LROC image of Surveyor 1 on the Moon. NASA/GSFC/Arizona State University
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On June 2, 1966 the Surveyor 1 spacecraft soft landed on the Moon, the first US spacecraft to set down on another body. Now, 43 years later the Lunar Reconnaissance Orbiter Camera has spotted this historic spacecraft, sitting silently on the Moon’s surface. The scene shows the spacecraft (annotated with an arrow, and the shadow shows up very well) just south of a 40 m diameter crater and about 110 m northwest of a 190 m diameter crater lined with boulders. The landing site is in the northeast corner of the Flamsteed Ring, a 100 km diameter impact crater almost completely buried by mare lavas such that all that remains exposed is the upper part of the original crater rim.
Surveyor 1 took its own picture on the Moon back in 1966. Credit: NASA
Surveyor 1 collected over 11,000 images, most during the first lunar day between landing and July 7, 1966. The spacecraft continued to operate until January 7, 1967. The Surveyor images demonstrated that the lunar surface was strong enough to support a landed vehicle or a human. The detailed images also indicated that the surface was composed of a granular material interpreted to be produced by the impact of various size meteors over billions of years.
And 43 years later we figured out some H20 and OH were also part of the mix.
LROC's second look at the Apollo 11 Landing Site [NASA/GSFC/Arizona State University]. Click for larger version.
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The Lunar Reconnaissance Orbiter Camera has taken a second look at the Apollo 11 landing site. These images were taken before LRO reached its science orbit of 50 km (31 miles) above the Moon, but the lighting is different from the previous images it took of this region, providing more detail and a whole new look at this historic site. This time the Sun was 28 degrees higher in the sky, making for smaller shadows and bringing out subtle brightness differences on the surface. The look and feel of the site has changed dramatically. See below for a close-up view.
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The astronaut path to the TV camera is visible, and you may even be able to see the camera stand (arrow). You can identify two parts of the Early Apollo Science Experiments Package (EASEP) – the Lunar Ranging Retro Reflector (LRRR) and the Passive Seismic Experiment (PSE). Neil Armstrong’s tracks to Little West crater (33 m diameter) are also discernable (unlabeled arrow). His quick jaunt provided scientists with their first view into a lunar crater.
Nice going LROC!
This article was edited on Sept. 30 to correct a mistake about LRO’s orbit at the time these images were taken. See our previous article on the first round of LROC’s images of various Apollo landing sites.
Artist impression of LCROSS approaching the Moon. Credit: NASA
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Based on new analysis of the latest lunar data, the science team for NASA’s Lunar Crater Observation and Sensing Satellite mission (LCROSS) decided to change the target crater for impact from Cabeus A to Cabeus (proper). The decision was based on a consensus that Cabeus shows, with the greatest level of certainty, the highest hydrogen concentrations at the south pole. The most current terrain models provided by JAXA’s Kaguya spacecraft and the LRO Lunar Orbiter Laser Altimeter (LOLA) was important in the decision process, as the latest models show a small valley in an otherwise tall Cabeus perimeter ridge, which will allow for sunlight to illuminate the ejecta cloud, making it easier to see from Earth.
The decisison was based on continued evaluation of all available data and consultation/input from members of the LCROSS Science Team and the scientific community, including impact experts, ground and space based observers, and observations from (LRO), Lunar Prospector (LP), Chandrayaan-1 and JAXA’s Kaguya spacecraft. This decision was prompted by the current best understanding of hydrogen concentrations in the Cabeus region, including cross-correlation between the latest LRO results and LP data sets.
As for the sunlight illuminating the ejecta cloud on Oct. 9, it should show up much better than previously estimated for Cabeus. While the ejecta does have to fly to higher elevations to be observed by Earth telescopes and observers, a shadow cast by a large hill along the Cabeus ridge, provides an excellent, high-contrast, back drop for ejecta and vapor measurements.
The LCROSS team concluded that Cabeus provided the best chance for meeting its mission goals. The team critically assessed and successfully advocated for the change with the Lunar Precursor Robotic Program (LPRP) office. The change in impact crater was factored into LCROSS’ most recent Trajectory Correction Maneuver, TCM7.
