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Muriel Bergé-Nguyen Jean-François Cretaux Stéphane Calmant Sarah Fleury Rysbek Satylkanov D. Chontoev Pascal Bonnefond 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(3):985-1001
Lake water height is a key variable in water cycle and climate change studies, which is achievable using satellite altimetry constellation. A method based on data processing of altimetry from several satellites has been developed to interpolate mean lake surface (MLS) over a set of 22 big lakes distributed on the Earth. It has been applied on nadir radar altimeters in Low Resolution Mode (LRM: Jason-3, Saral/AltiKa, CryoSat-2) in Synthetic Aperture Radar (SAR) mode (Sentinel-3A), and in SAR interferometric (SARin) mode (CryoSat-2), and on laser altimetry (ICESat). Validation of the method has been performed using a set of kinematic GPS height profiles from 18 field campaigns over the lake Issykkul, by comparison of altimetry’s height at crossover points for the other lakes and using the laser altimetry on ICESat-2 mission. The precision reached ranges from 3 to 7 cm RMS (Root Mean Square) depending on the lakes. Currently, lake water level inferred from satellite altimetry is provided with respect to an ellipsoid. Ellipsoidal heights are converted into orthométric heights using geoid models interpolated along the satellite tracks. These global geoid models were inferred from geodetic satellite missions coupled with absolute and regional anomaly gravity data sets spread over the Earth. However, the spatial resolution of the current geoid models does not allow capturing short wavelength undulations that may reach decimeters in mountaineering regions or for rift lakes (Baikal, Issykkul, Malawi, Tanganika). We interpolate in this work the geoid height anomalies with three recent geoid models, the EGM2008, XGM2016 and EIGEN-6C4d, and compare them with the Mean Surface of 22 lakes calculated using satellite altimetry. Assuming that MLS mimics the local undulations of the geoid, our study shows that over a large set of lakes (in East Africa, Andean mountain and Central Asia), short wavelength undulations of the geoid in poorly sampled areas can be derived using satellite altimetry. The models used in this study present very similar geographical patterns when compared to MLS. The precision of the models largely depends on the location of the lakes and is about 18 cm, in average over the Earth. MLS can serve as a validation dataset for any future geoid model. It will also be useful for validation of the future mission SWOT (Surface Water and Ocean Topography) which will measure and map water heights over the lakes with a high horizontal resolution of 250 by 250 m. 相似文献
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This paper explores and compares the perceptions of the risks associated with Mars Sample Return (MSR) among schoolchildren and adults. Comparable surveys were constructed and administered to two sample groups; science students aged 11–15 and adults with an interest in science aged 18 and over. Contingency table analyses were used to quantify any differences in perception between the two groups. Schoolchildren were less likely to consider Mars exploration to be quite or very useful (44.7% vs. 68.9%; p=0.005) and recorded significantly higher levels of risk perception regarding both a MSR mission and also towards other societal risks. These results have important implications for policy-makers, as they can inform education programs now that will enhance the viability and public support for future missions. 相似文献
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Sarah Jane Pell Anna Barbara Imhof Christian Waldvogel J. Michelle Kotler Marko Peljhan 《Acta Astronautica》2014
The arts offer alternative insights into reality, which are explored by science in general, and broadened by the activities conducted by the European Space Agency [4] and other space agencies. Similar to the way the members of ESA are ambassadors for spaceflight and science, artists and cultural professionals are ambassadors for human expression, experimentation, and exploration. In June 2011, the ESA Topical Team Arts and Sciences (ETTAS) held a three-day workshop at the European Astronaut Centre in Cologne, Germany. During this workshop, topics and ideas were discussed to develop initiatives between the arts, sciences and ESA. The aim was to foster and expand the human and cultural aspects of space exploration, and at the same time offer a means of communication that aims to reach audiences beyond the scope of traditional space-related channels. The consensus of the team was that establishing and sustaining a transdisciplinary professional community consisting of ESA representatives, scientists and artists would fuel knowledge transfer, and mutual inspiration. Potential ways to provide a sustainable cooperation within and between the various groups were discussed. We present the preliminary findings including a number of measures and mechanisms to initiate and conduct such an initiative. Plausible organisational measures, procedures and consequences, as well as a proposition on how to proceed are also discussed. Overall, the involvement and cooperation between the arts, space science research and ESA will enhance in the citizens of the ESA member states the sense of public ownership of ESA results, and participation in ESA?s research. 相似文献
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Sarah Lee Lippincott 《Space Science Reviews》1978,22(2):153-189
Unseen companions to nearby stars are found astrometrically through perturbations in the proper motion from photographs taken with long-focus telescopes. The number of known unseen astrometric companions to nearby stars with photocentric orbits has grown by thirty percent in the last few years. Individual cases are discussed and optimum epochs given for resolution of the components. Orbital analysis of the photocentric positions on the photographic plates provides all information for accurate mass determination of the components except for m and angular separation, , of the two components which must come from another technique. There are potentially thirty low luminosity stars including some likely sub-stellar objects whose masses could be instantly found with the observations of these additional two parameters.A list of the stars known within five parsecs as of 1978 July is given and the status of unseen companions to these stars is discussed on the basis of long interval astrometric coverage. 相似文献
