Lunar Prospector

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NASA Science News for October 13, 1999

Moon Water Remains a Mystery -- The July 31, 1999 crash of Lunar Prospector into the Moon did not liberate detectable signs of water, say scientists. The possibility of water-ice in shadowed lunar craters remains open.

NASA Headquarters, Washington, DC
Ames Research Center, Moffett Field, CA
University of Texas at Austin

Oct. 13, 1999


The controlled crash of NASA's Lunar Prospector spacecraft into a crater near the south pole of the Moon on July 31 produced no observable signature of water, according to scientists digging through data from Earth- based observatories and spacecraft such as the Hubble Space Telescope.

This lack of physical evidence leaves open the question of whether ancient cometary impacts delivered ice that remains buried in permanently shadowed regions of the Moon, as suggested by the large amounts of hydrogen measured indirectly from lunar orbit by Lunar Prospector during its main mapping mission.

Research group leaders from the University of Texas at Austin announced their results today at the annual meeting of the American Astronomical Society's Division for Planetary Sciences meeting in Padua, Italy.

In a low-budget attempt to wring one last bit of scientific productivity from the low-cost Lunar Prospector mission, NASA worked with engineers and astronomers at the University of Texas to precisely crash the barrel-shaped spacecraft into a specific shadowed crater. NASA accepted the team's proposal based on successful scientific peer review of the idea and the pending end of the spacecraft's useful life, although the chances of positive detection of water were judged to be less than 10 percent.

Worldwide observations of the crash were focused primarily on using sensitive spectrometers tuned to look for the ultraviolet emission lines expected from the hydroxyl (OH) molecules that should be a by-product of any icy rock and dust kicked up by the impact of the 354- pound spacecraft.

"There are several possible explanations why we did not detect any water signature, and none of them can really be discounted at this time," said Dr. Ed Barker, assistant director of the university's McDonald Observatory at UT Austin, who coordinated the observing campaign. These explanations include:

Although the crash did not confirm the existence of water ice on the Moon, "this high-risk, potentially high- payoff experiment did produce several benefits," said Dr. David Goldstein, the aerospace engineer who led the UT Austin team. "We now have experience building a remarkably complex, coordinated observing program with astronomers across the world, we established useful upper limits on the properties of the Moon's natural atmosphere, and we tested a possible means of true 'lunar prospecting' using direct impacts."

Lunar Prospector was launched on Jan. 6, 1998, from Cape Canaveral Air Station, FL, aboard an Athena 2 rocket. In March 1998, mission scientists announced their first tentative findings of the presence of water ice in shadowed craters near the Moon's south and north poles. They estimated later that up to six billion metric tons of water ice may be buried in these craters under about 18 inches of soil, in more concentrated deposits than originally thought. However, the evidence was indirect, they cautioned, based on reasonable scientific assumptions given the levels of hydrogen detected, from which water ice is inferred.

Since then, Prospector data have also been used to develop the first precise gravity map of the entire lunar surface. While the Moon's magnetic field is relatively weak, Prospector has confirmed the presence of local magnetic fields that create the two smallest magnetospheres in the Solar System. Another scientific landmark is the assembly of the first global maps of the Moon's elemental composition.

The $63 million Lunar Prospector mission was led by Dr. Alan Binder of the Lunar Research Institute, Tucson, AZ, and managed by NASA's Ames Research Center in Moffett Field, CA. It was built by Lockheed Martin Missiles & Space, Sunnyvale, CA. Other participating organizations included the Department of Energy's Los Alamos National Laboratory, NM, and NASA's Goddard Space Flight Center, Greenbelt, MD, and Jet Propulsion Laboratory, Pasadena, CA.

University of Texas-Austin
Austin, Texas 78713-7509

October 12, 1999

New efforts to find evidence of water on the moon came up dry, researchers at The University of Texas at Austin announced Wednesday (Oct. 13)

AUSTIN, Texas -- New efforts to find evidence of water on the moon came up dry, researchers at The University of Texas at Austin announced Wednesday (Oct. 13). But their research efforts have laid the groundwork for further investigations, as well as demonstrating a potentially useful new method for lunar prospecting.

The UT Austin group announced its findings at the annual meeting of the American Astronomical Society's Division for Planetary Sciences in Padua, Italy. In what was virtually a no-budget attempt to vaporize ice suspected to exist at the South Pole of the moon, NASA worked with engineers and astronomers at UT Austin to crash the space agency's successful Lunar Prospector spacecraft in a specific polar crater in a precise manner.

The July 31 crash took only seconds. But the painstaking analysis of information recorded by more than a dozen professional Earth- and space-based telescopes required several months. Hundreds of amateur telescope owners also observed as the spacecraft plunged into a permanently shadowed crater near the pole.

"As expected, we didn't make a big splash, or we all would have seen a water signal quickly," said Dr. David Goldstein, leader of the UT Austin team that proposed the crash. Goldstein, an aerospace engineer, is an associate professor in the UT Austin Department of Aerospace Engineering and Engineering Mechanics.

Prior to the crash, Goldstein worked to model and calculate the final orbit and crash of the Lunar Prospector with Dr. R. Steven Nerem, also an aerospace engineer and an associate professor in the department; aerospace engineering students J. Victor Austin and Jeong Yon Shim; and NASA engineers. Dr. Edwin S. Barker, research scientist with the UT Austin Department of Astronomy, coordinated worldwide observations of the crash.

Last year, the Lunar Prospector team reported the spacecraft's instruments had revealed possible signs of frozen water at the moon's north and south poles. At that point, the UT Austin team came up with the idea of a controlled crash.

"The way we aimed to detect water -- or its signature -- was through sensitive spectrometers tuned to look for the ultraviolet spectral emission lines expected from the hydroxyl (OH) molecules," said Barker. Barker and Shim analyzed the spectra from NASA's Hubble Space Telescope, McDonald telescope and the Keck I in Hawaii.

Scientists and engineers working on the project knew from the beginning that there was a low probability of proving existence of water on the moon and the research discussed in Padua did not confirm water's existence. But the researchers said several benefits resulted from this potentially high-payoff experiment, including:

"If we can identify any other spacecraft whose useful life is over, but may have sufficient fuel and controllability to repeat the impact experiment, we'd like to do it again," said Goldstein.

The team offered several possible reasons why the telescopic information has yielded no evidence of water, however, there is no way of knowing which of them might apply:

For a more detailed discussion and history of the project, plus illustrations (including target site, expected evolution of vapor cloud and animations) see:


1999 September 8 Issue 1999.09.08

Prospector Crash Created No Dust Cloud

The crash of the Lunar Prospector spacecraft more than a month ago failed to create an observable cloud of dust, but the search for water thrown up by the impact continues, sciences say.

David Goldstein, the University of Texas at Austin professor who first proposed the deliberate crash of the spacecraft into a permanently-shaded area near the lunar south pole, said that no professional nor amateur observers saw a cloud of dust that could have been created by the impact.

On the other hand, Goldstein noted, a lack of a dust plume created by the July 31 crash might improve chances of detecting water that was lifted into space by the force of the impact.

"The only way we could have seen dust would be if it had risen above the bright lunar surface and we might have seen it against the black of the sky," he said in a NASA Science News report September 3. "If we had seen a dust plume it might have meant that the spacecraft hit the near rim or the far rim of the crater."

Scientists had targeted a deep, permanently-shadowed region of a 50-km (30-mi.) crater near the south pole, where water ice is believed to exist, based on data from Prospector's neutron spectrometer. A crash in that area would have been unlikely to create a visible dust plume.

Data collected by groundbased and orbiting telescopes is being examined by astronomers to look for spectroscopic evidence of water. "Right now we don't know that water ice was not observed -- it might be in the data somewhere," he said. "We're still looking closely at spectra from the Hubble Space telescope, the McDonald Observatory, and Keck I."

If water is detected, it would eliminate nearly all doubts that water ice exists in shadowed regions of the lunar poles. The ice is thought likely to exist based on the Prospector data as well as earlier radar observations by the Clementine spacecraft, but the existence of water could only be strongly inferred from those data, and other scientists had proposed alternatives, from solar wind hydrogen to hydrated cement-like minerals, to explain the data.

However, a failure to detect water from the Prosector crash does not mean water does not exist on the Moon. Prior to the crash Goldstein estimated that the experiment had only a ten percent chance of detecting water ice, because of the uncertainties in the distribution of ice in the craters.

Goldstein said a University of texas team that observed the crash should report on its efforts to detect water and hydroxyl (OH), an ion formed by the disassociation of water, within the next several weeks.

NASA Space Science News for September 3, 1999

The Case of the Missing Moon Water: Lunar Prospector failed to kick up a visible dust cloud when it crashed into the Moon, but that doesn't mean it failed to strike water. Astronomers are still sifting through their data for elusive signatures of a tenuous water vapor cloud that may have resulted from the crash.

