phased-array medium gain antenna for downlink, and an omni-
directional low-gain antenna for downlink and uplink. There is no
on-board computer, all control is from the ground, commanding
a single on-board command and data handling unit. Data are
downlinked directly and also stored on a solid-state recorder
and downlinked after 53 minutes, to ensure all data collected
during communications blackout periods are received. 

Following launch on 7 January 1998 UT (6 January EST) aboard
a three-stage Athena 2 rocket, the Lunar Prospector had a 105
hour cruise to the Moon. During the cruise, the three instrument
booms were deployed. The MAG and APS collected calibration
data, while the GRS, NS, and ER outgassed for one day, after
which they also collected calibration data in cis-lunar space.
The craft was inserted into an 11.6-hour period capture orbit
about the Moon at the end of the cruise phase. After 24 hours
Lunar Prospector was inserted into a 3.5-hour period inter-
mediate orbit, followed 24 hours later (on 13 January 1998) by
tranfer into a 92 x 153 km preliminary mapping orbit, and then
on 16 January by insertion into the near-circular 100 km altitude
nominal lunar polar mapping orbit with an inclination of 90
degrees and a period of 118 minutes. Lunar calibration data
was collected during the 11.6- and 3.5-hour orbits. Lunar map-
ping data collection started shortly after the 118 minute orbit
was achieved. The data collection was periodically interrupted
during the mission as planned for orbital maintenance burns,
which took place to recircularize the orbit whenever the peri-
selene or aposelene was more than 20 to 25 km from the 100
km nominal orbit, about once a month. On 19 December 1998,
a maneuver lowered the orbit to 40 km to perform higher