PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 1977-12-01 NOTE = "INST.TXT contains the instrument description." END_OBJECT = TEXT END INSTRUMENT: LOW ENERGY CHARGED PARTICLE SPACECRAFT: VOYAGER 1 Instrument Information ====================== Instrument Id : LECP Instrument Host Id : VG1 PI Pds User Id : KRIMIGIS PI Full Name : STAMITIOS M. KRIMIGIS Instrument Name : LOW ENERGY CHARGED PARTICLE Instrument Type : CHARGED PARTICLE ANALYZER Build Date : 1977-09-05 Instrument Mass : 6.652000 Instrument Length : UNK Instrument Width : UNK Instrument Height : UNK Instrument Serial Number : 03 Instrument Manufacturer Name : JOHNS HOPKINS UNIVERSITY APPLIED PHYSICS LABORATORY Instrument Overview =================== The low energy charged particle experiment employs a set of many solid state detectors arranged to characterize, with various levels of energy, directional, and compositional discriminations, the in-situ charged particle environment of the spacecraft, both within interplanetary and planetary magnetospheric regions. Electrons can be characterized, with various electron rate energy channels, between 26 keV and greater than 10 meV (mode dependent). Ions, without mass species discriminations, can be characterized with various ion rate energy channels between 30 keV and greater than 152 keV (mode dependent). Rate data is telemetered as simple counts per accumulation time period. The different channels correspond to different onboard energy discrimination windows (for ions the discrimination values are mass species dependent, leading to some ambiguity). Above about 200 keV/nucleon, the ions can be discriminated as to their mass species composition by the use of multiple parameter measurements. These measurements consist of the energies that individual particles deposit in more than one detector. This information is telemetered both as ion rate data, obtained by on-board species identification circuitry (with various channels representing various energy-species combinations), and as particle multiple parameters data, consisting of pulse-height-analysis values from each of the affected particle detectors for each analyzed particle. (A maximum of about 2 to 5 particles per second can be analyzed in this fashion due to telemetry limitations. A priority scheme avoids saturation by one species group. there are three such groups defined: atomic number z = 1,2 each group in a rotating fashion.) Angular information is obtained through mechanical rotation of the detectors. The main detectors look within a single scan plane that is rotated 360 degrees, stopping at 8 different look sectors (one of the sectors is blocked to obtain a background measurement: sector 8). The lower energy detectors have full width viewcones of about 45 degrees. The scan plane is oriented such that a line that passes exactly between sectors 8 and 1, and also exactly between sectors 4 and 5, is exactly parallel to the roll axis of the spacecraft (which nominally points at earth). When the roll orientation of the spacecraft is such that the star sensor is locked on Canopus, the scan plane is tilted about 30 degrees out of the ecliptic plane, with sector 3 tilting towards north ecliptic (and also in the direction that is retrograde with respect to the planetary orbits). Sectors 1 and 8 point in the general direction of earth. The scan rate is variable between 48 seconds to 48 minutes per 360 degree scan. There are some electron detectors (whose properties are not as well established as the others) that view out of the scan plane described here (see [KRIMIGISETAL1977]). Some of the data is subject to substantial contamination depending on the region under consideration. Before the data from this instrument can be used, it is vital that the contamination descriptions be examined ('CONTAMINATION_ DESC') for each contamination type ('CONTAMINATION_ID') and that the contaminations levels be determined ('DATA_QUALITY_ID' AND 'DATA_QUALITY_DESC'). While sector 8 is the background sector for most (and generally the most used) data channels, sector 4 is the background sector for some channels. Of those channels documented in this catalog, sector 4 is the background sector for channels: ESA0, ESB0, AB10, AB12, AB13, PSA1, PSA2, PSA3, PSB1, PSB2, AND PSB3. Science Objectives ================== Characterize the energy spectra, angular distributions, species composition, spatial structures, and temporal variations of the hot plasmas, energetic particles, and particulate radiation that exist in the vicinity of the outer planets (Jupiter, Saturn, Uranus, and Neptune) and within the interplanetary environment. To study the mechanisms by which such particles are energized and transported throughout such systems. To study in particular the energization and transport processes associated with hot plasmas and particulate radiation in the vicinity of planetary bow shocks, magnetopauses, magnetotail plasma sheets, inner radiation zones, the auroral zones, etc., and