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PhilCo126
NASA taps (amateur) Astronomy community to help search for lunar water

Lunar CRater Observing and Sensing Satellite
LCROSS (Lunar CRater Observing and Sensing Satellite) is scheduled to launch with the Lunar Reconnaissance Orbiter,
known as LRO, aboard an Atlas V rocket from Cape Canaveral, Fla., in late 2008. After launch, the LCROSS shepherding spacecraft and the
Atlas V's Centaur upper stage rocket will fly by the moon and enter an elongated Earth orbit to position themselves for a rapid descent
into a permanently shadowed crater near the moon's south pole.
On final approach, the instrument-laden spacecraft and the upper stage will separate. They will hit the lunar surface about four
minutes apart. The spacecraft will fly through the Centaur debris plume and collect data before its own impact. The LCROSS impacts are
expected to be visible from Earth using 10-to-12 inch and larger telescopes.

http://lcross.arc.nasa.gov/

nprev
Yikes. Just gotta say that this has a MAJOR pucker factor from the description...four minutes is not a hell of a lot of time to relay data.
rogelio
Probably worrying too much, but how much precious lunar water will be wasted by this impact? Water that could be used some day by a polar moon base...
djellison
That's the whole point - we don't even know if there is any down there. It's by doing experiments like this that we can find out.

They're expecting to kick up perhaps 1,100 tons of regolith with the impact, and there's supposedly 6 billion tons of the (H2O) stuff down there. 0.000183 percent of the water, if it's there. Personally, I'm quite skeptical about it.

Doug
nprev
High risk for a potentially high payoff, I guess...but damn, that's a tight margin.
mchan
QUOTE (nprev @ Feb 27 2008, 03:06 PM) *
Yikes. Just gotta say that this has a MAJOR pucker factor from the description...four minutes is not a hell of a lot of time to relay data.

Kind of like a Ranger mission.
nprev
Yeah, but even more so. All Ranger had to do was snap pics; LCROSS is performing analysis (spectroscopic, I assume, but if so why does it have to fly through the Centaur's impact plume?) Almost sounds like it has some kind of onboard sample acq/analysis instrument, but can't see how such a thing would produce results in such a brief time.

EDIT : The payload consists of "cameras and spectrometers" (note the plural). Sounds like a full multispectral campaign in real time; every segment of the downlink chain better be at 100%.
centsworth_II
At least the nearness of the Moon will allow for
a much larger and faster data stream than that
from planetary missions. (I assume).
nprev
It should; at the risk of sounding like a complete jackass, I think that one of our esteemed comm experts stated that the bit rate is proportional to something like the fourth power of the distance.

Sure would like to know which DSS will the the primary for the encounter, though; the rain in Spain has caused us massive pain, in the past
tty
Maybe it could relay the data to LRO?
djellison
It doesn't need to - and nor could it anyway -neither LCROSS or LRO are equipped with appropriate hardware to do that.

Yes -it's a short period of time. So what? If it works, it works. Get a couple of DSN's pointing at it, good data rates are planned they'll have a few months of operations practice before the impact anyway. I'm not concerned about it to be honst.

Doug
nprev
Well...the coolness factor is undeniable. Gonna be one hell of a stunt if they pull it off!
dvandorn
Besides, it's not like there's a long cruise phase during which problems might crop up, right? Last I saw, the Moon isn't more than a few days away (unless you take a *real* slow route).

-the other Doug
djellison
Actually LCROSS does take a long route. It's a couple of months longer than LRO, involving Lunar flybys to target for the south pole.

Doug
mchan
LCROSS includes live RocketCam on the way down

Putting that on my calendar for next year.
nprev
If I read that correctly, this will be real time?
dvandorn
Wonderful! Assuming the "death plunge" is played live on NASA-TV, I'll have the honor of repeating Wally Schirra's classic line, shouted out as the astronauts watched a film made of Ranger VII's descent images:

"Pull up, you fool! Pull up!!!"

rolleyes.gif

-the other Doug
djellison
For those with access, this months Sky at Night (the extended BBC4 mix) is on www.bbc.co.uk/iplayer (go to channels, then BBC4). Chris Lintott visited the asembly facilities for LCROSS and LRO - and they actually imaged Chris and the scientists he was interviewing with LCROSS, with two nIR cameras, one sensitive to water, one not - so they can subtract the two images and identify where the water is. They were holding a bottle of water and it worked - very clever!

Doug
Phil Stooke
A few more LCROSS goodies:

http://lcross.arc.nasa.gov/astrWrkshpPres.htm

Phil
mchan
Such nice goodies. Thanks for posting link.

Regarding the "RocketCam", it will be on between 600 and 150 km with spacecraft covering distance in 3 minute (2.5 km/s) with ~0.8 Hz frame rate. The IR and spectrometer will continue until 2-3 seconds before impact. Ought to be a heck of a view of a death dive.
Guido
LCROSS will measure the amount of hydrogen in the Centaur debris plume to determine if there is water on the moon.
No hydrogen detected means no water, I suppose.
On the other hand, if hydrogen is indeed detected, this doesn't mean for sure there is water on the moon because the Atlas V's Centaur upper stage will still contain some hydrogen at the time of the impact! The hydrogen tank can not be vented for a full 100%.
Jim from NSF.com
QUOTE (Guido @ Mar 8 2008, 10:53 AM) *
LCROSS will measure the amount of hydrogen in the Centaur debris plume to determine if there is water on the moon.
No hydrogen detected means no water, I suppose.
On the other hand, if hydrogen is indeed detected, this doesn't mean for sure there is water on the moon because the Atlas V's Centaur upper stage will still contain some hydrogen at the time of the impact! The hydrogen tank can not be vented for a full 100%.


The amount of H2 in the tanks can be excluded from the measurements
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