The SIGMA/GranatTelescope: Calibration and Data Reduction

20 February 2001

journal article
research article
Published by American Astronomical Society in The Astrophysical Journal

Vol. 548 (2) , 990-1009
https://doi.org/10.1086/318997

Abstract

The SIGMA Telescope was a French experiment, designed to provide high-resolution images in the hard X-ray and soft γ-ray band (35-1300 keV). It featured a coded mask, a NaI(Tl) position-sensitive detector based on the Anger camera principle, and active and passive shielding devices. It was launched on 1989 December 1 on board the Soviet Granat satellite and successfully continued its in-orbit activities until 1997 October. During its lifetime, the SIGMA orbital conditions evolved. Its highly eccentric orbit, with perigee and apogee of 2000 and 200,000 km at the beginning of the mission, continuously evolved to reach 60,000 and 180,000 km. Moreover, Granat experienced both solar maximum and solar minimum environments. The orbital evolution was such that SIGMA was more and more exposed to cosmic-ray fluxes. We present the calibration of the telescope and the standard data reduction analysis. We discuss how the effects induced by the charged particle environment (mainly protons) affected the telescope performance and how we take these changes into account in the data reduction process.

Keywords

This publication has 15 references indexed in Scilit:

Sigma observations of the galactic center at 511 keV
The Astrophysical Journal, 1995
Imaging techniques applied to the coded mask SIGMA telescope
Experimental Astronomy, 1995
The Oriented Scintillation Spectrometer Experiment - Instrument description
The Astrophysical Journal Supplement Series, 1993
The background in a high earth orbit as measured by the soft γ-ray telescope SIGMA
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1992
In flight energy calibration and gain corrections for the hard X- and soft gamma-ray telescope Sigma
Experimental Astronomy, 1992
Calibration of detectors for soft gamma-ray astronomy: the Monte Carlo approach applied to the SIGMA telescope
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1991
Correction for detector uniformity of a gamma-ray telescope using coded aperture imaging
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1988
Gamma-Ray Imaging with a Rotating Hexagonal Uniformly Redundant Array
IEEE Transactions on Nuclear Science, 1984
Uniformly redundant arrays: digital reconstruction methods
Applied Optics, 1981
Coded aperture imaging with uniformly redundant arrays
Applied Optics, 1978