580 research outputs found
The plasma environment at geosynchronous orbit
A two-fold objective is considered: (1) to present a picture of the magnetosphere about geosynchronous orbit to the nonspecialist, and (2) to introduce a preliminary model. Particle anisotropies from ATS 6 are included. Omnidirectional electron fluxes are also considered
The 3 DLE instrument on ATS-5
The performance and operation of the DLE plasma electron counter on board the ATS 5 are described. Two methods of data presentation, microfilm line plots and spectrograms, are discussed along with plasma dynamics, plasma flow velocity, electrostatic charging, and wave-particle interactions
Active control of spacecraft charging on ATS-5 and ATS-6
Effects on spacecraft ground potential of active emission of charged particles are being investigated through experiments using the ATS-5 and ATS-6 spacecraft. Each spacecraft is equipped with ion engine neutralizers which emit low energy charged particles. Despite great differences in design between the two spacecraft, they attain similar potentials in similar environments. Therefore, effects on spacecraft potential of neutralizer operations can be used to compare the effects of operating the two different neutralizers (hot wire filament and plasma bridge). The neutralizers on both spacecraft were operated in eclipse. Results of these operations are presented and spacecraft responses compared
The effect of environmental plasma interactions on the performance of the solar sail system
Interaction between the solar sail and the natural plasma environment were examined for deleterious impacts upon the operation of the sail and its associated payload. Electrostatic charging of the sail in the solar wind and in near earth environment were examined. Deployment problems were studied. An analysis of electromechanical oscillations coupling the sail to the natural plasma was performed. As a result of these studies, it was concluded that none of these effects will have a significant negative impact upon the sail operation. The natural environment will be significantly perturbed and this will preclude measurements of electric and magnetic fields from an attached payload
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Study of effects of space power satellites on life support functions of the earth's magnetosphere
The effects of the Satellite Solar Power System (SSPS) on the life support functions of the earth's magnetosphere were investigated. Topics considered include: (1) thruster effluent effects on the magnetosphere; (2) biological consequences of SSPS reflected light; (3) impact on earth bound astronomy; (4) catastrophic failure and debris; (5) satellite induced processes; and (6) microwave power transmission. Several impacts are identified and recommendations for further studies are provided
On the importance of background subtraction in the analysis of coronal loops observed with TRACE
In the framework of TRACE coronal observations, we compare the analysis and
diagnostics of a loop after subtracting the background with two different and
independent methods. The dataset includes sequences of images in the 171 A, 195
A filter bands of TRACE. One background subtraction method consists in taking
as background values those obtained from interpolation between concentric
strips around the analyzed loop. The other method is a pixel-to-pixel
subtraction of the final image when the loop had completely faded out, already
used by Reale & Ciaravella 2006. We compare the emission distributions along
the loop obtained with the two methods and find that they are considerably
different. We find differences as well in the related derive filter ratio and
temperature profiles. In particular, the pixel-to-pixel subtraction leads to
coherent diagnostics of a cooling loop. With the other subtraction the
diagnostics are much less clear. The background subtraction is a delicate issue
in the analysis of a loop. The pixel-to-pixel subtraction appears to be more
reliable, but its application is not always possible. Subtraction from
interpolation between surrounding regions can produce higher systematic errors,
because of intersecting structures and of the large amount of subtracted
emission in TRACE observations.Comment: 9 pages, 9 figure
The Thomson Surface. II. Polarization
The solar corona and heliosphere are visible via sunlight that is
Thomson-scattered off of free electrons, yielding a radiance against the
celestial sphere. In this second part of a three-article series, we discuss
linear polarization of this scattered light parallel and perpendicular to the
plane of scatter in the context of heliopheric imaging far from the Sun. The
difference between these two radiances, (pB), varies quite differently with
scattering angle, compared to the sum that would be detected in unpolarized
light (B). The difference between these two quantities has long been used in a
coronagraphic context for background subtraction and to extract some
three-dimensional information about the corona; we explore how these effects
differ in the wider-field heliospheric imaging case where small-angle
approximations do not apply. We develop an appropriately-simplified theory of
polarized Thomson scattering in the heliosphere, discuss signal-to-noise
considerations, invert the scattering equations analytically to solve the three
dimensional object location problem for small objects, discuss exploiting
polarization for background subtraction, and generate simple forward models of
several classes of heliospheric feature. We conclude that pB measurements of
heliospheric material are much more localized to the Thomson surface than are B
measurements, that the ratio pB/B can be used to track solar wind features in
three dimensions for scientific and space weather applications better in the
heliosphere than corona; and that, by providing an independent measurement of
background signal, pB measurements may be used to reduce the effect of
background radiances including the stably polarized zodiacal light.Comment: v2: text as accepted by APJ (before proofs); formatted with
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