The MART-LIME High-Energy Telescope

MART-LIME is a coded mask imaging hard X-Ray telescope to be flown onboard the international SPECTRUM RG observatory in early 1996. This instrument, the heart of which is a high-pressure proportional counter sensitive to the 5—150 keV energy range, will be characterised by a limiting sensitivity of about 1 milliCrab for a 105 s observation period. The imaging capability of MART-LIME is provided by a coded-mask aperture system, used in conjunction with the position sensitive detector. The basic pattern of the square coded aperture is a 71 x 73 URA mask (twin prime). This is surrounded by an outer frame comprising 17 and 16 pixels, respectively, on adjacent sides, giving a mask of 105 x 105 pixels in total. With this configuration, a fully coded field-of-view of 5.2° x 5.2° is obtained, whilst a partially coded field-of-view is achieved up to 6°, the acceptance angle of the ferrite collimator. The basic concept of the MART-LIME telescope is presented.