Lunar Prospector Status Report #95

July 31 , 1999 - 10:000 p.m. EST (7:00 a.m. PST)

July 31, 1999. The final targeting burn was commanded an hour earlier to target the impact to hit a permanently shadowed crater near the south pole, at -87.7 deg latitude, 42 deg longitude. The timeline of maneuver activities is below (all times GMT, DOY 212, 7/31/99):

08:06 A3/A4 thruster heaters commanded on
08:11 Maneuver parameter file loaded and verified
08:16 Maneuver execute sent (started timer counting down for 1 hour)
08:59 Spacecraft passed over north pole behind the moon as seen from earth
This is the last time data was expected from the spacecraft.
09:16 Maneuver fired A3/A4 fired 276.5 sec, velocity decreased 44.3 m/s;
3.38 kg of propellant used (2.60 remaining is unusable)
09:52 Impact right over the south horizon as seen from earth

The University of Texas' David Goldstein coordinated the observations of the impact to look for confirmation that the hydrogen Lunar Prospector measured at the poles was really water. Two space telescopes monitored the impact: Hubble Space Telescope and SWAS. Two ground telescopes monitored the impact: McDonald Observatory at the University of Texas, and Keck Observatory in Hawaii. Other professional and amateur astronomers also observed.

No observatory reported seeing the debris plume. Data from the orbiting observatories will not be available until tomorrow. Analysis of the data from both the ground and orbiting observatories will take several days to determine whether or not the OH dissocation product of water was seen. Results will be reported at the Lunar Prospector web page, and the University of Texas' web page.

The spacecraft continued to collect and return good data for the MAG/ER instrument up until it last passed behind the moon at 08:59 GMT.