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P.L. Bernacca C. Facchinetti E. Fantino 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Purpose of the present study is to provide algorithms for and examples of how to simulate star visibility and tracking by a Telescope attached to the main truss of the International Space Station (ISS). 相似文献
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DTFT-based frequency lock loop for GNSS applications 总被引:1,自引:0,他引:1
Borio D. Camoriano L. Presti L. Fantino M. 《IEEE transactions on aerospace and electronic systems》2008,44(2):595-612
A frequency lock loop (FLL) for Global Navigation Satellite System (GNSS) applications is described here. The core element is the discrete time Fourier transform (DTFT), that leads to a maximum likelihood (ML) frequency estimation and can be conveniently implemented in a software defined radio (SDR) HW platform. The algorithm is based on the iterative evaluation of DTFTs in a single frequency until the incoming frequency is locked. 相似文献
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Reconstructed attitude data for the Hipparcos mission as obtained in the final stages of the data analysis for the published
catalogue is used to derive detailed information on the dynamics of the satellite. Most elements of the inertia tensor of
the satellite could be calibrated from the observed acceleration data, which are also used to reconstruct torques due to solar
radiation and gravity gradient, and the magnetic moment of the satellite and it's interaction with the magnetic field surounding
the Earth. The effects of the oblateness of the Earth on the gravity gradient are evaluated and shown to be negligable. The
magnetic field model includes both the `main' and the `disturbance' fields. The remaining systematic effects in residual torques
are most likely attributed to variations in the magnetic field that are local and are beyond the models used to describe it.
The angular momentum vector for one of the gyros was reconstructed from the torque it asserted on the satellite while it was
running in redundant mode.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
We present an introduction to four papers on further analysis of the raw Hipparcos data. This analysis has lead to the recognition
of how orbit, radiation and temperature conditions did or didn't affect the scientific results of the Hipparcos mission. It
also led the way to a new reduction of the scientific data that shows from its initial results a real potential for a substantial
improvement of the astrometric parameters for stars brighter than V=8.5. This short paper serves as an introduction to the four main papers, and provides some general references.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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We present a new method for a high-accuracy reconstruction of the attitude for a slowly spinning satellite. This method, referred
to as the fully-dynamic approach, explores the possibility to describe the satellite's attitude as that of a rigid body subject
to continuous external torques. The method is tried out on the Hipparcos data and is shown to reduce the noise for the along-scan
attitude reconstruction for that mission by about a factor two to three. The dynamic modelling is expected to give a more
accurate representation of the satellite's attitude than was obtained with a pure mathematical modelling. As such, it decreases
the degrees of freedom in the a posteriori reconstruction. Some of the decrease is obtained through accumulating and subsequently implementing information on high frequency
components in the solar radiation torques, which show to be systematic and predictable. This could be expected, as they are
primarily linked to the external geometry and optical properties of the satellite. In the context of an astrometric mission,
the methods presented here can only be applied as a final iteration step: the star positions that are used to reconstruct
the attitude are also part of the scientific objectives of the mission. An estimate for the potential of a re-reduction of
the Hipparcos data using the fully-dynamic model for the attitude reconstruction was obtained from test reductions of the
first 24 months of mission data. Improvement of the accuracies of the astrometric parameters for all stars brighter than Hp=9.0 appears possible. The noise on the astrometric parameters for these stars was affected significantly by the along-scan
attitude noise, which dominated for stars brighter than Hp=4.5. The possible improvement for stars brighter than about Hp=4.5 may, after iterations, be as much as a factor three. The reduced noise levels also allow a more accurate calibration
and monitoring of instrument parameters, leading potentially to a better understanding of the instrument and the scientific
data obtained with it.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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