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941.
Bertiger W.I. Lichten S.M. Katsigris E.C. 《Aerospace and Electronic Systems Magazine, IEEE》1989,4(2):16-25
High-accuracy orbits have been determined for satellites of the Global Positioning System (GPS), with submeter orbit accuracy demonstrated for two well-tracked satellites. Baselines of up to 2000 km in North America determined with the GPS orbits shows daily repeatability of 0.3-2 parts in 108 and agree with very long baseline interferometry (VLBI) solutions at the level of 1.5 parts in 10 8. Tests used to assess orbit accuracy include orbit repeatability from independent data sets, orbit prediction, ground baseline determination, and formal errors. One satellite tracked for eight hours each day shows RMS errors below 1 m even when predicted more than three days outside of a 1-week data arc. These results demonstrate the powerful relative positioning capability available from differential GPS tracking. Baselines have also been estimated between Florida and sites in the Caribbean region over 1000 km away, with daily repeatability of 1-4 parts in 108. The best orbit estimation strategies included data arcs of 1-2 weeks, process noise models for tropospheric fluctuations, combined processing of GPS carrier phase and pseudorange data, and estimation of GPS solar pressure coefficients 相似文献
942.
The results of an analysis of velocity fluctuations in the plasma sheet of the Earth's magnetotail measured onboard INTERBALL Tail Probe satellite are presented. The hodographs of the velocity in directions (Y, Z) and correlation functions are presented for a number of passages when the satellite was in the plasma sheet for a long time. The turbulent diffusion coefficients are calculated. A comparison of the obtained diffusion coefficients with those predicted theoretically in [1] is carried out. It is shown that the results of observations confirm theoretical predictions. 相似文献
943.
Eduard V. Vashenyuk Yury V. Balabin Leonty I. Miroshnichenko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(6):926-935
In this study we applied again to the outstanding solar particle event of 23 February 1956, the largest one in the entire history of observations of solar cosmic rays. Due to significant improvement of the analysis/modeling techniques and new understanding of physical processes in the solar atmosphere and interplanetary space, a possibility arises to interpret the old data in the light of modern concept of multiple particle acceleration at/near the Sun. In our new analysis the data of available then neutron monitors and muon telescopes are used. The technique of the analysis includes: (a) calculation of asymptotic cones of ground-based detectors; (b) modeling of cosmic ray detector responses at variable parameters of the flux of solar relativistic protons; (c) determination of primary solar proton parameters outside magnetosphere by comparison of computed responses with observations. Certain evidence was obtained that the flux of relativistic solar protons consisted of two distinct components: prompt and delayed ones. The prompt component with exponential energy spectrum caused a giant impulse-like increase at a number of European cosmic ray stations. The delayed component had a power-law spectrum and was a cause of gradual increase at cosmic ray stations in the North American region. A numerical simulation of the proton acceleration in the vicinity of the magnetic reconnection region brings to the proton spectrum with exponential dependence on energy. This agrees with observational data for the prompt component. It is also shown that the huge increase in ∼5000% on neutron monitors was due to the prompt component only with the exponential proton spectrum. The power-law spectrum of comparable intensity gave considerably smaller effect. 相似文献
944.
L.S. Novikov V.N. MileevK.K. Krupnikov A.A. MakletsovB.V. Marjin M.O. RjazantsevaV.V. Sinolits N.A. Vlasova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The results of magnetospheric plasma fluxes measurement in geosynchronous orbit are presented. The measurements were done onboard the geosynchronous Russian “Electro” spacecraft (SC) in 1995–1997 years. The diurnal variations of the plasma density and temperature were observed at various levels of geomagnetic activity. 相似文献
945.
A method of elimination of relative secular drifts in satellite formations is suggested for the case of influence of a perturbation
due to polar oblateness of the Earth. The method is applied to eliminate relative secular drifts in the case when a satellite
is controlled using an engine mounted along its orientation axis (the satellite is supplied with a passive magnetic attitude
control system) and with the help of a solar sail installed on one of the satellites. Analytical results are confirmed by
numerical simulation. 相似文献
946.
