Elimination of relative secular drift of orbits of two satellites caused by polar oblateness of the Earth

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.     

Scattering function of tropospheric aerosol according to the data of polarimetry of the twilight and night sky background

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.     

MESSENGER and the Chemistry of Mercury’s Surface

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.     

Powder gas diffusion into the surface layer of the aviation quick-firing gun barrel

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.     

Power law distribution in statistics of failures in operation of spacecraft onboard equipment

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.     

A mathematical model of vibration combustion in a tube with sudden cross-section change

The theoretical study of vibration combustion using a model of the pulsejet engine was carried out. The frequencies and amplitudes of gas vibrations that were calculated by the energy method are well agreed with experimental data.     

An investigation into instrumental nonlinear effects

High order spectral techniques are one of the most powerful tools for the identification of non-linear processes in space plasma turbulence. Without such tools it is impossible to determine, for example, the occurrence of non-linear interactions between spectral components. However, since the observations made by an instrument involve some internal processing, it is possible that non-linearities may arise from within the instrument itself rather than in the plasma. The possibility of such effects are investigated using data resulting from tests carried out using the Cluster Wideband electric field instrument.     

Unusually high geomagnetic activity in 2003

In 2003, geomagnetic activity was found to be considerably higher than in any other year of the current solar cycle. This was caused by the time coincidence of large low-latitude coronal holes and a significant burst of the flare and eruptive activity of the Sun. The features of recent intensification of the activity are discussed, and the long-period behavior of indices of the geomagnetic activity in the 23rd and previous cycles is compared. The large magnetic storms in October–November 2003 are analyzed in more detail.Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 6, 2004, pp. 563–573.Original Russian Text Copyright © 2004 by Belov, Gaidash, Ivanov, Kanonidi.     

Space Interferometry Mission instrument model and astrometric performance validation

The Space Interferometry Mission (SIM), performed very accurate astrometric measurements to measure the positions of stars using a 10 m baseline optical interferometer. The lack of signal from the science targets precludes using the star as a feedback signal to control the science interferometer delay line. In order to solve this problem SIM uses pathlength feed forward (PFF) control of the science interferometer. In the case of controlling the science interferometer optical path, the information to position the science delay line comes from a combination of internal metrology, external metrology, and guide interferometer measurements. The accuracy of the internal and external metrology measurements and the guide interferometer measurements are important for the quality of the feed forward signal and also for the ultimate astrometric performance of the instrument. An instrument model of SIM has been built to evaluate optical performance and to emulate various observational scenarios. The effect of averaging methods to reduce metrology cyclic error and the viability of on-orbit calibration maneuvers are studied. The model consists of a real-time dynamics formulation of the spacecraft and a real-time attitude control system. Simulation results investigate the sensitivity of the feed forward signal to the various error sources and time-varying terms.