Lunar Prospector Status Report #50

September 25, 1998 - 1:00 p.m. EST (10:00 a.m. PST)

The Lunar Prospector spacecraft continues to perform very well.

The procedure to turn the transmitter off during occultations with the propellant tank heater on is working well. There have been a few times where we have had slight delays in the turn on, 1 time due to operator error and 4 times due to station configuration delays. Of these events, 2 have caused the transmitter to be off for more than the storage loop on the spacecraft causing short outages of 4 minutes each (DOY 261 and 268). The lowest battery voltage seen since implementing the procedure on 9/16 is 25.06V, well above the 24.5V yellow limit.

No other commanding was done this week.

Plans are getting finalized for flipping the spacecraft 180Á. On Oct 5, the spacecraft spin axis will be reoriented from the north ecliptic pole to the orbit normal. This will provide good calibration data for the GRS instrument. On Oct 7, the spacecraft will be turned the other 90Á, putting the spin axis at the south ecliptic pole. This flip will allow the APS instrument to collect data it has missed due to the anomaly on one of its faces. Except for small drifts and special procedures, the spacecraft attitude will remain in this orientation for the rest of the mission.

Current spacecraft state (0000 GMT 9/25/98):

Orbit: 3120
Downlink: 3600 bps
Spin Rate: 12.00 rpm

Spin Axis Attitude (ecliptic):
Latitude: 87.4 deg
Longitude: 171 deg

Trajectory:
Periapsis Alt: 86.2 km
Apoapsis Alt: 110.8 km

Period: 118 min
Occultations: 46 minutes
Eclipses: 46 minutes
Propellant Remaining: 27.8 kg