors into narrow cylindrical beams,              
        pointed with high precision (either to the dichroic plate or          
        directly to the subreflector) by a series of drive motors and         
        gear trains that can rotate the movable components and their          
        support structures.                                                   
                                                                              
        The different antennas can be pointed by several means.  Two          
        pointing modes commonly used during tracking passes are               
        CONSCAN and 'blind pointing.' With CONSCAN enabled and a              
        closed loop receiver locked to a spacecraft signal, the               
        system tracks the radio source by conically scanning around           
        its position in the sky.  Pointing angle adjustments are              
        computed from signal strength information (feedback) supplied         
        by the receiver.  In this mode the Antenna Pointing Assembly          
        (APA) generates a circular scan pattern which is sent to the          
        Antenna Control System (ACS).  The ACS adds the scan pattern          
        to the corrected pointing angle predicts.  Software in the            
        receiver-exciter controller computes the received signal              
        level and sends it to the APA.  The correlation of scan               
        position with the received signal level variations allows the         
        APA to compute offset changes which are sent to the ACS.              
        Thus, within the capability of the closed-loop control                
        system, the scan center is pointed precisely at the apparent          
        direction of the spacecraft signal source.  An additional             
        function of the APA is to provide antenna position angles and         
        residuals, antenna control mode/status information, and               
        predict-correction parameters to the Area Routing Assembly            
        (ARA) via the LAN, which then sends this information to JPL           
        via the Ground Communications Facility (GCF) for antenna              
        status monitoring.                                                    
                                                                              
        During periods when excessive signal level dynamics or low            
        received signal levels are expected (e.g., during an                  
        occultation experiment), CONSCAN should not be used.  Under           
        these conditions, blind pointing (CONSCAN OFF) is used, and           
        pointing angle adjustments are based on a predetermined               
        Systematic Error Correction (SEC) model.                              
                                                                              
        Independent of CONSCAN state, subreflector motion in at least         
        the z-axis may introduce phase variations into the received           
        Radio Science data.  For that reason, during certain                  
        experiments, the subreflector in the 70-m and 34-m HEFs may           
        be frozen in the z-axis at a position (often based on                 
        elevation angle) selected to minimize phase change and signal         
        degradation.  This can be done via Operator Control Inputs            
        (OCIs) from the LMC to the Subreflector Controller (SRC)              
        which resides in the alidade room of the antennas.  The SRC           
        passes the commands to motors that drive the subreflector to          
        the desired position.  Unlike the 70-m and 34-m HEFs which            
        have azimuth-elevation (AZ-EL) drives, the 34-m STD antennas          
        use (hour angle-declination) HA-DEC drives.  The same                 
        positioning of the subreflector on the 34-m STD does not              
        create the same effect as on the 70-m and 34-m HEFs.                  
                                                                              
        Pointing angles for all three antenna types are computed by           
        the NOCC Support System (NSS) from an ephemeris provided by           
        the flight project.  These predicts are received and archived         
        by the CMC.  Before each track, they are transferred to the           
        APA, which transforms the direction cosines of the predicts           
        into AZ-EL coordinates for the 70-m and 34-m HEFs or into             
        HA-DEC coordinates for the 34-m STD antennas.  The LMC                
        operator then downloads the antenna AZ-EL or HA-DEC predict           
        points to the antenna-mounted ACS computer along with a               
        selected SEC model.  The pointing predicts consist of                 
        time-tagged AZ-EL or HA-DEC points at selected time intervals         
        along with polynomial coefficients for interpolation between          
        points.                                                               
                                                                              
        The ACS automatically interpolates the predict points,                
        corrects the pointing predicts for refraction and                     
        subreflector position, and adds the proper systematic error           
        correction and any manually entered antenna offsets.  The ACS         
        then sends angular position commands for each axis at the             
        rate of one per second.  In the 70-m and 34-m HEF, rate               
        commands are generated from the position commands at the              
        servo controller and are subsequently used to steer the               
        antenna.  In the 34-m STD antennas motors, rather than                
        servos, are used to steer the antenna; there is no feedback           
        once the 34-m STD has been told where to point.                       
                                                                              
        When not using binary predicts (the routine mode for                  
        spacecraft tracking), the antennas can be pointed using               
        'planetary mode' -- a simpler mode which uses right ascension         
        (RA) and declination (DEC) values.  These change very slowly          
        with respect to the celestial frame.  Values are provided to          
        the station in text form for manual entry.  The ACS                   
        quadratically interpolates among three RA and DEC points              
        which are on one-day centers.                                         
                                                                              
        A third pointing mode -- sidereal -- is available for                 
        tracking radio sources fixed with respect to the celestial            
        frame.                                                                
                                                                              
        Regardless of the pointing mode being used, a 70-m antenna            
        has a special high-accuracy pointing capability called                
        'precision' mode.  A pointing control loop derives the                
        main AZ-EL pointing servo drive error signals from a two-             
        axis autocollimator mounted on the Intermediate Reference             
        Structure.  The autocollimator projects a light beam to a             
        precision mirror mounted on the Master Equatorial drive               
        system, a much smaller structure, independent of the main             
        antenna, which is exactly positioned in HA and DEC with shaft         
        encoders.  The autocollimator detects elevation/cross-                
        elevation errors between the two reference surfaces by                
        measuring the angular displacement of the reflected light             
        beam.  This error is compensated for in the antenna servo by          
        moving the antenna in the appropriate AZ-EL direction.                
        Pointing accuracies of 0.004 degrees (15 arc seconds) are             
        possible in 'precision' mode.  The 'precision' mode is not            
        available on 34-m antennas -- nor is it needed, since their           
        beamwidths are twice as large as on the 70-m antennas.                
                                                                              
                                                                              
      DSCC Antenna Microwave Subsystem                                        
      --------------------------------                                        
        70-m Antennas: Each 70-m antenna has three feed cones                 
        installed in a structure at the center of the main reflector.         
        The feeds are positioned 120 degrees apart on a circle.               
        Selection of the feed is made by rotation of the                      
        subreflector.  A dichroic mirror assembly, half on the S-band         
        cone and half on the X-band cone, permits simultaneous use of         
        the S- and X-band frequencies.  The third cone is devoted to          
        R&D and more specialized work.                                        
                                                                              
