Lunar Prospector Status Report #59

December 4, 1998 - 1:00 p.m. EST (10:00 a.m. PST)

The Lunar Prospector spacecraft is operating well and all instruments continue to collect good data.

Transmitter cycling during propellant tank heater events was cancelled beginning 11/24 as eclipse durations have dropped below 40 minutes. If required, cycling will begin again sometime next year when the next eclipse season starts up.

On 12/2, 2 commands were sent to collect a high data rate MAG/ER snapshot.

On 12/4, a series of thruster burns were fired to dump 1.8 kg of propellant. Reducing the amount of propellant in the tanks will reduce the time the propellant tank heater is on, reducing the need for cycling the transmitter during the extended mission. Both spin thrusters were fired for an integer number of rotations in a series of four burns.

Current spacecraft state (0000 GMT 12/04/98):

Orbit: 3976
Downlink: 3600 bps
Spin Rate: 11.99 rpm

Spin Axis Attitude (ecliptic):
Latitude:-88.6 deg
Longitude: 265 deg

Trajectory:
Periapsis Alt: 91.1 km
Apoapsis Alt: 108.9 km
Period: 118 min

Occultations: none
Eclipses: 32 minutes
Propellant Remaining: 20.0 kg

On December 19, the orbit will be lowered from the nominal 100 km altitude mapping orbit to a 40 km altitude orbit. This will allow collection of data which can improve the gravity model in preparation for the extended mission. On January 16 the extended mission will begin, when the spacecraft will be lowered into a 25-30 km altitude orbit for six months.