NASA Ames Research Center
Moffett Field, CA 94035

Lunar Prospector Mission Update

July 31, 5:45 A.M. PDT

Lunar Prospector, "the little spacecraft that could," can't anymore. As a room full of viewers and observatories from around the world looked on, the LP Mission Control team successfully ended the Lunar Prospector mission at 2:52:00.8 a.m. PDT on July 31 when the spacecraft slammed into a deep crater near the south pole of the moon.

No visible debris plume was reported and it may be several days before data from ground- and space-based observatories and telescopes can be analyzed to determine if any water vapor was liberated by the impact.

Mission Control at NASA's Ames Research Center indicated that they are confident the small, spin-stabilized spacecraft hit its intended target precisely. The failure to reacquire a signal from the vehicle at the time it would have emerged from the dark side of the moon is proof that impact occurred. The absence of a visible debris plume is not a negative result. In fact, it increases the likelihood that the spacecraft impacted deep into the intended target crater.

The final sequence of events for Prospector began at 1:17 a.m. PDT when the Mission Control team successfully loaded a 60-minute pre-programmed countdown into Prospector's internal clock to initiate the final burn sequence. At 2:00 a.m. PDT, final loss of signal from Prospector occurred, as planned, when the spacecraft passed behind the moon for the last time. Alan Binder, Lunar Prospector Principal Investigator observed, "we don't want to hear from Prospector again - if we do, we've missed our mark." He was not to be disappointed.

The scheduled 4 minute 36.5 second burn was executed behind the moon at 2:17 a.m. "Prospector's engines should be burning full -- preparing to de-orbit," said Binder. "It is now hurtling towards its destiny at approximately 1.7 kilometers per second on a ballistic trajectory that will take it to its target crater."

The spacecraft's key scientific instruments continued to send data until the very end when signal was lost. "Once again, Prospector has done everything we have asked of it," said Binder. "This mission provided ten times better data than we expected. The spacecraft performed flawlessly to its very end. Scientists will be analyzing the tremendous volume of valuable data obtained for years to come," he concluded.

Analysis of data obtained during the mission-end experiment will be ongoing for days, and possibly weeks, to come. At the completion of that analysis, scientists will have a much better idea if Prospector has, in fact, provided the definitive evidence of water ice on the moon that they were seeking. A positive result may have the potential to open up expanded possibilities for solar system exploration. Failure to prove conclusively that water ice exists in the lunar polar regions by no means suggests that it is absent, according to mission scientists. It simply means that this particular bold experiment, acknowledged as high payoff but also with low probability of success, has not provided the conclusive evidence that was being sought.

NASA Space Science News for July 31, 1999

Farewell, Lunar Prospector: NASA's lunar orbiter crashed into the Moon Saturday morning, July 31, 1999, precisely on target.


Saturday, July 31, 1999 @ 1630 GMT


Lunar Prospector slammed into a deep crater near the south pole of the moon at 0952 GMT this morning, ending its 18-month mission to explore Earth's natural satellite.


Stay tuned for science news and images from Lunar Prospector's crash.

Also, there will be a Lunar Prospector End of Mission Educational live webcast on Saturday, July 31 from 12 noon to 1:30 pm (PDT), hosted by Lisa Chu-Thielbar, Mission Outreach Coordinator and the NASA QUEST group. Participate in the open chatroom.

NASA Space Science News for July 30, 1999

Amateur astronomers target Lunar Prospector: While professional astronomers watch for a nearly transparent cloud of water vapor, amateurs will monitor the Moon's south pole for visible signs of Lunar Prospector's crash.

"Lunar Prospector End of Mission & Overview" (35-page, PDF version press kit, approx. 544KB)

NASA Space Science News for July 28, 1999

A Stay of Execution for Lunar Prospector: The Lunar Prospector spacecraft survived the partial lunar eclipse of July 28 and is on track for a planned collision with the Moon on July 31. This story includes a video clip of this morning's eclipse as seen from Australia and new impact simulations from the University of Texas at Austin which suggest that the debris plume on July 31 may rise as high as 30 km above the target crater's rim.


The Lunar Prospector spacecraft continues to collect good science data in the extended mission orbit. Two of five science instruments are on: the Magnetometer (MAG) and the Electron Reflectometer (ER). The spectrometers were powered off today as part of the eclipse power sharing activities as described below.

The Lunar Prospector orbit was trimmed successfully Monday. This maneuver raised the altitude of periapsis by about 5 km to allow the spacecraft to safely orbit through the rest of the week. A brief timeline is below. Times are GMT, on DOY 207 [7/26/99]:

13:36 Thruster heaters commanded on
13:39 Loaded maneuver parameter file
14:01 Fire A1/A2 for 9.0 sec (1.44 m/s delta-V, 0.13 kg prop used)
14:04 Safed spacecraft

After the maneuver, the MAG/ER was configured to collect high resolution data during the full moon passage. A total of 27 commands were transmitted with no anomalies.

The LP spacecraft successfully survived today's lunar eclipse. Because the moon passed through the earth's shadow, the time of no sunlight was increased from the once per orbit lunar shadow duration of 36 minutes, to 67 minutes. For another 2:31, the sun was partially eclipsed by the earth, preventing the normal recharge of batteries. The spacecraft was not designed to survive this eclipse.

To increase the chance of survival, the spectrometer instruments were turned off, reducing the load. Because they would get very cold during the eclipse while they were turned off, they will not be turned on again during the last 3 days of the mission. The impact to their science analysis will be negligible. The MAG/ER was left on so that it could continue to get the high resolution full moon data through the end of the mission.

Other non-essential loads were powered off: the pressure transducer which measures the propellant tank pressure, and the earth-moon limb sensor. These were turned back on at the end of the event. Also turned off was the primary heater relay. This prevented the highest load of the spacecraft, the propellant tank heaters, from coming on at a time when the battery was unable to support the load. This relay was turned back on at the end of the event as well.

The spacecraft transmitter is the second highest load on the spacecraft, and it was turned off for every occultation (when the s/c is behind the moon as seen from the tracking station), plus extra time as needed to allow battery recharge. It was turned on as much as power allowed to prevent it from getting too cold as well as to allow collection of data to monitor the spacecraft status.

Activities are listed below, times are GMT, DOY 209 (7/28/99). Umbra is when the entire sun is blocked by the earth as seen from the spacecraft. Penumbra is when only part of the sun is blocked. Occultation times are not listed, but they overlap closely with the lunar shadow events.

07:25 - Pressure Transducer commanded off
07:26 - Earth/Moon Sensor Commanded off
07:33 - Spectrometers commanded off
08:32 - Transmitter commanded off
08:37 - Entered Lunar Shadow
09:02 - Entered Earth Penumbra (first time)
                (can't tell from data since sun still blocked by moon)
09:12 - Exit Lunar Shadow
09:22 - Transmitter commanded on
09:30 - Exit Earth Penumbra (first time)
10:16 - Entered  Earth Penumbra (2nd time)
10:23 - Transmitter commanded off
10:29 - Entered Lunar Shadow
10:52 - Entered Earth Umbra (can't tell, since sun is already blocked by moon)
11:03 - Exit Lunar Shadow (can't tell, since sun is still blocked by earth)
11:34 - Transmitter commanded on
11:36 - Exit Earth Umbra but only partial sun (3rd interval of Earth Penumbra)
12:06 - Transmitter commanded off
12:20 - Entered Lunar Shadow
12:55 - Exit Lunar Shadow
13:13 - Tranmistter commanded on - battery voltage very low (21.5 V)
13:14 - Primary Heaters commanded off
13:15 - Transmitter commanded off
13:42 - Exit Earth Penumbra
13:54 - Transmitter commanded on - battery charging, at 30.1 V
14:04 - Transmitter commanded off
14:11 - Enter Lunar Shadow
14:47 - Exit Lunar Shadow
14:54 - Transmitter commanded on - battery charging, at 29.0 V
15:52 - Transmitter commanded off
16:03 - Enter Lunar Shadow
16:38 - Exit Lunar Shadow
16:42 - Transmitter commanded on - battery charging, at 29.8 V
17:18 - Battery fully charged (33.0 V); EMS commanded on
17:19 - Pressure Transducer commanded on
17:20 - Primary Heaters commanded on (creates very high load as all
                heaters turn on at once)
17:47 - Transmitter commanded off
17:54 - Enter Lunar Shadow
18:30 - Exit Lunar Shadow
18:37 - Transmitter commanded on - battery charging very slowly
              (all heaters are on), at 28.7 V
19:14 - Transmitter commanded off
19:46 - Enter Lunar Shadow
20:22 - Exit Lunar Shadow
21:00 - Transmitter commanded on - battery fully charged (33.3 V), heater
              load back to normal.

A total of 53 commands were sent with no anomalies.

The spacecraft is still cooler than normal but is warming as expected.