        The Antenna Microwave Subsystem (AMS) accepts the received S-         
        and X-band signals at the feed horn and transmits them                
        through polarizer plates to an orthomode transducer.  The             
        polarizer plates are adjusted so that the signals are                 
        directed to a pair of redundant amplifiers for each                   
        frequency, thus allowing simultaneous reception of signals in         
        two orthogonal polarizations.  For S-band these are two Block         
        IVA S-band Traveling Wave Masers (TWMs); for X-band the               
        amplifiers are Block IIA TWMs.                                        
                                                                              
        34-m STD Antennas: These antennas have two feed horns, one            
        for S-band signals and one for X-band.  The horns are mounted         
        on a cone which is fixed in relation to the subreflector.  A          
        dichroic plate mounted above the horns directs energy from            
        the subreflector into the proper horn.                                
                                                                              
        The AMS directs the received S- and X-band signals through            
        polarizer plates and on to amplification.  There are two              
        Block III S-band TWMs and two Block I X-band TWMs.                    
                                                                              
        34-m HEF Antennas: Unlike the other antennas, the 34-m HEF            
        uses a single feed for both S- and X-band.  Simultaneous S-           
        and X-band receive as well as X-band transmit is possible             
        thanks to the presence of an S/X 'combiner' which acts as a           
        diplexer.  For S-band, RCP or LCP is user selected through a          
        switch so neither a polarizer nor an orthomode transducer is          
        needed.  X-band amplification options include two Block II            
        TWMs or an HEMT Low Noise Amplifier (LNA).  S-band                    
        amplification is provided by an FET LNA.                              
                                                                              
                                                                              
      DSCC Receiver-Exciter Subsystem                                         
      -------------------------------                                         
        The Receiver-Exciter Subsystem is composed of three groups of         
        equipment: the closed-loop receiver group, the open-loop              
        receiver group, and the RF monitor group.  This subsystem is          
        controlled by the Receiver-Exciter Controller (REC) which             
        communicates directly with the DMC for predicts and OCI               
        reception and status reporting.                                       
                                                                              
        The exciter generates the S-band signal (or X-band for the            
        34-m HEF only) which is provided to the Transmitter Subsystem         
        for the spacecraft uplink signal.  It is tunable under                
        command of the Digitally Controlled Oscillator (DCO) which            
        receives predicts from the Metric Data Assembly (MDA).                
                                                                              
        The diplexer in the signal path between the transmitter and           
        the feed horn for all three antennas (used for simultaneous           
        transmission and reception) may be configured such that it is         
        out of the received signal path (in listen-only or bypass             
        mode) in order to improve the signal-to-noise ratio in the            
        receiver system.                                                      
                                                                              
        Closed Loop Receivers: The Block IV receiver-exciter at the           
        70-m stations allows for two receiver channels, each capable          
        of L-Band (e.g., 1668 MHz frequency or 18 cm wavelength),             
        S-band, or X-band reception, and an S-band exciter for                
        generation of uplink signals through the low-power or                 
        high-power transmitter.  The Block III receiver-exciter at            
        the 34-m STD stations allows for two receiver channels, each          
        capable of S-band or X-band reception and an exciter used to          
        generate an uplink signal through the low-power transmitter.          
        The receiver-exciter at the 34-m HEF stations allows for one          
        channel only.                                                         
                                                                              
        The closed-loop receivers provide the capability for rapid            
        acquisition of a spacecraft signal and telemetry lockup.  In          
        order to accomplish acquisition within a short time, the              
        receivers are predict driven to search for, acquire, and              
        track the downlink automatically.  Rapid acquisition                  
        precludes manual tuning though that remains as a backup               
        capability.  The subsystem utilizes FFT analyzers for rapid           
        acquisition.  The predicts are NSS generated, transmitted to          
        the CMC which sends them to the Receiver-Exciter Subsystem            
        where two sets can be stored.  The receiver starts                    
        acquisition at uplink time plus one round-trip-light-time or          
        at operator specified times.  The receivers may also be               
        operated from the LMC without a local operator attending              
        them.  The receivers send performance and status data,                
        displays, and event messages to the LMC.                              
                                                                              
        Either the exciter synthesizer signal or the simulation               
        (SIM) synthesizer signal is used as the reference for the             
        Doppler extractor in the closed-loop receiver systems,                
        depending on the spacecraft being tracked (and Project                
        guidelines).  The SIM synthesizer is not ramped; instead it           
        uses one constant frequency, the Track Synthesizer Frequency          
        (TSF), which is an average frequency for the entire pass.             
                                                                              
        The closed-loop receiver AGC loop can be configured to one of         
        three settings: narrow, medium, or wide.  It will be                  
        configured such that the expected amplitude changes are               
        accommodated with minimum distortion.  The loop bandwidth             
        (2BLo) will be configured such that the expected phase                
        changes can be accommodated while maintaining the best                
        possible loop SNR.                                                    
                                                                              
        Open-Loop Receivers: The Radio Science Open-Loop Receiver             
        (OLR) is a dedicated four channel, narrow-band receiver which         
        provides amplified and downconverted video band signals to            
        the DSCC Spectrum Processing Subsystem (DSP).                         
                                                                              
        The OLR utilizes a fixed first Local Oscillator (LO)                  
        frequency and a tunable second LO frequency to minimize phase         
        noise and improve frequency stability.  The OLR consists of           
        an RF-to-IF downconverter located in the antenna, an IF               
        selection switch (IVC), and a Radio Science IF-VF                     
        downconverter (RIV) located in the SPC.  The RF-IF                    
        downconverters in the 70-m antennas are equipped for four IF          
        channels: S-RCP, S-LCP, X-RCP, and X-LCP.  The 34-m HEF               
        stations are equipped with a two-channel RF-IF: S-band and            
        X-band.  The IVC switches the IF input between the 70-m and           
        34-m HEF antennas.                                                    
                                                                              
