BANGALORE: Less than three weeks before India's first date with

Mars

,

' s spacecraft authorization committee will meet on Thursday to plan a crucial test—firing of the Mars orbiter's main engine before its rendezvous with the red planet on September 24.

Getting up close

IsroIf Isro gets it right, India will be the first to succeed in a Mars mission on the first attempt. The US, Russia and the European Space Agency succeeded only after repeated attempts.The 440N liquid engine of the Mars Orbiter Mission (MoM) had last fired on December 1 for the trans—Mars injection when mission control slingshot the spacecraft from an Earth orbit to the Martian trajectory. About 300 days later, the engine will have to fire again for a reverse effect — to slow down the spacecraft so it is captured into the Martian orbit."Since the engine has been idle for more than 300 days, we may have to test fire it," Isro chairman K Radhakrishnan told TOI.There is some uncertainty over a couple of valves and parts malfunctioning because of the corrosive fuel. After firing for the trans—Mars Injection, the primary fuel channel has been disabled to prevent leaks. The planned test—firing will be carried out using a secondary channel which will remain open for the actual firing on September 24 to remain in the Martian orbit. The test is not without handicaps. Since the spacecraft is moving at a speed of more than 22km per second, test—firing for a mere five seconds can take it away from the trajectory by more than 100km. This deviation will have to be factored in while carrying out the final orbit—capture manoeuvre around Mars.If the engine fails the test, scientists will have enough time to plan and use the eight smaller thrusters to inject MoM into the Martian orbit which, however, may not be the intended 372km x 80,000km orbit. MoM project director S Arunan will make a presentation before the authorization committee which will take a final call on this. The panel chaired by Space Applications Centre director A S Kiran Kumar will also discuss if another trajectory correction should be carried out around September 14.Till Wednesday, MoM had travelled around 630 million km along an arc, and is now, as the crow flies, more than 200 million km from Earth. At slightly less than 6 million km from Mars, it is moving at a speed of about 80,500kmph."It's going to be some hair—splitting days," said Radhakrishnan, his mobile phone beeping frequently with updates from S Arunan, the project director. "Of the 22 Mars orbiter missions tried by different countries, only nine have been successful."Project director Arunan is confident. "So far our mission has been on track and we are reaching the last phase of getting into the Martian orbit. Every mission has an element of uncertainty. That makes it thrilling," he said.November 5, 2013: PSLV—C25 lifts off from Sriharikota and injects MoM into an elliptical parking orbit 250km at its nearest point to earth and 23,550km at the farthestDecember 1, 2013: After six orbit raising manoeuvers over a month, MoM is slingshot into the Mars transfer trajectory using the 440N Liquid Engine on boardSeptember 03, 2004: After a series of trajectory correction manoeuvres, MoM has travelled more than 630million km along an arc and more than 200m km of radio distanceSeptember 24, 2014: The liquid engine onboard and the spacecraft will be fired again to insert MoM into the Martian orbitThe spacecraft will focus on in—depth study of morphology of the Martian surface and probe the composition of its atmosphere and space environmentFor visual referencehttp://isrohq.vssc.gov.in/isr0dem0v2/index.php/exploration1/mars—explorationhttp://www.isro.org/mars/navigation.aspx