K3PGP
Experimenter's Corner
Lunar
Prospector Status Report #30
May 1, 1998 - 1:00 p.m. EST
(10:00 a.m. PST)
The Lunar Prospector spacecraft continues to perform very well and instruments are collecting good data.
Several maneuvers were performed in the last week: a test pulse firing in reparation for the larger precession maneuver (planned for 3 days later), reorientation of the spin axis to improve the Sun angle, a circularization set of burns to adjust the orbit, and a spin trim to maintain nominal rate.
On April 23 (DOY 113), commands were sent to set the telemetry to read out thruster temperatures at a high rate for the test on April 24 (DOY 114).
Lunar Prospector executed a 2-pulse reorientation maneuver at 8:31AM (PDT) April 24 (GMT 114/1531). Engines used were A1 and A4, each executed one .2 second pulse, for a total reorientation of approximately 0.15 degrees.
On April 27 (DOY 117), the spin axis was precessed by 8.5 deg by firing 40 .2-sec pulses. Engines A1 and A4 were fired at 8:08AM (PDT) (117/1508).
A set of circularization burns were fired on May 1 (DOY 121). At 8:50AM 15:50 GMT), thrusters A3 and A4 were fired for 38.8 seconds to increase he s/c velocity by 6.0 m/s, raising periapsis (lowest point in orbit) from 5 km to 112 km. At 9:54 (16:54), thrusters A3 and A4 were fired for 37.1 seconds at the ascending node to make a new periapsis with altitude 88 km y slowing the spacecraft down by 5.74 m/s. The target orbit is now 88 x 12 km but with apoapsis (highest point in orbit) and periapsis flipped. he spin rate was trimmed with a spin down maneuver at 10:35 (17:35 GMT). thruster T1 was fired for 0.7 seconds to reduce the spin rate from 12.15 to 1.95 rpm.
After the maneuver burns, the high-level voltage on the GRS instrument was increased by one count with a GHV1LEV command.
Current spacecraft state 9:00 (1600 GMT 5/1/98) [before all burns today]:
Orbit: 1330
Downlink: 3600 bps
Spin Rate: 11.96 rpm
Spin Axis Attitude (ecliptic):
Latitude: 88.9 deg
Longitude: 79.1 deg
Trajectory:
Periselene Alt: 85 km
Aposelene Alt: 114 km
Period: 118 minutes
Occultations: none
Eclipses: 45 minutes
The navigation team will need several hours to confirm the orbit burns, but preliminary data shows that everything went nominally.
Lisa Chu Thielbar
NASA Ames Research Center
Moffett Field, CA 94035-1000
lchu-thielbar@mail.arc.nasa.gov
Contents of this website are ©1997-98 of K3PGP and of the originating authors.