        The RIV contains the tunable second LO, a set of video                
        bandpass filters, IF attenuators, and a controller (RIC).             
        The LO tuning is done via DSP control of the POCA/PLO                 
        combination based on a predict set.  The POCA is a                    
        Programmable Oscillator Control Assembly and the PLO is a             
        Programmable Local Oscillator (commonly called the DANA               
        synthesizer).  The bandpass filters are selectable via the            
        DSP.  The RIC provides an interface between the DSP and the           
        RIV.  It is controlled from the LMC via the DSP.  The RIC             
        selects the filter and attenuator settings and provides               
        monitor data to the DSP.  The RIC could also be manually              
        controlled from the front panel in case the electronic                
        interface to the DSP is lost.                                         
                                                                              
        RF Monitor -- SSI and PPM: The RF monitor group of the                
        Receiver-Exciter Subsystem provides spectral measurements             
        using the Spectral Signal Indicator (SSI) and measurements of         
        the received channel system temperature and spacecraft signal         
        level using the Precision Power Monitor (PPM).                        
                                                                              
        The SSI provides a local display of the received signal               
        spectrum at a dedicated terminal at the DSCC and routes these         
        same data to the DSP which routes them to NOCC for remote             
        display at JPL for real-time monitoring and RIV/DSP                   
        configuration verification.  These displays are used to               
        validate Radio Science Subsystem data at the DSS, NOCC, and           
        Mission Support Areas.  The SSI configuration is controlled           
        by the DSP and a duplicate of the SSI spectrum appears on the         
        LMC via the DSP.  During real-time operations the SSI data            
        also serve as a quick-look science data type for Radio                
        Science experiments.                                                  
                                                                              
        The PPM measures system noise temperatures (SNT) using a              
        Noise Adding Radiometer (NAR) and downlink signal levels              
        using the Signal Level Estimator (SLE).  The PPM accepts its          
        input from the closed-loop receiver.  The SNT is measured by          
        injecting known amounts of noise power into the signal path           
        and comparing the total power with the noise injection 'on'           
        against the total power with the noise injection 'off.' That          
        operation is based on the fact that receiver noise power is           
        directly proportional to temperature; thus measuring the              
        relative increase in noise power due to the presence of a             
        calibrated thermal noise source allows direct calculation of          
        SNT.  Signal level is measured by calculating an FFT to               
        estimate the SNR between the signal level and the receiver            
        noise floor where the power is known from the SNT                     
        measurements.                                                         
                                                                              
        There is one PPM controller at the SPC which is used to               
        control all SNT measurements.  The SNT integration time can           
        be selected to represent the time required for a measurement          
        of 30K to have a one-sigma uncertainty of 0.3K or 1%.                 
                                                                              
                                                                              
      DSCC Transmitter Subsystem                                              
      --------------------------                                              
        The Transmitter Subsystem accepts the S-band frequency                
        exciter signal from the Block III or Block IV Receiver-               
        Exciter Subsystem exciter and amplifies it to the required            
        transmit output level.  The amplified signal is routed via            
        the diplexer through the feed horn to the antenna and then            
        focused and beamed to the spacecraft.                                 
                                                                              
        The Transmitter Subsystem power capabilities range from 18 kw         
        to 400 kw.  Power levels above 18 kw are available only at            
        70-m stations.                                                        
                                                                              
                                                                              
      DSCC Tracking Subsystem                                                 
      -----------------------                                                 
        The Tracking Subsystem primary functions are to acquire and           
        maintain communications with the spacecraft and to generate           
        and format radiometric data containing Doppler and range.             
                                                                              
        The DSCC Tracking Subsystem (DTK) receives the carrier                
        signals and ranging spectra from the Receiver-Exciter                 
        Subsystem.  The Doppler cycle counts are counted, formatted,          
        and transmitted to JPL in real time.  Ranging data are also           
        transmitted to JPL in real time.  Also contained in these             
        blocks is the AGC information from the Receiver-Exciter               
        Subsystem.  The Radio Metric Data Conditioning Team (RMDCT)           
        at JPL produces an Archival Tracking Data File (ATDF) tape            
        which contains Doppler and ranging data.                              
                                                                              
        In addition, the Tracking Subsystem receives from the CMC             
        frequency predicts (used to compute frequency residuals and           
        noise estimates), receiver tuning predicts (used to tune the          
        closed-loop receivers), and uplink tuning predicts (used to           
        tune the exciter).  From the LMC, it receives configuration           
        and control directives as well as configuration and status            
        information on the transmitter, microwave, and frequency and          
        timing subsystems.                                                    
                                                                              
        The Metric Data Assembly (MDA) controls all of the DTK                
        functions supporting the uplink and downlink activities.  The         
        MDA receives uplink predicts and controls the uplink tuning           
        by commanding the DCO.  The MDA also controls the Sequential          
        Ranging Assembly (SRA).  It formats the Doppler and range             
        measurements and provides them to the GCF for transmission to         
        NOCC.                                                                 
                                                                              
        The Sequential Ranging Assembly (SRA) measures the round trip         
        light time (RTLT) of a radio signal traveling from a ground           
        tracking station to a spacecraft and back.  From the RTLT,            
        phase, and Doppler data, the spacecraft range can be                  
        determined.  A coded signal is modulated on an uplink carrier         
        and transmitted to the spacecraft where it is detected and            
        transponded back to the ground station.  As a result, the             
        signal received at the tracking station is delayed by its             
        round trip through space and shifted in frequency by the              
        Doppler effect due to the relative motion between the                 
        spacecraft and the tracking station on Earth.                         
                                                                              
                                                                              
      DSCC Spectrum Processing Subsystem (DSP)                                
      ----------------------------------------                                
        The DSCC Spectrum Processing Subsystem (DSP) located at the           
        SPC digitizes and records on magnetic tapes the narrowband            
        output data from the RIV.  It consists of a Narrow Band               
        Occultation Converter (NBOC) containing four Analog-to-               
        Digital Converters (ADCs), a ModComp CLASSIC computer                 
        processor called the Spectrum Processing Assembly (SPA), and          
        two to six magnetic tape drives.  Magnetic tapes are known as         
        Original Data Records (ODRs).  Electronic near real-time              
        transmission of data to JPL (an Original Data Stream, or ODS)         
        may be possible in certain circumstances;                             
                                                                              
