By 8:15 am on September 24, the world will know whether India has made it to the Martian orbit on its first mission to the Red Planet.
“Between 7:30 am and 8:15 am on September 24, only a few essential commands will be loaded onto the spacecraft to manoeuvre it. It is around 8:15 am that we will be able to declare the mission successful if everything has gone as planned,” Isro scientific secretary V Koteswara Rao and Mars Programme Director M Annadurai told Deccan Herald.
The senior Isro officials said critical operations, including entry into Mars' sphere of influence and the firing of the engine after 300 days, to signal that the Mars orbiter is coasting, were slated for September 22. The engine will be fired for four seconds on September 22 to test whether it is doing well.
The engine, fired in real-time operations on September 24, will have to run for a fairly long duration—24.23 minutes around the time of injection of the spacecraft into the Martian atmosphere. Before this, however, operations on the spacecraft at the Peenya Isro centre, (Isro Tracking, Telemetry and Command Network) would be tracked from 4 am.
At 4:17 am, there will a change of antenna. Forward rotation will starts at 6:56 am. The orbiter will encounters an eclipse between 7:12 am and 7:37 am—when sunlight will not fall on the spacecraft and it will be managed by thruster control. At 7:14 am, the orbiter's altitude will be managed using thrusters. The liquid engine burn will begin at 7:17 am, with confirmation coming at 7:30 am.
After the eclipse ends, the engine will stop at 7.41 am, following which the orbiter will move into the Martian orbit. It will then be rotated to keep it on the required trajectory.
The spacecraft’s estimated arrival altitude after the engine firing will be 515 km from Mars—its nearest point to the planet. While the liquid engine firing at 7:30 am will signal that the mission has been be successful, it is not until the burning period ends that the declaration will be made.
Isro will receive the signals once the engine stops at 7:41 am. Each signal will take 12.5 minutes to reach earth. Each both-way communication will take 25 minutes, which is why the success of the mission will not be declared at the closure of the engine at 7:41 am.
In case the original plan doesn’t work, with the engine failing to fire, Plan B will come into force.
All the eight small thrusters apart from the engine will be fired to sustain the momentum of the spacecraft. They may perform the function of the engine, but will propel the spacecraft to a Martian orbit that is not as good as the one planned currently.
Isro confirmed with Jet Propulsion Laboratories in the US that the coordinates of the spacecraft. Annadurai made it clear that the Nasa spacecraft MAVEN, slated to land on Mars on September 22, would not cross the path of Mangalyaan-1.