Lunar Prospector Status Report #77

April 09, 1999 - 1:00 p.m. EST (10:00 a.m. PST)

The Lunar Prospector spacecraft continues to collect 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.

Investigation into the commanding anomalies during last week's maneuver sequence continues. Since the last report, all commands (a total of 42) have executed normally. Procedures are being generated to allow for redundant commanding if required during maneuver commanding.

Cycling of the transmitter during propellant tank heater events was discontinued on DOY 083. Even with the load slightly reduced by keeping the Earth Moon Sensor and Pressure Transducer off, there have been 4 eclipses during heater events where the battery has dropped to the yellow low voltage limit. The maximum eclipse occurred on April 3 and the length of eclipses will slowly get shorter. Also, as fuel is burned during orbit maintenance burns, the heater cycle will shorten, causing less of an impact during a given orbit.

Current spacecraft state (0000 GMT 4/9/99, DOY 099):

Orbit: 5591
Downlink: 3600 bps
Spin Rate: 12.09 rpm

Spin Axis Attitude (ecliptic):

Latitude: -88.6 deg
Longitude: 016 deg

Trajectory:
Periapsis Alt: 22.5 km
Apoapsis Alt: 37.5 km
Period: 111 min

Occultations: none
Eclipses: 49 minutes
Propellant Remaining: 13.61 kg

The next orbit maintenance burn is scheduled for late in the afternoon local time on April 20 (DOY 111 GMT).