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Proceedings Paper

RHESSI imager and aspect systems
Author(s): Alex Zehnder; Jacek Bialkowski; F. Burri; Martin Fivian; Reinhold Henneck; A. Mchedlishvili; P. Ming; J. Welte; Knud Thomsen; David Clark; Brian R. Dennis; Gordon J. Hurford; David W. Curtis; Peter R. Harvey; David H. Pankow
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Paper Abstract

RHESSI uses nine Rotating Modulation Collimators (RMCs) for imaging, each consisting of a pair of grids mounted on the rotating spacecraft. The angular resolutions range from 2.3 arcsec to 3arcmin. The relative twist between the two grids of each pair is the most critical parameter. It must be less than 20 arcsec for the finest grid. After precision alignment, it is monitored by the Twist Monitoring System (TMS) to a few arcsec. The Sun-pointing must be known better than 0.4 arcsec for the image reconstruction. This is achieved by the Solar Aspect System (SAS), which consists of a set of three Sun sensors. Each sensor is focusing the filtered Sun light onto a linear CCD. The onboard Aspect Data Processor (ADP) selects the 6 limb positions, which over-define the pointing offset of the Sun center in respect to the imaging axis of the imager. The Roll Angle System (RAS) continuously measures the roll angle of RHESSI within arcmin accuracy. The RAS is a continuously operating CCD star scanner. The time of the passage of a star image over the CCD is recorded and defines the roll angle, comparing its pixel position and amplitude with a star map.

Paper Details

Date Published: 11 February 2003
PDF: 19 pages
Proc. SPIE 4853, Innovative Telescopes and Instrumentation for Solar Astrophysics, (11 February 2003); doi: 10.1117/12.460290
Show Author Affiliations
Alex Zehnder, Paul Scherrer Institut (United States)
Jacek Bialkowski, Paul Scherrer Institut (United States)
F. Burri, Paul Scherrer Institut (United States)
Martin Fivian, Paul Scherrer Institut (United States)
Reinhold Henneck, Paul Scherrer Institut (United States)
A. Mchedlishvili, Paul Scherrer Institut (United States)
P. Ming, Paul Scherrer Institut (United States)
J. Welte, Paul Scherrer Institut (United States)
Knud Thomsen, Paul Scherrer Institut (United States)
David Clark, NASA Goddard Space Flight Ctr. (United States)
Brian R. Dennis, NASA Goddard Space Flight Ctr. (United States)
Gordon J. Hurford, NASA Goddard Space Flight Ctr. (United States)
David W. Curtis, Univ. of California/Berkeley (United States)
Peter R. Harvey, Univ. of California/Berkeley (United States)
David H. Pankow, Univ. of California/Berkeley (United States)

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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