首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Lunar swirls are optically bright, sinuous albedo features found on the Moon. The Mini-RF synthetic aperture radar on the Lunar Reconnaissance Orbiter has provided a comprehensive set of X- and S-Band radar images of these enigmatic features, including the first radar observations of swirls on the farside of the Moon. A few general remarks can be made about the nature of the lunar swirls from this data set. First, the average radar properties of lunar swirls are identical to nearby non-swirl regions, in both total radar backscatter and circular polarization ratio (CPR). This implies that average centimeter-scale roughness and composition within the high-albedo portions of the swirls do not differ appreciably from the surroundings, and that the high optical reflectance of the swirls is related to a very thin surface phenomenon (less than several decimeters thick) not observable with X- or S-Band radar. Secondly, bright swirl material appears to be stratigraphically younger than a newly discovered impact melt flow at Gerasimovich D. This observation indicates that the swirls are capable of forming over timescales less than the age of the crater. The Mini-RF data set also provides clues to the origin of the lunar swirls. In at least one case, the presence of an enhanced crustal magnetic field appears to be responsible for the preservation of a high-albedo ejecta blanket around an otherwise degraded crater, Descartes C. The degree of degradation of Descartes C suggests it should not be optically bright, yet it is. This implies that the enhanced albedo is related to its location within a magnetic anomaly, and hence supports an origin hypothesis that invokes interaction between the solar wind and the magnetic anomaly.  相似文献   

2.
Doppler tracking data from the Lunar Orbiter series of spacecraft have been used in a more complete analysis of the spherical harmonic coefficients of the lunar gravitational field through thirteenth degree and order. The value obtained for the mass of the Moon,GM = 4902.84 km3 s–2, is in good agreement with previous results and with results obtained by alternate procedures. Acceleration contour plots, derived from the gravitational coefficients, show correlations with surface features on the near side of the Moon, but are of questionable validity for the far side because of the lack of direct tracking data on the far side. Based on the most recent gravitational field data, the current estimate for the polar moment of inertia of the Moon isC/Ma 2 = 0.4019-0.002 +0.004. This value indicates that the interior of the Moon can be homogeneous, but some results presented strongly suggest that the Moon is differentiated, with an excess of mass in the direction toward the Earth.Paper presented at the NATO Advanced Study Institute on Lunar Studies, Patras, Greece, September, 1971.  相似文献   

3.
Side-looking spacecraft radar imagery has thus far been produced only from an orbit around the Moon. This was a part of the Apollo Lunar Sounder Experiment (ALSE) of the Apollo 17 mission in December, 1972. This paper reports results of a radargrammetric evaluation of overlapping Apollo 17 synthetic aperture radar images (wavelength 2 m). The potential to map from single images and to reconstruct 3D stereoscopic models is studied. The relative height accuracy achieved is about ± 100 m and is thus competitive with that obtained with the vidicon camera that is presently used for planetary exploration.NAS-NRC Resident Research Associate.  相似文献   

4.
An overview of radiophysical investigations of the lunar soil and plasma shell by active radar detection with the use of spacecraft is presented. The possibility is analyzed of conducting bistatic measurements using the Irkutsk Incoherent Scattering Radar and the onboard radar system RLK-L which is being developed for the orbital station of the Luna-Resurs mission.  相似文献   

5.
Lunar radar mappings carried out in the late 1960's and 1970's have provided several valuable insights into lunar surface processes. These radar mappings used the delay-Doppler technique developed by Gordon Pettengill and his colleagues. These radar mappings also needed the narrow antenna beams, now available with large radio telescopes such as those at the Arecibo and Haystack Observatories. Two-element radar interferometers have provided resolution of the delay-Doppler ambiguity at meter wavelengths and provided topographic information at centimeter wavelengths. These techniques have provided high-resolution lunar radar-maps at 3.8-cm, 70-cm, and 7.5-m wavelengths, a set of wavelengths which span the window available for Earth-based radar mapping of the Moon.These radar maps have been used along with other Earth-based and Apollo orbital measurements to define surface units. The radar maps and these other data can describe physical properties such as small-scale (centimeter sized) blockiness and surface chemistry (titanium and iron) content. These estimates of lunar surface properties rely heavily upon extrapolation of surface sampling results.Presented at the IAU-COSPAR Julian Schmidt Symposium on 100 Years of Lunar Mapping held at Lagonissi, Greece, 25–27 May, 1978.  相似文献   

