NASA announced Monday that it intends to send a lunar impactor mission to the Moon in 2008, along with the Lunar Reconnaissance Orbiter, to search for south polar lunar ice.
The Ames Research Center-designed Lunar Crater Observation and Sensing Satellite (LCROSS) takes advantage of over 1,000 kg in extra mission mass gained from a switch from the Delta II to an EELV class launch vehicle for LRO earlier this year.
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NASA had been concerned with stability problems with the Delta IIâ€™s rotating upper stage related to LROâ€™s heavy fuel load, and made the decision in January to switch to an EELV class vehicle for the launch. This allowed a large additional payload to be sent, and NASA competitively evaluated internal agency proposals for just such a mission.
The ground rules were that the mission not exceed $80 million in cost or 1,000 kg in mass. LCROSS was selected from over 40 proposals submitted by field centers, aided by its double-impact feature.
On Monday NASA announced that it had selected Amesâ€™s $73 million LCROSS impactor as the final payload. LCROSS utilizes both a small spacecraft and the upper stage of the EELV class vehicle that sent both LRO and LCROSS to the Moon.
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Under the mission plan, the vehicle’s upper stage that put the two spacecraft on a lunar trajectory, called the Earth Departure Upper Stage (EDUS), will impact the Moon near its south pole (possibly at Shackleton crater) with over 200 times the energy of the Lunar Prospector impact in 1999, creating a 1000-tonne, 70-km high plume.
The impact will be observed by the Shepherding Spacecraft (S-S/C), which will itself impact the moon about 15 minutes later.
S-S/C will observe the impact of the 2,000 kg EDUS with a variety of instruments, including infrared spectrometers and at least two visible cameras, as it flies the through the impact plume.
Then the 700 kg S-S/C will hit the moon, affording ground-based observatories the chance to study two large artificial impacts. EDUS and S-S/C, which together make up the LCROSS mission, will arrive at the Moon apart from LRO, and will separate just before impact.
NASA hopes to observe hypothesized water ice deposits in the impact plume with LCROSS, which would allow future lunar astronauts to make fuel, air, and water in-situ on the Moon, greatly simplifying the logistics needs of a lunar base.
Other finalists for the mission included a microsatellite, another impactor, and a small ‘hopper’ lander designed by Raytheon.
Meanwhile, NASAâ€™s second planned robotic lunar mission, RLEP-2 (Robotic Lunar Exploration Program-2) is apparently encountering serious trouble. Originally targeted for launch as early as 2009, the RLEP-2 lander has been pushed back to at least 2011.
It has apparently exceeded its budget by several hundred million dollars and is facing possible cancellation or replacement with a smaller mission, according to NASAWatch.com.
The Raytheon hopper lander appears to be a candidate for this mission as well, despite its loss to LCROSS in the LRO secondary payload competition.
The current design for RLEP-2 includes an extremely large, $750 million lander proposed by Marshall Space Flight Center, which will probably land at Shackleton crater using an RL-10 engine and explore the area using a rover or a hopper.
The lander will be powered by RTGs and is planned to release 1-4 small communications satellites into a 2000-km high lunar polar orbit to allow lander relay back to Earth. It is hoped that the design can be used for an unmanned logistics resupply mission for later manned missions.
There is a large payload capability possible on the lander, but the budgetary problems make it unclear if and when this lander will fly and how large the final spacecraft will be.
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