The prime and redundant star sensors have been functioning satisfactorily, ISRO claimed. The primary coil of the solenoid flow control valve was used successfully for the first three orbit-raising operations.
During the fourth orbit-raising operations held today, the redundancies built-in for the propulsion system were exercised, namely, (a) energising the primary and redundant coils of the solenoid flow control valve of 440 Newton Liquid Engine and (b) logic for thrust augmentation by the attitude control thrusters, when needed.
However, when both primary and redundant coils were energised together, as one of the planned modes, the flow to the Liquid Engine stopped.
The thrust level augmentation logic, as expected, came in and the operation continued using the attitude control thrusters. This sequence resulted in reduction of the incremental velocity.
While this parallel mode of operating the two coils is not possible for subsequent operations, they could be operated independently in sequence.
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