Development of UV Astronomical Instruments for Balloon and Space Payloads

Abstract

At Indian Institute of Astrophysics, we conduct high altitude balloon ex- periments for atmospheric and astronomical observations in UV wavelength

range. To carry out observations of astronomical sources, a fine pointing sys- tem is usually required. One of the prime requirements for such a pointing

system is a precision attitude determination sensor. As part of this thesis, I have developed a sensor which determines it’s orientation with respect to a fixed inertial coordinate system using bright stars which are fixed in the sky and act as reference points, and hence called a star sensor. We estimated the requirements for the imaging system of the sensor and simulated the sky

coverage of the sensor. We also made a MATLAB tool to evaluate the perfor- mance of various algorithms required to obtain orientation information from

images. Such a sensor has wide application on satellites carrying telescopes, earth observation cameras and high gain directional antennae. The system was designed keeping in mind its applications on a balloon platform as well as it’s portability to a satellite platform. Calibration and testing of such a high accuracy sensor are critical to use it efficiently as a part of a pointing control system. In this thesis, we describe the development, calibration and validation of the star sensor from block diagram to fabrication and the methods we used for its calibration. The electronics subsystem designed for the star sensor could be used to readout other image sensors and carry out various low level image processing tasks.