During the last days of the mission, the LCROSS team will continue to refine the exact point of impact within Cabeus crater to avoid rough spots, and to maximize solar illumination of the debris plume and Earth observations.
This image of LCROSS impact site Cabeus A was taken by the Advanced Moon Imaging Experiment (AMIE) on board ESA’s SMART-1 mission. The picture was taken from about 500 km, with small-field (about 50 km across) high resolution view (50 m/pixel). Image credit: B.Grieger, B.H. Foing & ESA/SMART-1/ AMIE team
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ESA’s SMART-1 team has released an image of the future impact site of NASA’s Lunar Crater Observation and Sensing Satellite (LCROSS). The SMART-1 team searched through their database to find images of Cabeus A, where LCROSS will search for water ice by making two impacts into this crater at the lunar south pole. The impacts are scheduled for 11:30 and 11:34 am UT on 9 October 2009. This image was taken four years ago by SMART-1, a spacecraft that ended its mission in 2006 by deliberately crashing to the Moon, similar to what LCROSS will do, hoping to exhume materials buried under the lunar surface, particularly water ice. “This is like gathering evidence for a Crash Scene Investigation, but before the action takes place,” said Bernard Foing, SMART-1 project scientist.
Cabeus A is permanently shadowed, so ice lying inside the crater could be protected from the Sun’s harsh rays. LCROSS will send the upper stage Centaur rocket crashing into Cabeus A and a shepherd spacecraft will fly into the plume of dust generated and measure its properties before making a second impact with the lunar surface. Astronomers will observe both impacts using ground and space-based telescopes. The SMART-1 spacecraft also concluded its mission with a controlled bouncing impact on 3 September 2006. The event was observed with ground-based telescopes and the flash from the impact was detected at infrared wavelengths.
Foing and Bjoern Grieger, the liaison scientist for SMART-1’s AIMIE camera searched through SMART-1’s database for images of Cabeus A, taken four years ago at conditions where solar elevation and direction were similar to those of LCROSS impact. The SMART-1 image is at high resolution as the spacecraft was at its closest distance of 500 km from the South Pole.
“We are pleased to contribute these ESA SMART-1 observations of the LCROSS target site in order to help in the planning and interpretation of impact observations,” said Foing. “The coordination and exchange of information between lunar missions is an important step for future exploration of the Moon. Cooperation is vital if we are ever to see ‘villages’ of robotic landers and eventual lunar bases, as recommended by the International Lunar Exploration Working Group.”
The distribution of water (light blue) around a small young crater on the Moon. Credits: ISRO/NASA/JPL-Caltech/USGS/Brown Univ.
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The Moon has been turned upside down. Figuratively, of course. La Luna still orbits and phases as it always has, but we are now looking at the moon anew. From this day forward we know the chemistry of the Moon is different than what we have thought for decades, the geology might vary from what is in textbooks today, and the physics of how the solar wind interacts with a rocky body without an atmosphere has implications not yet fully investigated. So, what does this mean for our future human and robotic exploration of our closest companion in space?
“The Moon continues to surprise us,” said Carle Pieters, principal investigator for the Moon Mineralogy Mapper (M cubed) at Thursdays press conference. “Widespread water has been detected on the surface of the Moon. You have to think outside of the box on this. This is not what any of us expected decades ago.”
Immediately, space enthusiasts’ thoughts turn to how finding water on the Moon will make future exploration there so much easier.
“Scientists thought they knew fairly accurately what the surface of the moon was like and these results show that they didn’t – or at least not completely,” said Dr. Chris Welch, astronautics and space systems expert at Kingston University in London. “Finding so much more water could make living on the moon much easier in the future…If there is water on the moon – in whatever form – then we have a potential reservoir that could be used for drinking or to make into hydrogen and oxygen which could be used as rocket propellant. Also, of course, we could use the oxygen to breathe.”
