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B. Rizk C. Drouet dAubigny C.W. Hergenrother B.J. Bos D.R. Golish R. Malhotra D.S. Lauretta J. Butt J. Patel M. Fitzgibbon C. May E.B. Bierhaus S. Freund M. Fisher S. Cambioni C.A. Bennett S.S. Balram-Knutson K. Harshman M. Moreau 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(1):672-691
We analyzed high-angular rate streaks first recorded by OSIRIS-REx’s MapCam during a 2017 search for Earth Trojan asteroids. We interpret them as water-ice particles that translated across the imager’s field of view, originating from the spacecraft itself. Their translation velocities approximated 0.1–1?m/s based on reasonable conclusions about their range. Pursuing several lines of investigation to seek a coherent hypothesis, we conclude that the episodic releases of the water ice particles are associated with spacecraft attitudes that resulted in solar illumination of previously shadowed regions. This correlation suggests that the OSIRIS-REx spacecraft itself possesses micro-climatic zones consisting of hot regions and cold traps that may temporarily potentially pass volatiles back and forth before losing most of them. 相似文献
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I. G. Mitrofanov A. Bartels Y. I. Bobrovnitsky W. Boynton G. Chin H. Enos L. Evans S. Floyd J. Garvin D. V. Golovin A. S. Grebennikov K. Harshman L. L. Kazakov J. Keller A. A. Konovalov A. S. Kozyrev A. R. Krylov M. L. Litvak A. V. Malakhov T. McClanahan G. M. Milikh M. I. Mokrousov S. Ponomareva R. Z. Sagdeev A. B. Sanin V. V. Shevchenko V. N. Shvetsov R. Starr G. N. Timoshenko T. M. Tomilina V. I. Tretyakov J. Trombka V. S. Troshin V. N. Uvarov A. B. Varennikov A. A. Vostrukhin 《Space Science Reviews》2010,150(1-4):183-207
The design of the Lunar Exploration Neutron Detector (LEND) experiment is presented, which was optimized to address several of the primary measurement requirements of NASA’s Lunar Reconnaissance Orbiter (LRO): high spatial resolution hydrogen mapping of the Moon’s upper-most surface, identification of putative deposits of appreciable near-surface water ice in the Moon’s polar cold traps, and characterization of the human-relevant space radiation environment in lunar orbit. A comprehensive program of LEND instrument physical calibrations is discussed and the baseline scenario of LEND observations from the primary LRO lunar orbit is presented. LEND data products will be useful for determining the next stages of the emerging global lunar exploration program, and they will facilitate the study of the physics of hydrogen implantation and diffusion in the regolith, test the presence of water ice deposits in lunar cold polar traps, and investigate the role of neutrons within the radiation environment of the shallow lunar surface. 相似文献
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I. G. Mitrofanov M. L. Litvak A. B. Varenikov Y. N. Barmakov A. Behar Y. I. Bobrovnitsky E. P. Bogolubov W. V. Boynton K. Harshman E. Kan A. S. Kozyrev R. O. Kuzmin A. V. Malakhov M. I. Mokrousov S. N. Ponomareva V. I. Ryzhkov A. B. Sanin G. A. Smirnov V. N. Shvetsov G. N. Timoshenko T. M. Tomilina V. I. Tret’yakov A. A. Vostrukhin 《Space Science Reviews》2012,170(1-4):559-582
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Mitrofanov IG Sanin AB Golovin DV Litvak ML Konovalov AA Kozyrev AS Malakhov AV Mokrousov MI Tretyakov VI Troshin VS Uvarov VN Varenikov AB Vostrukhin AA Shevchenko VV Shvetsov VN Krylov AR Timoshenko GN Bobrovnitsky YI Tomilina TM Grebennikov AS Kazakov LL Sagdeev RZ Milikh GN Bartels A Chin G Floyd S Garvin J Keller J McClanahan T Trombka J Boynton W Harshman K Starr R Evans L 《Astrobiology》2008,8(4):793-804
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
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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
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