Current spacecraft state (2110 GMT 7/28/99, DOY 209):

Orbit: 7028
Downlink:  3600 bps
Spin Rate: 12.18 rpm
Spin Axis Attitude (ecliptic):
     Latitude:  -88.7 deg
     Longitude: 055 deg
     Periapsis Alt:  10.9 km
     Apoapsis Alt:   49.1 km
     Period:         111 min
Occultations:  41 minutes
Eclipses:      36 minutes
  remaining:   9.38 kg

The next activity is the spin-up, scheduled for tomorrow, 7/29 at 15:32 GMT. This will be the first step in setting the spacecraft up for the targetted impact. Impact is now scheduled for 09:51 GMT on 7/31 (one minute earlier than reported last week). It was moved up to optimize timing with Hubble Space Telescope observations.

There is also a simulation of teh September 1998 Lunar Eclipse. You will need Java Scripts active to view.

Greenbelt, MD

July 28, 1999


Numerous ground and space-based observatories will assist NASA in a search for water in material hurled upward from the planned impact of the Lunar Prospector (LP) spacecraft in the early morning hours of July 31. Flight dynamics controllers at NASA's Goddard Space Flight Center, Greenbelt, Md., are guiding the spacecraft to the designed crash inside a crater near the south pole of the Moon. Scientists believe there may be water ice near the surface in the crater bottom, which is in permanent shadow.

Energy from the impact, equivalent to crashing a two-ton car at more than 1,100 miles per hour, may liberate up to 40 pounds of water in vapor form, experts predict.

"While the probability of success for such a bold undertaking is low, the potential science payoff is tremendous," said Dr. Guenter Riegler, Director of the Research Program Management Division in the Office of Space Science at NASA Headquarters, Washington, D.C.

"This impact is unlike the other Moon missions of the 1960's and 70s' where the incoming trajectory was almost perpendicular to the lunar surface," said David Folta, the Goddard Lunar Prospector Team Lead in the Guidance, Navigation, and Control center (GN&C). "The difficulty of this maneuver is that Lunar Prospector is already in orbit about the Moon and the angle of impact is only 6.5 degrees. Achieving this grazing impact is similar to hitting the middle of a pie pan laid on home plate with a baseball thrown from second base at over 100 miles per hour. In this case, LP is the baseball and the rim of the pie pan represents the rim of the crater, almost four kilometers above the floor of the crater. The tolerance for error in the final trajectory is plus or minus three percent. Any greater error in the negative direction will result with an impact with the crater rim before reaching its destination. A larger error in the positive direction will result in a complete miss of the targeted crater."

"The Hubble Space Telescope's STIS (Space Telescope Imaging Spectrograph) instrument will monitor the impact site, searching for a glow of ultraviolet light emitted by the OH molecule (which consists of one atom each of oxygen and hydrogen)," said Dr. David Leckrone, senior scientist for Hubble at Goddard. "The OH would be produced by the breakup of water molecules (H2O) by ultraviolet sunlight, which is intense in the vacuum of space. This is the same technique astronomers use to look for the signature of water in comets. The OH emission tends to be bright and easily detected, compared to other indicators of water that would be available to HST. "From its vantage point above the Earth's atmosphere, and with its unsurpassed image clarity and sensitivity, HST is well suited for this job. It will be a difficult observation, but we've taken extra care to assure that it is executed correctly. It's hard to predict what to expect. But the idea of performing a "controlled" experiment on the surface of the Moon, monitored by an array of earth and space-based telescopes, is exciting in its own right. Certainly, the direct verification of the existence of water on the Moon would be an important milestone in the exploration of the solar system," said Leckrone.

NASA's Submillimeter Wave Astronomy Satellite (SWAS) will join the hunt for water. "SWAS is the only observatory that can directly confirm the presence of complete water molecules by detecting characteristic microwave radiation from water vapor," said Dr. Gordon Chin, SWAS Project Scientist at Goddard. "The observations will be challenging. We can't follow our normal procedure of pointing the spacecraft at its target using guide stars because the Moon is too bright -- it would blind the star sensor. Instead, we must rely on the spacecraft's gyroscopes and a detailed knowledge of the Moon's position relative to SWAS. However, SWAS is extraordinarily sensitive to water. If water is present, and there are no unusual complications, we should detect it even in the small amounts predicted."

To reach the crater target, two maneuvers are used, one to raise the highest part of the orbit to increase the incoming angle into the crater and to adjust the time of impact, and another that targets the exact latitude, longitude, and angle of impact. As with the primary and extended mission, the Goddard GN&C is providing the trajectory design, maneuver generation, and navigation for this event. Folta has only several hours to re-target the final inbound flight before final impact July 31 at 5:51 a.m. EDT using the navigation data provided by Mark Beckman, also of the GN&C.

This effort to gain additional science data about the Moon's composition was proposed to NASA by an external team of engineers and astronomers led by Dr. David Goldstein of the University of Texas at Austin.

"We have had an interest in thin planetary atmospheres for a while and how comet impacts might have led to the accumulation of water ice at the lunar poles," said Goldstein. "We were thinking about how the Leonid meteorite impacts on the Moon might be seen when we realized that since the Lunar Prospector mission was scheduled to end anyway, Lunar Prospector could become an artificial meteorite in which the time, position and energy of impact would be precisely known. Our team at the U. of Texas suggested the idea to the Lunar Prospector team, and they were enthusiastic about the opportunity to produce significant scientific results right up until the very end of the mission."

Images to support this story.

Further information about Lunar Prospector.

Los Alamos National Laboratory

Spacecraft crash to end productive mission

LOS ALAMOS, N.M., July 27, 1999 -- Scientists at the Department of Energy's Los Alamos National Laboratory hope the controlled crash of NASA's Lunar Prospector spacecraft into the moon Saturday will provide final proof for what they believe they have already measured: the presence of frozen water on the moon.

Mission scientists acknowledge a small chance of success, but they hope the crash will kick up a cloud of debris that includes a small quantity of water buried at the lunar poles. Earth-based telescopes and the Hubble Space Telescope will scan the debris cloud for signs of the water.

Los Alamos scientists built three of the instruments aboard Prospector, including the one whose measurements quantified the amount of water-ice that could reside in numbingly cold lunar craters. The two other instruments measure geologic composition and outgassing from seismic events.

Lunar Prospector, part of NASA's Discovery Program of low-cost, fast-track space missions, was envisioned and is led by Alan Binder of the Lunar Research Institute.

The technology and skills behind Los Alamos' three on-board spectrometers -- one for measuring neutrons, one for gamma rays, and one for alpha particles -- were born in Los Alamos' nuclear weapons mission and honed on various satellites for monitoring compliance with weapons nonproliferation treaties. Astrophysical and solar system studies have been a natural follow-on for these capabilities.

"Lunar Prospector represents the first time neutron spectroscopy has been applied to planetary exploration," said Bill Feldman, leader of the Los Alamos team. Feldman has been ecstatic since the first data came rolling in.

"The data returned have been absolutely beautiful," Feldman said. "This is everything one could have dreamed of."

The neutron measurements rely on high-energy cosmic rays slamming into the lunar soil. The cosmic rays generate a microscopic spray of nuclear particles, including neutrons. The neutrons bounce around in the soil, losing a little energy in each collision, before emerging from the soil and heading upward to where an orbiting spacecraft can detect them.

The Los Alamos spectrometer measures neutrons in three energy ranges: fast, medium and slow. The relative proportion of the three neutron energies is a key indicator of the material in the lunar soil.

In particular, hydrogen is very efficient at moderating the energy of the neutrons; over regions with enhanced hydrogen the detector receives a deficit of medium-energy neutrons. Scientists believe water molecules are the most likely form for any hydrogen resident in the lunar soil.

The Lunar Prospector team has now combined data from the craft's high-altitude and low-altitude orbits. The lower-altitude observations provide higher-resolution maps.

"Both results argue for small, unresolved deposits of hydrogen around the northern pole," Feldman said. "The concentrations extend over a larger area around the southern pole, and these data are consistent with islands of enhanced hydrogen deposits -- which we interpret as water ice -- immersed within regolith evenly spread with enhanced hydrogen."

The scientists estimate a hydrogen abundance equivalent to about two billion tons of water in total near the moon's poles. Soil bearing enhanced hydrogen and perhaps frozen water would allow engineers to contemplate ways to mine this precious resource to support colonization.

In research led by Los Alamos' David Lawrence, scientists have used the gamma-ray data to trace out key elements in the lunar soil that bear on the moon's formation and evolution. Cosmic ray-sparked collisions create many of the gamma rays that emerge from the lunar soil, but one key element, thorium, generates its own distinct gamma ray as a result of radioactive decay.

Thorium is part of a chemical amalgam dubbed "KREEP." KREEP represents the last part of a planet's or moon's molten mix to solidify. When it freezes, the KREEP is sandwiched between the relatively lightweight material that floated to the top of the melt to form the crust and the heavier material that sank to form the mantle.

Thorium or other KREEP constituents seen on the surface are evidence of volcanic processes or large meteor impacts that can punch through the crust and dredge up material from the interior.