to study the interaction of such media with planetary satellites and the planetary atmospheres and ionospheres. Operational Considerations ========================== Instrument operates continuously sampling data over uniform accumulation intervals. The accumulation intervals are different for the different channels of information (almost 100 channels). The scan head of the LECP Instrument usually scans back-and-forth continuously (forward by 315 degrees and then back by 315 degrees). The scanning head pauses at 8 different scan sectors for periods ranging between 6 seconds and 48 seconds (for the encounter time periods) and takes about 0.5 seconds to scan between the sectors. Specially scanning modes for Voyager 2 at Uranus and Neptune have been developed whereby 1 or 2 quick scans are performed followed by 6 to 12 minutes of no scanning. Also, for Voyager 2 at Jupiter there was an extended period of no scanning. The roll orientation of the spacecraft is of crucial importance as to the type of data returned since that orientation determines the orientation of the scan plane of the LECP Instrument. That orientation also has safety consequences since a poor orientation could expose the LECP detectors to ring particulate damage. Calibration =========== The instrument was calibrated on the ground by placing it into beam chambers (e.g. Van DeGraf machines) and firing calibrated beams of known composition at it. Also, a radioactive source is positioned behind the 'sunshield' positioned at sector 8 for in-flight calibration of some detector-electronic gains. Also, the instrument has a calibration mode whereby pulses of known strength are sent into the pre-amplifier chains following the detectors. Information about calibration can be found in: [KRIMIGISETAL1977], [KRIMIGISETAL1981], [ARMSTRONGETAL1981], Geophysical Research, Vol. 86, p 8301, 1981. 'LECP' Detector =============== Total Fovs : 8 Data Rate : 600 Scan Mode Id : UNK Sample Bits : 10 Detector Type : SOLID STATE Detector Aspect Ratio : 0.000000 Nominal Operating Temperature : 273.000000 The LECP Instrument consists of a variety (about 28) of 'Solid State Detectors' that are used individually and in combinations (using coincidence and anti-coincidence criterion) to detect and characterize nuclear particles. The detector thicknesses range from 2 to 2450 microns to cover a very broad range of particle energy and mass characteristic. Detectors count particles that have appropriate discriminated characteristics with an efficiency that approaches 1. Therefore the sensitivity is strictly a function of the geometric factors of the detectors (geometric factors associated with different data channels are documented elsewhere in this catalog) and the energy and species band-widths of the data channels (also documented elsewhere). The geometric factors have units of area X Steradians (CM^2 X STR). 'LECP' Section Parameter 'ELECTRON RATE' ---------------------------------------- Instrument Parameter Name : ELECTRON RATE Sampling Parameter Name : ENERGY PER NUCLEON Instrument Parameter Unit : COUNTS/SECOND Minimum Instrument Parameter : 0.000000 Maximum Instrument Parameter : 0.000000 Minimum Sampling Parameter : 0.026000 Maximum Sampling Parameter : 20.000000 Noise Level : 0.000000 Sampling Parameter Interval : 0.000000 Sampling Parameter Resolution : 0.000000 Sampling Parameter Unit : MEV PER NUCLEON A measured parameter equaling the number of electrons hitting a particle detector per specified accumulation interval. The counted electrons may or may not be discriminated as to their energies (e.g. greater than E1, or between E1 and E2). 'LECP' Section Parameter 'ION RATE' ----------------------------------- Instrument Parameter Name : ION RATE Sampling Parameter Name : ATOMIC NUMBER Instrument Parameter Unit : COUNTS/SECOND Minimum Instrument Parameter : 0.000000 Maximum Instrument Parameter : 0.000000 Minimum Sampling Parameter : 1.000000 Maximum Sampling Parameter : 26.000000 Noise Level : 0.000000 Sampling Parameter Interval : 0.000000 Sampling Parameter Resolution : 0.000000 Sampling Parameter Unit : ATOMIC NUMBER A measured parameter equaling the number of ions striking a particle detector per specified accumulation interval. The counted ions may or may not be discriminated as to their energies (e.g. energy/nucleon or energy/charge between E1 and E2 or greater than E1) and/or as to their ion composition (atomic number Z or mass number greater than Z1 or M1, or between Z1 and Z2 or M1 and M2). 