But the message the scientists wanted everyone to take away from today’s press conference is that a combination of water (H2O) and hydroxyl (OH) that resides in upper millimeter of the lunar surface doesn’t actually amount to much. The average amount of water, if extracted, is about a quart (1 liter) of water per ton of surface soil, or about 16 ounces (.5 liters) of water might be present for every 1,000 pounds (450 kg) of surface soil near the moon’s poles. For soil near the equator, only about two tablespoons of water is believed to be present in every 1,000 pounds (450 kg).
“That is truly astounding, and generating much excitement,” said Jim Green, director of the Planetary Science Division at NASA. “But please keep in mind that even the driest deserts on the Earth have more water than are at the poles and the surfaces of the moon.”
So maybe this water on the Moon is not such a big deal.
But there’s still the very real possibility that there could be water ice underneath the regolith on the Moon or buried deep within craters at the poles. Fairly recent (within the past million years) impact craters on the moon were found to have ejecta “rich” with water and hydroxyl, according to M cubed data, which implies recently those molecules are buried under the surface.
Plus the scientists hinted at data showing Goldschmidt Crater at the Moon’s north pole could be filled with water ice. The image on the left shows albedo, or the sunlight reflected from the surface of the moon. The image on the right shows where infrared light is absorbed in the characteristic manner that indicates the presence of water and hydroxyl molecules. That image shows that signature most strongly at the cool, high latitudes near the poles. The blue arrow indicates Goldschmidt crater, a large feldspar-rich region with a higher water and hydroxyl signature. Image credit: ISRO/NASA/JPL-Caltech/Brown Univ.
Additionally, what the scientists at today’s briefing found most astonishing about the new findings is that the water and hydroxyl show up at all latitudes, even at the equator in sunlight, where it is quite hot, and that there are a wide variety of hydroxyl bearing minerals at the surface. This is telling us there are some dynamic processes happening on a moon we thought to be bone dry and basically dead.
There appears to be a cycle of water being created and lost during a lunar day. Without an atmosphere, the moon is exposed to solar wind, which includes hydrogen ions. The hydrogen is able to interact with oxygen in lunar soil to create water molecules. The water appears to be created at night on the Moon, lost during the “hottest” parts of the two-week lunar day; then as it cools near evening, the cycle repeats itself. So, regardless of the type of terrain on the Moon, the entire surface of the moon will be hydrated at least for part of the day. The scientists said similar hydration effects may be present on any body in our solar system that doesn’t have an atmosphere, including asteroids and Mercury.
Those implications are huge for our explorations of other moons and worlds.
But back to the Moon. “Before this press conference, it was thought to be impossible to have water on the surface of the Moon in hot sunlight, especially on the surface at the equator,” said Roger Clark, with the M cubed and Cassini mission. Small amounts of water and hydroxyl (blue) were detected on the surface of the moon at various locations. This image illustrates their distribution at high latitudes toward the poles. Image credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS
Could water be a renewable resource on the Moon? If the water is constantly being created, could a devise be built to extract or collect the water? Easy availability of water would have an immense impact on any future human exploration on the Moon, be it brief sorties or permanent colonies.
This is intriguing,” said Pieters, “but we need to go back and re-determine this silicate surface and the vacuum around it. This is an environment we know very little about, and the physics is in its infancy.”
Discussing the implications, Pieters said first, the source of the water needs to be determined, whether it is actually from the solar wind, comets, meteorites, possibly an outgassing from the interior. “There are fundamental questions we need to understand about this silicate body,” she said. “Clearly this has to be a marriage between geology and space physics.”
And what about the “follow the water” mantra NASA has been following in regards to Mars? Could the “where there’s water, there’s life” hypothesis pertain to the Moon? Is there water on the Moon? While these new details about the Moon are groundbreaking, Welch does not believe the new findings show there is or could once have been life on the moon, but he says further research is needed. “There need to be more detailed science missions, preferably with astronauts landing on the moon, to analyse the soil in space.”
Certainly, the upcoming LCROSS impact on the Moon’s south pole will be watched with even greater interest. But what about future exploration?
Will this impel the Constellation Program to continue as planned with a return to the Moon? The Obama administration has some big decision to make in regards to NASA, and it’s hard to imagine this new information about the Moon won’t have some impact on the future path the space agency will take.
