UV imaging telescope for the Indian Multiwavelength Astronomy Satellite

Abstract

The UV Imaging Telescope is a part of the proposed Indian Multiwavelength Astronomy Satellite mission. The initiate for an astronomy mission has ben taken by several institution in India, after the successful demonstration of satellite and launch technologies. A base level proposal has been prepared that envisages two major payloads on a platform that can be launched into a low inclination orbit wit an altitude between 500 to 700 km. Apart from the UV telescope, the other major payload would be an x-ray proportional counter with total area in the range 4000-5000 squ cm. The goal for the mission lifetime is five years. The primary objective of the UV Imaging Telescope is an all-sky survey in two bands with the wavelength region 120 to 300 nm. Initially, alternate telescope configurations are being considered: the aperture of the telescope will be 50 to 60 cm and there will be two parallel channels for observations, one for the range 120-190 nm and the other longwards of 190 nm. The goal for spatial resolution on the sky over a full field of 2 degrees is 3 to 4 seconds of arc, depending on the detector. It is expected that the three axis stabilized platform will be able to achieve a pointing stability of better than 2 seconds of arc. The detectors of choice are photocathode, MCP and readout anode combinations for the two wavebands; the use of CCD detectors has, however not been ruled out at this stage. Each channel will have a filter changing mechanism, with a provision for up to 4 full size filter and up to 12 small filters. Though there are some science drivers for grism field spectroscopy, the design aspects of this are not specified at this stage. The all-sky survey is expected to reach a UV limiting magnitude of 20 depending on the detector(s) chosen. After the all sky survey, deeper surveys over selected regions of the sky are planned. Scheduling of guest observer targeted programs will also be done, interspersed with programs for the x-ray payload. The launch of the mission is expected between the years 2002 and 2004.