Lunar Prospector Status Report #74

March 19, 1999 - 1:00 p.m. EST (10:00 a.m. PST)

The Lunar Prospector spacecraft is operating well and collecting good science data in the extended mission orbit. Four of five science instruments are on: the Gamma Ray Spectrometer (GRS), the Neutron Spectrometer (NS), the Magnetometer (MAG) and the Electron Reflectometer (ER). Data continues to be collected for the Doppler Gravity Experiment (DGE) as well.

Cycling of the spacecraft transmitter was reinitiated on DOY 071 (March 12). During two eclipses after cancelling the procedure, the battery voltage reached the top of the yellow low limit, so the procedure was reestablished to increase margin as eclipses lengthen slightly before reaching a maximim in early April. There was one event (DOY 072), where the transmitter on command was delayed due to station problems, causing a 96 minute loss of data.

On DOY 072, the battery voltage reached the top of the yellow low limit even with the transmitter cycling procedure being implemented. Because the transmitter cannot be turned off for longer periods without losing data and the risk to the spacecraft is considered low, the procedure has not been modified, but the battery is being very closely monitored.

On DOY 076, commands were sent to the MAG/ER instrument to collect bursts of high rate data sets over the largest magnetic anomaly on the moon.

The next orbital maintenance burn is scheduled for March 24.

Current spacecraft state (0000 GMT 03/19/99):

Orbit: 5319
Downlink: 3600 bps
Spin Rate: 12.00 rpm

Spin Axis Attitude (ecliptic):
Latitude: -89.5 deg
Longitude: 330 deg

Trajectory:
Periapsis Alt: 14.8 km
Apoapsis Alt: 45.2 km
Period: 111 min

Occultations: 49 minutes
Eclipses: 48 minutes
Propellant Remaining: 14.78 kg