Lunar Prospector Status Report #85

June 4, 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.

The transmitter was turned off for short intervals 22 times this week during eclipse periods when the propellant tank heater was on. Burning propellant has reduced the period of the heater, and we are now experiencing about 3 heater events each day. The battery voltage dropped to the yellow low limit for 2 heater events.

The MAG/ER was commanded to higher resolution mode on 5/28 for the full moon passage 5/30; and was commanded back to normal mode 5/31.

On June 1 (local), the sixth maneuver to maintain the extended orbit was executed. There were no anomalies and the timeline is given below. No spin or attitude reorientation trims were required.

152/23:15 A1/A2 thruster heaters commanded on
152/23:20 Loaded maneuver parameters
152/23:40 Fire part 1 - A1/A2 thrusters 45.7 sec (7.2 m/s; used 0.57 kg prop)
153/00:20 Commanded A1/A2 thruster heaters on
153/00:22 Loaded maneuver parameters
153/00:51 Fire part 2 - A1/A2 thrusters 45.1 sec (7.1 m/s; used 0.55 kg prop)
153/00:52 Safe spacecraft

All commands (148 total) executed normally this week.

Current spacecraft state (0000 GMT 6/4/99, DOY 155):

Orbit: 6317
Downlink: 3600 bps
Spin Rate: 12.12 rpm

Spin Axis Attitude (ecliptic):
Latitude: -88.4 deg
Longitude: 041 deg

Trajectory:
Periapsis Alt:17.5 km
Apoapsis Alt: 42.5 km
Period: 111 min

Occultations: 44 minutes
Eclipses: 42 minutes
Propellant Remaining: 10.68 kg
The next orbit maintenance burn is scheduled for June 28, GMT (afternoon of June 27, PST).