6.
Boulder tracks from 19 different locations on the Moon, observable in Lunar Orbiter photographs, have been examined. Measurements of the track width indicate that some of the boulders sank considerably deeper than others. It is suggested that lunar surface materials vary from place to place; the state of compaction (density of lunar soil) is probably one of the significant variables. Using bearing capacity theory, modified to be applicable to the rolling boulder problem by theoretical studies and extensive testing, the friction angle of the lunar soil was estimated. Most of the results were between 24 and 47 degrees with an arithmetic average of 37 degrees. These values suggest corresponding density variations of 1.25 to 2.00 g/cm3.  相似文献   

7.
Lunar rilles and Hawaiian volcanic features: Possible analogues   总被引：1，自引：0，他引：1  
In this paper we consider the origin of rilles on the lunar maria, both sinuous and those having straight line segments, from the point of view of lava tubes formed in surface lava flows, and also in terms of collapses along active fissures. Terrestrial examples of tube formation and collapse, as well as the large-scale collapse of a chain of craters built over an active fissure were observed on the Island of Hawaii by the writers and serve as the basis of comparison with lunar topography shown on Orbiter photographs of the Moon. We also consider the origin of apparent flow channels on steep slopes on the Moon, and conclude that these are often related to early stages in the formation of covered lava tubes.Paper presented to the NATO Advanced Study Institute on Lunar Studies, Patras, Greece, September, 1971.  相似文献   

8.
Age of geological units, surface mineralogical composition, volcanism, tectonics and cratering are major keys for unravelling the geodynamic and geological history of a planet. Thanks to the extensive exploration of the 1960s and 1970s and the compositional mapping of the 1990s missions (Galileo, Clementine and Luna Prospector), the Moon has a unique geological dataset among the extraterrestrial Solar System bodies. The recent and on-going missions, along with the future plans for lunar exploration, will together acquire an extraordinary amount of data. This should provide a solid basis to meet broad objectives like the constraints on the heterogeneity of Lunar composition and the presence of water deposits, the understanding of volcanic and tectonic evolution as well as more specific issues such as the genetic classification of volcanic domes, origin of the dark-halos craters, lava flow emplacement mechanisms, and the kinematics and deformational styles of tectonic structures. The Italian small mission MAGIA (Missione Altimetrica Gravimetrica geochImica lunAre) will be equipped with an integrated context camera and imaging spectrometer, a high resolution camera and a radar altimeter. The spatial and spectral resolution of these instruments will provide data products complementing past and ongoing Lunar mission data, particularly for the polar regions where a full resolution coverage is planned. A general review of some still unanswered questions on lunar surface composition, cold traps, volcanism, tectonics and cratering records is presented here in order to illustrate the potential contribution of MAGIA to these subjects.  相似文献   

9.
The Apollo Lunar Sounder Experiment that is scheduled to orbit the Moon on Apollo 17 consists of a three frequency coherent radar system and an optical recorder. The coherent radar can be used to measure both phase and amplitude characteristics of the radar echo. Measurement methods that are related to the phase and amplitude will be used to determine the surface profile, locate subsurface features and ascertain near surface electrical properties of the lunar surface. The key to the coherent radar measurement is a highly stable oscillator that preserves an accurate phase reference (2 or 3 electrical degrees) over a long period of time. This reference provides a means for reducing surface clutter so that subsurface features are more easily detected and also provides a means of measuring range to the surface to within a fraction of a wavelength.  相似文献   

10.
In 1970, the Soviet Lunokhod 1 rover delivered a French-built laser reflector to the Moon. Although a few range measurements were made within three months of its landing, these measurements—and any that may have followed—are unpublished and unavailable. The Lunokhod 1 reflector was, therefore, effectively lost until March of 2010 when images from the Lunar Reconnaissance Orbiter (LRO) provided a positive identification of the rover and determined its coordinates with uncertainties of about 100 m. This allowed the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) to quickly acquire a laser signal. The reflector appears to be in excellent condition, delivering a signal roughly four times stronger than its twin reflector on the Lunokhod 2 rover. The Lunokhod 1 reflector is especially valuable for science because it is closer to the Moon’s limb than any of the other reflectors and, unlike the Lunokhod 2 reflector, we find that it is usable during the lunar day. We report the selenographic position of the reflector to few-centimeter accuracy, comment on the health of the reflector, and illustrate the value of this reflector for achieving science goals.  相似文献   

