From Fishing Hamlet to Red Planet by Indian Space Research Organization

Author:Indian Space Research Organization
Language: eng
Format: epub
Publisher: HarperCollins Publishers India
Published: 2015-03-17T16:00:00+00:00

ONE SOLAR PANEL OF APPLE NOT DEPLOYING

APPLE spacecraft was built around a solid apogee boost motor and hence raised many configuration issues among which was locating the 4p Sun sensor segments that were practically covered by the solar panels. It was also debated whether there was any risk of solar panel not deploying but this apprehension was dismissed saying that there was no mission without solar panel deployment. As it turned out, one solar panel did not deploy in orbit and this posed the problem of one side of 4p Sun sensor being covered by the solar panel. Only a 10° to 15° field of view was available, posing a problem for Sun acquisition. The mission team did not leave it to the fate and meticulously planned acquisition at a very low rate. Even starting with practically very low rates the Sun acquisition was unsuccessful in two attempts. A very quick analysis with practically no time to do any simulations, a new technique with reverse direction was tried, resulting in successful Sun acquisition. Later, APPLE served for the intended mission life, giving valuable experience on three-axis stabilisation, VHF telemetry and telecommand from geosynchronous orbit, the problems of atmospheric scintillation, etc.

One lesson that came loud and clear was that one should never assume that such a failure (as the non-deployment of a solar panel) would automatically lead to total mission failure. The operations team would never give up till the very end and that all contingencies have to be addressed in the configuration exercise itself. Managing INSAT-2E for more than ten years of successful operations, in spite of losing both the Earth sensors in the beginning itself, and managing TES (Technology Experiment Satellite) after seeing serious degradation of both batteries, again much beyond the design life, are testimony to the resilience of the ISRO team. In other words, not to give up anything till the very end and not to make assumptions that something would not fail are two major lessons learnt from the APPLE experience.

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