NASA's next mission to Moon will not merely orbit the gray satellite, but crash two vehicles into its South Pole to hunt for water ice, the space agency said Monday.
In addition to mapping the Moon to support future astronaut missions, NASA's Lunar Reconnaissance Orbiter (LRO) spaceflight will also aim a spent fuel stage and impactor probe at a southern crater rich in hydrogen and, possibly, ice.
"I think aggressively touching the Moon is an understatement," said Scott Horowitz, NASA's associate administrator for the Exploration Systems Mission Directorate, in a Monday press conference. "What this mission buys is an early attempt to know what some of the resources we're going to have...we know for sure that for human exploration to succeed we're going to have to essentially live off the land."
Astronomers know that hydrogen exists in some form on the permanently-shadowed crater floors along the Moon's polar regions from past lunar orbiters. The Pentagon's Clementine spacecraft hinted at water ice in a crater called Shackleton in 1994, while NASA's Lunar Prospector unmistakable signs of hydrogen on the Moon's surface.
NASA hopes its LRO and crash missions will provide solid answers on the presence water ice on the Moon, and whether it exists in forms that may prove useful for future astronauts. Under the space agency's exploration vision, a four-astronaut Moon mission is slated for no later than 2020.
Set to launch with LRO in October 2008, the $73 million Lunar Crater Observation and Sensing Satellite (LCROSS) is a bare-bones spacecraft designed to use cameras and spectrometers to watch its 4,409-pound (2,000-kilogram) upper stage slam into hydrogen-rich Shackleton Crater, mission managers said.
"It's got the mass of an SUV and we'll send it into the South Pole of the Moon," LCROSS project manager Daniel Andrews, of NASA's Ames Research Center, said of the upper stage. "We will create a substantial plume [and] excavate some sample material, some of which we think will be water ice."
The 1,940-pound (880-kilogram) LCROSS probe will fly through the resulting plume and use its instruments to scan for water while taking photographs, then - 15 minutes after the upper stage booster's impact - the "shepherding" satellite will also crash into the crater floor, Andrews said.
"We know that we can steer it sufficiently to sample another region of the crater," Andrews said, adding that smashing into the same place twice would likely not yield additional valuable data.
A network of ground-based observatories will observe the impact and plume from Earth while LRO, India's Chandrayaan-1 lunar orbiter and other spacecraft examine the Moon crash from their respective locations, LCROSS mission managers said.
Slamming water-sniffing probes into objects is no strange feat for NASA.
The space agency crashed its Impactor probe into the comet Tempel 1 on July 4, 2005 while its parent Flyby craft and other space and ground-based observers looked on during the Deep Impact mission. NASA's Lunar Prospector orbiter also crashed into the Moon in July 1999, also in the hope of stirring up water ice, though researchers believe it may have hit at too shallow an angle to do much science.
"The models show that it kicked up a lot of material but mostly skidded on the surface," said Butler Hine, NASA's Robotic Lunar Exploration Program manager, of the earlier Moon crash.
Europe's SMART-1 orbiter - currently circling the Moon - is also expected to crash into the lunar surface later this year.
But LCROSS mission managers expect their crash-destined duo to carve a Moon crater 16 feet (4.8 meters) deep, about 100 feet (30 meters) wide and toss up about 2.2-million pounds (1,000 metric tons) of lunar material.
That's enough lunar material to fill 10 space shuttle payload bays to the brim, Andrews said, adding that the plume could reach up to 40 miles (64 kilometers) above the lunar surface.
Lunar piggyback ride
The LCROSS mission is a late add-on to NASA's LRO mission.
Horowitz said the secondary payload became possible when NASA decided to switch to a larger rocket booster to allow extra safety and design margin for LRO.
LCROSS was chosen after a brief competition among 19 contenders, each of which were restrained by a 2,204-pounds (1,000-kilogram) spacecraft weight cap and a cost of no more than $80 million.
NASA finally chose LCROSS out of four finalists, which included a similar Moon impact proposal that did not make use of the rocket's upper stage, an orbital microsatellite and a small, hopping lunar lander, Horowitz said.
The key to LCROSS lies in its Moon crashing fate. Unlike LRO, which is expected to generate extremely detailed maps, the LCROSS effort will actually bite into the lunar surface at a speed of 5,592 miles per hour (or about 2.5 kilometers per second).
"You never quite know what's there for sure until you touch it," said Hine of the Moon's surface. "And once we get the answer to that, it will help us plan out future human missions."
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