A&A 411, L141-L148 (2003)
DOI: 10.1051/0004-6361:20031367

Letter

ISGRI: The INTEGRAL Soft Gamma-Ray Imager

F. Lebrun¹, J. P. Leray¹, P. Lavocat¹, J. Crétolle¹, M. Arquès², C. Blondel¹, C. Bonnin¹, A. Bouère¹, C. Cara¹, T. Chaleil³, F. Daly¹, F. Desages⁴, H. Dzitko¹, B. Horeau¹, P. Laurent¹, O. Limousin¹, F. Mathy², V. Mauguen¹, F. Meignier¹, F. Molinié³, E. Poindron¹, M. Rouger⁴, A. Sauvageon¹ and T. Tourrette<sup>1

1</sup>  CEA-Saclay, DSM/DAPNIA/Service d'Astrophysique, 91191 Gif-sur-Yvette Cedex, France,
²  CEA-Grenoble, LETI, 17 rue des Martyrs, Grenoble Cedex 9, France,
³  CEA-Saclay, DSM/DAPNIA/SIS, 91191 Gif-sur-Yvette Cedex, France,
⁴  CEA-Saclay, DSM/DAPNIA/SEDI, 91191 Gif-sur-Yvette Cedex, France

(Received 17 July 2003 / Accepted 4 September 2003)

Abstract
For the first time in the history of high energy astronomy, a large CdTe gamma-ray camera is operating in space. ISGRI is the low-energy camera of the IBIS telescope on board the INTEGRAL satellite. This paper details its design and its in-flight behavior and performances. Having a sensitive area of 2621 cm² with a spatial resolution of 4.6 mm, a low threshold around 12 keV and an energy resolution of ~8% at 60 keV, ISGRI shows absolutely no signs of degradation after 9 months in orbit. All aspects of its in-flight behavior and scientific performance are fully nominal, and in particular the observed background level confirms the expected sensitivity of 1 milliCrab for a 10 ⁶ s observation.

Key words: space telescope -- cadmium telluride detectors -- gamma-ray astronomy -- calibration -- INTEGRAL -- IBIS.

Offprint request: F. Lebrun, flebrun@cea.fr

© ESO 2003

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