        The DSP is operated through the LMC.  Using the SPA-R                 
        software, the DSP allows for real-time frequency and time             
        offsets (while in RUN mode) and, if necessary, snap tuning            
        between the two frequency ranges transmitted by the                   
        spacecraft: coherent and non-coherent.  The DSP receives              
        Radio Science frequency predicts from the CMC, allows for             
        multiple predict set archiving (up to 60 sets) at the SPA,            
        and allows for manual predict generation and editing.  It             
        accepts configuration and control data from the LMC, provides         
        display data to the LMC, and transmits the signal spectra             
        from the SSI as well as status information to NOCC and the            
        Project Mission Support Area (MSA) via the GCF data lines.            
        The DSP records the digitized narrowband samples and the              
        supporting header information (i.e., time tags, POCA                  
        frequencies, etc.) on 9-track magnetic tapes in 6250 or 1600          
        bpi GCR format.                                                       
                                                                              
        Through the DSP-RIC interface the DSP controls the RIV filter         
        selection and attenuation levels.  It also receives RIV               
        performance monitoring via the RIC.  In case of failure of            
        the DSP-RIC interface, the RIV can be controlled manually             
        from the front panel.                                                 
                                                                              
        All the RIV and DSP control parameters and configuration              
        directives are stored in the SPA in a macro-like file called          
        an 'experiment directive' table.  A number of default                 
        directives exist in the DSP for the major Radio Science               
        experiments.  Operators can create their own table entries.           
                                                                              
        Items such as verification of the configuration of the prime          
        open-loop recording subsystem, the selection of the required          
        predict sets, and proper system performance prior to the              
        recording periods will be checked in real-time at JPL via the         
        NOCC displays using primarily the remote SSI display at NOCC          
        and the NRV displays.  Because of this, transmission of the           
        DSP/SSI monitor information is enabled prior to the start of          
        recording.  The specific run time and tape recording times            
        will be identified in the Sequence of Events (SOE) and/or DSN         
        Keyword File.                                                         
                                                                              
        The DSP can be used to duplicate ODRs.  It also has the               
        capability to play back a certain section of the recorded             
        data after conclusion of the recording periods.                       
                                                                              
                                                                              
      DSCC Frequency and Timing Subsystem                                     
      -----------------------------------                                     
        The Frequency and Timing Subsystem (FTS) provides all                 
        frequency and timing references required by the other DSCC            
        subsystems.  It contains four frequency standards of which            
        one is prime and the other three are backups.  Selection of           
        the prime standard is done via the CMC.  Of these four                
        standards, two are hydrogen masers followed by clean-up loops         
        (CUL) and two are cesium standards.  These four standards all         
        feed the Coherent Reference Generator (CRG) which provides            
        the frequency references used by the rest of the complex.  It         
        also provides the frequency reference to the Master Clock             
        Assembly (MCA) which in turn provides time to the Time                
        Insertion and Distribution Assembly (TID) which provides UTC          
        and SIM-time to the complex.                                          
                                                                              
        JPL's ability to monitor the FTS at each DSCC is limited to           
        the MDA calculated Doppler pseudo-residuals, the Doppler              
        noise, the SSI, and to a system which uses the Global                 
        Positioning System (GPS).  GPS receivers at each DSCC receive         
        a one-pulse-per-second pulse from the station's (hydrogen             
        maser referenced) FTS and a pulse from a GPS satellite at             
        scheduled times.  After compensating for the satellite signal         
        delay, the timing offset is reported to JPL where a database          
        is kept.  The clock offsets stored in the JPL database are            
        given in microseconds; each entry is a mean reading of                
        measurements from several GPS satellites and a time tag               
        associated with the mean reading.  The clock offsets provided         
        include those of SPC 10 relative to UTC (NIST), SPC 40                
        relative to SPC 10, etc.                                              
                                                                              
                                                                              
    Optics - DSN                                                              
    ============                                                              
      Performance of DSN ground stations depends primarily on size of         
      the antenna and capabilities of electronics.  These are                 
      summarized in the following set of tables.  Note that 64-m              
      antennas were upgraded to 70-m between 1986 and 1989.                   
      Beamwidth is half-power full angular width.  Polarization is            
      circular; L denotes left circular polarization (LCP), and R             
      denotes right circular polarization (RCP).                              
                                                                              
                           DSS S-Band Characteristics                         
                                                                              
                               64-m      70-m     34-m     34-m               
           Transmit                                STD      HEF               
           --------           -----     -----    -----    -----               
           Frequency (MHz)    2110-     2110-    2025-     N/A                
                               2120      2120     2120                        
           Wavelength (m)     0.142     0.142    0.142     N/A                
           Ant Gain (dBi)                62.7     55.2     N/A                
           Beamwidth (deg)              0.119     0.31     N/A                
           Polarization                L or R   L or R     N/A                
           Tx Power (kW)               20-400       20     N/A                
                                                                              
           Receive                                                            
           -------                                                            
           Frequency (MHz)    2270-     2270-    2270-    2200-               
                               2300      2300     2300     2300               
           Wavelength (m)     0.131     0.131    0.131    0.131               
           Ant Gain (dBi)      61.6      63.3     56.2     56.0               
           Beamwidth (deg)              0.108     0.27     0.24               
           Polarization       L & R     L & R   L or R   L or R               
           System Temp (K)       22        20       22       38               
                                                                              
                DSS X-Band Characteristics (N/A for Galileo)                  
                                                                              
                               64-m      70-m     34-m     34-m               
           Transmit                                STD      HEF               
           --------           -----     -----    -----    -----               
           Frequency (MHz)     8495      8495     N/A     7145-               
                                                           7190               
           Wavelength (m)     0.035     0.035     N/A     0.042               
           Ant Gain (dBi)                74.2     N/A        67               
           Beamwidth (deg)                        N/A     0.074               
           Polarization      L or R    L or R     N/A    L or R               
           Tx Power (kW)        360       360     N/A        20               
                                                                              
