It is wake-up time today for Mangalyaan, which is about to complete its 300-day journey to Mars, as scientists at the Indian Space Research Organisation will fire up the main liquid engine that has been dormant for most of the journey, just two days before the spacecraft will be put in the Red Planet's orbit.

According to a post by ISRO, the Mars Orbiter Mission has already entered the Gravitational Sphere of Influence of Mars, at a radius of 5.8 lakh kilometers. 

MOM has reached Mars' neighbourhoodISRO

The engine trail will begin at 2 30 pm on Monday, and the 440 Newton Liquid Apogee Motor engine, will be fired up for a crucial four seconds, said to be the biggest challenge for the mission before the Mars Orbiter Insertion on 24 September. Scientists will also have to conduct a trajectory correction maneuver on Monday, the day when NASA's Mars Mission MAVEN reportedly entered Mars' orbit successfully.

"The engine will be fired for nearly 4 seconds and almost half a kg of fuel will be needed for this operation," Koteshwar Rao, scientific secretary at ISRO told The Hindustan Times.

There is, of course, a Plan B in case the four-second trial of the liquid engine fails, and that is the firing of eight thrusters to help put Mangalyaan in the orbit.

There are just two days left before the actual insertion of MOM into Mars' orbit, which could make India the first nation to achieve its Mars Mission on the first attempt.

The Mars Orbit Insertion will be an about a four-hour process, starting at 4:17 am on Wednesday, and concluding only by 7:52 am.

Here's the entire process explained by ISRO.

The D-Day Schedule for MangalyaanISRO

ISRO has also put out a video to explain how the Mars Orbit Insertion will take place.