November 12, 2013
NEW DELHI — India’s first Mars orbiter suffered an engine anomaly Nov. 11 as attempts were made to raise the spacecraft’s orbit around Earth, but the mission remains on track, a senior scientist says.
The Mars Orbiter Mission (MOM) was boosted by a Polar Satellite Launch Vehicle (PSLV-C25) from the Sriharikota spaceport in south India on Nov. 5. Over the next 10 days, scientists at the Indian Space and Research Organization (ISRO) are scheduled to raise the apogee of the orbiter to around 200,000 km (124,274 mi.) in preparation for leaving Earth orbit and reaching Mars by September 2014.
However, a problem with the liquid fuel thruster caused the 1,350-kg (3,000-lb.) vehicle to fall short of the mark. The maneuver to raise the apogee of the “Maangalyaan” probe from 71,623 km to 100,000 km could only achieve 78,276 km, since the incremental velocity imparted to the spacecraft was only 35 m/s against the targeted 130 m/s, the ISRO scientist says.
This was the first orbit-raising move to fall short of the objective after three successful maneuvers in a series of five engine burns known as “midnight maneuvers” that began following the launch.
While conducting the orbit-raising operations since Nov. 7, ISRO scientists have been testing and exercising other functions essential for Trans-Mars Injection and Mars Orbit Insertion.
During the first three orbit-raising operations, mission controllers successfully exercised the spacecraft’s prime and redundant chains of gyros, accelerometers, 22-Newton attitude control thrusters, and attitude and orbit control electronics, as well as the associated logics for their fault detection isolation and reconfiguration, the ISRO official says.
“The prime and redundant star sensors have been functioning satisfactorily,” the official adds. “The primary coil of the solenoid flow control valve was used successfully for the first three orbit-raising operations.”
During the fourth orbit-raising operation on Nov. 11, the built-in redundancies for the propulsion system were exercised. However, “when both primary and redundant coils were energized together, as one of the planned modes, the flow to the liquid engine stopped,” the ISRO scientist explains.
While the parallel mode of operating the two coils was not possible for subsequent operations, they can be operated independently in sequence, he says.