ISRO’s fourth orbit raising of Mars spacecraft fails, another bid planned
12 Nov 2013
The Indian Space Research Organisation (ISRO), after successfully completing three orbit raising manoeuvres on the Mars Orbiter since its 5 November launch, made an unsuccessful attempt to raise the spacecraft's orbit to 1,00,000 km today.
In the fourth orbit-raising operation, conducted early this morning, ISRO could raise the spacecraft's apogee (farthest point to Earth) from 71,623 km to 78,276 km against the planned apogee of 1,00,000 km.
ISRO is now planning a supplementary orbit raising manoeuvre for Mars Orbiter tomorrow after manoeuvres to impart an incremental velocity of 35 metres per second (as against 130 metres / second) originally planned to raise apogee to about 100,000 km failed to achieve the desired results.
ISRO said the spacecraft is in normal health and a supplementary orbit-raising operation is planned tomorrow (November 12, 2013) at 0500 hrs IST to raise the apogee to nearly 1 lakh km.
ISRO said during the orbit-raising operations conducted since 7 November 2013, it has been testing and exercising the autonomy functions progressively, that are essential for injecting the spacecraft to the 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.
''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,'' ISRO said in a website release.
While this parallel mode of operating the two coils is not possible for subsequent operations, they could be operated independently in sequence, it added.
After successfully completing these operations, the mission is expected to take on the ''crucial event'' of the trans-Mars injection around 12:42 am on 1 December.
ISRO's PSLV C 25 successfully injected the 1,350-kg Mars Orbiter into an orbit around Earth some 44 minutes after its launch at 2:38 pm from Satish Dhawan Space Centre at Sriharikota on 5 November, marking the successful completion of the first stage of the Rs450-crore mission.
