INSTRUMENT_HOST_ID = LP INSTRUMENT_HOST_NAME = LUNAR PROSPECTOR INSTRUMENT_HOST_TYPE = SPACECRAFT Instrument Host Overview ======================== Lunar Prospector (LP) is a small, simple, spin-stabilized spacecraft with minimal operational requirements. Its fueled mass is 305 kg. The spacecraft bus is a graphite-epoxy drum that is 1.37 m in diameter and 1.28 m tall. Power is provided by solar cells mounted on the surface of the bus assembly, which produce an average of 186 w. There is also a rechargeable, 4.8 amp-hr NiCd battery for power during night side passes. The science instruments are mounted on three 2.5 m booms. The Gamma Ray Spectrometer is mounted on one boom, the Neutron Spectrometer and Alpha Particle Spectrometers are mounted on another boom, and the Magnetometer and Electron Reflectometer are mounted on the third boom. The Magnetometer instrument is mounted on a 1.2 m long boom extending beyond the main boom to isolate it from the Electron Reflectometer. The spacecraft bus houses three fuel tanks, six engines, and five electronic units. The fuel tanks at launch hold 138 kg of hydrazine pressurized with helium. There are two aft axial engines, two forward axial engines, and two tangential engines. The communication system consists of an S-band transponder, an omni antenna with 3-pi steradian antenna pattern for uplink and downlink, and a medium gain antenna for downlink. The engineering-only downlink data rate is 300 bps and the science/engineering downlink data rate is 3600 bps. Command and control of the spacecraft is achieved by a simple Command and Data Handling (C&DH) unit. As an individual command is uplinked to the spacecraft, the C&DH directs the command to the appropriate subsystem. All science and engineering data are collected by the C&DH and then are buffered and formatted for downlink by the C&DH. The data are downlinked at 1800 bps immediately and simultaneously dumped into a solid state recorder. The data stored on the solid state recorder is downlinked 53 minutes later. These delayed data frames are interleaved into the real-time data stream, yielding a total downlink rate of 3600 bps. The purpose of the delayed stream is to receive data acquired during communications blackout periods and to eliminate the need for a commandable data recorder. The LP spacecraft clock or frame counter increments once every 2 seconds. It is stored in a 24-bit register. This means that the clock will reset after about 33.5 million seconds or about once per year. The clock reset on January 30, 1999 at about 12:09 UTC, which was early in the Extended Mission. Spacecraft Coordinate System ============================ The Trans-Lunar Injection (TLI) stage and spacecraft body coordinate system is discussed below. The origin of coordinates is: a) in the separation plane between the spacecraft and the adapter of the TLI stage; and b) at the geometric center of the equilateral triangle defined by the bolt holes for the separation nuts. The Z axis is normal to the separation plane. The +Z direction is towards the medium gain antenna (forward) end of the spacecraft. The X axis is in the separation plane between the spacecraft and the adapter of the TLI stage. The -X direction is parallel to the centerline of instrument boom No. 1 and towards the Gamma Ray Spectrometer. The Y axis is defined by the right-hand rule. Instrument Host Overview - DSN ============================== The Deep Space Network (DSN) is a telecommunications facility managed by the Jet Propulsion Laboratory of the California Institute of Technology for the U.S. National Aeronautics and Space Administration (NASA). The primary function of the DSN is to provide two-way communications between the Earth and spacecraft exploring the solar system. To carry out this function it is equipped with high-power transmitters, low-noise amplifiers and receivers, and appropriate monitoring and control systems. The DSN consists of three complexes situated at approximately equally spaced longitudinal intervals around the globe at Goldstone (near Barstow, California), Robledo (near Madrid, Spain), and Tidbinbilla (near Canberra, Australia). Two of the complexes are located in the northern hemisphere while the third is in the southern hemisphere. Each complex includes several antennas, defined by their diameters, construction, or operational characteristics: 70-m diameter, standard 34-m diameter, high-efficiency 34-m diameter (HEF), and 34-m beam waveguide (BWG). These DSN complexes, in conjunction with telecommunications subsystems onboard planetary spacecraft, constitute the major elements of instrumentation for radio science investigations. Science Packages ================ The Lunar Prospector spacecraft has five science instruments. The instruments are a Gamma Ray Spectrometer (GRS), a Neutron Spectrometer (NS), an Alpha Particle Spectrometer (APS), a Magnetometer (MAG), and an Electron Reflectometer (ER). A Doppler Gravity Experiment (DGE) uses Doppler tracking data for deriving gravity measurements. In addition, the spacecraft spin rate and attitude are determined on the ground from data derived from a sun sensor and an IR Earth/Moon limb crossing sensor. References ========== Binder, A.B., W.C. Feldman, G.S. Hubbard, A.S. Konopliv, R.P. Lin, M.H. Acuna, and L.L. Hood, Lunar Prospector searches for polar ice, a metallic core, gas release events, and the moon's origin, Eos, Trans. AGU, 79, 97, 1998. (https://doi.org/10.1029/98EO00061) Asmar, S.W., and N.A. Renzetti, The Deep Space Network as an instrument for radio science research, Jet Propulsion Laboratory Publication 80-93, Rev. 1, 15 April 1993.