"We've conclusively demonstrated that the surface occurrence of KREEP is mainly confined to the nearside region in and around the Imbrium basin," Lawrence said. Imbrium basin, one of the distinctive dark areas that make up the "man in the moon," was created by an ancient meteor impact nearly four billion years ago.

"One possible implication of this result is that KREEP was not uniformly distributed over the entire moon, but mostly confined to the nearside region," Lawrence said.

On the moon's far side, the highest thorium abundance occurs near Imbrium's antipode, the surface point defined by a line drawn from Imbrium, through the moon's center and out the other side. This suggests material ejected by the Imbrium impact traveled around the moon and settled out at the antipode.

"These data will play an important part in refining theories for how the moon formed and evolved," Lawrence said.

Los Alamos' third instrument aboard Lunar Prospector is an alpha particle spectrometer. Alpha particles are emitted in various radioactive decay processes, including that of radon, a gas that accumulates underground and can be released in seismic events. Scientists intend to analyze the data for signs of such seismic activity, but have not yet had time to do so.

The most recent scientific results from the Los Alamos team will appear in the Journal for Geophysical Research and Geophysical Research Letters. Team members include Feldman, Lawrence, Rick Elphic, Bruce Barraclough and Tom Prettyman. Sylvestre Maurice and Isabel Genetay of the Midi- Pyrenees Observatory in France are co-authors.

This work has been supported by the Department of Energy, NASA, Lockheed-Martin and the Observatoire Pic Midi.

Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy.

NASA Headquarters, Washington, DC
Ames Research Center, Moffett Field, CA
University of Texas at Austin

July 28, 1999


In one final blast of scientific productivity, NASA's Lunar Prospector mission will end abruptly in the early morning hours of July 31 with a controlled crash into a crater near the south pole of the moon.

The scripted, violent end of Lunar Prospector at 5:51 a.m. EDT is designed to provide direct evidence of the existence of water ice in permanently shadowed craters near the moon's poles.

Scientists hope that the estimated 3,800-mph impact will exhume water vapor and rocky debris that may be detectable for several hours, although data analysis could take days or even weeks if the signal is faint. Coordinated observing teams will use NASA's Hubble Space Telescope and Submillimeter Wave Astronomy Satellite, and ground-based instruments including the McDonald Observatory in Texas and the Keck telescope in Hawaii, to seek signs of the water vapor or its byproducts.

While the probability of successful detection is estimated to be less than 10 percent, it will be a fittingly creative finish to a low-cost Discovery Program mission that has exceeded all expectations after more than 6,800 lunar orbits in 18 months.

"Regardless of the outcome of this final bold experiment, Lunar Prospector has yielded a gold mine of science data," said Dr. Henry McDonald, director of NASA's Ames Research Center, Moffett Field, CA, which has managed the mission. "We now have invaluable global maps of the moon's gravitational and magnetic fields, and the distribution of its key elements, giving us a much better understanding of the origin, evolution and composition of our rocky neighbor."

Launched on Jan. 6, 1998, from Cape Canaveral Air Station, FL, aboard an Athena 2 rocket, Lunar Prospector reached the moon in four days. Shortly after entering orbit over the lunar poles, its five science instruments began expanding the limited equatorial measurements made by the Apollo command modules into global, high-resolution data sets.

Lunar Prospector's data gathering has resulted in a series of discoveries and new scientific tools, including:

In exceeding its design life, the $63 million Prospector mission has exhausted the bulk of its fuel and battery power. Although the drum-shaped probe will have a mass of only 354 pounds (161 kilograms) at the end, its impact energy will be equivalent to crashing a two-ton car at more than 1,100 miles per hour.

Further information about Prospector and its science data return can be obtained at the project Web site.

Additional information about the end-of-mission sequence is available at:

Dr. Alan Binder of the Lunar Research Institute, Tucson, AZ, led the Lunar Prospector team. The spacecraft was built by Lockheed Martin, Sunnyvale, CA. Other participating organizations include the Department of Energy's Los Alamos National Laboratory, NM; NASA's Goddard Space Flight Center, Greenbelt, MD; and NASA's Jet Propulsion Laboratory, Pasadena, CA. An external team of engineers and astronomers led by Dr. David Goldstein of the University of Texas at Austin will conduct the end-of-mission telescopic observations and data analysis.

July 28, 1999

UA astronomers will watch for Lunar Prospector plume Saturday -- and wish Gene Shoemaker a final happy landing

TUCSON, ARIZ. -- When Lunar Prospector crash dives into the moon's south pole early Saturday morning, Tucson-based observers hope for clear skies and a good view.

Also watching intently will be a University of Arizona planetary scientist who is sending a memorial tribute aboard the satellite.

UA astronomers and others observing near Tucson are part of an extensive network that will be searching for water vapor in Lunar Prospector's impact plume.

Since its launch in January 1998, Lunar Prospector has scored a number of scientific coups, as well as a followup confirmation of possible water-ice deposits at the north and south lunar poles. The question is whether the hydrogen it detected exists in water ice or in hydrogen-containing compounds called hydrates. Not all scientists agree this experiment will definitively answer the question. (For more on that, see news online at However, the answer is of scientific and practical interest for future space explorers. Sending a pint of water to the moon costs $10,000. So picking it up at the south lunar pole could turn out to be one of the biggest bargains in this part of the solar system.

Aerospace engineers at the University of Texas in Austin were the first to conceive of crashing Lunar Prospector into a frigid, shadowed crater at the lunar south pole just before the satellite runs out of fuel. The 354-pound (161 kg) Lunar Prospector will be traveling at 3,600 mph (5,793 kph) or faster. If the impact plume it generates is large enough - and that's a big "if," scientists emphasize - observers might discover the first irrefutable proof of water on the moon. But scientists caution that it may take weeks or months of data crunching before this is confirmed.

The project was approved by officials at the NASA Ames Research Center in Moffett Field, Calif., which manages the mission, and at NASA Headquarters in Washington, D.C. Observers will watch for the impact plume with telescopes at several locations including Texas, California, and Hawaii. Those involved will include the Hubble Space Telescope, the Keck 1 telescope, and the MacDonald Observatory telescopes.

If monsoon clouds don't obscure their views. Ann L. Sprague and Stephen M. Larson, both of the UA Lunar and Planetary Laboratory (LPL), will observe with telescopes in the Santa Catalina Mountains north of Tucson. Other astronomers will use the McMath-Pierce and WIYN telescopes on Kitt Peak, southwest of Tucson.

Sprague and her colleagues will use the UA's 1.54 meter (61-inch) telescope on Mount Bigelow to monitor sodium in the moon's diaphanous atmosphere before, during and after impact. They are trying to learn more about the structures of the thin atmospheres on the moon and planet Mercury by using spectroscopy to look for sodium and other elements..

Larson will install special filters on the 1.52 -meter (60-inch) NASA reflector telescope on Mount Lemmon to look for OH, a byproduct of water. "Given the moon's low declination and the monsoon weather, I don't expect anything close to Keck or HST results, but I'll be looking anyway," he said.

The 61-inch telescope was built by the late Gerard Kuiper, who founded LPL, in the early 1960s to survey the moon in preparation for the lunar spacecraft missions being proposed at that time. Kuiper died in 1973. His ashes were placed at the 61-inch telescope during a small LPL celebration last month. The Mount Lemmon 60-inch telescope, also built by Kuiper, was used for lunar laser ranging observations after Apollo 11.


The filters Larson will use are the same ones he used in photographing Comet Hale-Bopp from Tucson in April 1997. One of those images rides on a small, polycarbonate capsule that is hitching a ride to the moon aboard Lunar Prospector. The capsule is wrapped in a piece of brass foil inscribed with Larson's image of Comet Hale-Bopp, an image of Meteor Crater in northern Arizona and a passage from Shakespeare's "Romeo and Juliet."

Inside the capsule are the ashes of the late Eugene M. Shoemaker. Shoemaker was a pioneering planetary geologist famous for his work on extraterrestrial impacts and for his later collaboration with his wife, Carolyn, in the study and discovery of comets. He was killed in a July 1997 auto accident in Australia. LPL Associate Professor Carolyn C. Porco conceived, designed and produced this tribute honoring Shoemaker in time for the Lunar Prospector launch only months after Shoemaker's death.

"It was legend among planetary scientists that Gene's life-long dream was to go to the moon and study its geology firsthand," Porco said. "At his journey's end - thirty years to the month after humans first set foot on the moon - Eugene M. Shoemaker will become the first inhabitant of Earth to be sent to rest on another celestial body," Porco said.

Porco has produced replicas of the Shoemaker tribute foil for museum display. They have been sent to the Smithsonian Air and Space Museum in Washington, D.C.; the Adler Planetarium in Chicago, the Hayden Planetarium in New York and the U.S. Geological Survey headquarters in Reston, Va.,

Copies also have been given to the U.S. Geological Survey Gene Shoemaker Building, which is under construction in Flagstaff, Ariz.; the Meteor Crater Visitor Center; NASA Ames Research Center; NASA Headquarters; and the UA Lunar and Planetary Laboratory.

