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排序方式: 共有322条查询结果,搜索用时 62 毫秒
61.
This paper reports on the objectives of the German space processing programme with sounding rockets and the scientific results obtained thus far. 相似文献
62.
Results on radar cross section (RCS) measurements and inverse synthetic aperture radar images of a Mooney 231 aircraft using a ground-to-air measurement system (GTAMS) and a KC-135 airplane using an airborne radar are presented. The Mooney 231 flew in a controlled path in both clockwise and counterclockwise orbits, and successively with the gear down, flaps in the take-off position and with the speed brakes up. The data indicates that RCS pattern measurements from both ground-based and airborne radar of flying aircraft are useful and that the inverse synthetic aperture radar (ISAR) images obtained are valuable for signature diagnostics 相似文献
63.
We discuss the scientific objective, instrument design, and calibration of a miniaturized Jamin-Mascart interferometer which is to perform an accurate measurement of the refractive index of the Jovian atmosphere in the pressure range 2.5 to 10 bar. The instrument is to perform this measurement in December 1995 aboard the entry probe of the NASA Galileo spacecraft. From the data obtained the mole fraction of helium in the atmosphere of Jupiter is to be calculated with an estimated uncertainty of ± 0.0015. The instrument has a total mass of 1.4 kg and consumes 0.9 W of electrical power. 相似文献
64.
N. Panafidina U. Hugentobler H. Krásná R. Schmid M. Seitz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(1):51-62
Within the analysis of space geodetic observations, errors of the applied subdaily Earth rotation model can induce systematic effects in different estimated parameters. In this paper, we focus on the impact of the subdaily Universal Time (UT1) model on the celestial pole offsets (CPO) estimated from very long baseline interferometry (VLBI) observations. We provide a mechanism that describes the error propagation from the subdaily UT1 into the daily CPO.In typical 24-h VLBI sessions the observed quasars are well distributed over the sky. But the observations, if looked at from the Earth-fixed frame, are not homogeneously distributed. The amount of observations performed in different terrestrial directions shows an irregularity which can be roughly compared to the case where the observations are collected in only one Earth-fixed direction. This peculiarity leads to artefacts in VLBI solutions, producing a correlation between the subdaily variations in UT1 and the position of the celestial pole. As a result errors in diurnal terms of the subdaily UT1 model are partly compensated by the estimated CPO. We compute for each 24-h VLBI session from 1990 until 2011 the theoretical response of the CPO to an error in the subdaily UT1 by setting up a least-squares adjustment model and using as input the coordinates of the observed quasars and observation epochs. Then real observed response of the estimated CPO derived from the VLBI session solutions is compared to the predicted one. A very good agreement between the CPO values estimated from VLBI and the predicted values was achieved. The presented model of error propagation from the subdaily UT1 into the daily CPO allows to predict and explain the behaviour of CPO estimates of VLBI solutions computed with different subdaily Earth rotation models, what can be helpful for testing the accuracy of different subdaily tidal models. 相似文献
65.
M R Sims C T Pillinger I P Wright J Dowson S Whitehead A Wells J E Spragg G Fraser L Richter H Hamacher A Johnstone N P Meredith C de la Nougerede B Hancock R Turner S Peskett A Brack J Hobbs M Newns A Senior M Humphries H U Keller N Thomas J S Lingard T C Ng 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1999,23(11):1925-1928
The aim of the proposed Beagle 2 small lander for ESA's 2003 Mars Express mission is to search for organic material on and below the surface of Mars and to study the inorganic chemistry and mineralogy of the landing site. The lander will have a total mass of 60kg including entry, descent, and landing system. Experiments will be deployed on the surface using a robotic arm. It will use a mechanical mole and grinder to obtain samples from below the surface, under rocks, and inside rocks. Sample analysis by a mass spectrometer will include isotopic analysis. An optical microscope, an X-ray spectrometer and a Mossbauer spectrometer will conduct in-situ rock studies. 相似文献
66.
J.P. Pabari Y.B. Acharya U.B. Desai S.N. Merchant 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
It is known that a wireless sensor network uses some sort of sensors to detect a physical quantity of interest, in general. The wireless sensor network is a potential tool for exploring the difficult-to-access area on the earth and the concept may be extended to space applications in future. Recently, lunar water has been detected by a few lunar missions using remote sensing techniques. The lunar water is expected to be in the form of ice at very low temperatures of permanently dark regions on the moon. To support the remote observations and also to find out potential ice bearing sites on the moon, in-situ measurement of the lunar ice is essential. However, a rover may not be able to reach the permanently shadowed regions due to terrain irregularity. One possibility to access such areas is to use a wireless sensor network on the lunar surface. 相似文献
67.
Shailendra S. Srivastava N.K. Vyas Jagdish Rai B. Kartikeyan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009,44(9):1058-1066
Rayleigh optical depth is an integral part of many radiative transfer problems. This paper discusses different elements and approaches of its determination. Then, it presents a method, which ensures more realistic estimate of Rayleigh optical depth by using refractive index and depolarization factor (including rotational Raman lines) adjusted according to the state and composition of the atmosphere. It is based on the published experimental and theoretical results. The Rayleigh optical depth calculations are compared with the Elterman’s model calculations for trend analysis purpose. Rayleigh optical depths are found to be around 3.4% lower than previous researchers, as they ignored the constraints of conservation of angular momentum in the rotational/vibrational transitions of the molecules during scattering. 相似文献
68.
The relationship between proton aurora and geomagnetic pulsations Pc1, which are an indicator of development of ion-cyclotron instability in the equatorial magnetosphere, are studied on the basis of the observations of proton aurora from the IMAGE satellite, observations of particle fluxes onboard the low-orbiting NOAA satellites, and geomagnetic pulsation observations at the Lovozero observatory. A conclusion is drawn that the subauroral spots in the proton emission projected into the magnetosphere near the plasmapause are two-dimensional images at the ionospheric “screen” of the region of intense scattering of energetic protons into the loss cone at the development of an ion-cyclotron instability. 相似文献
69.
U. von Zahn V.I. Moroz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1985,5(11):173-195
Our current knowledge on the composition of the Venus atmosphere in the altitude range from the surface to 100 km is compiled. Gases that have been measured, and whose mixing ratios are assumed to be constant with altitude, are CO2, N2, He, Ne, Ar, and Kr. Gases that have been identified in the lower and/or middle atmosphere, but whose mixing ratios may depend on altitude, latitude and/or local time, are CO, H2O, HCl, HF, and SO2. Conflicting data or only upper limits exist on some important trace gases, such as O2, H2, and Cl2. The latter two are key constituents in the photochemistry of the middle atmosphere of Venus. The chapter concludes with a listing of the isotopic abundances of elements measured in the Venus atmosphere. 相似文献
70.
U. Hellden 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(11):165-168
A study of aerial photography from 1962 and satellite data from later periods did not indicate any evidence for a continuous Sahara desert movement southwards, large shifts in land system borders, southward sand and dune complex encroachment or systematic growth of village “desert patches”. A study of the potential of a transformed normalized difference green leaf density vegetation indicator for drought impact and green biomass monitoring is in progress. 相似文献