[meteorite-list] Lunar Prospecting: Probe Ready to Touch Moon Water

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 5 Oct 2009 12:23:42 -0700 (PDT)
Message-ID: <200910051923.n95JNg7U011748_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/lcross/091005preview/

Lunar prospecting: Probe ready to touch moon water
BY STEPHEN CLARK
SPACEFLIGHT NOW
October 5, 2009

An enterprising robotic explorer will smash into the lunar frontier
Friday in search of water ice hidden deep inside the darkest corners of
the moon, spewing hundreds of thousands of pounds of dust high above the
surface in a celestial event visible from Earth.

Just four minutes will decide the outcome of three years of
preparations, four months of space travel, and a $79 million investment
put into the bold mission.

Four minutes is the time that nine science instruments on the LCROSS
probe will be able to directly study a cloud of dust thrown high above
the moon by the impact of an empty Centaur rocket stage.

LCROSS is "a very exciting mission culminating in a real crescendo
event," said Dan Andrews, the project manager from NASA's Ames Research
Center at Moffett Field, Calif.

The sensors will scan the debris for the chemical signature of water,
providing definitive proof for a decade-old hypothesis that ice exists
on Earth's inhospitable companion.

The Clementine and Lunar Prospector missions of the 1990s sensed
elevated levels of hydrogen at the moon's poles. Scientists believed the
hydrogen was from trapped water ice. The high concentrations were
centered on permanently shadowed craters, lightless meteor impact sites
that are unimagineably cold.

"And by cold, I mean cold," says Tony Colaprete, the mission's principal
investigator from Ames.

According to scientists, temperatures at the bottoms of the craters
could be as low as -240 degrees Celsius, or -400 degrees Fahrenheit. At
those temperatures, water tends to freeze instead of sublimating into
gas, Colaprete said.

"At the poles, the sun never comes more than a degree-and-a-half or so
above the horizon, so the crater rims can constantly shadow the crater
floors," Colaprete said.

The time scales are just as mind-boggling.

"There are portions of the crater floors that are in permanent shadow.
They could have been permanently shadowed for a billion or two billion
years, maybe more," Colaprete said.

Data from the Lunar Reconnaissance Orbiter, a counterpart to the LCROSS
mission, have independently verified the presence of hydrogen, even
hinting the potential water ice was more widespread than earlier thought.

Scientists also announced last month that three spacecraft found
evidence of water in lunar regions previously thought unable to support it.

Those recent findings have set the stage for an experiment to "reach out
and touch the water," said Mike Wargo, chief lunar scientist from NASA's
exploration directorate.

If LCROSS proves water resides on the moon, it could be a boon for
engineers in the early stages of planning for a human return to the
lunar surface.

"It's certainly intriguing to know that there might be water deposits in
places where you could go and live off the land versus bringing that
water from Earth," said Todd May, the lunar robotic precursor program
manager at the Marshall Space Flight Center in Huntsville, Ala.

Water could not only help quench the thirst of astronauts, but also
supply oxygen, electricity and even rocket propellant for the return
trip to Earth.

NASA says the latest estimates predict impact at exactly 1131:30 GMT
(7:31:30 a.m. EDT) Friday morning. That time could shift by a few
seconds based on new navigation solutions in the coming days.

Scientists have tapped Cabeus crater for the cosmic collision, a
60-mile-wide depression near the moon's south pole.

Cabeus was the subject of a late crater switch announced last week based
on a recent analysis of results from LRO and Japan's Kaguya spacecraft.

The LCROSS shepherding spacecraft, a six-sided platform built by
Northrop Grumman Corp. using off-the-shelf parts, has been towing the
Atlas 5 rocket's Centaur upper stage through deep space since its launch
on June 18.

Having been drained of its propellant and safed shortly after launch,
the 41-foot-long, 10-foot-wide inert Centaur has a mass comparable to a
large sports utility vehicle, according to Andrews.

The two vehicles will part ways at about 0150 GMT Friday (9:50 p.m. EDT
Thursday), according to NASA.

After separating from the Centaur, the shepherding satellite will fire
its engines to back away from the rocket. Lunar gravity will be pulling
both objects toward the moon.

"We burn some propellant and decelerate our inevitable acceleration into
the moon to buy us time between the two impacts," Andrews said.

The probe will open up to a distance of nearly 400 miles from the
Centaur, equivalent to about four minutes of flight time between the
vehicles.

That will give the shepherding satellite enough time for its
make-or-break chance to detect iron-clad evidence of water inside Cabeus.

