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Lunar Reconnaissance Orbiter

Background for the LRO LEND EPO Program

The Lunar Reconnaissance Orbiter (LRO) mission launched in June 2009 as part of NASA’s Robotic Lunar Exploration Program. LRO is a robotic mission that set out to map the moon's surface and, after a year of exploration, was extended with a unique set of science objectives. LRO observations have enabled numerous groundbreaking discoveries, creating a new picture of the moon as a dynamic and complex body. These developments have set up a scientific framework through which to challenge and improve our understanding of processes throughout the solar system. The payload includes six instruments to perform the exploration/science measurement investigations for the LRO program. The following are a brief summary of the six instruments:

  1. Lunar Exploration Neutron Detector (LEND) – principal investigator, Dr. Igor Mitrofanov, Institute for Space Research, Moscow. LEND will map the flux of neutrons from the lunar surface to search for evidence of water ice and provide measurements of the space radiation environment which can be useful for future human exploration.
  2. Lunar Orbiter Laser Altimeter (LOLA) – principal investigator, Dr. David E. Smith, NASA Goddard Space Flight Center, Greenbelt, MD. LOLA will determine the global topography of the lunar surface at high resolution, measure landing site slopes and search for polar ices in shadowed regions.
  3. Lunar Reconnaissance Orbiter Camera (LROC) – principal investigator, Dr. Mark Robinson, Northwestern University, Evanston, IL. LROC will acquire targeted images of the lunar surface capable of resolving small-scale features that could be landing site hazards, as well as wide-angle images at multiple wavelengths of the lunar poles to document changing illumination conditions and potential resources.
  4. Diviner Lunar Radiometer Experiment – principal investigator, Prof. David Paige, UCLA, Los Angeles, CA. Diviner will map the temperature of the entire lunar surface at 300 meter horizontal scales to identify cold-traps and potential ice deposits.
  5. Lyman-Alpha Mapping Project (LAMP) – principal investigator, Dr. Alan Stern, Southwest Research Institute, Boulder, CO. LAMP will observe the entire lunar surface in the far ultraviolet. LAMP will search for surface ices and frosts in the polar-regions and provide images of permanently shadowed regions illuminated only by starlight.
  6. Cosmic Ray Telescope for the Effects of Radiation (CRaTER) – principal investigator, Prof. Harlan Spence, Boston University, MA. CRaTER will investigate the effect of galactic cosmic rays on tissue-equivalent plastics as a constraint on models of biological response to background space radiation.

Lunar Exploration Neutron Detector

photo of the LEND instrument
The LEND instrument measures the flux of neutrons from the Moon, which are produced by the continuous cosmic ray bombardment of the lunar surface.

Of particular interest for this E/PO program is the Lunar Exploration Neutron Detector (LEND). Planetary remote sensing neutron and gamma ray spectrometers have been successfully flown on a number of space flight missions to obtain elemental composition of the surfaces of the Moon and Mars. The LEND experiment will obtain by measurement of the neutron flux from the surface of the Moon, the distribution of hydrogen that may be interpreted as water ice in polar-regions. This will be done with a spatial resolution better than any previous mission; five kilometer spatial resolution will be attained in the polar-regions.

The basic principal involved in remote sensing neutron and gamma ray remote sensing spectroscopy is as follows. The interaction of galactic-cosmic rays with a planetary surface results in a cascade of secondary particles mostly neutrons. The proposed investigations by LEND are based on detection of neutron fluxes from the Moon, produced within 1-2 meters below the surface by these galactic cosmic rays. Initial high-energy neutrons are moderated and absorbed by nuclei of the major soil-constituting elements. The leakage flux of neutrons has three major components: low energy thermal neutrons, epithermal or moderate energy neutrons, and high-energy neutrons. The neutrons can also produce gamma rays by inelastic scattering and capture reactions. The spectrum of gamma rays lines characterize the composition of soil-constituting elements H, C, O, Mg, Al, Si, Cl, S, Ca, Ti, Fe, K, Th and U. The energy spectrum of leaking neutrons depends on the composition of the surface but most significantly on the hydrogen concentration. Hydrogen nuclei are the best moderators of high-energy neutrons due to in-elastic collisions. Even a very small fraction of hydrogen, at the level of 100 ppm, is known to make the measurable change of neutron fluxes from the surface of the Moon. The gamma ray system is not as sensitive to the detection of H compared to neutron measurements. Thus, for mapping of the hydrogen content of the Lunar surface and sub-surface by LRO, the LEND instrument was chosen.

