which are attached to the array as a part of zero-g simulation. The effects of these additional masses of friction have been modelled and the analysis has been carried out. The predicted deployment time matched within 10% of the experimental measurements. At the end of deployment the panels latch-up and shock is experienced. This also has been estimated assuming the system behaves as a single degree of freedom system as this gives the upper limit of the shock value. This estimate is 25% higher than the measured value. 4. INSAT-II Solar Array Mechanism The largest indigenous Indian National Satellite—Series II (INSAT-IITS) of 2000 kg lift-off mass, will need 1100 watts of EOL power for its multi-purpose missions with VHRR and communication payloads. Since the VHRR has a passive radiation cooler which requires an unobstructed view of space on the north side of spacecraft, a more complex solar array mechanism is the outcome, with complete panel stack on the south face and a balancing solar sail at the end of a boom on the north to counter the solar radiation torque (Fig. 14). [3]. 4.1 Design The 5-panel T-shaped solar array design with an area of 14.75 m2 (Fig. 11) is a tradeoff of BAPTA load, balancing boom length and array area in addition to other interface requirement considerations. A two step type deployment is adopted. The deployment of the first three panels and yoke is in accordion mode with pyro initiation (Fig. 12) and CCL control, while the remaining two panels deploy in the next step in a transverse direction, when initiated by another pyro device. Deviating from the earlier methods, the hold-down bolts have been located symmetrically within the panel area itself, as shown in Fig. 11. Apart from other advantages, most importantly, this arrangement will bring down the amplitude of large area panel vibration. The six holddown bolts of INSAT-IITS are as shown in Fig. 13 to incorporate debris control and smooth ejection features.
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