Lunar Prospector Status Report #69

February 11, 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.

The Alpha Particle Spectrometer (APS) instrument was turned off Feb. 8 because it was generating noise that was affecting the Neutron Spectrometer (NS) instrument. The APS will be left off for one month to ensure at least one month of clean data from the NS. After one month, the APS will be turned on again to continue investigation of the anomaly.

Cycling of the spacecraft transmitter continues. The transmitter is powered off for occultations (when the spacecraft goes behind the moon and no data is received at Earth anyways) to reduce battery drain during propellant tank heater events. During one heater event (Feb. 7), the station was not properly configured and the command did not transmit. There was no effect on the battery.

A new gravity model was delivered to the project today by the Doppler Gravity Experient Investigator. Doppler data from the first 10 days of operations in the 30 km altitude orbit was included in the data set to generate this model.

Current spacecraft state (0000 GMT 02/11/99):

Orbit: 4853
Downlink: 3600 bps
Spin Rate: 12.09 rpm

Spin Axis Attitude (ecliptic):
Latitude: -88.5 deg
Longitude: 331 deg

Trajectory:
Periapsis Alt: 26.5 km
Apoapsis Alt: 33.5 km
Period: 111 min

Occultations: 40 minutes
Eclipses: 45 minutes
Propellant Remaining: 15.95 kg