The participants chosen for this program will learn the scientific and technical approaches to planetary remote sensing neutron and gamma ray spectroscopy in relation to the exploration and goals of the LRO mission. Among the activities they might be involved in are the following:

  1. Study results obtained by measurements made by remote sensing instruments on previous missions, including Apollo, Lunar Prospector, and Mars Odyssey.
  2. Participate in laboratory studies on advanced neutron and gamma-ray detectors for future missions.
  3. Help develop data analysis tools to evaluate laboratory data or to improve the mapping capability of existing data sets.
  4. Participate in analyzing data taken during calibration of the LEND instrument in both Russia and in the U.S.
  5. Learn about the other instruments on LRO that have similar exploration objectives as LEND and how results may be combined to improve the mission results.
  6. Be involved in the analysis of the LEND data during the LRO mission.
  7. Participate in synthesis of the LEND results with results from other instruments on the LRO mission to better understand and confirm results concerning the detection of water ice in the polar regions and the radiation environment on the Moon.

References

General
Introduction to Planetary Remote Sensing Gamma-Ray Spectroscopy, L.G. Evans, R.C. Reedy, and J.I. Trombka, in Remote Geochemical Analysis: Elemental and Mineralogical Composition, 167-198, C.M. Pieters and P.A.J. Englert, eds., Cambridge University Press, 1993.

Planetary Neutron Spectroscopy from Orbit, W. Feldman, et al., in Remote Geochemical Analysis: Elemental and Mineralogical Composition, 213-234, C.M. Pieters and P.A.J. Englert, eds., Cambridge University Press, 1993.

Neutron Spectroscopy, Y.A. Surkov et al., in Remote Geochemical Analysis: Elemental and Mineralogical Composition, 427-436, C.M. Pieters and P.A.J. Englert, eds., Cambridge University Press, 1993.
Apollo
Composition of the Moon as Determined from Orbit by Gamma-Ray Spectroscopy, A. Metzger, in Remote Geochemical Analysis: Elemental and Mineralogical Composition, 341-366, C.M. Pieters and P.A.J. Englert, eds., Cambridge University Press, 1993.

Lunar Prospector
Fluxes of Fast and Epithermal Neutrons from Lunar Prospector: Evidence for Water Ice at the Lunar Poles, W. Feldman et al., Science, 281, 1496-1500, 1998.

Major Compositional Units of the Moon: Lunar Prospector Gamma-Ray Spectrometer, D.J. Lawrence et al., Science, 281, 1484-1489, 1998.

Mars Odyssey
Maps of Subsurface Hydrogen from the High Energy Neutron Detector, Mars Odyssey, I. Mitrofanov et al., Science, 297, 78-81, 2002.

Distribution of Hydrogen in the Near Surface of Mars: Evidence for Subsurface Ice Deposits, W.V. Boynton et al., Science, 297, 81-85, 2002.

The Mars Odyssey Gamma-Ray Spectrometer Instrument Suite, W.V. Boynton et al., Space Sciences Reviews, 110, 37-83, 2004.

 

Position Description for SPS

Dr. Jacob Trombka, of NASA Goddard Space Flight Center, leads a group of scientists, computer scientists, and engineers that design, develop, calibrate, and fly instruments on planetary missions. These instruments are used to determine the composition of planetary surfaces by measuring the X-ray, gamma-ray, and neutron fluxes from the planet. Current missions include the Mars Odyssey in orbit around Mars since 2002, the MESSENGER mission to Mercury launched in 2004, and the Lunar Reconnaissance Orbiter (LRO) to be launched in 2008.

On January 14, 2004, NASA was given the mandate for exploration activities including “a human return to the moon by the year 2020”. To achieve this vision, a series of robotic missions to the Moon are planned to prepare for human exploration. The first of these missions is the Lunar Reconnaissance Orbiter (LRO) scheduled to be launched near the end of 2008. The LRO objectives are to define those characteristics of the Moon that are needed to prepare for the safe return of humans to the Moon. From 1969 to 1972, the United States successfully landed six pairs of astronauts on the Moon and returned them safely to the Earth. What else needs to be known about the Moon for safe and eventually sustainable return? The measurement objectives of LRO will help to answer these questions and contribute to the space program’s return to the Moon.

The intern(s) will be primarily involved in supporting the Goddard co-investigators on one of the scientific instruments on the LRO mission; LEND (Lunar Energetic Neutron Detector). The goal of this instrument is to locate and map frozen water ice in the permanently showed polar craters on the Moon.

Examples of areas that the interns may be working in are summarized below:

  1. Analyze data, similar to LEND data that is being taken around Mars by the HEND (High Energy Neutron Detector) instrument on Mars Odyssey. The Planetary Data System will used to access Mars data. Test various software techniques for analyzing neutron data. Other Mars Odyssey data sets, such as the gamma-ray and laser altimeter, will be used to interpret the context for the HEND data.

 

  1. The LEND engineering unit is scheduled to arrive at Goddard in March 2007. The engineering unit is the first pre-flight unit that has all the operating characteristics of the eventual flight unit. Learn the operations of the engineering unit and analyze data taken during acceptance testing and calibration.
  1. Learn about the other instruments on LRO and how these expected results will be combined to meet the exploration objectives of the mission. In particular, interact with the members of the science and engineering team of the Lunar Orbital Laser Altimeter (LOLA), the other LRO instrument being developed at Goddard. Learn what results can be expected from LOLA and how these results can be used to map the LEND results on to the lunar surface.