Additional copies have gone to Carolyn Shoemaker: NASA Chief Administrator Dan Goldin; Wesley Huntress, formerly head of the NASA Space Sciences Division; and Bruce Babbitt, U.S. Secretary of the Interior.

For more information on the Shoemaker tribute, see the UA News Services release of Jan. 6, 1998, "Lunar spacecraft carries ashes, special tribute to Shoemaker," at:

View the tribute online at:

Larson's Comet Hale-Bopp image is available by FTP to host server with anonymous login (email as password).


Moon burial for geologist

By BBC News Online Science Editor Dr David Whitehouse US geologist Gene Shoemaker, killed in a 1997 car crash in Australia, is soon to become the first person to be buried on another planet.

When the tiny Lunar Prospector spacecraft crashes into a dark crater near the Moon's south pole on Saturday, it will deposit onto the lunar surface the ashes of the pioneering astro-geologist.

Major impact

He was a legend among geologists. Almost on his own he invented the science of the study of cosmic impacts and he played a key role in training the Apollo moonwalkers to explore the Moon in a scientific manner.

Full story here.

Stanford University


The case against water ice on the moon

By David F. Salisbury

On July 31, NASA intends to crash the Lunar Prospector spacecraft into a small crater near the moon's south pole. The 354-pound spacecraft will be traveling at about 3,800 miles per hour when it plows into the lunar surface. The purpose for such a violent end to the $63-million mission is to find out whether there is any water ice hidden in the bottom of the crater, which is shrouded in perpetual shadow.

But two Stanford researchers predict that, rather than ice, the spacecraft is more likely to hit deposits of "hydrous" lunar minerals that contain the constituents of water chemically bound into their crystal structure. Von R. Eshleman, professor emeritus of electrical engineering, and George A. Parks, professor emeritus of geological and environmental sciences, argue that water ice left on the moon from past cometary impacts has most likely combined chemically with the water-free powdered rock that covers most of the lunar surface. They outlined their reasoning in a letter that was published in the July 23 issue of the journal Science.

NASA scientists and other advocates for establishing a permanent base on the moon are eager to find a source of accessible water because it could provide water, oxygen and rocket fuel for human colonists. Water ice would be ideal for this purpose. But, if Eshleman and Parks are right, "the constituents of water are there, but obtaining water would require large amounts of energy and so would be much harder and more expensive," says Eshleman, who has been involved with radioscience investigations of the moon and planets since the 1950s.

When Prospector crashes on the moon, the Hubble space telescope, along with a number of its space and Earth-based cousins, will be focused on the site. They will be equipped with sensitive instruments that can determine the composition of the plume of lunar material that the Prospector kicks up. Mission scientists predict that this plume could contain as much as 40 pounds of water, which sunlight should break down into hydrogen and hydroxyl ions. If the cloud contains significant amounts of hydroxyl ions, mission scientists argue that it will verify their assertion that large amounts of water ice exist in the region, something that they have predicted based on indirect evidence collected by the spacecraft's instruments.

The two Stanford scientists argue that this test, however dramatic, will not be definitive. If their theory is correct, they consider it unlikely that the spacecraft will kick up significant signs of water. But it is not impossible that the energy from the impact might cause some of the particles of hydrous rock to chemically dissociate, producing hydrogen and hydroxyl ions and reconstituting some of the water that it has held in chemical bondage, perhaps for billions of years.

The idea that the polar craters on the moon and the planet Mercury may contain water ice dates back to the early 1960s. Scientists recognized that the bottoms of some of these craters must be shrouded in perpetual shadow, shielded from sunlight by their uplifted rims. These shaded areas should have a constant temperature of around 170 degrees Celsius below zero, making them the coldest places on their respective worlds. As a result, each time Mercury or the moon was hit by a water-bearing comet, the water molecules it deposited would either end up in one of these "cold sinks" or escape into space.

In fact, radar observations of Mercury appear to have found water ice in some of its polar craters. At least, the radar reflections closely resemble those produced by ice-covered objects, like several outer planet satellites. On the moon itself, however, the evidence has been more ambiguous.

The strongest evidence in favor of the existence of ice on the moon is measurements taken with an instrument called a neutron spectrometer flown aboard the Prospector. This instrument cannot detect water ice directly, but has measured excess levels of hydrogen in the lunar polar regions.

Radar images taken of the lunar poles, however, have not found the characteristic signature of ice found on Mercury or other ice-covered objects in the solar system. So proponents have explained the radar returns as coming from "stealthy ice," ice that is either buried below a layer of lunar dust or mixed with lunar material to some depth.

Eshleman and Parks consider this highly unlikely, pointing out that the hydrogen detected by Prospector is to be expected if all the ice has combined with surface minerals. In the past, scientists thinking about this situation have simply assumed that water molecules freezing out would clump together to form ice. They haven't given any thought to the chemical nature of the material the ice would be forming on or the nature of the chemical interactions that might occur.

The Stanford researchers point out that the moon rocks brought back to Earth during the Apollo program indicate that the material covering the lunar surface is anhydrous, that is, it doesn't contain any water at all. Due to continual micrometeorite bombardment, this material has been ground up into a fine powder. "The surface of these particles is covered with broken bonds that will grab hold of any water molecules that come along," says Eshleman. Although no samples were returned from the lunar poles, there is no reason for the material there to be basically different from that which covers the rest of the moon, he argues.

According to Eshleman, this anhydrous lunar material contains two of the same ingredients as Portland cement and should have similar properties. While the lunar material is naturally anhydrous, Portland cement is made from common earth materials that are heated to drive out all the water.

"What happens when you put an ice cube on a layer of Portland cement in a vacuum and at a very low temperature?" Eshleman asks. "We predict that the ice will eventually disappear as it is absorbed by the cement."

Eshleman and Parks predict that the lunar material should react in a similar fashion. What is more, they calculate that this is a one-way process: Once water is incorporated into the lunar minerals, the resulting material would be extremely stable.

Furthermore, the radar reflection of the resulting hydrous material should be nearly identical to that of the anhydrous material, and so can explain the radar data from the poles without having to bury or mix the ice as proposed by the Prospector team, the Stanford scientists say.

The response of the Prospector mission scientists -- W. C. Feldman and colleagues from Los Alamos National Laboratory, S. Maurice from the Observatoire Midi-Pyrenees in Toulouse, France, and Alan Binder from the Lunar Research Institute in Gilroy, Calif. -- is that Eshleman and Parks' suggestions "are worthy of more extended quantitative analysis." The Prospector researchers defend their position by asserting that the hydroxyl ions that they measure must be coming from something. The levels that they have detected are extremely high and are concentrated in two southern polar craters that are in continuous shadow, making water ice a likely source. They also say that the amount of water ice that they expect to find is too small to detect by radar unless it takes the form of pure ice.

So, regardless of what happens when Prospector crashes, it is unlikely to resolve the question of whether there are potentially valuable caches of water ice hidden in perpetual shadow near the moon's pole.

NASA Space Science News for July 27, 1999

Web Site Announcement: is a new Science@NASA site devoted to the end of the Lunar Prospector mission. It includes science news, images and animations, and tips for amateur astronomers wishing to observe the spacecraft's scheduled crash into the Moon on July, 31.

Note: readers who photograph tonight's partial lunar eclipse are invited to send their images to Tony Phillips (as an email attachment to on Wednesday morning for possible inclusion in a headline updating the post-eclipse status of Lunar Prospector. Thanks!

NASA Space Science News for July 26, 1999

Lunar Prospector in Eclipse: The partial lunar eclipse of July 28 poses a last-minute threat to Lunar Prospector, which is scheduled to crash into the Moon in search of water just three days later.

NASA Space Science News for July 21, 1999

Bracing for impact - Professional and amateur astronomers are preparing to observe the Moon on July 31st when Lunar Prospector plunges into a permanently shadowed crater in search of water. This story explains what scientists expect to happen when the spacecraft hits the Moon and how amateurs might be able to observe the impact.

AAVSO News Flash No. 472


We have received the following request from Dr. Tony Phillips, astronomer and science writer with the NASA Space Science News web site ( at NASA Marshall Space Flight Center, for observations of the impact of the Lunar Prospector on Saturday, July 31, 09:51 UT:

Scientists involved with the Lunar Prospector crash into the Moon are encouraging amateurs to observe the impact this Saturday morning, July 31 at 0951 UTC. Most professional astronomers will be using large telescopes with sensitive spectrometers to look for a tenuous cloud of water vapor. The vapor cloud will be invisible through typical amateur telescopes. However, amateur astronomers can contribute by watching for a impact plume that may be visible for up to several minutes after impact. Theoretical calculations suggest that the plume will likely be very dim and probably impossible to see so near to the sunlit edge of the full moon. Nevertheless there are many uncertainties in the physical models so scientists are urging amateurs to monitor the impact. Telescopes equipped with low-light astro-video recorders are considered best for scientifically useful observations, but still cameras and simple visual observations are also valuable. Details and observing tips for amateurs may be found at FAX: 760-872-1382) who will forward them to the appropriate scientists at NASA/Ames and the University of Texas at Austin. We would particularly appreciate digital images and video sent to Tony Phillips as email attachments as soon as possible after the July 31st collision for posting on

NASA Space Science News for June 3, 1999

Is Lunar Prospector destined for a Watery Grave? - NASA's first mission to the Moon in 25 years could end with a splash on July 31, 1999, when ground controllers deliberately crash the Lunar Prospector spacecraft into a south polar crater in search of elusive lunar water.

