India’s Mars Orbiter Mission suffered a minor hiccup when the fourth orbit-raising operation was conducted on Monday, with the spacecraft unable to reach its intended apogee (farthest point to earth) of 1 lakh km during the fourth orbit-raising operation, achieving only 78,276 km.
In order to rectify the shortcoming, Isro will now conduct a supplementary orbit-raising operation in the early hours of November 12 where it intends to raise the apogee to nearly 1 lakh km.
Following the successful launch on November 5 from its spaceport in Sriharikota, Isro planned to execute six orbit raising operations for the next 10 days. While the first three were successful, during the fourth the apogee of the spacecraft was raised from 71,623 km to 78,276 km by imparting an incremental velocity of 35 metres/second, against 130 metres/second.
Scientists at the space agency said the spacecraft was in normal health and that the crucial December 1 trans-Mars injection would be carried out as planned to enable the spacecraft to undertake its 300-day journey to the red planet.
Isro further said that during the orbit-raising operations conducted since November 7, it had been testing and exercising progresively the autonomy functions that are essential for Trans-Mars Injection (TMI) and Mars Orbit Insertion (MOI).
“During the first three orbit-raising operations, the prime and redundant chains of gyros, accelerometers, 22 Newton attitude control thrusters, attitude and orbit control electronics as well as the associated logics for their fault detection isolation, and reconfiguration have been exercised successfully. The prime and redundant star sensors have been functioning satisfactorily. The primary coil of the solenoid flow control valve was used successfully for the first three orbit-raising operations,” the space agency said in a statement.
Further elaborating on what happened during the fourth orbit raising operation on Monday, it said the redundancies built-in for the propulsion system were exercised, namely energising the primary and redundant coils of the solenoid flow control valve of 440 Newton Liquid Engine and 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,” it added.
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