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11.
Boynton  W.V.  Feldman  W.C.  Mitrofanov  I.G.  Evans  L.G.  Reedy  R.C.  Squyres  S.W.  Starr  R.  Trombka  J.I.  d'Uston  C.  Arnold  J.R.  Englert  P.A.J.  Metzger  A.E.  Wänke  H.  Brückner  J.  Drake  D.M.  Shinohara  C.  Fellows  C.  Hamara  D.K.  Harshman  K.  Kerry  K.  Turner  C.  Ward  M.  Barthe  H.  Fuller  K.R.  Storms  S.A.  Thornton  G.W.  Longmire  J.L.  Litvak  M.L.  Ton'chev  A.K. 《Space Science Reviews》2004,110(1-2):37-83
The Mars Odyssey Gamma-Ray Spectrometer is a suite of three different instruments, a gamma subsystem (GS), a neutron spectrometer, and a high-energy neutron detector, working together to collect data that will permit the mapping of elemental concentrations on the surface of Mars. The instruments are complimentary in that the neutron instruments have greater sensitivity to low amounts of hydrogen, but their signals saturate as the hydrogen content gets high. The hydrogen signal in the GS, on the other hand, does not saturate at high hydrogen contents and is sensitive to small differences in hydrogen content even when hydrogen is very abundant. The hydrogen signal in the neutron instruments and the GS have a different dependence on depth, and thus by combining both data sets we can infer not only the amount of hydrogen, but constrain its distribution with depth. In addition to hydrogen, the GS determines the abundances of several other elements. The instruments, the basis of the technique, and the data processing requirements are described as are some expected applications of the data to scientific problems.  相似文献   
12.
The scientific objectives of neutron mapping of the Moon are presented as 3 investigation tasks of NASA's Lunar Reconnaissance Orbiter mission. Two tasks focus on mapping hydrogen content over the entire Moon and on testing the presence of water-ice deposits at the bottom of permanently shadowed craters at the lunar poles. The third task corresponds to the determination of neutron contribution to the total radiation dose at an altitude of 50 km above the Moon. We show that the Lunar Exploration Neutron Detector (LEND) will be capable of carrying out all 3 investigations. The design concept of LEND is presented together with results of numerical simulations of the instrument's sensitivity for hydrogen detection. The sensitivity of LEND is shown to be characterized by a hydrogen detection limit of about 100 ppm for a polar reference area with a radius of 5 km. If the presence of ice deposits in polar "cold traps" is confirmed, a unique record of many millions of years of lunar history would be obtained, by which the history of lunar impacts could be discerned from the layers of water ice and dust. Future applications of a LEND-type instrument for Mars orbital observations are also discussed.  相似文献   
13.
ExoMars is a two-launch mission undertaken by Roscosmos and European Space Agency. Trace Gas Orbiter, a satellite part of the 2016 launch carries the Fine Resolution Neutron Detector instrument as part of its payload. The instrument aims at mapping hydrogen content in the upper meter of Martian soil with spatial resolution between 60 and 200 km diameter spot. This resolution is achieved by a collimation module that limits the field of view of the instruments detectors. A dosimetry module that surveys the radiation environment in cruise to Mars and on orbit around it is another part of the instrument.This paper describes the mission and the instrument, its measurement principles and technical characteristics. We perform an initial assessment of our sensitivity and time required to achieve the mission goal. The Martian atmosphere is a parameter that needs to be considered in data analysis of a collimated neutron instrument. This factor is described in a section of this paper. Finally, the first data accumulated during cruise to Mars is presented.  相似文献   
14.
Mitrofanov  I. G.  Kozyrev  A. S.  Lisov  D. I.  Litvak  M. L.  Malakhov  A. A.  Mokrousov  M. I.  Benkhoff  J.  Owens  A.  Schulz  R.  Quarati  F. 《Space Science Reviews》2021,217(5):1-47
Space Science Reviews - Volatiles and refractories represent the two end-members in the volatility range of species in any surface-bounded exosphere. Volatiles include elements that do not interact...  相似文献   
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