LCROSS uses spent Centaur as lunar kinetic impactor
In an impressive display of recycling, the expended Centaur upper stage will become a directed kinetic impactor for the upcoming Lunar CRater Observation and Sensing Satellite, planned for launch in late 2008.
The LCROSS project was devised by a team headed by Daniel Andrews, who is currently the project manager at NASA Ames Research Center.
It was proposed in January 2006, as an add-on to the Lunar Reconnaissance Orbiter. Northrop Grumman Space Technology is building the craft, as an accelerated schedule, low cost mission spacecraft using existing NASA systems and commercial components, together with Northrop's spacecraft design expertise.
LCROSS will travel to the Moon as a co-manifested payload aboard the launch vehicle for the Lunar Reconnaissance Orbiter. The Mission Objectives of the LCROSS are to advance the Vision for Space Exploration by confirming the presence or absence of water ice in permanently shadowed craters at the Moon's North or South Pole. LCROSS will also provide technologies and modular, reconfigurable subsystems that can be used to support future mission architectures.
The LCROSS mission will deliver the 2,000-kilogram impactor to a lunar crater with 10 kilometer footprint accuracy, creating a 1,000 ton plume of lunar ejecta - more than 200 times the energy of Lunar Prospector. This ejecta plume will be examined for water ice and vapor. The Hubble Space Telescope, LRO and Chandra as well as leading earth-based observatories will examine the near IR region for signatures.
The Centaur is maneuvered by a small "adapter" Shepherding Spacecraft between the Centaur and LRO payload. After the LRO separates to head off to the moon for its own mission, the S-S/C guides the Centaur into a lunar impact trajectory, separates from the Centaur about seven hours before impact, and follows the Centaur a few minutes behind. After Centaur impact, the S-S/C flies through the Centaur impact plume, and relays its observations via the Deep Space Network. These include high-resolution spatial and temporal measurements of the impact, plume and fresh Centaur crater. These measurements are made by the science payload, which consists of two near-infrared spectrometers, a visible light spectrometer, two mid-infrared cameras, two near-infrared cameras, a visible camera and a visible radiometer. Once observations are made by the Shepherding Spacecraft, it becomes a 700-kilogram impactor as well.
A major milestone, thermal vacuum testing of the LCROSS spacecraft, was completed June 5 at the Northrop Grumman facility in Redondo Beach, Calif. To simulate the harsh conditions of space, technicians subjected the spacecraft to over 13 days of heating and cooling cycles during which temperatures reached as high as 230 Fahrenheit and as low as minus 40 degrees. Previous testing for the LCROSS spacecraft included acoustic vibration tests. Those tests simulated launch conditions and checked mating of connection points to the Atlas V rocket's Centaur upper stage and the adapter ring for the LRO.
"The spacecraft steadily has taken shape since Ames delivered the science payload in January," said Andrews. "It is a testament to the hard work, perseverance and expertise of the NASA and Northrop Grumman teams that the spacecraft has completed these critical tests ahead of schedule."
After launch, the LCROSS spacecraft and the Atlas V's Centaur upper stage rocket will execute a fly-by of the moon and enter into an elongated Earth orbit to position the satellite for impact on a lunar pole. On final approach, the spacecraft and the Centaur will separate. The Centaur will strike the surface of the moon, creating a debris plume that will rise above the surface. Four minutes later, LCROSS will fly through the debris plume, collecting and relaying data back to Earth before impacting the lunar surface and creating a second debris plume. Scientists will observe both impacts to gather additional information.
The Centaur crater will be about 25 meters across. The idea of examining an impact plume was tried when the Lunar Prospector reached the end of its observations, back in 1999. But the observational instruments were all earth based, and the impact was smaller by about a factor of 200. No water was detected.