'LECP' Section Parameter 'PARTICLE MULTIPLE PARAMETERS' ------------------------------------------------------- Instrument Parameter Name : PARTICLE MULTIPLE PARAMETERS Sampling Parameter Name : ATOMIC NUMBER Instrument Parameter Unit : MEV X MEV Minimum Instrument Parameter : 0.000000 Maximum Instrument Parameter : 0.000000 Minimum Sampling Parameter : 1.000000 Maximum Sampling Parameter : 26.000000 Noise Level : 0.000000 Sampling Parameter Interval : 0.000000 Sampling Parameter Resolution : 0.000000 Sampling Parameter Unit : ATOMIC NUMBER A set of measured parameters which yield multiple pieces of information about each particle (generally ions) that Q enters the system. These pieces of information can, for example, consist of the energy deposited by a single particle in two or more separate detectors, or the time-of-flight between two different detectors plus the energy deposited in a third, etc.. The multiple pieces of information can be used to perform mass, atomic number, and/or charge state discriminations on ions. The information can be discriminated on-board and telemetered in the form of ion rate channels, or the multiple information about each particle analyzed can be telemetered for obtaining the finest species discriminations. (the following table is excerpted from: [MAUKETAL1991]) TABLE 1. Voyager 2 LECP Channel Characteristics ---------------------------------------------------------- Effective Field of Energy Channel Species, View, Passband,* [epsilon]G, Designation Z deg MeV/nucleon cm^2 sr ---------------------------------------------------------- Ion/Proton Channels PL01 Z>=1 45 0.028-0.043 1.13x10^-1 PL02 Z>=1 45 0.043-0.080 1.13x10^-1 PL03 Z>=1 45 0.080-0.137 1.13x10^-1 PL04 Z>=1 45 0.137-0.215 1.13x10^-1 PL05 Z>=1 45 0.215-0.540 1.13x10^-1 PL06 Z>=1 45 0.54-0.99 1.13x10^-1 PL07 Z>=1 45 0.99-2.14 1.13x10^-1 PL08 Z>=1 45 2.14-3.5 1.13x10^-1 39 Z>=2 60 0.035-0.069** 9.7x10^-2 38 Z>=6 60 0.069-0.20** 9.7x10^-2 32 Z=1 60 0.33-0.61 2.6x10^-3 1 Z=1 60 0.52-1.45 4.4x10^-1 33 Z=2 60 0.23-0.48 9.7x10^-2 Electron Channels E[beta]01 45 0.022-0.035 6x10^-3 E[beta]02 45 0.035-0.061 6x10^-3 E[beta]03 45 0.061-0.112 6x10^-3 E[beta]04 45 0.112-0.183 3.9x10^-3 E[beta]05 45 0.183-0.5 2x10^-3 E[gamma]06 45 >0.252 8.1x10^-3*** E[gamma]07 45 >0.480 3.5x10^-3*** E[gamma]08 45 >0.853 1.7x10^-4*** E[gamma]09 45 >1.20 ---------------------------------------------------------- Note: this table shows only a subset (the most commonly used) of the channels available. * For Z>=1 channels, passband is given for protons only. ** Indicates oxygen passband. *** [epsilon]G for the difference between adjacent integral channels. Electronics =========== Timed accumulations of particle counts satisfying various analog pulse-height discrimination levels. Timed accumulations of particle counts satisfying simultaneous analog pulse-height discriminations for multiple detectors. Pulse-height analog-to- digital conversions from multiple, simultaneous detectors for direct telemetry. Operational Modes ================= FAR ENCOUNTER ------------- Data Path Type : UNK Instrument Power Consumption : 4.725000 Used in the vicinity of planetary encounters. High intensity detectors turned off (A, B, DELTA, DELTA PRIME). (Affected channels are documented in detailed level catalog.) Bit Rate allocated 1/3 for Particle Multiple Parameters (PMP) data, also called Pulse Height Analysis data, and 2/3 for Rate data (counts/second). Full composition discrimination capabilities enabled (in both Rate and PMP forms). Angular scanning is typically 6.4 minutes per 360 degree scan but is often changed. Experiment Bit Rate is 600 bits per second. Electrons measured up to 0.5 MEV. minimum sample time is 0.4 sec. NEAR ENCOUNTER -------------- Data Path Type : UNK Instrument Power Consumption : 4.525000 Sometimes used at the closest-in positions during a planetary encounter. The high intensity detectors are turned on (A, B, DELTA, DELTA PRIME). (Affected channels are documented in the detailed level catalog.) Particle Multiple Parameter (PMP) composition discrimination capabilities are turned off (including the rate channels derived from the multiple para- meter information). All data appears in rate (counts/second) form. Angular scanning is typically 6.4 minutes per 360 degrees scan but is often changed. Scanning cyclics driven by the spacecraft computer are included. Experiment Bit Rate is 600 bits per second. Electrons are measured up to greater than 10 MEV. Minimum sample time is 0.4 sec. Instrument Mounting =================== Cone Offset Angle : UNK Cross Cone Offset Angle : UNK Twist Offset Angle : UNK LECP Instrument is mounted on the science boom about half way between the boom's spacecraft anchor point and imaging scan platform. The mounting is such that the 360 degree scan plane of the LECP scanning head (not to be confused with the scanning of the imaging instruments) is coplanar with the spacecraft's roll axis. Also, on the Canopus star lock the LECP scan plane is about 30 degrees rotated away from the ecliptic plane. A line passing between sectors 1 and 8, and between sectors 4 and 5, is parallel to the spacecraft roll axis. Sectors 1 and 8 point in the general direction or earth, and with the Canopus lock, sector 3 points generally in the retrograde direction (referring to the direction with respect to the directions of motion of the orbiting planets) and about 30 degrees north of the ecliptic.