[meteorite-list] NASA Ames Spacecraft to Smash into a Pole of the Moon in Search of Ice

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Aug 22 16:36:38 2006
Message-ID: <200608222033.NAA24688_at_zagami.jpl.nasa.gov>

http://www.nasa.gov/centers/ames/research/exploringtheuniverse/lcross.html

John Bluck
NASA Ames Research Center, Moffett Field, Calif.
Phone: 650/604-5026
E-mail: jbluck_at_mail.arc.nasa.gov

NASA Ames Spacecraft to Smash into a Pole of the moon in Search of Ice
August 16, 2006

In the near vacuum of space there will be silence as a large NASA rocket
smashes into one of the moon's polar regions in early 2009. There is no
air to transmit sound waves where the rocket will strike, but the ground
will shake. The 4,410-pound (2,000-kilogram) NASA rocket will be
hurtling 1.56 miles per second (2.5 kilometers per second) towards the
lunar surface. The Lunar CRater Observation and Sensing Satellite
(LCROSS) will carry out this lunar collision mission and experiment.

As well as being soundless, some craters near the moon's poles are in
permanent shadow and are so cold that ice could remain there for eons.
When the LCROSS rocket's upper stage violently collides with the surface
of a shadowed lunar crater, the massive impact will jolt up a huge
cloud, or 'plume,' of lunar material - soil and maybe even water ice.
Finding water ice is the main purpose of LCROSS. However, if LCROSS does
not detect ice will not mean that there is no ice at the lunar poles,
according to scientists.

If there is enough of it, water ice would be as valuable as gold to
astronauts on the moon because launching anything into space from
Earth's surface costs as much as $10,000 per pound (0.45 kilogram.)
Astronauts could drink life-sustaining moon water or make it into rocket
fuel. If there is adequate water near one of the lunar poles that
astronauts could use, that water could save NASA huge sums of money.

"Our objective is to detect and measure water in the lunar soil," said
Tony Colaprete, the LCROSS principal investigator and a planetary
scientist at NASA Ames Research Center, Moffett Field, Calif. "It's just
like prospectors used to do when they were looking for precious metals.
They would drill a hole in the side of a riverbank, stick a piece of
dynamite in there and then blast a chunk of earth off. They would then
sift through the debris - using a variety of methods - to detect ores,"
said Colaprete. "They'd wash the debris into the river and use slurry -
a mix of water and debris - to separate gold from the rest of the dirt."

</centers/ames/images/content/149250main_lcross_moon.jpg> "We're doing
the same thing. We're blasting a hole in the moon about half the size of
an Olympic-size swimming pool. Instead of slurry and a tin pan, we're
using a suite of instruments both at the moon and on Earth (to detect
water and other materials)," he said. "We expect to excavate at least
220 tons (200 metric tons) of moon dirt," Colaprete noted. The impact
will be visible to a number of lunar-orbiting satellites and possibly
also to Earth-based telescopes.

What triggered NASA's interest in locating possible water near the
moon's poles? Both the Clementine (in 1994) and the Lunar Prospector (in
1998) spacecraft found indirect -- but not definitive proof -- that
water ice may exist in the dark shadows of craters in the lunar south
pole area - gloomy, extremely cold places that never see the light of
day. Lunar Prospector found evidence of hydrogen, which along with
oxygen, comprises water. Soon, LCROSS mission scientists hope to find
solid proof of water.

LCROSS will be a 'secondary payload' when it is launched for its journey
to the moon in October 2008. That is, LCROSS will be a hitchhiker. It
will ride the same rocket as the Lunar Reconnaissance Orbiter (LRO),
another NASA mission to the moon. The rocket, an Atlas V with a Centaur
upper stage, will launch from Cape Canaveral Air Force Station, Florida.

The LCROSS spacecraft will arrive in the lunar vicinity independent of
the LRO satellite. Instead of arriving at the moon in a few days like
LRO, LCROSS will orbit Earth twice for about 80 days, and then will
strike one of the lunar poles in January 2009.

The reason that the LCROSS spacecraft will take so long to arrive at the
moon is that the spacecraft will use 'lunar gravity assist' to change
the second stage Centaur rocket's trajectory so that the space vehicle
will strike its target near one of the moon's poles. During a gravity
assist maneuver, a spacecraft approaches a planet or a moon, and the
spacecraft's orbit is affected, causing the probe to shift direction.