We can only hope this news brings more public and congressional interest in NASA’s future.
Schematic showing the stream of charged hydrogen ions carried from the Sun by the solar wind. One possible scenario to explain hydration of the lunar surface is that during the daytime, when the Moon is exposed to the solar wind, hydrogen ions liberate oxygen from lunar minerals to form OH and H2O, which are then weakly held to the surface. At high temperatures (red-yellow) more molecules are released than adsorbed. When the temperature decreases (green-blue) OH and H2O accumulate. [Image courtesy of University of Maryland/F. Merlin/McREL]
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Three different spacecraft have confirmed there is water on the Moon. It hasn’t been found in deep dark craters or hidden underground. Data indicate that water exists diffusely across the moon as hydroxyl or water molecules — or both — adhering to the surface in low concentrations. Additionally, there may be a water cycle in which the molecules are broken down and reformulated over a two week cycle, which is the length of a lunar day. This does not constitute ice sheets or frozen lakes: the amounts of water in a given location on the Moon aren’t much more than what is found in a desert here on Earth. But there’s more water on the Moon than originally thought.
The Moon was believed to extremely dry since the return of lunar samples from the Apollo and Luna programs. Many Apollo samples contain some trace water or minor hydrous minerals, but these have typically been attributed to terrestrial contamination since most of the boxes used to bring the Moon rocks to Earth leaked. This led the scientists to assume that the trace amounts of water they found came from Earth air that had entered the containers. The assumption remained that, outside of possible ice at the moon’s poles, there was no water on the moon.
Forty years later, an instrument on board the ill-fated Chandrayaan-1 spacecraft, the Moon Mineralogy Mapper (M cubed) found that infrared light was being absorbed near the lunar poles at wavelengths consistent with hydroxyl- and water-bearing materials.
M3 analyzes the way that light from the sun reflects off the lunar surface to understand what materials comprise the lunar soil. Light is reflected in different wavelengths off of different minerals, and specifically, the instrument detected wavelengths of reflected light that would indicate a chemical bond between hydrogen and oxygen. Given water’s well-known chemical symbol, H2O, which represents two hydrogen atoms bonded to one oxygen atom, this discovery was a source of great interest to the researchers.
The instrument can only see the very uppermost layers of the lunar soil – perhaps to a few centimeters below the surface. The scientists were looking for a signature of water in the craters near the poles, but found evidence for water instead on the sunlit portions of the moon. This was certainly unexpected and the science team from M3 looked and re-looked at their data for several months.
Confirmation came from a recent flyby of the re-purposed Deep Impact probe, on its way to rendezvous with another comet in 2010. In June of 2009, the spectrometer on board also showed strong evidence that water is ubiquitous over the surface of the moon.
Jessica Sunshine and colleagues with Deep Impact also found the presence of bound water or hydroxyl in trace amounts over much of the Moon’s surface. Their results suggest that the formation and retention of these molecules is an ongoing process on the lunar surface – and that solar wind could be responsible for forming them.
Still another spacecraft, the Cassini spacecraft while on its way to Saturn, also flew by the Moon in 1999. Roger Clark, a U.S. Geological Survey spectroscopist on the M3 team, reanalyzed archival data from Cassini, and that data as well agreed with the finding that water appears to be widespread across the lunar surface.
There are potentially two types of water on the moon: exogenic, meaning water from outside sources, such as comets striking the moon’s surface, and endogenic, meaning water that originates on the moon. The M3 research team, which includes Larry Taylor of the University of Tennessee, Knoxville, suspect that the water they’re seeing in the moon’s surface is endogenic.
But where did the water come from?
The team from M3 believe it may come from the solar wind.
As the sun undergoes nuclear fusion, it constantly emits a stream of particles, mostly protons, which are positively charged hydrogen atoms. On Earth, the atmosphere and magnetism prevent us from being bombarded by these protons, but the moon lacks that protection, meaning the oxygen-rich minerals and glasses on the surface of the moon are constantly pounded by hydrogen in the form of protons, moving at velocities of one-third the speed of light.
