Indian Mars mission hit by snag
India's mission to Mars has hit a snag, after a planned engine burn failed to raise the spacecraft's orbit around Earth by the intended amount.
The problem occurred during a manoeuvre designed to boost the craft's maximum distance from 71,623km to 100,000km.
A problem with the liquid fuel thruster caused the 1,350kg vehicle to fall short of the mark.
But the head of the Indian Space Research Organisation (Isro) said the spacecraft remained "healthy".
As a solution, the Mars Orbiter Mission (MOM) - known informally as Mangalyaan, or Mars-craft - will be commanded to execute an additional thruster firing at 05:00 IST on Tuesday (23:30 GMT on Monday) to make up for the shortfall.
Instead of flying directly to Mars, the probe is scheduled to orbit Earth until the end of the month, building up the necessary velocity to break free from our planet's gravitational pull.
This was the fourth in a series of five engine burns known as "midnight manoeuvres" because several constraints require that they are carried out in the early hours of the morning.
Speaking to Pallava Bagla, science editor at Indian broadcasting network NDTV, Isro's chairman K Radhakrishnan said: "The spacecraft is healthy and it encountered a problem when a specific redundancy test was being conducted and it failed to reach the desired velocity it was to achieve."
In that redundancy test, two coils in the liquid engine were supposed to be energised simultaneously.
The failure of that test and the spacecraft's consequently reduced velocity raised the spacecraft's apogee (the point in its orbit farthest away from Earth) from 71,623km to just 78,276km - about 25% of the way to the target of 100,000km.
Mr Bagla told BBC News that the attempt on Monday morning used up about 2kg of the craft's 852kg fuel load.
But he added that the spacecraft's insertion into Earth orbit after launch on 5 November had been so precise, 6kg of liquid fuel had been saved. Even with Monday's glitch, the mission still had a fuel surplus of 4kg.
Nevertheless, Mr Radhakrishnan said that a failure analysis committee would examine why the problem occurred.
If the additional firing on Tuesday can successfully bridge the gap, a final midnight manoeuvre on 16 November will boost the apogee to 192,000km.
On 1 December, the engine will be fired again for its "trans-Martian injection", despatching the craft on a 300-day journey to Mars.
On 24 September next year, the engine will be fired again to slow down the spacecraft, enabling it to be captured by Mars' gravity and placed into orbit.
India's PSLV rocket - the second choice for the mission after a beefier launcher failed - was not powerful enough to send the MOM on a direct flight to Mars.
So engineers opted for a method of travel called a Hohmann Transfer Orbit to propel the spacecraft from Earth to Mars with the least amount of fuel possible.
At a cost of about $72m (£45m), the MOM is extremely cheap by the standards of planetary missions.