11.
The European SMART-1 mission to the Moon, primarily a testbed for innovative technologies, was launched in September 2003 and will reach the Moon in 2005. On board are several scientific instruments, including the point-spectrometer SMART-1 Infrared Spectrometer (SIR). Taking into account the capabilities of the SMART-1 mission and the SIR instrument in particular, as well as the open questions in lunar science, a selection of targets for SIR observations has been compiled. SIR can address at least five topics: (1) Surface/regolith processes; (2) Lunar volcanism; (3) Lunar crust structure; (4) Search for spectral signatures of ices at the lunar poles; and (5) Ground truth and study of geometric effects on the spectral shape. For each topic we will discuss specific observation modes, necessary to achieve our scientific goals. The majority of SIR targets will be observed in the nadir-tracking mode. More than 100 targets, which require off-nadir pointing and off-nadir tracking, are planned. It is expected that results of SIR observations will significantly increase our understanding of the Moon. Since the exact arrival date and the orbital parameters of the SMART-1 spacecraft are not known yet, a more detailed planning of the scientific observations will follow in the near future.  相似文献   

12.
There are many surface units in Mare Serenitatis and in the adjacent Montes Haemus that can be defined by remote, Earth-based observations at visual, infrared, and radar wavelengths. These highland and mare surface units are obvious in color-difference photographs and in radar images, while the infrared images have little or no differences. These characteristics are consistent with units having definite chemical differences. However, a better definition of these surfaces requires the synthesis of many more data sets.Paper presented at the Lunar Science Institute Conference on Geophysical and Geochemical Exploration of the Moon and Planets, January 10–12, 1973.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7–100, sponsored by the National Aeronautics and Space Administration.  相似文献   

13.
The D-CIXS X-ray spectrometer on ESA's SMART-1 mission will provide the first global coverage of the lunar surface in X-rays, providing absolute measurements of elemental abundances. The instrument will be able to detect elemental Fe, Mg, Al and Si under normal solar conditions and several other elements during solar flare events. These data will allow for advances in several areas of lunar science, including an improved estimate of the bulk composition of the Moon, detailed observations of the lateral and vertical nature of the crust, chemical observations of the maria, investigations into the lunar regolith, and mapping of potential lunar resources. In combination with information to be obtained by the other instruments on SMART-1 and the data already provided by the Clementine and Lunar Prospector missions, this information will allow for a more detailed look at some of the fundamental questions that remain regarding the origin and evolution of the Moon.  相似文献   

14.
This paper presents a definition study of a laser altimeter for the topographic exploration of Mercury. The reference scenario is the BepiColombo mission, a cornerstone mission of European Space Agency (ESA) planned for 2012. BepiColombo will offer the chance to make a remarkable new contribution to our knowledge of the Solar System, by venturing into the hot region near the Sun and exploring Mercury, the most enigmatic of the earth's sisters among the terrestrial planets. First images of Mercury surface were acquired by Mariner 10 in 1974 and 1975 offering a coverage and resolution comparable to Earth-based telescopic coverage of the Moon before spaceflight. BepiColombo mission can be very beneficial by using an optical rangefinder for Mercury exploration. In fact starting from the first missions in 1970s until today, laser altimeters have been demonstrating to be particularly appropriate as part of the scientific payload whenever the topography of earth, lunar and planetary surface is the scientific objective of a space mission.Our system design is compliant to Mercury Polar Orbiter (MPO) of the mission. System performance analysis is carried out simulating main hermean topographic features and the potential targets on the planet by means of analytical models and computer codes and several plot are presented to analyse the performance of the instrument.  相似文献   

15.
The paper describes the lunar ephemeris EPM-ERA 2012. It is a part of the Ephemerides of Planets and the Moon (EPM) developed at the Institute of Applied Astronomy (IAA) of the Russian Academy of Sciences (RAS). In order to construct EPM-ERA 2012, 17580 lunar laser ranging (LLR) observations for 1970–2012 have been processed including 21 observations from the Lunokhod 1 reflector found by the Lunar Reconnaissance Orbiter (LRO) at the end of 2010. EPM-ERA 2012 is compared with American ephemerides DE403, DE405, DE421 ephemeris, and the French ephemeris INPOP10. The possibility of the use of the ephemeris EPM-ERA 2012 to address contemporary problems of ephemeris astronomy is considered.  相似文献   

16.
Preparing for future human exploration of the Moon and beyond is an interdisciplinary exercise, requiring new technologies and the pooling of knowledge and expertise from many scientific areas. The European Space Agency is working to develop a Lunar Lander, as a precursor to future human exploration activities. The mission will demonstrate new technologies and perform important preparatory investigations. In the biological sciences the two major areas requiring investigation in advance of human exploration are radiation and its effects on human physiology and the potential toxicity of lunar dust. This paper summarises the issues associated with these areas and the investigations planned for the Lunar Lander to address them.  相似文献   

