Lunar Prospector Status Report #48

September 11, 1998 - 1:00 p.m. EST (10:00 a.m. PST)

The Lunar Prospector spacecraft continues to perform very well.

There were two commands sent this past week (9/11) to adjust the gain of the GRS instrument.

The spacecraft successfully survived the penumbral eclipse which occured at 1100 GMT on 9/6/98. Due to the geometry of the orbit around the moon, as the moon pass through the Earth's penumbra, the spacecraft saw the sun blocked twice - the first time up to 83% of the sun was blocked; the second time, only 15% of the sun was blocked. Estimates are that there was an extra 8% Depth of Discharge (DOD) on the battery due to the first event. Since the spacecraft was also passing through 45 minute lunar night passes, the total discharge on the battery was about 50%, well within normal operations. There had been some concern that the propellant tank heaters might come on during this event, causing a much larger discharge, but this did not happen until after both penumbral events. No battery discharge was seen during the second penumbral event. Events were as follows (249 is the Day of Year):

249/0752 Commanded GRS gain change

249/0755 Commanded Pressure transducer off

249/0756 Commanded Earth-Moon limb sensor off

249/0903 Enter Lunar night pass and Earth occultation (loss of signal [LOS])

249/0948 Exit Lunar night pass

249/0949 Exit Earth occultation (acquisition of signal [AOS])

249/1023 Enter Earth penumbral shadow

249/1040 Began battery discharge

249/1057 Max penumbra (83% sunlight blocked)

249/1100 Enter Lunar night pass with DOD 8%

249/1101 Enter Earth occultation (LOS)

249/1131 Exit Earth penumbral shadow

249/1145 Exit Lunar night pass

249/1146 Exit Earth occultation (AOS) battery recharging nicely

249/1218 Enter Earth penumbral shadow

249/1235 Max penumbra (15% sunlight blocked)

249/1250 Commanded Pressure transducer on

249/1251 Commanded Earth-Moon Limb sensor on

249/1253 Exit Earth penumbral shadow - saw no battery discharge; battery fully charged

249/1258 Enter Lunar night pass and Earth occultation (LOS)

249/1335 Tank heaters on

249/1353 Exit Lunar night pass and Earth occultation (AOS)

Current spacecraft state (0000 GMT 9/11/98):

Orbit: 2937
Downlink: 3600 bps
Spin Rate: 12.00 rpm

Spin Axis Attitude (ecliptic):
Latitude: 88.3 deg
Longitude: 189 deg

Trajectory:
Periapsis Alt: 91.1 km
Apoapsis Alt: 105.9 km

Period: 118 min
Occultations: 45 minutes
Eclipses: 45 minutes