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Sarah M. Cook Dale A. Lawrence 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(9):2696-2705
The heliogyro solar sail employs high aspect ratio blades that are rigidized by spinning about the central spacecraft, eliminating the need for structural booms typically used to tension traditional square sails. The easily scalable heliogyro gains its maneuverability by actuating the blades at their root with sinusoidal pitch profiles. The blade vibration caused by maneuvering must be attenuated using active control since there is little inherent damping in the blade material. Due to the small root pitch control torques required, on the order of 2 µNm, compared to the large friction torques associated with a root pitch actuator, it has only recently been shown that a single blade heliogyro impedance controller can add damping to the lowest frequency torsional modes of the blade in the presence of modeled actuator friction torques. However, the need to measure blade twist away from the actuator at the root creates a non-collocated control system. Some inherent damping at the blade’s higher frequency modes is therefore needed to stably add damping to the larger-magnitude low-frequency modes, hence control design is sensitive to the accuracy of the blade damping model. Recently, damping characterization tests performed on a small-scale heliogyro blade in a high-vacuum chamber invalidated the assumption of a linear viscous torsional blade damping model that was previously used in blade control designs. This paper describes the formulation of three modal damping models based on the new experimental data and their integration into the single blade heliogyro model. A comparison of the robustness and performance envelopes for the baseline proximal blade twist feedback controller using these damping models shows the ability to meet the required settling time of less than 720 s necessary for a heliogyro technology demonstration mission. This comparison of physically realizable root pitch control systems for a heliogyro blade is critical to increasing the sailcraft to Technology Readiness Level three. 相似文献
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Guhathakurta Madhullika Sittler Ed Fisher Richard Kucera Theresa Gibson Sarah McComas Dave Skoug Ruth 《Space Science Reviews》2001,97(1-4):45-50
The large-scale coronal magnetic fields of the Sun are believed to play an important role in organizing the coronal plasma
and channeling the high and low speed solar wind along the open magnetic field lines of the polar coronal holes and the rapidly
diverging field lines close to the current sheet regions, as has been observed by the instruments aboard the Ulysses spacecraft from March 1992 to March 1997. We have performed a study of this phenomena within the framework of a semi-empirical
model of the coronal expansion and solar wind using Spartan, SOHO, and Ulysses observations during the quiescent phase of the solar cycle. Key to this understanding is the demonstration that the white
light coronagraph data can be used to trace out the topology of the coronal magnetic field and then using the Ulysses data to fix the strength of the surface magnetic field of the Sun. As a consequence, it is possible to utilize this semi-empirical
model with remote sensing observation of the shape and density of the solar corona and in situ data of magnetic field and
mass flux to predict values of the solar wind at all latitudes through out the solar system. We have applied this technique
to the observations of Spartan 201-05 on 1–2 November, 1998, SOHO and Ulysses during the rising phase of this solar cycle and speculate on what solar wind velocities Ulysses will observe during its polar passes over the south and the north poles during September of 2000 and 2001. In order to do
this the model has been generalized to include multiple streamer belts and co-located current sheets. The model shows some
interesting new results.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Charles E. Schlemm II Richard D. Starr George C. Ho Kathryn E. Bechtold Sarah A. Hamilton John D. Boldt William V. Boynton Walter Bradley Martin E. Fraeman Robert E. Gold John O. Goldsten John R. Hayes Stephen E. Jaskulek Egidio Rossano Robert A. Rumpf Edward D. Schaefer Kim Strohbehn Richard G. Shelton Raymond E. Thompson Jacob I. Trombka Bruce D. Williams 《Space Science Reviews》2007,131(1-4):393-415
NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission will further the understanding of
the formation of the planets by examining the least studied of the terrestrial planets, Mercury. During the one-year orbital
phase (beginning in 2011) and three earlier flybys (2008 and 2009), the X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft
will measure the surface elemental composition. XRS will measure the characteristic X-ray emissions induced on the surface
of Mercury by the incident solar flux. The Kα lines for the elements Mg, Al, Si, S, Ca, Ti, and Fe will be detected. The 12°
field-of-view of the instrument will allow a spatial resolution that ranges from 42 km at periapsis to 3200 km at apoapsis
due to the spacecraft’s highly elliptical orbit. XRS will provide elemental composition measurements covering the majority
of Mercury’s surface, as well as potential high-spatial-resolution measurements of features of interest. This paper summarizes
XRS’s science objectives, technical design, calibration, and mission observation strategy. 相似文献
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