NASA Ames Research Center
Moffett Field, CA

June 2, 1999


The mission of NASA's Lunar Prospector will end on July 31, 1999, when ground controllers attempt to direct the spacecraft to impact the surface of the Moon inside a permanently shadowed crater near the lunar south pole.

This effort to gain additional science data about the Moon's composition was proposed to NASA by an external team of scientists led by Dr. David Goldstein of the University of Texas in Austin. Although the Lunar Prospector spacecraft will weigh only 354 pounds (161 kilograms) at mission end, the energy at impact will be the equivalent of crashing a two-ton car at more than 1,100 miles per hour.

Scientists hope that the direct impact into a lunar crater will liberate up to 40 pounds of water vapor that may be detectable from ground- and space-based observatories. A positive detection of water vapor or its byproduct, OH, would provide definitive proof of what some scientists have long suspected -- the presence of water ice in the lunar polar regions.

"While the probability of success for such a bold undertaking is low, the potential science payoff is tremendous," said Dr. Guenter Riegler, Director of the Research Program Management Division in the Office of Space Science at NASA Headquarters, Washington, DC.

"External peer reviews of this plan have been very favorable, and we have concluded that it is both technically and operationally feasible," Riegler said. "Since the implementation costs are minimal and the mission is scheduled to end anyway, it seems fitting to give Lunar Prospector the chance to provide scientific data right up to the very end of its highly successful mission."

Lunar Prospector was launched on Jan. 6, 1998, with a one-year primary and six-month extended mission to explore the lunar surface remotely. In March 1998, mission scientists announced that science instruments aboard Lunar Prospector had detected sufficiently large quantities of hydrogen at the lunar poles to infer the presence of water ice. In September, scientists estimated that up to six billion metric tons of water ice may be buried in the permanently shadowed craters of the Moon's poles.

The current plan calls for a controlled impact of the Lunar Prospector spacecraft in the early morning hours of July 31 directly into the Mawson crater, located at the southern lunar pole. This crater is ideal for the proposed experiment. It is only 31 to 38 miles (50 to 60 kilometers) across and has a rim which is high enough to provide a permanent shadow, yet it is low enough to provide for a suitable spacecraft impact trajectory. Data from other observations suggest that the crater could contain a high concentration of water ice. Finally, the crater is observable at impact time from Earth-based observatories and orbiting platforms.

"A positive spectral detection of water vapor or its photo-dissociated byproduct, OH, would provide definite proof of the presence of water ice in the lunar regolith," Goldstein said. However, scientists warn that the failure to observe the desired signal does not mean that water ice is not present. The model could be wrong, the spacecraft may not impact the desired region or the impact energy may be insufficient to liberate an observable plume of water vapor or OH. The overall probability of success is estimated to be about 10 percent.

Observing time has been granted at the University of Texas McDonald Observatory and on the Hubble Space Telescope. It is also being sought at other sites from which the Moon is clearly visible in the early morning hours of July 31.

Goldstein and his team will present a detailed description of their proposal in the June 15 issue of "Geophysical Research Letters."

Further information about Lunar Prospector can be obtained at the project website.

Lunar Prospector was the first of NASA's Discovery class of "faster, better, cheaper" space exploration missions. The $63 million mission is managed by NASA Ames Research Center, Moffett Field, CA.

University of Texas, Austin College of Engineering
Austin, Texas 78713-7509

June 1, 1999

UT Austin researchers and NASA to crash spacecraft to find lunar ice

AUSTIN, Texas -- Is there water on the moon? Researchers at The University of Texas at Austin have designed a quick experiment to find out -- crash a retired lunar module into the moon's south pole, which is believed to contain ice.

UT engineers and an astronomer are teaming up with researchers from NASA-Ames and the Los Alamos National Laboratory to analyze the debris created by the crash and check for evidence of water.

"The discovery of ice on the moon would be of great importance for human exploration of space. Space explorers could separate the ice into hydrogen and oxygen and use it for rocket fuel. They could use the liquid water to build and supply a lunar base," reasons Professor David Goldstein, a UT Austin aerospace engineer who helped design the experiment, along with Professor Steve Nerem, also a UT Austin aerospace engineer.

Goldstein identified a NASA spacecraft now orbiting the moon called "Lunar Prospector," whose mission will end this summer when it runs out of fuel and crashes into the moon.

His group has proposed to make Prospector's end a controlled crash, targeting a crater at the moon's south pole believed to have ice patches. Using some of the world's most powerful telescopes, Goldstein's group can measure the plume of water vapor created by the crash, thereby proving water's existence on the moon. The crash is planned July 31.

Prospector, as part of its primary mission, clearly detected hydrogen at the moon's poles. Hydrogen, along with oxygen, make up water, so Prospector found strong, but inconclusive, evidence of water at the poles. Prospector found the hydrogen inside permanently shadowed craters, craters whose floors never see direct sunlight, which would melt any ice.

"It really is a long-shot experiment," admits Goldstein. "We are crashing Prospector into a permanently shadowed polar crater, which means we cannot see the crash. But we hope to create a barely measurable plume of debris containing ice crystals, dust and water vapor, which will rise out of the crater for a few minutes. In addition, although the moon generally has no atmosphere, we hope the vapor produced by the crash may produce a very thin atmosphere that we can detect several hours later."

Goldstein's group is coordinating observations from UT's McDonald Observatory, the Hubble Space Telescope and the Keck Observatory in Hawaii. NASA has provided preliminary approval for the project, although final approval is pending.

Goldstein's plan "Impacting Lunar Prospector in a Cold Trap to Detect Water Ice" is to be published in a forthcoming issue of the Geophysical Research Letters and presented at the American Geophysical Union's spring conference June 1-4 in Boston.

Lunar propsector: extended mission

NASA Ames news release 98-74

December 18, 1998

Lunar Prospector to gather data closer to moon's surface

On Dec. 19, mission controllers at NASA's Ames Research Center, Moffett Field, CA, will command the Lunar Prospector spacecraft into a 40-kilometer (approximately 25-mile) lunar polar orbit, down from its current 100 kilometer (63 mile) mapping orbit, signaling the transition to the spacecraft's extended mission.

The spacecraft will remain in the new 40-kilometer orbit for about four weeks, and will then be commanded to an even closer 25-30 kilometer (approximately 15 to 19 mile) orbital path in January 1999. These actions will officially complete the end of the very successful primary mission, which began in January 1998.

"Lunar Prospector's instruments have gathered such superior data that we have far exceeded our primary mission objectives," said Sylvia Cox, NASA's Mission Manager for Lunar Prospector. "This success raises our expectations about getting an even closer look at the lunar surface, collecting data at higher resolutions, and gaining further insights about our closest celestial neighbor."

The extended mission is expected to continue through June 1999, during which time the five instruments onboard will gather additional science data at significantly higher resolutions. These higher resolutions will enable scientists to continue to refine their estimates concerning the concentration and form of hydrogen detected at the north and south lunar poles, which mission scientists interpret as deposits of water ice. Mapping of the Moon's magnetic and gravity fields will also benefit greatly from the lower orbit. Additionally, initial global maps of the Moon's elements will be confirmed with the close-up data.

September 3, 1998: Lunar prospector findings indicate larger amounts of polar water ice

January 7, 1998


Lunar Prospector successfully launched on January 6, 1998 at 02:29 UT. Launch took place from Launch Complex 46 (LC-46) at Cape Canaveral Air Station (CCAS), Florida, after a delay of one day. This Sunday, Lunar Propector will reach his polar orbit around the Moon. The spacecraft will then start prospecting the lunar surface at an altitude of approximately 63 miles (100 km) during a one-year mission.

Ames Research Center

Lunar Prospector Mission Status Report

January 7, 1998 12:30 a.m. EST (9:30 p.m. PST, Jan. 6)

NASA's Discovery program of low-cost, science-focused space exploration missions got a major boost Tuesday evening with the successful launch of Lunar Prospector. At the current time, all spacecraft systems are operational and Lunar Prospector is on its way to the Moon.

The compact spacecraft, atop a Lockheed Martin Athena II launch vehicle, roared off Spaceport Florida's pad 46 at the new, commercial launch complex at Cape Canaveral, FL, on schedule at 9:28:44 p.m. EST (6:28:44 p.m. PST), less than one second into the opening of today's launch window.

