BANGALORE: If things go as planned by Isro, India's Mars orbiter craft would leave the Earth's sphere of influence (SOI) shortly after midnight on Saturday on a nearly 300-day voyage in deep space to the red planet after the "most important" manoeuvre of the ambitious mission.

Indian Space Research Organisation is readying for a 'critical' Trans-Mars Injection (TMI) with firing of the 440 Newton liquid apogee motor (LAM) on board the Mars Orbiter Mission (MOM) spacecraft, launched on November 5, for 23 minutes beginning from 00.49 hours on Sunday (December 1).

This enables orbiter spacecraft to escape from SOI and travel to the vicinity of Mars in September 2014, when the LAM is fired again to slow it down to be captured by Martian gravity into an orbit around it.

"Everything is normal. Everything is going on well", MOM programme director M Annadurai said this afternoon.

"It (TMI) is a very, very critical thing....when compared to any other mission".

Ever since India's first interplanetary spacecraft was launched by Polar Satellite Launch Vehicle in its 25th flight (PSLV-C25) from Sriharikota spaceport on November five, it was in earth-bound orbit.

"TMI is a major operation by which we are pushing the spacecraft into Mars transfer trajectory with the velocity required to leave the earth's sphere of influence", another Isro official said.

"TMI is a precise operation because one has to ensure that the spacecraft gets into the right trajectory. It has to be done at the precise perigee (nearest point to earth). It's the most important manoeuvre of the mission", the official said.

This injection has to be precise as it will estimate where the spacecraft would be on September 24 (at 6.45 am IST) -- plus or minus 50 kms from the designated elliptical orbit around Mars (366 kms X 80,000 kms).

The ambitious rendezvous to Mars, which tugs at the human imagination like no other planet, is primarily a technological mission considering the critical mission operations and stringent requirements on propulsion and other bus systems of the spacecraft.

The spacecraft has been configured to carry out observation of physical features of Mars and limited study of Martian atmosphere with five payloads.

Isro has incorporated autonomous features in MOM spacecraft to handle contingencies.