           Receive                                                            
           -------                                                            
           Frequency (MHz)    8400-     8400-    8400-    8400-               
                               8500      8500     8500     8500               
           Wavelength (m)     0.036     0.036    0.036    0.036               
           Ant Gain (dBi)      71.7      74.2     66.2     68.3               
           Beamwidth (deg)              0.031    0.075    0.063               
           Polarization       L & R     L & R    L & R    L & R               
           System Temp (K)       27        20       25       20               
                                                                              
                                                                              
    Electronics - DSN                                                         
    =================                                                         
                                                                              
      DSCC Open-Loop Receiver                                                 
      -----------------------                                                 
        The open loop receiver block diagram shown below is for 70-m          
        and 34-m High-Efficiency (HEF) antenna sites.  Based on a             
        tuning prediction file, the POCA controls the DANA                    
        synthesizer the output of which (after multiplication) mixes          
        input signals at both S- and X-band to fixed intermediate             
        frequencies for amplification.  These signals in turn are             
        down converted and passed through additional filters until            
        they yield baseband output of up to 25 kHz in width.  The             
        baseband output is digitally sampled by the DSP and either            
        written to magnetic tape or electronically transferred for            
        further analysis.                                                     
                                                                              
           S-Band                                          X-Band             
          2295 MHz                                        8415 MHz            
           Input                                            Input             
             |                                                |               
             v                                                v               
            ---     ---                              ---     ---              
           | X |❮--|x20|❮--100 MHz        100 MHz--❯|x81|--❯| X |             
            ---     ---                              ---     ---              
             |                                                |               
          295|                                                |315            
          MHz|                                                |MHz            
             v                                                v               
            ---     --                 33.1818       ---     ---              
           | X |❮--|x3|❮------           MHz ------❯|x11|--❯| X |             
            ---     --        |115          |        ---     ---              
             |                |MHz          |                 |               
             |                |             |                 |               
           50|      71.8181  ---           ---                |50             
          MHz|         MHz-❯| X |         | X |❮-10 MHz       |MHz            
             v               ---           ---                v               
            ---               ^             ^                ---              
           | X |❮--60 MHz     |             |      60 MHz--❯| X |             
            ---               |             |                ---              
             |        9.9     | 43.1818 MHz |      9.9        |               
             |        MHz      -------------       MHz        |               
             |         |             ^              |         |               
           10|         v             |              v         |10             
          MHz|        ---       ----------         ---        |MHz            
             |------❯| X |     |   DANA   |       | X |❮------|               
             |        ---      |Synthesizr|        ---        |               
             |         |        ----------          |         |               
             v         v             ^              v         v               
          -------   -------          |           -------   -------            
         |Filters| |Filters|    ----------      |Filters| |Filters|           
         |3,4,5,6| |  1,2  |   |   POCA   |     |  1,2  | |3,4,5,6|           
          -------   -------    |Controller|      -------   -------            
             |         |        ----------          |         |               
           10|         |0.1                      0.1|         |10             
          MHz|         |MHz                      MHz|         |MHz            
             v         v                            v         v               
            ---       ---                          ---       ---              
           | X |-   -| X |                        | X |-   -| X |             
            ---  | |  ---                          ---  | |  ---              
             ^   | |   ^                            ^   | |   ^               
             |   | |   |                            |   | |   |               
            10   | |  0.1                          0.1  | |   10              
            MHz  | |  MHz                          MHz  | |  MHz              
                 | |                                    | |                   
                 v v                                    v v                   
               Baseband                               Baseband                
                Output                                 Output                 
                                                                              
                                                                              
        Reconstruction of the antenna frequency from the frequency of         
        the signal in the recorded data can be achieved through use           
        of one of the following formulas.                                     
                                                                              
        Radio Science IF-VF (RIV) Converter Assembly at 70-m and 34-m         
        High-Efficiency (HEF) antennas:                                       
                                                                              
           FSant=3*[POCA+(790/11)*10^6] + 1.95*10^9 - Fsamp - Frec            
                                                                              
           FXant=11*[POCA-10^7] + 8.050*10^9 - 3*Fsamp + Frec                 
                                                                              
        Multi-Mission Receivers at 34-m Standard antennas (DSS 42 and 61;     
        the diagram above does not apply):                                    
                                                                              
           FSant=48*POCA + 3*10^8 - 0.75*Fsamp + Frec                         
                                                                              
           FXant = (11/3)*[48*POCA + 3*10^8 - 0.75*Fsamp] + Frec              
                                                                              
         where                                                                
           FSant = S-band antenna frequency                                   
           FXant = X-band antenna frequency                                   
           POCA  = POCA frequency                                             
           Fsamp = sampling frequency                                         
           Frec  = frequency of recorded signal                               
                                                                              
                                                                              
    Filters - DSN                                                             
    =============                                                             
                                                                              
      DSCC Open-Loop Receiver                                                 
      -----------------------                                                 
        Nominal filter center frequencies and bandwidths for the              
        Open-Loop Receivers are shown in the table below.                     
                                                                              
         Filter      Center Frequency    3 dB Bandwidth                       
         ------      ----------------    --------------                       
            1             0.1 MHz              90 Hz                          
            2             0.1 MHz             450 Hz                          
            3            10.0 MHz            2000 Hz                          
            4            10.0 MHz            1700 Hz (S-band)                 
                                             6250 Hz (X-band)                 
            5            10.0 MHz           45000 Hz                          
            6            10.0 MHz           21000 Hz                          
                                                                              
        MMR filters (DSS 42 and 61) include the following:                    
                                                                              
         Filter      Center Frequency    3 dB Bandwidth                       
         ------      ----------------    --------------                       
            5             Unknown            2045 Hz (S-band)                 
                                             7500 Hz (X-band)                 
                                                                              
    Detectors - DSN                                                           
    ===============                                                           
                                                                              