The launch vehicle's three stages worked as planned, rocketing the craft to an altitude of 62,500 feet after 88 seconds at Stage 1 burnout. All additional milestones were achieved on schedule during the remainder of the ascent phase, culminating in attainment of a successful "parking orbit" around the Earth at an altitude of 125 statute miles.

After completing almost three-quarters of a revolution around the Earth, the vehicle's Trans Lunar Injection (TLI) stage completed a successful 64 second burn, blasting the small spacecraft out of Earth orbit and setting the spin-stabilized vehicle on its 105 hour "coasting" mission to the Moon.

Telemetry and tracking data were acquired on schedule at launch (T) plus 6 minutes and 20 seconds at Antigua, at T + 20 minutes and 23 seconds at Ascension, and at T + 51 minutes and 40 seconds at Australia. Deep Space Network data acquisition at Goldstone, CA occurred at T + 1 hour and 18 minutes, as scheduled. Payload separation from the third stage of the launch vehicle was successful completed at T + 55 minutes and 15 seconds. Spacecraft turn-on was accomplished 56 minutes and 30 seconds after launch.

Lunar Prospector will conduct a one-year primary mission, mapping the surface composition and internal structure, volatile activity, and magnetic and gravity fields of the Moon from an altitude of approximately 63 miles. Additional mapping at altitudes as low as 6 miles above the lunar surface is planned over the following 6 months. Lunar Prospector is expected to provide definitive evidence of the presence or absence of water ice in the shaded lunar polar regions.

The Lunar Prospector spacecraft was built for NASA by Lockheed Martin Missiles and Space, Sunnyvale, CA. The Athena II launch vehicle was provided by Lockheed Martin Astronautics, Denver, CO. Science instruments and other important contributions were provided by the Los Alamos National Laboratory, the U.C. Berkeley Space Science Laboratory, the University of Arizona, Tucson, AZ, and NASA's Goddard Space Flight Center, Greenbelt, MD and Jet Propulsion Laboratory, Pasadena, CA. Alan Binder of the Lunar Research Institute, Gilroy, CA is the Principal Investigator. The Lunar Prospector mission manager is Scott Hubbard of NASA's Ames Research Center, Moffett Field, CA.

Los Alamos National Laboratory
Los Alamos, New Mexico


LOS ALAMOS, N.M., Dec. 30, 1997 -- Sometime in the next month or so, Los Alamos National Laboratory scientists will gather information bearing on a major question impacting the future of space colonization: does the moon have water?

Three Los Alamos instruments on the National Aeronautics and Space Administration's Lunar Prospector, scheduled for a Jan. 5, 1998, launch, will look for water, map the location of valuable elements and gather data on events that release gases from below the surface of Earth's nearest neighbor.

"If we can find sufficient water, it's going to be a land rush like the Oklahoma Sooners," said Bill Feldman, project leader for the Los Alamos instrument package. Los Alamos is a Department of Energy laboratory.

Feldman is confident that Los Alamos' neutron spectrometer will find water if it is there -- even if it occurs in a very small amount -- most likely in the form of dirty ice in permanently shaded craters near the moon's poles. The instrument, which detects and distinguishes neutrons of different energies, should find even faint traces of any ice that is within three feet of the lunar surface.

Ever since last year, when radar mapping instruments on the Clementine probe suggested the possible presence of water on the moon, the importance of Lunar Prospector has grown. Ice, likely deposited by comet and meteoroid impacts, would open the way to interplanetary colonization.

"Water is the key resource that will support life as well as travel from the moon to the planets. Besides sustaining life for moon colonies, hydrogen from the ice can be extracted for rocket fuel," Feldman said.

"I am sure that there are people who would colonize the moon once sufficient water is available," he continued. "The moon is one of the best environments you could possibly have for any number of scientific and commercial enterprises."

In addition to serving as a fueling station for interplanetary travel, a moon colony could provide a base for important research in radio, ultraviolet and infrared astronomy.

Lunar Prospector will take four and one-half days to reach the moon, but Los Alamos scientists will turn on their three instruments -- the neutron spectrometer, an alpha particle detector and a gamma ray spectrometer -- 90 minutes after launch. They want to calibrate the sensors in transit to the moon and make sure everything is working perfectly when the spacecraft reaches its polar orbit around the moon.

After three high-altitude orbital maneuvers at the moon and about a week after launch, Lunar Prospector will settle into its mapping orbit, skimming about 60 miles above the lunar surface.

The neutron spectrometer, the latest in a long line of such instruments built for Los Alamos' nonproliferation programs for the past 35 years, detects neutrons that escape into space when cosmic rays strike the upper layers of the moon's surface.

The spectrometer measures neutrons it encounters in three different ranges of speed, or energy. Neutrons that strike heavy elements bounce around like a ping-pong ball without losing much energy, whereas neutrons bouncing against hydrogen -- the lightest element and a principal component of water -- give up their energy to the hydrogen relatively quickly. The detector will see very few medium-energy neutrons in an area with hydrogen, because the high-energy neutrons generated by cosmic rays quickly become lower energy neutrons. If the detector sees few or no medium-energy neutrons, water must be present.

Feldman said the instrument could give indications of water within a few days of beginning its mapping work, if a lot of water is present, or it could take weeks to make a determination.

"If it's a small spot of ice in a large field of view, it will produce only a small dip in the data," he explained. "That will take a lot of tweaking and a lot of interpretation, and I'll be loath to say anything definite until we're really sure."

Prospector also will carry a Los Alamos gamma ray spectrometer experiment that will provide global maps of the major rock-forming elements on the lunar surface. The instrument records the spectrum of gamma rays and neutrons emitted by elements contained in the moon's crust. The map of certain elements will provide clues to lunar evolution, and tell future lunar '49ers where to look for such valuable elements as aluminum, iron, uranium and titanium.

The moon was sampled during Apollo missions 25 years ago, but along a near-equatorial orbit that covered only 20 percent of the moon. Lunar Prosepctor will map the elements over the remainder of the moon's surface.

An alpha particle spectrometer from Los Alamos will give scientists more information about the moon's minor -- by Earth standards -- seismic activity. Lunar magma that cooled just beneath the outer crust contains uranium, and as uranium-238 decays it produces radon. If moonquakes vent radon to the surface, the spectrometer will capture the evidence by recording the alpha particle signatures of radon's radioactive decay.

The three spectrometers were tested for a year and integrated with Lunar Prospector by Lockheed Martin, which built the spacecraft. The mission is scheduled to last one year.

Lunar Prospector is part of NASA's Discovery Mission series. Alan Binder of Lockheed-Martin Missile and Space Corporation is the principal investigator. Southwest Research Institute in Texas provided electronics for the Los Alamos instruments. Los Alamos staff members Bruce Barraclough and Dick Belian are scientific collaborators on the project and Ken Fuller of Los Alamos' Space Engineering Group was the principal engineer.

Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy.

University of California-Berkeley

January 5, 1998

Lunar Prospector mission could answer puzzles about the moon's magnetic field

By Robert Sanders

BERKELEY -- Today's launch of the first NASA moon mission in 25 years -- the Lunar Prospector -- will carry into lunar orbit a UC Berkeley experiment to measure the patchwork of weak magnetic fields on the moon's surface.

The moon lacks a strong magnetic field like the Earth's, but exhibits a much weaker surface field that varies from place to place, from 100 to 10,000 times fainter than Earth's field. UC Berkeley astrophysicists hope that a complete mapping of the faint fields on the surface -- last attempted 25 years ago by Apollo 15 and 16 -- will reveal the history of the lunar surface, including whether it once had a global magnetic field like the Earth.

"The moon may well have had a global magnetic field 3.8 billion years ago, but that died away," said Robert Lin, a professor of physics at UC Berkeley and one of the principal investigators for the magnetic mapping project. "These magnetic anomalies may be left over from that period, yielding information about that primordial era.

"We hope that by mapping the magnetic field of the entire moon and comparing that with surface features and the results of other mapping onboard Lunar Prospector, we can solve this puzzle and find out what the old field was."

Lin and project engineer David Curtis at UC Berkeley's Space Sciences Laboratory built the instrument, called an electron reflectometer, that will fly aboard Lunar Prospector.

Prospector, scheduled for launch from Cape Canaveral at 8:31 p.m. EST today (Jan. 5), is one of NASA's much-touted "faster, better, cheaper" missions, and the third to be launched in its Discovery Program. Its predecessors were the recent successful Mars Pathfinder mission and the Near Earth Asteroid Rendezvous (NEAR) mission launched in 1996. Prospector is a joint project of NASA Ames Research Center and Lockheed Martin Missiles and Space.