When those protons hit the lunar surface with enough force, suspects Taylor, they break apart oxygen bonds in soil materials, and where free oxygen and hydrogen are together, there’s a high chance that trace amounts of water will be formed. These traces are thought to be about a quart of water per ton of soil.
“The isotopes of oxygen that exist on the moon are the same as those that exist on Earth, so it was difficult if not impossible to tell the difference between water from the moon and water from Earth,” said Taylor. “Since the early soil samples only had trace amounts of water, it was easy to make the mistake of attributing it to contamination.”
Lead image caption: Schematic showing the stream of charged hydrogen ions carried from the Sun by the solar wind. One possible scenario to explain hydration of the lunar surface is that during the daytime, when the Moon is exposed to the solar wind, hydrogen ions liberate oxygen from lunar minerals to form OH and H2O, which are then weakly held to the surface. At high temperatures (red-yellow) more molecules are released than adsorbed. When the temperature decreases (green-blue) OH and H2O accumulate. Image courtesy of University of Maryland/F. Merlin/McREL
This image shows daytime and nighttime lunar temperatures recorded by Diviner. Credit: NASA/UCLA
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The Lunar Reconnaissance Orbiter has successfully completed its testing and calibration phase and is now in its science and mapping orbit of the moon. Already, the spacecraft has made significant progress in creating the most detailed atlas of the moon’s south pole, and Thursday mission scientists reported some of the early science results, including “tantalizing” hints of water at the Moon’s south pole. So far, the data returned from LRO’s seven instruments “exceed our wildest expectations,” said Richard Vondrak, LRO project scientist at NASA Goddard Space Flight Center . “We’re looking at the moon now with new eyes.”
Last Tuesday, a final maneuver put LRO 50 km (31 miles) above the Moon, closer than any previous orbiter. LRO has already proved its keen eyes, imaging fine details of the Apollo landing sites earlier this summer with the LROC, the Lunar Reconnaissance Orbiter Camera.
Coldest place in the solar system
According to the first measurements from the Diviner instrument, which has infrared radiation detectors, LRO found that temperatures at about 35 Kelvin, or -238º Celsius deep in some permanently shaded regions. Vondrak said that these bitterly cold regions at the south pole “are perhaps the coldest part of the solar system.” With such cold temperatures, volatiles like water ice could be present, preserved for billions of years. This image shows neutron flux detections around the lunar south pole from LEND. Credit: NASA/Institute for Space Research (Moscow)
And indeed, first results from LRO’s Lunar Exploration Neutron Detector, or LEND instrument found hallmarks of hydrogen—a potential marker of water— not only in deep, dark craters, but in unexpected places as well.
“What it also seems to indicate is that the hydrogen is not confined to permanently shadowed craters,” said Vondrak. “Some of the permanently shadowed craters do indeed contain hydrogen. Others, on the other hand, do not appear to have hydrogen. And in addition, there appears to be concentrations of hydrogen that are not confined to the permanently shadowed regions.”
Surface topography This mosaic shows altitude measurements from the LOLA instrument. Credit: NASA's Goddard Space Flight Center
Data from LRO’s Lunar Orbiter Laser Altimeter, or LOLA, give scientists a detailed look at the topography of the lunar south pole, shown here. Red regions are high altitude, and blue regions are low altitude.
Some of the first results have turned up fresh craters, unknown boulders, and smooth sites that would be good landing sites for future humans or robotic missions. However, most regions are filled with rough terrain, which will make in situ exploration difficult. The roughness is probably a result of the lack of atmosphere and absence of erosion from wind or water, according to David Smith, LOLA principal investigator.
Another instrument, LRO’s Cosmic Ray Telescope for the Effects of Radiation instrument is exploring the lunar radiation environment and its potential effects on humans during record high, “worst-case” cosmic ray intensities accompanying the extreme solar minimum conditions of this solar cycle, showing damaging amounts of radiation at various points. This Mini-RF image shows radar imagery of the lunar south pole. Credit: NASA/APL/LPI
The Mini RF Technology Demonstration on LRO has confirmed communications capability and produced detailed radar images of potential targets for LRO’s companion mission, LCROSS, the Lunar Crater Observation and Sensing Satellite, which will impact the moon’s south pole on Oct. 9.