      DSCC Open-Loop Receivers                                                
      ------------------------                                                
        Open-loop receiver output is detected in software by the              
        radio science investigator.                                           
                                                                              
                                                                              
      DSCC Closed-Loop Receivers                                              
      --------------------------                                              
        Nominal carrier tracking loop threshold noise bandwidth at            
        both S- and X-band is 10 Hz.  Coherent (two-way) closed-loop          
        system stability is shown in the table below:                         
                                                                              
            integration time            Doppler uncertainty                   
                 (secs)               (one sigma, microns/sec)                
                 ------               ------------------------                
                    10                            50                          
                    60                            20                          
                  1000                             4                          
                                                                              
                                                                              
    Calibration - DSN                                                         
    =================                                                         
      Calibrations of hardware systems are carried out periodically           
      by DSN personnel; these ensure that systems operate at required         
      performance levels -- for example, that antenna patterns,               
      receiver gain, propagation delays, and Doppler uncertainties            
      meet specifications.  No information on specific calibration            
      activities is available.  Nominal performance specifications            
      are shown in the tables above.  Additional information may be           
      available in [DSN810-5].                                                
                                                                              
      Prior to each tracking pass, station operators perform a series         
      of calibrations to ensure that systems meet specifications for          
      that operational period.  Included in these calibrations is             
      measurement of receiver system temperature in the configuration         
      to be employed during the pass.  Results of these calibrations          
      are recorded in (hard copy) Controller's Logs for each pass.            
                                                                              
      The nominal procedure for initializing open-loop receiver               
      attenuator settings is described below.  In cases where widely          
      varying signal levels are expected, the procedure may be                
      modified in advance or real-time adjustments may be made to             
      attenuator settings.                                                    
                                                                              
                                                                              
      Open-Loop Receiver Attenuation Calibration                              
      ------------------------------------------                              
        The open-loop receiver attenuator calibrations are performed          
        to establish the output of the open-loop receivers at a level         
        that will not saturate the analog-to-digital converters.  To          
        achieve this, the calibration is done using a test signal             
        generated by the exciter/translator that is set to the peak           
        predicted signal level for the upcoming pass.  Then the               
        output level of the receiver's video band spectrum envelope           
        is adjusted to the level determined by equation (3) below (to         
        five-sigma).  Note that the SNR in the equation (2) is in dB          
        while the SNR in equation (3) is linear.                              
                                                                              
           Pn = -198.6 + 10*log(SNT) + 10*log(1.2*Fbw)              (1)       
                                                                              
           SNR = Ps - Pn                               (SNR in dB)  (2)       
                                                                              
           Vrms = sqrt(SNR + 1)/[1 + 0.283*sqrt(SNR)]  (SNR linear) (3)       
                                                                              
           where    Fbw = receiver filter bandwidth (Hz)                      
                    Pn  = receiver noise power (dBm)                          
                    Ps  = signal power (dBm)                                  
                    SNT = system noise temperature (K)                        
                    SNR = predicted signal-to-noise ratio                     
                                                                              
                                                                              
    Operational Considerations - DSN                                          
    ================================                                          
      The DSN is a complex and dynamic 'instrument.' Its performance          
      for Radio Science depends on a number of factors from equipment         
      configuration to meteorological conditions.  No specific                
      information on 'operational considerations' can be given here.          
                                                                              
                                                                              
    Operational Modes - DSN                                                   
    =======================                                                   
                                                                              
      DSCC Antenna Mechanical Subsystem                                       
      ---------------------------------                                       
        Pointing of DSCC antennas may be carried out in several ways.         
        For details see the subsection 'DSCC Antenna Mechanical               
        Subsystem' in the 'Subsystem' section.  Binary pointing is            
        the preferred mode for tracking spacecraft; pointing                  
        predicts are provided, and the antenna simply follows those.          
        With CONSCAN, the antenna scans conically about the optimum           
        pointing direction, using closed-loop receiver signal                 
        strength estimates as feedback.  In planetary mode, the               
        system interpolates from three (slowly changing) RA-DEC               
        target coordinates; this is 'blind' pointing since there is           
        no feedback from a detected signal.  In sidereal mode, the            
        antenna tracks a fixed point on the celestial sphere.  In             
        'precision' mode, the antenna pointing is adjusted using an           
        optical feedback system.  It is possible on most antennas to          
        freeze z-axis motion of the subreflector to minimize phase            
        changes in the received signal.                                       
                                                                              
                                                                              
      DSCC Receiver-Exciter Subsystem                                         
      -------------------------------                                         
        The diplexer in the signal path between the transmitter and           
        the feed horns on all three antennas may be configured so             
        that it is out of the received signal path in order to                
        improve the signal-to-noise ratio in the receiver system.             
        This is known as the 'listen-only' or 'bypass' mode.                  
                                                                              
                                                                              
      Closed-Loop vs. Open-Loop Reception                                     
      -----------------------------------                                     
        Radio Science data can be collected in two modes: closed-             
        loop, in which a phase-locked loop receiver tracks the                
        spacecraft signal, or open-loop, in which a receiver samples          
        and records a band within which the desired signal presumably         
        resides.  Closed-loop data are collected using Closed-Loop            
        Receivers, and open-loop data are collected using Open-Loop           
        Receivers in conjunction with the DSCC Spectrum Processing            
        Subsystem (DSP).  See the Subsystems section for further              
        information.                                                          
                                                                              
                                                                              
      Closed-Loop Receiver AGC Loop                                           
      -----------------------------                                           
        The closed-loop receiver AGC loop can be configured to one of         
        three settings: narrow, medium, or wide.  Ordinarily it is            
        configured so that expected signal amplitude changes are              
        accommodated with minimum distortion.  The loop bandwidth is          
        ordinarily configured so that expected phase changes can be           
        accommodated while maintaining the best possible loop SNR.            
                                                                              
