IR Earth horizon sensors are used for attitude determination of satellites. Simulation of IR horizon and ground calibration are major problems for testing sensors used in low altitude orbits due to geometrical constraints. A large earth simulator and a test facility with a 3500 mm. diameter disc have been developed for the calibration and the qualification of different types of IR earth sensors used on-board Indian Remote Sensing (IRS) satellites. The unique design of the test facility enables the simulation of the satellite altitudes, roll and pitch angles, IR radiation from space and Earth, gradients due to seasonal changes in radiance and thermo-vacuum environments of the sensor under test. The sensor performance can be tested either in open air conditions or under clean vacuum conditions at different temperatures of the sensor. The gradient of the Earth's IR radiation which changes with latitudes and seasons, and the Sun and the Moon interference can also be simulated. A computer based data acquisition system along with the instrumentation is used for controlling and monitoring vacuum, linear and rotary motions, temperature distribution on the earth disc and also for monitoring and recording of the sensor outputs. This paper describes the methodology behind various simulations and the testing involved. The constructional details of the large earth simulator and the alignment of the sensor with respect to the earth simulator are explained. A few of the actual sensor test results obtained are also included.

Date Published: 7 December 1988
PDF: 8 pages
Proc. SPIE 0972, Infrared Technology XIV, (7 December 1988); doi: 10.1117/12.948303

Published in SPIE Proceedings Vol. 0972:
Infrared Technology XIV
Irving J. Spiro, Editor(s)