LRO’s prime science mission will last a year.
“The LRO instruments, spacecraft, and ground systems continue to operate essentially flawlessly,” said Craig Tooley, LRO project manager at Goddard “The team completed the planned commissioning and calibration activities on time and also got a significant head start collecting data even before we moved to the mission’s mapping orbit.”
“There’s still an awful lot to be done,” says Michael Wargo, chief lunar scientist at NASA Headquarters in Washington, D.C. “And the maps will only get better.”
See more information, including more images and flyover videos here.
The Earth is a water-dominated planet. (Image credit: Ian O'Neill)
Tides refer to the rise and fall of our oceans’ surfaces. It is caused by the attractive forces of the Moon and Sun’s gravitational fields as well as the centrifugal force due to the Earth’s spin. As the positions of these celestial bodies change, so do the surfaces’ heights. For example, when the Sun and Moon are aligned with the Earth, water levels in ocean surfaces fronting them are pulled and subsequently rise.
The Moon, although much smaller than the Sun, is much closer. Now, gravitational forces decrease rapidly as the distance between two masses widen. Thus, the Moon’s gravity has a larger effect on tides than the Sun. In fact, the Sun’s effect is only about half that of the Moon’s.
Since the total mass of the oceans does not change when this happens, part of it that was added to the high water regions must have come from somewhere. These mass-depleted regions then experience low water levels. Hence, if water on a beach near you is advancing, you can be sure that in other parts of the world, it is receding.
Most illustrations containing the Sun, Moon, Earth and tides depict tides to be most pronounced in regions near or at the equator. On the contrary, it is actually in these regions where the difference in high tide and low tide are not as great as those in other places in the world.
This is because the bulging of the oceans’ surface follows the Moon’s orbital plane. Now, this plane is not in line with the Earth’s equatorial plane. Instead, it actually makes a 23-degree angle relative to it. This essentially allows the water levels at the equator to seesaw within a relatively smaller range (compared to the ranges in other places) as the orbiting moon pulls the oceans’ water.
Not all tides are caused by the relative positions of these celestial bodies. Some bodies of water, like those that are relatively shallow compared to oceans, experience changing water levels because of variations in the surrounding atmospheric pressure. There are also other extreme situations wherein tides are manifested but have nothing to do with astronomical positioning.
A tidal wave or tsunami, for example, makes use of the word ‘tide’ and actually exhibits rise and fall of water levels (in fact, it is very noticeable). However, this phenomena is caused entirely by a displacement of a huge amount of water due to earthquakes, volcanic eruptions, underwater explosions, and others. All these causes take place on the Earth’s surface and have nothing to do with the Moon or Sun.
A thorough study of tides was conducted by Isaac Newton and included in his published work entitled Philosophiæ Naturalis Principia Mathematica.
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Artist concept of Chandrayaan-1 orbiting the moon. Credit: ISRO
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After giving up on re-establishing contact with the Chandrayaan-1 lunar orbiter, Indian Space Research Organization (ISRO) Chairman G. Madhavan Nair announced the space agency hopes to launch its first mission to Mars sometime between 2013 and 2015. Nair said the termination of Chandrayaan-1, although sad, is not a setback and India will move ahead with its plans for the Chandrayaan-2 mission to land an unmanned rover on the moon’s surface to prospect for chemicals, and in four to six years launch a robotic mission to Mars.
“We have given a call for proposal to different scientific communities,” Nair told reporters. “Depending on the type of experiments they propose, we will be able to plan the mission. The mission is at conceptual stage and will be taken up after Chandrayaan-2.”
On the decision to quickly pull the plug on Chandrayaan-1, Nair said, “There was no possibility of retrieving it. (But) it was a great success. We could collect a large volume of data, including more than 70,000 images of the moon. In that sense, 95 percent of the objective was completed.”