Because of lunar gravity assist, LCROSS will approach the moon's poles
with more velocity -- 1.56 miles per second (2.5 kilometers per second)
-- and will strike the lunar surface more squarely -- at 70 degrees to
the moon's horizon -- a steeper impact angle that will produce a bigger
plume. LCROSS also will take longer to reach the moon, and NASA will
have more time to track the spacecraft, control it and precisely aim it
at a crater.

On the way to the moon, the LCROSS spacecraft's two main parts, the
Shepherding Spacecraft and the Centaur second stage, will remain coupled.

As the spacecraft nears one of the moon's poles, the upper Centaur stage
will separate, and then will impact a crater in that region. A plume
from the upper stage crash will develop as the Shepherding Spacecraft
heads in toward the moon.

The Shepherding Spacecraft will fly through the impact plume, sending
back real-time images and spectra of the plume material taken by
infrared cameras and spectrometers. After sending back these data, the
Shepherding Satellite will become a 1,543-pound (700-kilogram)
'impactor' as well. The second impact will provide another opportunity
for lunar-orbiting satellites and Earth-based observatories to study the
nature of the lunar soil in the second, smaller plume.

In 1988 during the Lunar Prospector lunar orbital mission, scientists
estimated that as much as 6 billion metric tons of water ice could be
under about 18 inches of lunar soil in the craters. However, Lunar
Prospector did not provide proof positive of ice. Scientists now are
determining how best to detect water - if any -- in the mammoth plumes
of moon dust that will result from the two LCROSS impacts. Because the
impacts will be so complicated, scientists need to understand them
before they happen. Then, researchers can properly plan the science
observations scientists would like to make.

"An impact is a very complex event," Colaprete observed. "There are a
number of processes that occur one after the other, and some
simultaneously, each of which contains clues about the moon's materials
and the impact."

Scientists must consider factors that include how long the lunar dust
will linger above the lunar landscape, how bright the initial impact
flash will be and how much material will fly up from the surface. To
analyze the impact before it will happen has required a team of
scientists -- the people who designed the mission.

The team is a dozen scientists strong. All of them are co-investigators
on the LCROSS mission. They are from across the United States and work
at NASA as well as Brown University, Providence, R.I.; University of
California, Santa Cruz; Stanford University, Stanford, Calif.; Northrop
Grumman, Redondo Beach, Calif.; and the SETI Institute, Mountain View,
Calif.

The team includes impact specialists, astronomers, spectroscopists
(scientists who analyze light and other radiation to determine material
composition) and planetary scientists. Some team members are experts in
two or more fields of study.

The team met at NASA Ames in the spring of 2006 to share their outlooks
for the mission and to take a critical look at the mission design to
make sure all objectives would be met.

"In the morning of the first day of our meeting, we heard from our
impact specialists, including Peter Schultz of Brown University and Erik
Asphaug and Don Korycansky both of the University of California, Santa
Cruz," Colaprete said. "What we heard were their current expectations
for the size and duration of the impact."

"We're going to be using the LCROSS as if we're kicking a divot out of
the surface of the moon to expose what's below," Schultz said. "Every
time you go into a sand trap on the golf course -- a place you don't
want to be -- you pitch up sand with your sand wedge. If you watch your
friend do this, you can (see) this cone of debris fly out of the trap.
The formation of the cloud of sand is similar to what will (happen)
during LCROSS."

Scientists used NASA Ames' Vertical Gun Range to simulate the lunar
impacts by firing small pellets into materials that represented the
lunar surface. "It's very cool," Schultz said. "In experiments -- just
like in a science fiction movie -- you need to slow everything down to
imagine what you would see at the scale of LCROSS. We slow it down by a
factor of a thousand. We are using high-speed video and other special
imaging," he explained.

What Schultz and others find out from the Vertical Gun tests may help
them to refine their estimates of the impact flash, how hot the ejecta
will become and how fast it will cool, ejecta trajectories and what the
physical state of any water in the ejecta may be.

"We've watched all these complex processes every time we do an
experiment at the Ames Gun Range. The (LCROSS) impact (on the moon) will
be in the dark, and all we'll see at first is just a faint flash. And
then we'll see this expanding ring of debris as it comes out of the
darkness and is lit by sunlight," Schultz said.

"So, what we're really after is to bring material up into the sunlight
for the very first time," he explained. "We want to know if this
material contains ice. What we get to do is the same thing we do in the
gun range at Ames (only) at a much larger scale."

According to Schultz, there will be a whole suite of instruments looking
at the plume of lunar material above the moon. "The instruments we'll
have on board will allow us to detect what makes up the surface and
subsurface. We are going to try to get as much out of this one-second
event when the crater is formed (as we can). But then we'll watch the
material emerge into a cloud and a ring for about minute or more,"
Schultz continued.