17.
There is a growing body of evidence that points to the survival of water or hydrous minerals on the Moon and the potential for large aqueous reservoirs in shadowed craters at the lunar poles. CheMin, an XRD/XRF instrument that is currently under development, could provide a definitive test of whether the polar hydrogen signal measured by the recent Lunar Prospector mission is an indication of a significant water reservoir or merely reflects an anomalously rich accumulation of solar-wind hydrogen. Proposed enhancements of CheMin could be used in conjunction with a drilling system capable of penetrating the upper few tens of centimeters of the lunar regolith to search for ices or hydrous minerals. This advanced version of the CheMin instrument would be within the size, mass, and power constraints of Ariane 5 micromissions.  相似文献   

18.
The volume FeO and TiO_2 abundances(FTAs) of lunar regolith can be more important for understanding the geological evolution of the Moon compared to the optical and gamma-ray results. In this paper, the volume FTAs are retrieved with microwave sounder(CELMS) data from the Chang'E-2 satellite using the back propagation neural network(BPNN) method. Firstly, a three-layered BPNN network with five-dimensional input is constructed by taking nonlinearity into account. Then, the brightness temperature(TB) and surface slope are set as the inputs and the volume FTAs are set as the outputs of the BPNN network.Thereafter, the BPNN network is trained with the corresponding parameters collected from Apollo, Luna,and Surveyor missions. Finally, the volume FTAs are retrieved with the trained BPNN network using the four-channel TBderived from the CELMS data and the surface slope estimated from Lunar Orbiter Laser Altimeter(LOLA) data. The rationality of the retrieved FTAs is verified by comparing with the Clementine UV-VIS results and Lunar Prospector(LP) GRS results. The retrieved volume FTAs enable us to re-evaluate the geological features of the lunar surface. Several important results are as follows. Firstly, very-low-Ti(1.5 wt.%) basalts are the most spatially abundant, and the surfaces with TiO_2 5 wt.% constitute less than 10% of the maria. Also, two linear relationships occur between the FeO abundance(FA) and the TiO_2 abundance before and after the threshold, 16 wt.% for FA. Secondly, a new perspective on mare volcanism is derived with the volume FTAs in several important mare basins, although this conclusion should be verified with more sources of data. Thirdly, FTAs in the lunar regolith change with depth to the uppermost surface,and the change is complex over the lunar surface. Finally, the distribution of volume FTAs hints that the highlands crust is probably homogeneous, at least in terms of the microwave thermophysical parameters.  相似文献   

19.
Illumination conditions of the lunar polar regions using LOLA topography   总被引：3，自引：0，他引：3  
E. Mazarico  G.A. Neumann  M.T. Zuber 《Icarus》2011,211(2):1066-1081
We use high-resolution altimetry data obtained by the Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter to characterize present illumination conditions in the polar regions of the Moon. Compared to previous studies, both the spatial and temporal extent of the simulations are increased significantly, as well as the coverage (fill ratio) of the topographic maps used, thanks to the 28 Hz firing rate of the five-beam instrument. We determine the horizon elevation in a number of directions based on 240 m-resolution polar digital elevation models reaching down to ∼75° latitude. The illumination of both polar regions extending to ∼80° can be calculated for any geometry from those horizon longitudinal profiles. We validated our modeling with recent Lunar Reconnaissance Orbiter Wide-Angle Camera images. We assessed the extent of permanently shadowed regions (PSRs, defined as areas that never receive direct solar illumination), and obtained total areas generally larger than previous studies (12,866 and 16,055 km2, in the north and south respectively). We extended our direct illumination model to account for singly-scattered light, and found that every PSR does receive some amount of scattered light during the year. We conducted simulations over long periods (several 18.6-years lunar precession cycles) with a high temporal resolution (6 h), and identified the most illuminated locations in the vicinity of both poles. Because of the importance of those sites for exploration and engineering considerations, we characterized their illumination more precisely over the near future. Every year, a location near the Shackleton crater rim in the south polar region is sunlit continuously for 240 days, and its longest continuous period in total darkness is about 1.5 days. For some locations small height gains (∼10 m) can dramatically improve their average illumination and reduce the night duration, rendering some of those particularly attractive energy-wise as possible sites for near-continuous sources of solar power.  相似文献   

20.
  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号