The mechanism design progressed in a series of iterations with new inputs from analysis and tests being incorporated progressively, while keeping in pace with spacecraft's milestones. The studies conducted were on materials for thermal behaviour pattern, theoretical simulation of deployment dynamics, structural dynamics and correlations with experimental data. Being the first in the series of ISRO's communication satellites, many uncertainties and associated interface changes were to be absorbed in the design. 2.1 Design The array sizing was determined on the basis of generating 280 watts of power. A total array area of 2.86 m2 shared equally by two panels of 1.1 X 1.3 m each was specified. A single step deployment was adopted, by which, on initiation of a pyrotechnic device, all the clamp-down latches got released and the spring powered array and yoke deployed automatically (Fig. 1). The closed table loop control device (CCL), shown in Fig. 2, comprising of a coordinating rope with pulley sets, ensured the mechanism was a single degree of freedom system and also provided redundancy for spring torque. The pyrotechnic device was in itself a redundant system, with two opposing guillotines facing each other, and each of them powered by a separate dimple motor with an individual electrical connection. The 1 Amp—1 watt NO-FIRE and 5 Amp ALL-FIRE characteristics were the currently accepted pyrotechnic safety and reliability standards. The thermal protection system design was based on the predicted temperature extremes. Temperature compensation springs were introduced along all wire rope interconnections. The mechanism parts and the exposed surfaces of array were provided with thermal protection device in the form of thermal paint, low emissivity tape and high reflectivity tape, as per design.
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