Today at 10:30:33 UTC, the Lunar Crater Observation and Sensing Satellite (LCROSS) passed the periselene at an altitude of 3200km above the lunar surface. The spacecraft entered a so-called Lunar Gravity Assist, Lunar Return Orbit (LGALRO) around the Earth, to position it on the path for impact at one of the Moon’s poles. Mission’s final target will be determined about a month before the impact to ensure ideal observing conditions for the LRO, Hubble and ground-based telescopes on Earth.
This swingby was the first test of the Medium Gain Antenna (MGA) to support high science rate. The data handling unit (DHU) and other scientific instruments were powered up for the first time. During the first 30 minutes of the coverage, the spacecraft collected data from three targets on the lunar surface for 5 minutes each (with short slews in between). First, the instruments turned to Mendeleev (Lat 5.7°N,Lon 140.9°E), a large ancient impact basin with uniform floor deposits. The uniformity of Mendeleev provided a good calibration target for onboard down-looking instruments.
At 12:30 UTC the spacecraft started data collection from surface target #2 – the Goddard crater located in the north region of Mare Marginis. The actual target, Goddard C, is a worn iron-rich crater with mare basalt flows mixed with rugged highlands-type material approximately 49km in diameter.
Finally, at around 12:40 UTC, the onboard instruments were pointed at the Giordano Bruno (Lat 35.9°N, 102.8°E) from the altitude of 9351 km above the surface.
After the data collection from surface targets was completed, the LCROSS carried out a series of lunar limb observations, a technique used for alignment.
After the swingby, the LCROSS spacecraft entered approximately 4-month long cruising phase during which it will perform 6 planned trajectory correction manuevers (TCM) and 3 science payload calibrations (SciCal). The last two TCMs are planned for the final targeting phase at T-72 hours and at T-11 hours before the impact on October 9.