A 750 mm balloon-borne telescope for far-infrared astronomical observations

Abstract

A balloon-borne 750 mm Cassegrain telescope has been developed for far-infrared (FIR) astronomical observations. This telescope uses a three-axis stabilised balloon platform with approximately 30 sec of arc (RMS) pointing accuracy. Design and overall properties of this telescope system are presented. Some of the special features of the payload are highlighted, viz., cheap and lightweight mirrors made in epoxy resin; the in-flight relative phase adjustment facility between the detector signal processing system and the secondary mirror chopper. This telescope was flown at an altitude of 32 km on December 10, 1980 for conducting far-infrared observations. The telescope flight details and performance are presented and compared with the design goals. To illustrate the scanning capability of the telescope, a map of Orion-A obtained using it is presented.