Lunar Prospector Status Report #8

January 13, 1998 - 10:00 a.m. EST (7:00 a.m. PST)

The Mission Control Center at NASA's Ames Research Center reports that the Lunar Prospector spacecraft was successfully placed in its mapping orbit this morning, when the third Lunar Orbit Insertion burn was completed. Firing the two aft axial thrusters for 27 minutes, the orbit was nearly circularized at about 100 km altitude. All science instruments are collected good data, and the spacecraft is working perfectly.

The LOI#3 flyby altitude was 89 km, at an inclination of 89.93 deg. Initial estimates from the navigation team are that the burn was about 4% low, and the orbit is about 92x160 km. The burn lasted 27 minutes and used about 23.5 kg of propellant. The spacecraft now has 34 kg of propellant for maintaining the mapping orbit during the one year nominal mission.ehind the Moon as seen from Earth and continuous communications can be maintained.

After the burn, the spin rate was trimmed back to 12 rpm for science requirements. Tomorrow the science instrument gains will be tweaked to match the data seen in the mapping orbit. Thursday the orbit will be circularized, the attitude oriented to the nominal attitude (spin axis perpendicular to the ecliptic plane) and the antenna switched to the medium gain antenna.

Lunar occultations, where the spacecraft passes behind the moon as seen from the earth ground stations, will start later today.

The timelinen of activities is given below:
013/10:27 GMT thruster heaters turned on
10:38 GMT command sent to start the maneuver with 1 hour time delay
11:38 - 12:05 LOI burn: 27.0 minutes, 23.5 kg of propellant
12:07 GMT engines safed
12:18 GMT spin thruster heater turned on
12:54-13:01 - expected occulation did not occur because of underburn
13:11 GMT spin trim: 2.0 second burn; spin rate 13.1 to 12.01 rpm