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The 1999 Impact of Lunar Prospector into the Lunar South Pole

Lunar Prospector impacted the moon back in 1999. This is a copy of the old web page from that time. Some of the old links no longer function, some do.

Impact occurred at 09:52:02 GMT on July 31 1999
(5:52am Eastern Daylight Time, 02:52am Pacific Daylight Time)
New – 12/2/99:The Learning Technologies Channel covers the mission.

News as of 10/13/99: A press release on the findings of the Prospector Impact Project. Also see this for more info.

NEWS as of 9/3/99: Nasa’s Space Science News has a nice article about the ongoing work to identify signs of water in the data aquired during the impact. See The Case of the Missing Moon Waterfor more.

NEWS as of 8/3/99:Several observatories have now reported how their observations went. As expected for a one-shot event, there were a few glitches. However, several places had very good weather and took their planned sequences of observations. While none of the larger observatories so far report having detected a clear dust plume, this was to be expected. All those with good data are now going to begin the detailed analysis of what they saw. This analysis may take days to weeks, depending on the exact details. If there is an unexpectedly strong signal, there might be an earlier release of findings. However, we expect a difficult time determining if there is a weak signal for the different species beside the bright background of the sunlit moon. Thanks to all of you who stayed up late (or got up early) and spent hours in preparation for the unique event!

Post-impact News:The Lunar Prospector team did not reacquire the signal from Prospector, so it has definitely hit the moon. So far no visual sightings of a dust cloud have been reported, but observations of the water and other volitiles is still ongoing.

Last Prospector News: The final command sequence has been successfully loaded by the Lunar Prospector Team. Everything is a GO for the de-orbit burn at 09:15:55.2 . We are on schedule for an 09:52:02 impact.

Previous Latest News: Preliminary reports following the 1st burn indicate that the boost was slightly stronger than planned. This put Prospector in a slightly higher orbit and the impact will occur 1 minute later than planned. The impact will occur at 09:52:02 UT.

Jump directly to:

NEW – There’s an image of the impact site taken last night with the 82″ at McDonald on the observation page.
NEW NEW– And now the image has an arrow showing the impact location.

Interactive: Check out the Impact Bulletin Board

Amateur observers should have a look at LunarImpact.comfor tips on observing the event.



The Lunar Prospectorhas been circling the Moon at an altitude of about 30 kilometers (19 miles), gathering geological data through its array of instruments. Now, with Prospector’s useful life approaching an end, we’re planning one last dramatic experiment: a controlled crash into a permanently shadowed crater in the hope of liberating a water vapor plume that could be viewed from Earth and establish definitively that water ice exists on the lunar surface.

Lunar Prospector data support the contention that water ice reservoirs exist in the permanently shaded craters near the lunar poles. Yet as the mission approaches its conclusion on July 31, 1999, the question remains whether the detected hydrogen abundance is actually water ice or is hydrogen in some other form, for example, hydrated minerals or adsorped solar wind. NASA has now approved plans for a novel approach to confirming the ice finding. Rather than allowing the vehicle to crash at an unknown point, our plans call for a controlled impact of Lunar Prospector into a polar craterat the end of July. The impact energy is high, equivalent to a 4000lb car crash at 1,100mph. The hope is that the crash will liberate perhaps 40 lbs. of water vapor that may be detected by ground- and space-based observatories. A positive spectral detection of water vapor or its photo-dissociated byproduct, OH, would give us definite proof of the presence of water ice in the regolith.




Also, Click here to see a video of all four of the University of Texas team members (Goldstein, Nerem, Barker, and Austin) together.

Beta video tapes of the above listed interviews may be made available to accredited media upon request. Please see press inquiriesbelow.



Impacting Lunar Prospector in a Cold Trap to Detect Water Ice in the June 15 issue of Geophysical Research Letters.



A slideshowof a talk given on July 17, 1999 by Steve Nerem.


In the Press

The initial Nasa Press Releaseof June 2, 1999.

Time magazine: NASA: One Giant Smash-up for Mankind

Sky & Telescope: Lunar Prospector to Make a Splash

Space Science News: Lunar Prospector heads for a Watery Grave

Bracing for Impact from NASA Space Science News.

NASA Looks for Ice on the Moonfrom the Associated Press on Yahoo News.

Listento a report about the project on National Public Radio (NPR).

NASA Aims for Deep Impact, on Moon and Sciencein the Washington Post.

And for the amateur astronomers out there:
Lunar Impact on Phil Plait’s site and
http://www.LunarImpact.coma whole domain dedicated to the event!

From ABC News: Crashing Into the Moon.

The Case of the Missing Moon Waterfrom Space Science News.

NEW – The Learning Technologies Channelcovers the mission.


Press Inquiries

Press inquiries may be directed to:<BR>(<STRONG>NOTE:</STRONG> Ms. Becky Rische is not available till next week and press should contact Robert Meckle instead.)<BR><STRONG>Becky Rische</STRONG><BR>UT College of Engineering Public Affairs Office<BR><A href=”mailto:brische@mail.utexas.edu” data-mce-href=”mailto:brische@mail.utexas.edu”>brische@mail.utexas.edu</A><BR>512-471-7272<BR>or<BR><STRONG>Robert Meckel</STRONG><BR>UT Public Affairs Office<BR><A href=”mailto:rob@opa.wwh.utexas.edu” data-mce-href=”mailto:rob@opa.wwh.utexas.edu”>rob@opa.wwh.utexas.edu</A><BR>512-471-3151

Computational Fluid Physics Lab
Aerospace Engineering and Engineering Mechanics
College of Engineering
The University of Texas at Austin
Send comments to: david@cfdlab.ae.utexas.edu
Last revised: April 2, 2003