SUPPLEMENTARY ORBIT RAISING MANOEUVRE PLANNED
FOR MARS ORBITER SPACECRAFT
In the fourth orbit-raising operation conducted this
morning (Nov 11, 2013), the apogee (farthest point to Earth) of Mars Orbiter
Spacecraft was raised from 71,623 km to 78,276 km by imparting an incremental
velocity of 35 metres/second (as against 130 metres/second originally planned
to raise apogee to about 100,000 [1 lakh] km). The spacecraft is in normal
health. A supplementary orbit-raising operation is planned tomorrow (November
12, 2013) at 0500 hrs IST to raise the apogee to nearly 1 lakh km.
During the orbit-raising operations conducted since November 7, 2013, ISRO has
been testing and exercising the autonomy functions progressively, 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.
During the fourth orbit-raising operations held today (November 11, 2013), 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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