The second impact must be observed from Earth and other spacecraft
because the Shepherding Satellite carrying all the LCROSS instruments is
the impactor for the follow-up collision with the moon.

During their meeting at Ames, scientists also considered the mission
time line and how they will coordinate their observations of the impact
from the Earth, and from satellites orbiting the moon. Astronomers
Jennifer Heldmann of the SETI Institute and Diane Wooden of NASA Ames
are leading the effort to coordinate and define Earth and moon-based
observations of the impact.

"We are encouraging the science community to observe the impacts from
ground based telescopes, Earth-based telescopes and Earth and
moon-orbiting satellites," said Heldmann. We also encourage amateur
astronomers to observe the LCROSS impacts and plumes," Heldmann added.

Because scientists will use many instruments at various locations to
observe the impacts, researchers will be able to combine independent
measurements to potentially come to more concrete conclusions about the
presence of water and other materials in lunar soil.

Large telescopes including the Keck II telescopic on Mauna Kea mountain
in Hawaii will make observations of the LCROSS moon impacts. According
to scientists, the Hubble Space Telescope may also be called upon to
observe the impacts. In addition, LCROSS researchers plan to use three
satellites orbiting the moon to study the impacts. One is NASA's Lunar
Reconnaissance Orbiter (LRO); another is India's Chandrayaan-1 and
Japan's SELenological and ENgineering Explorer (SELENE) - all of which
have yet to be launched.

Mission planetary scientists include Colaprete and Heldmann. Schultz and
Asphaug also are planetary scientists, but they will concentrate on
impact studies for the LCROSS mission.

Spectroscopists include Wooden and Tony Ricco, a chemist from Stanford.
They will search for clues of water and other minerals by looking at the
initial impact flash of light and then the sunlight colors reflected
from the dust cloud with special instruments on spacecraft and through
telescopes. The instruments include special cameras and spectrometers.

Spectrometers are instruments that separate light beams into bands of
color. Some of the color bands the spectrometer will see are invisible
to human beings. Combinations of the bands are unique -- like
fingerprints or barcodes. These color band combinations are 'signatures'
that can identify virtually all materials.

According to Ricco, spectral signatures of water vapor, water ice and
water bound in minerals show up in the infrared part of the spectrum.
"These signatures are of keen interest, so the reflected light from the
dust plume will be examined carefully for their presence using a unique
spectrometer adapted for the LCROSS mission," Ricco said.

"The LCROSS mission will make two impacts separated by about 10
minutes," said Wooden. "The dust and water ice cloud lofted into
sunlight will be observable from ground-based telescopes. Imagine an
umbrella-shaped cloud that emerges from the limb (a heavenly body's
outer disk edge) of the pole of the moon. If the cloud contains water
ice, the ice will become water vapor, and the energetic ultraviolet
solar photons (sunlight) will break it down further into hydroxyl (OH-),
which can be detected for hours or even days," she explained.

"Also, dust grains will reveal their compositions when they are warmed
by the sunlight. The ground-based observations are very important to the
studying the longer (tens of minutes to hours) evolution of the cloud,"
Wooden added.

According to Wooden, it is just this kind of cloud that a comet impact
would have created during the heavy bombardment period of the early
solar system some four billion years ago. "If the water vapor in such a
cloud was dispersed to the poles, it would have refrozen there - making
the source of water ice that we now seek to find," said Wooden.

"NASA Ames will host a site selection workshop on Oct. 16 - Oct. 17,
2006, to ask the science community to give us their suggestions as to
where the LCROSS impact should occur on the moon - at either the north
or south pole," said Heldmann.

According to Colaprete, the LCROSS proposal named Shackleton Crater in
the south pole area as an example around which scientists and engineers
could develop a mission design. "The process for selecting the impact
target will be modeled after the successful Mars Exploration Rover
landing site selection method," Colaprete said.

The LCROSS prime contractor for the spacecraft and the spacecraft
integration is Northrop Grumman.

For images related to the LCROSS mission, please visit:

http://www.nasa.gov/centers/ames/multimedia/images/2006/lunarorbiter.html

For information about the Clementine mission to the moon, please see:

http://science.nasa.gov/headlines/y2005/14apr_moonwater.htm

To read a fact sheet about the Lunar Prospector mission, please visit:

http://discovery.nasa.gov/prospector.html
Received on Tue 22 Aug 2006 04:33:01 PM PDT


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