Contact with Chandrayaan-1 may have been lost because its antenna rotated out of direct contact with Earth, ISRO officials said. Earlier this year, the spacecraft lost both its primary and back-up star sensors, which use the positions of stars to orient the spacecraft.
The loss of Chandrayaan-1 comes less than a week after the spacecraft’s orbit was adjusted to team up with NASA’s Lunar Reconnaissance Orbiter for a Bi-static radar experiment. During the maneuver, Chandrayaan-1 fired its radar beam into Erlanger Crater on the moon’s north pole. Both spacecraft listened for echoes that might indicate the presence of water ice – a precious resource for future lunar explorers. The results of that experiment have not yet been released.
Chandrayaan-1 craft was designed to orbit the moon for two years, but lasted 315 days. It will take about 1,000 days until it crashes to the lunar surface and is being tracked by the U.S. and Russia, ISRO said.
The Chandrayaan I had 11 payloads, including a terrain-mapping camera designed to create a three-dimensional atlas of the moon. It is also carrying mapping instruments for the European Space Agency, radiation-measuring equipment for the Bulgarian Academy of Sciences and two devices for NASA, including the radar instrument to assess mineral composition and look for ice deposits. India launched its first rocket in 1963 and first satellite in 1975. The country’s satellite program is one of the largest communication systems in the world.
Chandrayaan-1, India’s first unmanned mission to the Moon, successfully entered lunar orbit on November 8, 2008
NASA’s Lunar Reconnaissance Orbiter and India’s Chandrayaan-1 will team up on August 20 to perform a Bi-Static radar experiment to search for water ice in a crater on the Moon’s north pole. Both spacecraft will be in close proximity approximately 200 km above the lunar surface, and both are equipped with radar instruments. The two instruments will look at the same location from different angles, with Chandrayaan-1’s radar transmitting a signal which will be reflected off the interior of Erlanger crater, and then be picked up by LRO. Scientists will compare the signal that bounces straight back to Chandrayaan with the signal that bounces at a slight angle to LRO to garner unique information, particularly about any water ice that may be present inside the crater.
Both spacecraft are equipped with a NASA Miniature Radio Frequency (RF) instrument that functions as a Synthetic Aperture Radar (SAR), known as Mini-SAR on Chandrayaan 1 and Mini-RF on LRO.
“The advantage of a Bi-Static experiment is that you’re looking at echoes that are being reflected off the Moon at an angle other than zero,” said Paul Spudis,principal investigator for Chandrayaan-1’s Mini-SAR,discussing the mission on The Space Show. “Mono-static radar sends a pulse, and you are looking in the same phase or incident angle. But with Bi-Static, you can look at it from a different angle. The significance of that is ice has a very unique bi-static response.”
Erlanger Crater from the Lunar Orbiter. Credit: NASA
Stewart Nozette, Mini-RF principal investigator from the Universities Space Research Association’s Lunar and Planetary Institute, said, “An extraordinary effort was made by the whole NASA team working with ISRO to make this happen”
While this coordination sounds easy, this experiment is extremely challenging because both spacecraft are traveling at about 1.6 km per second and will be looking at an area on the ground about 18 km across. Due to the extreme speeds and the small point of interest, NASA and ISRO need to obtain and share information about the location and pointing of both spacecraft. The Bi-Static experiment requires extensive tracking by ground stations of NASA’s Deep Space Network, the Applied Physics Laboratory, and ISRO.
Even with the considerable planning and coordination between the U.S. and India the two instrument beams may not overlap, or may miss the desired location. Even without hitting the exact location Scientists may still be able to use the Bi-Static information to further knowledge already received from both instruments.
“The international coordination and cooperation between the two agencies for this experiment is an excellent opportunity to demonstrate future cooperation between NASA and ISRO, “says Jason Crusan, program executive for the Mini-RF program, from NASA’s Space Operations Mission Directorate, Washington, D.C.
![NAC image blown up two times showing Tranquility Base [NASA/GSFC/Arizona State University].](https://www.universetoday.com/wp-content/uploads/2009/09/Apollo-11-close-up.jpg "NAC image blown up two times showing Tranquility Base [NASA/GSFC/Arizona State University].")
