Lunar Prospector - Spacecraft and Subsystems

Spacecraft and Subsystems

The spacecraft was a graphite-epoxy drum, 1.36 m (4.5 ft) in diameter and 1.28 m (4.2 ft) high with three radial 2.5 m (8.2 ft) instrument booms. A 1.1 m (3.6 ft) extension boom at the end of one of the 2.5 m booms held the magnetometer. Total initial mass (fully fueled) was 296 kg (650 lb). It was spin-stabilized (nominal spin rate 12 rpm) with its spin axis normal to the ecliptic plane. The spacecraft was controlled by six hydrazine monopropellant 22-newton thrusters (two aft, two forward, and two tangential). Three fuel tanks mounted inside the drum held 138 kg (300 lb) of hydrazine pressurized by helium. The power system consisted of body-mounted solar cells which produced an average of 186 W and a 4.8 A·h rechargeable NiCd battery. Communications were through two S-band transponders, a slotted, phased-array medium-gain antenna for downlink, and an omnidirectional low-gain antenna for downlink and uplink. The on-board computer was a Harris 80C86 with 64 kilobytes of EEPROM and 64 kilobytes of static RAM. All control was from the ground, the computer echoing each command to the ground for verification there. Once the command was ground-verified, an "execute" command from the ground told the computer to proceed with execution of the command. The computer built telemetry data as a combination of immediate data and also read from a circular queue buffer which allowed the computer to repeat data it had read 53 minutes earlier. This simple solid-state recorder ensured that all data collected during communications blackout periods would be received, providing the blackout was not longer than 53 minutes.

The probe also carried a small amount of the remains of Dr. Eugene Shoemaker (April 28, 1928 – July 18, 1997), astronomer and co-discoverer of Comet Shoemaker-Levy 9, to the moon for a space burial.