CHENNAI: Cruising towards its historic rendezvous with the red planet, India's Mars Orbiter Mission MOM ) on Monday entered the Mars gravitational sphere of influence ahead of its scheduled orbit insertion on September 24."Our navigators' calculations show that MOM has entered the gravitational sphere of influence of Mars," ISRO said on its social networking site, adding, the spacecraft was within 5.4 lakh km radius of the Mars' gravitational sphere of influence.After being launched from ISRO's spaceport of Sriharikota on November 5 last year, the MOM had left Earth's orbit on December 1 and began its historic voyage to put India on the list of elite nations, which has sent a mission to Mars."MOM has entered the Mars gravitational sphere of influence this morning and we will perform certain procedures on the mission today. The fourth trajectory correction manoeuvre and test firing of main liquid engine will be test fired for 3.968 seconds," an ISRO official said.Now that the spacecraft has entered the Mars' influence, its velocity has to be controlled so that it does not escape the Mars' influence, he said, adding, the spacecraft is scheduled to enter the Mars orbit insertion at 7.30am IST on September 24.(Scientists and engineers from the Isro monitor Mars Orbiter Mission (MOM) at the Isro centre in Bangalore.)The crucial fourth trajectory correction manoeuvre and test-fire of the main liquid engine on the spacecraft is scheduled for 2.30pm on Monday.The MOM, India's first interplanetary mission, was launched by India's workhorse Polar Satellite Launch Vehicle from the spaceport of Sriharikota in Andhra Pradesh.