When the Centaur slams into the moon at 5,600 mph, it will excavate more
than 350 metric tons of lunar regolith, throwing some of the material up
to six miles above the surface and 30 miles away from the impact site.

At that altitude, the debris will be exposed to sunlight and illuminated
for the first time in ages.

Scientists expect the Centaur to leave a crater some 66 feet wide and 13
feet deep.

The Centaur will strike the moon nearly head-on, a much steeper angle
than earlier impacts. The Lunar Prospector, SMART 1 and Kaguya probes
ended their missions with controlled crashes at much lower angles,
limiting the potential for valuable science data.

Also rapidly plummeting to its own sacrificial impact, the shepherding
spacecraft will spend the mission's four-minute climax giving scientists
an up close view of what is inside the polar craters.

Nine instruments, including five cameras, will be collecting data and
beaming the information live back to ground controllers stationed at Ames.

A video camera provided by Ecliptic Enterprises Corp. will capture live
video and downlink the imagery at a few frames per second.

Four more near-infrared and mid-infrared cameras will also monitor the
debris cloud, gathering more detailed data on the thermal properties of
the ejecta and looking for signs of water. Those imagers were built by
Goodrich Sensors Unlimited, Thermoteknix Ltd. and the Indigo unit of
FLIR Systems Inc.

Three spectrometers attached to telescopes will be the workhorses of the
instrument suite to determine the precise composition of the lunar dust.
Colaprete said their results will be the most definitive of the mission.

A photometer aboard LCROSS will also measure the brightness of the
Centaur's fiery impact about 1,000 times per second, creating a
highly-detailed light curve of the luminance of the flash.

The mission's entire catalog of data will be streamed live to the
science operations center because the LCROSS probe is destined for its
own smaller destructive crash.

"There's nothing left of LCROSS when it's done, just the data that was
sent out," Andrews said.

The shepherding spacecraft should strike the moon at 1135:45 GMT
(7:35:45 a.m. EDT), according to early estimates.

"The impact sounds spectacular, and it will be. But you have to consider
impacts of this size hit the moon three or four times a month,
essentially once a week," Colaprete said. "What's unique about the
LCROSS impact is we know exactly where and when, so we can actually get
and coordinate all of these eyes to look at it."

Those eyes not only include LCROSS, but also instruments on LRO, the
Hubble Space Telescope, and the Earth Observing 1 technology
demonstration satellite. Sweden's Odin radio astronomy satellite and the
commercial GeoEye spacecraft, primarily used for Earth imagery, will
also turn toward the moon for supplemental observations.

A network of telescopes on Earth will also play a critical role.

The W.M. Keck Observatory, Gemini North Telescope and Infrared Telescope
Facility in Hawaii are slated to study the ejecta plume when it comes
into view. Other facilities in California, Arizona and New Mexico are
also primary participants in the impact event.

In addition to other international observatories, officials have put
together a loosely-organized group of amateur astronomers and watch
parties to collect extra data and engage the public.

Mission planners timed and positioned the impact to be in view of much
of the United States. Observers west of the Mississippi River will be
most favored.

Weather permitting, modest telescopes with apertures of 10 to 12 inches
could catch a glimpse of the stream of rock and possible ice thrown into
space by the event.

The LCROSS impact will also occur with a nearly full moon high in the
skies of the ground observation sites, maximizing their potential
scientific return.

LCROSS, which stands for the Lunar Crater Observation and Sensing
Satellite, was chosen from 19 proposals to fill extra space on the Atlas
5 rocket that was to launch the much larger LRO mission.

Officials announced LCROSS would join the LRO launch in 2006. The
missions finally got underway three years later.

LRO entered orbit around the moon four days after launch, while LCROSS
and the attached Centaur swung by the moon into an ultra-high Earth
orbit to wait for its much more dramatic lunar appointment.

The spacecraft is fine-tuning its trajectory toward the moon with a
series of small thruster firings. Two more burns are planned before the
satellite releases the Centaur, and a third burn called a braking
maneuver will back the probe away from the rocket body.

A software glitch in August caused the craft to burn nearly half of its
propellant, putting the probe in jeopardy for a few weeks until
controllers could ensure a similar problem would not doom the mission.

"Having survived this test and emerged with the moon and full mission
success still in our sights was quite an accomplishment," said Paul
Tompkins, an LCROSS flight director, in a blog posting Sunday.
Received on Mon 05 Oct 2009 03:23:42 PM PDT