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Proceedings Paper

Roll Angle System (RAS) for the High-Energy Solar Spectroscopic Imager HESSI
Author(s): Reinhold Henneck; Jacek Bialkowski; F. Burri; Martin Fivian; W. Hajdas; A. Mchedlishvili; P. Ming; Knud Thomsen; J. Welte; Alex Zehnder; M. Dettwyler; F. Buerki; Gordon J. Hurford; David W. Curtis; David H. Pankow
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Paper Abstract

The purpose of the HESSI RAS is to provide information on the roll angle of the rotation spacecraft. Precise knowledge of the roll angle is a necessary ingredient for image reconstruction. The RAS is a continuously operating star scanner that points out radially and observes stars at 75 degrees from the Sun direction using a commercial lens and a fast CCD. The passage of a star image over the CCD charges one or several pixels above threshold and the timing of this signal defines the roll angle, once the star has been identified by comparing its pixel position and amplitude with a star map. Roll angles at intermediate times are inferred by assuming uniform rotation. With a limiting star magnitude of mv equals 3 we expect to observe at least 1 star per revolution over 1 year; on the average we will detect about 10 stars/revolution.

Paper Details

Date Published: 22 October 1999
PDF: 6 pages
Proc. SPIE 3765, EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy X, (22 October 1999); doi: 10.1117/12.366530
Show Author Affiliations
Reinhold Henneck, Paul Scherrer Institut (Switzerland)
Jacek Bialkowski, Paul Scherrer Institut (Switzerland)
F. Burri, Paul Scherrer Institut (Switzerland)
Martin Fivian, Paul Scherrer Institut (United States)
W. Hajdas, Paul Scherrer Institut (Switzerland)
A. Mchedlishvili, Paul Scherrer Institut (Switzerland)
P. Ming, Paul Scherrer Institut (Switzerland)
Knud Thomsen, Paul Scherrer Institut (Switzerland)
J. Welte, Paul Scherrer Institut (Switzerland)
Alex Zehnder, Paul Scherrer Institut (Switzerland)
M. Dettwyler, Eidgenoessische Technische Hochschule Zuerich (Switzerland)
F. Buerki, Eidgenoessische Technische Hochschule Zuerich (Switzerland)
Gordon J. Hurford, Univ. of California/Berkeley (United States)
David W. Curtis, Univ. of California/Berkeley (United States)
David H. Pankow, Univ. of California/Berkeley (United States)

Published in SPIE Proceedings Vol. 3765:
EUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy X
Oswald H. W. Siegmund; Kathryn A. Flanagan, Editor(s)

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