                                                                              
      Coherent vs. Non-Coherent Operation                                     
      -----------------------------------                                     
        The frequency of the signal transmitted from the spacecraft           
        can generally be controlled in two ways -- by locking to a            
        signal received from a ground station or by locking to an             
        on-board oscillator.  These are known as the coherent (or             
        'two-way') and non-coherent ('one-way') modes, respectively.          
        Mode selection is made at the spacecraft, based on commands           
        received from the ground.  When operating in the coherent             
        mode, the transponder carrier frequency is derived from the           
        received uplink carrier frequency with a 'turn-around ratio'          
        typically of 240/221.  In the non-coherent mode, the                  
        downlink carrier frequency is derived from the spacecraft             
        on-board crystal-controlled oscillator.  Either closed-loop           
        or open-loop receivers (or both) can be used with either              
        spacecraft frequency reference mode.  Closed-loop reception           
        in two-way mode is usually preferred for routine tracking.            
        Occasionally the spacecraft operates coherently while two             
        ground stations receive the 'downlink' signal; this is                
        sometimes known as the 'three-way' mode.                              
                                                                              
                                                                              
      DSCC Spectrum Processing Subsystem (DSP)                                
      ----------------------------------------                                
        The DSP can operate in four sampling modes with from 1 to 4           
        input signals.  Input channels are assigned to ADC inputs             
        during DSP configuration.  Modes and sampling rates are               
        summarized in the tables below:                                       
                                                                              
        Mode   Analog-to-Digital Operation                                    
        ----   ----------------------------                                   
          1    4 signals, each sampled by a single ADC                        
          2    1 signal, sampled sequentially by 4 ADCs                       
          3    2 signals, each sampled sequentially by 2 ADCs                 
          4    2 signals, the first sampled by ADC #1 and the second          
                           sampled sequentially at 3 times the rate           
                            by ADCs #2-4                                      
                                                                              
             8-bit Samples               12-bit  Samples                      
            Sampling  Rates              Sampling  Rates                      
         (samples/sec per ADC)        (samples/sec per ADC)                   
         ---------------------        ---------------------                   
                 50000                                                        
                 31250                                                        
                 25000                                                        
                 15625                                                        
                 12500                                                        
                 10000                        10000                           
                  6250                                                        
                  5000                         5000                           
                  4000                                                        
                  3125                                                        
                  2500                                                        
                                               2000                           
                  1250                                                        
                  1000                         1000                           
                   500                                                        
                   400                                                        
                   250                                                        
                   200                          200                           
                                                                              
        Input to each ADC is identified in header records by a Signal         
        Channel Number (J1 - J4).  Nominal channel assignments are            
        shown below.                                                          
                                                                              
             Signal Channel Number              Receiver                      
                                        (70-m or HEF)  (34-m STD)             
             ---------------------      -------------  ----------             
                      J1                    X-RCP       not used              
                      J2                    S-RCP       not used              
                      J3                    X-LCP         X-RCP               
                      J4                    S-LCP         S-RCP               
                                                                              
                                                                              
    Location - DSN                                                            
    ==============                                                            
      Station locations are documented in [GEO-10REVD].  Geocentric           
      coordinates are summarized here.                                        
                                                                              
                            Geocentric  Geocentric  Geocentric                
      Station              Radius (km) Latitude (N) Longitude (E)             
      ---------            ----------- ------------ -------------             
      Goldstone                                                               
        DSS 12 (34-m STD)  6371.997815  35.1186672   243.1945048              
        DSS 13 (develop)   6372.117062  35.0665485   243.2051077              
        DSS 14 (70-m)      6371.992867  35.2443514   243.1104584              
        DSS 15 (34-m HEF)  6371.9463    35.2402863   243.1128186              
        DSS 16 (26-m)      6371.9608    35.1601436   243.1264200              
        DSS 18 (34-m STD)      UNK          UNK          UNK                  
                                                                              
      Canberra                                                                
        DSS 42 (34-m STD)  6371.675607 -35.2191850   148.9812546              
        DSS 43 (70-m)      6371.688953 -35.2209308   148.9812540              
        DSS 45 (34-m HEF)  6371.692    -35.21709     148.97757                
        DSS 46 (26-m)      6371.675    -35.22360     148.98297                
        DSS 48 (34-m STD)      UNK          UNK          UNK                  
                                                                              
      Madrid                                                                  
        DSS 61 (34-m STD)  6370.027734  40.2388805   355.7509634              
        DSS 63 (70-m)      6370.051015  40.2413495   355.7519776              
        DSS 65 (34-m HEF)  6370.021370  40.2372843   355.7485968              
        DSS 66 (26-m)      6370.036     40.2400714   355.7485976              
        DSS 48 (34-m STD)      UNK          UNK          UNK                  
                                                                              
                                                                              
    Measurement Parameters - DSN                                              
    ============================                                              
                                                                              
      Open-Loop System                                                        
      ----------------                                                        
        Output from the Open-Loop Receivers (OLRs), as sampled and            
        recorded by the DSCC Spectrum Processing Subsystem (DSP), is          
        a stream of 8- or 12-bit quantized voltage samples.  The              
        nominal input to the Analog-to-Digital Converters (ADCs) is           
        +/-10 volts, but the precise scaling between input voltages           
        and output digitized samples is usually irrelevant for                
        analysis; the digital data are generally referenced to a              
        known noise or signal level within the data stream itself --          
        for example, the thermal noise output of the radio receivers          
        which has a known system noise temperature (SNT).  Raw                
        samples comprise the data block in each DSP record; a header          
        record (presently 83 16-bit words) contains ancillary                 
        information such as:                                                  
                                                                              
         time tag for the first sample in the data block                      
         RMS values of receiver signal levels and ADC outputs                 
         POCA frequency and drift rate                                        
                                                                              
                                                                              
      Closed-Loop System                                                      
      ------------------                                                      
        Closed-loop data are recorded in Archival Tracking Data Files         
        (ATDFs), as well as certain secondary products such as the            
        Orbit Data File (ODF).  The ATDF Tracking Logical Record              
        contains 117 entries including status information and                 
        measurements of ranging, Doppler, and signal strength.                
                                                                              
