Lunar Prospector Status Report #89

July 01 , 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.

On June 27, the ER instrument was commanded to high resolution mode to collect data during the full moon (which occurred June 28). On June 30, it was commanded back to normal mode. During the commanding on June 30, there was one command that did not get received by the spacecraft. Because of that, as well as noise in the downlink (which prevented verification of the uplink) and a procedural error, the commands had to be resent several times. The instrument is operating well and there were no unexplained anomalies.

On June 29, the 7th Extended Mission Orbit Correction burn was executed. There were no anomalies and the timeline is summarized below. Analysis shows that performance was only 0.3% off from the prediction.

180/14:45 thruster heaters commanded on
180/14:49 loaded maneuver parameters
180/15:11 fired A1/A2 thrusters for 47.3 sec (7.51 m/s DV, 0.59 kg propellant)
180/15:55 thruster heaters commanded on
180/15:58 loaded maneuver parameters
180/16:22 fired A1/A2 thrusters for 46.9 sec (7.47 m/s DV, 0.58 kg propellant)
180/16:24 safed spacecraft (cleared maneuver parameters)

Of 74 commands transmitted to the spacecraft this week, only one did not execute (ER command 6/30). It is believed that this was due to intermittent coherent interference to the uplink due to reflections off the moon.

Current spacecraft state (0000 GMT 7/01/99, DOY 182):

Orbit: 6666
Downlink: 3600 bps
Spin Rate: 12.12 rpm

Spin Axis Attitude (ecliptic):
Latitude: -88.4 deg
>Longitude: 045 deg

Trajectory:
Periapsis Alt: 17.6 km
Apoapsis Alt: 42.4 km
Period: 111 min

Occultations: 38 minutes
Eclipses: none
Propellant Remaining: 9.51 kg

The next orbit maintenance burn is scheduled for July 26. It will be much smaller than previous burns, since the orbit only has to be maintained for a few days before setting up for the targeted impact scheduled for July 31.