The faint magnetic field on the moon's surface was first detected by magnetometers placed by Apollo astronauts on the surface, and then remotely mapped by a UC Berkeley experiment aboard Apollo 15 in 1971 and Apollo 16 in 1972, using instruments built by Lin and now professor emeritus of physics Kinsey Anderson. Those instruments obtained only a crude measurement of the fields, and over only about 10 percent of the lunar surface, in a band around the equator.

Now, 25 years later, Lin and Anderson are collaborating again to send an updated instrument aboard Lunar Prospector to map the entire surface of the moon with ten times the resolution, down to 20-30 kilometers (12-20 miles). A complete map of the surface should be complete within about six months, Lin said, at which point the instrument will remap in even greater detail the areas of high magnetic field, down to a few kilometers resolution -- a scale of about a mile.

The origin of the faint fields is a mystery, though last November similar but somewhat stronger surface fields were detected on the planet Mars by Mars Global Surveyor, by an instrument also built by Lin and Curtis in collaboration with Goddard Space Flight Center and Centre d'Etude Spatiale des Rayonnements, Toulouse.

Some lunar magnetic hot spots, such as a strip called Rima Sirsalis, may date from about 3.8 billion years ago, a time when the moon may have had a global magnetic field as large as that of the Earth today.

Other hot spots may carry hints of the moon's past magnetic field. They may have been created when asteroids struck the surface, melted, and during cooling captured the magnetic field at the site of impact.

Still others may be the result of more recent asteroid or comet impacts. One puzzling finding from the earlier mappings by the Apollo subsatellites was that regions of high magnetic field seem to be exactly opposite large impact craters, that is, on the side of the moon directly opposite a large impact crater. New information from Lunar Prospector will show whether that was a coincidence or not, and may suggest an explanation.

Two other areas of strong magnetic field seem to be associated with a surface feature called an albedo swirl -- a swirled region of contrasting light and dark, reminiscent of cream stirred into coffee. More detailed mapping will show whether this too is mere coincidence or a real association, perhaps caused by a juxtaposition of irregular magnetic fields.

Magnetic field information also could provide constraints on the physical processes undergone by the moon in its evolution, such as how the core formed, the thermal evolution of the crust, tectonic processes and erosion.

The electron reflectometer is one of five scientific instruments aboard Lunar Prospector, which will fly in a polar orbit at an altitude of about 100 kilometers (63 miles) above the surface. Three of these -- a neutron spectrometer, a gamma ray spectrometer and an alpha particle spectrometer -- are designed to "prospect" for minerals, water ice and gases on the lunar surface. In particular, the neutron spectrometer will seek to confirm the detection of ice in craters at the poles, as reported earlier based on radar measurements by the Defense Department's Clementine probe during a lunar fly-by in 1994.

A combined magnetometer/electron reflectometer will measure the moon's magnetic field above the surface and at the surface, respectively. Finally, a Doppler gravity experiment will provide the best measurements to date of the moon's gravitational field, allowing future moon missions to use fuel more efficiently.

The electron reflectometer, which measures the energy and incoming direction of electrons, is a very sensitive detector of surface magnetic fields, as serendipitously discovered by Lin and Anderson during the Apollo 15 and 16 missions to the moon. While flying identical instruments on these two missions, originally designed to look at charged particles around the moon, they found that many electrons were coming from the surface.

It turned out that these were being reflected by surface magnetic fields acting as magnetic mirrors. Charged electrons from the solar wind corkscrew around the magnetic fields as they approach the surface, and as the magnetic field increases they spiral tighter and tighter until, if the field is strong enough or the angle of approach shallow enough, they reverse direction and corkscrew back into space.

These electrons are measured by the reflectometer, which looks in all directions as the satellite rotates through one revolution.

"By looking at the number and angle at which they come in, we get a measure of the strength of the magnetic field at the surface," Lin said.

The data is shipped directly via the Internet from NASA Ames Research Center, which controls the satellite, to UC Berkeley for analysis.

Prospector will be launched by an inexpensive Lockheed Martin launch vehicle, Athena II, taking its maiden voyage. A three-stage rocket, it will put the satellite in a parking orbit around Earth while its systems are deployed and checked. After all systems are go, the satellite will be kicked into a lunar orbit. The electron reflectometer and related magnetometer -- provided by Goddard Space Flight Center to measure magnetic fields at the position of the satellite -- will be deployed on one of three booms projecting from the body of the spacecraft.

NASA Headquarters, Washington, DC
Ames Research Center, Mountain View, CA

March 12, 1997


Construction and assembly of NASA's Lunar Prospector spacecraft, designed to obtain the first complete compositional and gravity maps of the Moon, has been completed in preparation for its scheduled September 1997 launch.

Functional and environmental spacecraft tests will be conducted over the next several months, according to project manager Tom Dougherty of Lockheed Martin Missiles & Space, Sunnyvale, CA. Once this activity is successfully completed, current plans call for the spacecraft to be shipped to Spaceport Florida in late August for launch on September 24, 1997.

"We're delighted with progress to date," said Scott Hubbard, NASA Lunar Prospector mission manager at Ames Research Center, Mountain View, CA. "Lockheed Martin and its construction team put a detailed program into place and executed it well within the established schedule and with tight cost control."

The total cost of the mission to NASA, including launch, mission operations and data analysis, is $63 million.

Why is NASA going back to the Moon? Despite a high level of scientific and public interest, particularly during the Apollo era, major gaps remain in scientific knowledge about Earth's nearest planetary neighbor, according to project scientists. Over 75 percent of the lunar surface is not mapped in detail, and important questions about the Moon's history, composition and internal processes remain unanswered.

During its planned one-year polar orbiting mission, Lunar Prospector will map the Moon's surface composition, gravity and magnetic fields, and try to detect volatile release activity. This information should provide insights into the origin and evolution of the Moon. Lunar Prospector also should directly determine the existence or absence of water ice in the Moon's polar regions, which has been suggested by analysis of indirect, radar-based data from the Clementine mission.

As the first peer-reviewed, competitively selected mission in NASA's "faster, better, cheaper" Discovery Program series, Lunar Prospector is an embodiment of the Agency's new way of doing business. With an emphasis on minimized risk, lowered costs, and rapid turnaround time, and its prime focus on delivery of science data, Lunar Prospector will help usher in a new era of Solar System exploration missions.

"Lunar Prospector is serving as a pathfinder in many different ways," said Hubbard. The mission has "already made history in terms of management style, technical approach, cost management and focused science. Technical insight rather than detailed programmatic oversight was used to ensure innovation and maximum return on investment. The Ames program office paid close attention to the progress of the project and its schedule, cost and science return, but provided no detailed specifications. The Principal Investigator was given the flexibility to implement the best available approach," he said.

The Lunar Prospector spacecraft is a small, spin-stabilized vehicle with a fully fueled mass of 660 pounds. It is 4.5 feet high and 4 feet in diameter, with three 8-foot booms or masts. Solar cells mounted on its outer surface will provide more than 200 watts of power.

Five scientific instruments are mounted on the booms to isolate them from the main structure and electronics. A neutron spectrometer will have the capability to locate as little as one cup of water in about a cubic yard of lunar soil (regolith). The discovery of water ice in the lunar polar regions would mean that water, necessary for life support and a potential source of both oxygen and hydrogen to produce rocket propellant, could be available for use by future lunar explorers.

A gamma-ray spectrometer will provide global maps of the elemental composition of the surface layer of the Moon. Improved knowledge of the concentrations of such elements as uranium, thorium, potassium, iron, titanium, oxygen, silicon, aluminum, magnesium and calcium will aid in understanding the composition and evolution of the lunar crust.

An alpha particle experiment will provide information on the level of tectonic and volcanic lunar out-gassing activity. It will map the locations and frequency of radon gas release events on the Moon, a body thought to be tectonically and volcanically dead until Apollo provided evidence that it may still have some limited activity.

A magnetometer and electron reflectometer will map local lunar magnetic fields, known to be weak compared to the global magnetic field of the Earth. This will help determine the origin of such fields and may provide information on the size and composition of the lunar core.

The Doppler gravity experiment will provide the first global gravity map of the Moon, essential for planning follow-on robotic and human exploration missions. It also will provide data on density differences in the crust, internal densities and the nature of the core.

When Lunar Prospector is launched, it will take five days to reach the Moon, making two midcourse maneuvers, deploying booms, and collecting calibration data via its science instruments en route. Once the spacecraft reaches the Moon, it will be put into a circular, 118-minute, 62-mile altitude, polar-mapping orbit to begin its mission.

If fuel is available at the end of the one-year nominal mission, lunar mapping may be extended at altitudes as low as 6.2 miles over areas of special interest. After the fuel needed for orbital maintenance is depleted, the spacecraft will eventually impact on the lunar surface.

The Lunar Prospector mission is being implemented for NASA by Lockheed Martin, Sunnyvale, CA, with important contributions from Los Alamos National Laboratory, the University of California- Berkeley Space Science Laboratory, the Goddard Space Flight Center, Greenbelt, MD, and the Jet Propulsion Laboratory, Pasadena, CA.

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