                                                                              
    ACRONYMS AND ABBREVIATIONS - DSN                                          
    ================================                                          
      ACS      Antenna Control System                                         
      ADC      Analog-to-Digital Converter                                    
      AGC      Automatic Gain Control                                         
      AMS      Antenna Microwave System                                       
      APA      Antenna Pointing Assembly                                      
      ARA      Area Routing Assembly                                          
      ATDF     Archival Tracking Data File                                    
      AZ       Azimuth                                                        
      CMC      Complex Monitor and Control                                    
      CONSCAN  Conical Scanning (antenna pointing mode)                       
      CRG      Coherent Reference Generator                                   
      CUL      Clean-up Loop                                                  
      DANA     a type of frequency synthesizer                                
      dB       deciBel                                                        
      dBi      dB relative to isotropic                                       
      DCO      Digitally Controlled Oscillator                                
      DEC      Declination                                                    
      deg      degree                                                         
      DFLR     Deutsche Forschungsanstalt fur Luft- und Raumfahrt             
      DMC      DSCC Monitor and Control Subsystem                             
      DSCC     Deep Space Communications Complex                              
      DSN      Deep Space Network                                             
      DSP      DSCC Spectrum Processing Subsystem                             
      DSS      Deep Space Station                                             
      DTK      DSCC Tracking Subsystem                                        
      E        east                                                           
      EL       Elevation                                                      
      FET      Field Effect Transistor                                        
      FFT      Fast Fourier Transform                                         
      FTS      Frequency and Timing Subsystem                                 
      GCF      Ground Communications Facility                                 
      GCR      Group Coded Recording                                          
      GHz      gigahertz                                                      
      GPS      Global Positioning System                                      
      GSFC     Goddard Space Flight Center                                    
      HA       Hour Angle                                                     
      HEF      High-Efficiency (as in 34-m HEF antennas)                      
      HEMT                                                                    
      HGA      High Gain Antenna                                              
      IF       Intermediate Frequency                                         
      IVC      IF Selection Switch                                            
      JPL      Jet Propulsion Laboratory                                      
      K        Kelvin                                                         
      km       kilometer                                                      
      kW       kilowatt                                                       
      L-band   approximately 1668 MHz                                         
      LAN      Local Area Network                                             
      LCP      Left-Circularly Polarized                                      
      LGA      Low Gain Antenna                                               
      LMC      Link Monitor and Control                                       
      LNA      Low-Noise Amplifier                                            
      LO       Local Oscillator                                               
      m        meters                                                         
      MCA      Master Clock Assembly                                          
      MCCC     Mission Control and Computing Center                           
      MDA      Metric Data Assembly                                           
      MHz      Megahertz                                                      
      MMR      Multi-Mission Radio (Science)                                  
      MON      Monitor and Control System                                     
      MSA      Mission Support Area                                           
      N        north                                                          
      NAR      Noise Adding Radiometer                                        
      NASA     National Aeronautics and Space Administration                  
      NASCOM   NASA Communications                                            
      NBOC     Narrow-Band Occultation Converter                              
      NIST     SPC 10 time relative to UTC                                    
      NIU      Network Interface Unit                                         
      NOCC     Network Operations and Control System                          
      NRV      NOCC Radio Science/VLBI Display Subsystem                      
      NSS      NOCC Support System                                            
      OCI      Operator Control Input                                         
      ODF      Orbit Data File                                                
      ODR      Original Data Record                                           
      ODS      Original Data Stream                                           
      OLR      Open Loop Receiver                                             
      PLO      Programmable Local Oscillator                                  
      POCA     Programmable Oscillator Control Assembly                       
      PPM      Precision Power Monitor                                        
      RA       Right Ascension                                                
      REC      Receiver-Exciter Controller                                    
      RCP      Right-Circularly Polarized                                     
      RF       Radio Frequency                                                
      RIC      RIV Controller                                                 
      RIV      Radio Science IF-VF Converter Assembly                         
      RMDCT    Radio Metric Data Conditioning Team                            
      RTLT     Round-Trip Light Time                                          
      S-band   approximately 2100-2300 MHz                                    
      sec      second                                                         
      SEC      System Error Correction                                        
      SIM      Simulation                                                     
      SLE      Signal Level Estimator                                         
      SNR      Signal-to-Noise Ratio                                          
      SNT      System Noise Temperature                                       
      SOE      Sequence of Events                                             
      SPA      Spectrum Processing Assembly                                   
      SPC      Signal Processing Center                                       
      SRA      Sequential Ranging Assembly                                    
      SRC      Sub-Reflector Controller                                       
      SSI      Spectral Signal Indicator                                      
      STD      Standard (as in 34-m STD antennas)                             
      TID      Time Insertion and Distribution Assembly                       
      TSF      Tracking Synthesizer Frequency                                 
      TWM      Traveling Wave Maser                                           
      Tx       Transmitter                                                    
      UNK      unknown                                                        
      UTC      Universal Coordinated Time                                     
      VF       Video Frequency                                                
      X-band   approximately 7800-8500 MHz"                                   
                                                                              
 END_OBJECT                       = INSTRUMENT_INFORMATION                    
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "ANDERSONETAL1992"                        
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "ANDERSONETAL1996"                        
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "ARMSTRONG1989"                           
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "ASMAR&HERRERA1993"                       
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "ASMAR&RENZETTI1993"                      
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "CAMPBELLETAL1978"                        
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "DSN810-5"                                
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "FJELDBOETAL1976"                         
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "GEO-10REVD"                              
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "HINSON&MAGALHAES1991"                    
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "HOWARDETAL1992"                          
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "HUBBARD&ANDERSON1978"                    
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "KLIOREETAL1975"                          
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "LINDALETAL1981"                          
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "TAYLOR&WEISBERG1989"                     
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "TYLERETAL1992"                           
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "WILL1981"                                
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
 OBJECT                           = INSTRUMENT_REFERENCE_INFO                 
  REFERENCE_KEY_ID                = "WOO1993"                                 
 END_OBJECT                       = INSTRUMENT_REFERENCE_INFO                 
                                                                              
END_OBJECT                        = INSTRUMENT                                
                                                                              
END