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Proceedings Paper

RHESSI aspect system and in-flight calibration
Author(s): Martin Fivian; Reinhold Henneck; Alex Zehnder
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Paper Abstract

Precise knowledge of the pointing and the roll angle of the rotating spacecraft is needed in order to reconstruct images with 2 arcsec resolution using the modulation patterns seen on each of the detectors of the bi-grid rotating collimators. Therefore, the aspect system consists of two subsystems of sensors, the Solar Aspect System (SAS) and Roll Angle System (RAS). The transmitted data consists of Solar limb data from the SAS (CCD pixels around the intersection of a Solar image with three linear CCDs) and Star event data from the RAS (CCD pixels induced by passages of Star images over a linear CCD). In order to meet the RHESSI requirements, the reconstructed pointing needs to be ≤ 0.4 arcsec (rms) relatively (≤ 1 arcsec absolutely) and the determination of the roll angle needs to be better than 1 arcmin (rms). Beside of understanding and calibrating each sensor, the error budget on the aspect system requires an alignment of the relevant features of the 1.55 m extended telescope on a micron level. This could be achieved by a combination of on-ground and in-flight calibration.

Paper Details

Date Published: 11 February 2003
PDF: 11 pages
Proc. SPIE 4853, Innovative Telescopes and Instrumentation for Solar Astrophysics, (11 February 2003); doi: 10.1117/12.460365
Show Author Affiliations
Martin Fivian, Paul Scherrer Institut (Switzerland)
Reinhold Henneck, Paul Scherrer Institut (Switzerland)
Alex Zehnder, Paul Scherrer Institut (Switzerland)


Published in SPIE Proceedings Vol. 4853:
Innovative Telescopes and Instrumentation for Solar Astrophysics
Stephen L. Keil; Sergey V. Avakyan, Editor(s)

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