On Monday next week, Indian Space Research Organization (ISRO) will face one of the biggest challenges of its Mars mission as Mangalyaan enters the last leg of its journey.

The challenge is of a safe landing on the surface of Mars by switching on the engine of the spacecraft that has been lying dormant for 10 months. This engine needs to be fired for mere four seconds so as to slow down the spacecraft.

If the engine fails to ignite on September 22 then the space organization have other plans in mind, whereby they will nudge the spacecraft's path towards a Martian orbit by firing eight smaller thrusters on September 24. So, it means that whether the engines work or not, the Mars orbiter is expected to reach its destination within a week.

Till now the ISRO engineers have not yet uploaded the commands that have to be executed on September 22 and 24. As the spacecraft is far away, and would be 224 million km from the earth on September 24, it will take 12.5 minutes for signals to arrive.

It is a very big achievement considering the fact that despite a small glitch a few days after the launch, the mission has so far run smoothly throughout the 98% of its journey. Also, it was a big thing that the spacecraft's trajectory was so close to the intended path that ISRO did not have to do a correction exercise that was planned for the last month.

ISRO Chairman K Radhakrishnan said, "We have crossed several situations that we have not faced before. We are now preparing for all contingencies on September 24".