A balloon-borne imaging telescope for high-energy astrophysics |
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| Authors: | T Villela J Braga F D'Amico U B Jayanthi J A Neri |
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| Institution: | (1) Divisão de Astrofísica, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, SP, Brazil |
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| Abstract: | We describe an imaging telescope for observations of celestial sources in the energy range between 30 keV and 1.8 MeV onboard stratospheric balloons. The detector is a 41 cm diameter, 5 cm thick NaI(Tl) crystal coupled to 19 photomultipliers in an Anger camera configuration. It is surrounded by a plastic scintillator 15 cm thick on the sides, 0.2 cm thick at the top and 20 cm thick at the bottom. The imaging device is based upon a 19 × 19 element square MURA (Modified Uniformly Redundant Array) coded mask mounted in an one-piece mask-antimask configuration. The detector's spatial resolution is about 10 mm at 100 keV. This is the first experiment to use such a mask pattern and configuration for astrophysical purposes. The expected 3 sensitivity for an on-axis source observed for 104 s at a residual atmosphere of 3.5 g cm–2 is 1.44 × 10–5 photons cm–2 s–1 keV–1 at 100 keV and 1.00 × 10–6 photons cm–2 s–1 keV–1 at 1 MeV. The angular resolution is approximately 14 arcminutes over a 13°field of view. The instrument is mounted in an automatic platform with a capability for pointing and stabilization in both azimuth and elevation axis with 2 arcmin accuracy.Presented at the 2nd UN/ESA Workshop, held in Bogotá, Colombia, 9-13 November, 1992. |
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