Friday, June 19, 2009

Re-Play: Atlas V-LRO/LCROSS launch

The United States began its return to the Moon, Thursday evening, with the launch of an Atlas V-Centaur carrying the first of two critical robotic precursor missions, the nation's first since 1998.

Much of the data obtained in the mission of Lunar Prospector (1998-1999) and also during the lunar orbit of the Department of Defense test platform Clementine in 1994 drove the design and engineering put into both vehicles launched to the Moon on Thursday; the Lunar Reconnaissance Orbiter (LRO) and on-board partner LCROSS, the Lunar CRater Remote Observation and Sensing Satellite.

Both missions are reported to be in excellent health, having separated to begin very different flight plans, though each will dramatically cross paths one final time next October.

LRO has been handed off to NASA's Goddard Space Flight Center in Greenbelt, Maryland, and should reach the point in space where the Moon will be, crossing under the lunar South Pole and then slowed into an eccentric transfer orbit, early Tuesday morning. Lunar Orbital insertion is currently expected at 0943 UT.

Afterward begins a gradual circularizing of LRO's orbit, eventually to a very altitude averaging 30 mile over the surface, where a highly-anticipated year-long deep physical survey of the Moon of unprecedented resolution should begin.

LCROSS, handed off to its control office at NASA Ames at Moffett Field, California, should swing under the Moon's South Pole, and with the assistance of the Moon's gravity speed up and bend a path northward behind the Moon to begin the first of many large orbits around Earth with apogees each orbit as high as the Moon's orbit.

Eventually, that highpoint and the Moon in its own orbit should occupy the same space at the same instant, and LCROSS will have to yield, in dramatic fashion, next October 9.

Consisting of the Centaur second-stage and a shepherding satellite designed around the second stage's payload ring, the plan call for LCROSS eventually to be aimed toward a spot near the Moon's South Pole for a planned very high speed impact.

The target will be one of several candidate craters around the Moon's South Pole with interiors in permanent shadow from direct sunlight.

Both Clementine and Lunar Prospector detected the presence of hydrogen, believed to be rare on the lunar surface after the Apollo Era and before. In relative high concentration near the Moon's less directly explored polar regions, it has been hoped this might be indication of water, perhaps locked into the lunar surface there, in places where the Sun never shines.

Before the planned impact, the LCROSS shepherding satellite will separate from the Centaur upper stage to allow it to follow 400 seconds behind the far heavier second stage to directly pipe direct observations of the impact to the groundfor the short time prior to it's own similar demise.

Timed properly, both the impacts and their debris clouds, rising into sunlight, should be observable by telescopes from Earth, and LRO will orbit directly over both impact locations immediately afterwards, before continuing onward on it's long tour.


Tony said...

I believe you have your Ames and Goddard references mixed up in this post. LRO is the Goddard mission and LCROSS is the Ames mission.

Joel Raupe said...

By golly, you were right on target. That's what I get for not proofing after an intern, normally quite talented.

Sincere thanks!

Joel Raupe