The paper contains the photometric and polarimetric analysis of the sky background near the zenith during the twilights and
the nights of different years and seasons. The period of enhanced tropospheric aerosol content during the summer 2009 is noticed.
The aerosol scattering of solar emission is separated from the total twilight sky background, and similar data on lunar emission
is taken from the night sky background. The results are compared with the data of relatively clear troposphere of winter 2006.
The observational data are used to construct the polarization scattering function of tropospheric aerosol particles during
the nighttime. 相似文献
947.
J. G. Trotignon J. L. Michau D. Lagoutte M. Chabassière G. Chalumeau F. Colin P. M. E. Décréau J. Geiswiller P. Gille R. Grard T. Hachemi M. Hamelin A. Eriksson H. Laakso J. P. Lebreton C. Mazelle O. Randriamboarison W. Schmidt A. Smit U. Telljohann P. Zamora 《Space Science Reviews》2007,128(1-4):713-728
The main objective of the Mutual Impedance Probe (MIP), part of the Rosetta Plasma Consortium (RPC), is to measure the electron
density and temperature of Comet 67P/Churyumov-Gerasimenko’s coma, in particular inside the contact surface. Furthermore,
MIP will determine the bulk velocity of the ionised outflowing atmosphere, define the spectral distribution of natural plasma
waves, and monitor dust and gas activities around the nucleus. The MIP instrumentation consists of an electronics board for
signal processing in the 7 kHz to 3.5 MHz range and a sensor unit of two receiving and two transmitting electrodes mounted
on a 1-m long bar. In addition, the Langmuir probe of the RPC/LAP instrument that is at about 4 m from the MIP sensor can
be used as a transmitter (in place of the MIP ones) and MIP as a receiver in order to have access to the density and temperature
of plasmas at higher Debye lengths than those for which the MIP is originally designed. 相似文献
948.
William V. Boynton Ann L. Sprague Sean C. Solomon Richard D. Starr Larry G. Evans William C. Feldman Jacob I. Trombka Edgar A. Rhodes 《Space Science Reviews》2007,131(1-4):85-104
The instrument suite on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft is well suited
to address several of Mercury’s outstanding geochemical problems. A combination of data from the Gamma-Ray and Neutron Spectrometer
(GRNS) and X-Ray Spectrometer (XRS) instruments will yield the surface abundances of both volatile (K) and refractory (Al,
Ca, and Th) elements, which will test the three competing hypotheses for the origin of Mercury’s high bulk metal fraction:
aerodynamic drag in the early solar nebula, preferential vaporization of silicates, or giant impact. These same elements,
with the addition of Mg, Si, and Fe, will put significant constraints on geochemical processes that have formed the crust
and produced any later volcanism. The Neutron Spectrometer sensor on the GRNS instrument will yield estimates of the amount
of H in surface materials and may ascertain if the permanently shadowed polar craters have a significant excess of H due to
water ice. A comparison of the FeO content of olivine and pyroxene determined by the Mercury Atmospheric and Surface Composition
Spectrometer (MASCS) instrument with the total Fe determined through both GRNS and XRS will permit an estimate of the amount
of Fe present in other forms, including metal and sulfides. 相似文献
949.
The results of numerical simulation for the diffusion processes “powder gases-steel” occurring in the barrel of a quick-firing small-caliber gun are presented. 相似文献
950.
The possibility of using the statistics of recurrence time for extreme events is studied in this paper having in mind the
problems of control and prediction of failures in spacecraft operation. The information about failures onboard satellites
of various types presented by the US National Geophysical Data Center was analyzed. It was found that the probability density
of recurrence intervals followed a power law of the Pareto type with an index equal to 2.3. The obtained result is consistent
both with the theory of normal catastrophes and with the principle of self-organization of criticality for metastable active
heterogeneous environment. A practical consequence of the obtained result consists in the fact that predictions of these extreme
events should not rely on traditional models with the second-order Pearson statistics. To make predictions, the models are
necessary that take into account the power law distribution of recurrence intervals for failures on satellites. The failures
should be considered in these models as extreme events connected with manifestation of the space environment factors. 相似文献