Mangalyaan engine to be test fired as spacecraft enters sphere of influence of Mars
Features Monday, September 22, 2014 - 05:30
The News Minute| September 22, 2014| 12.15 am IST After cruising through 666-million km across the solar orbit, for over nine months, the Mars Orbiter Mission (MOM) spacecraft will be inserted into the Martian orbit on September 24 at 7.30 a.m. But as a pre cursor to that, on Monday, as the spacecraft enters the sphere of influence of Mars, scientists at ISRO will test fire the main engine or the 440 Newton liquid apogee motor (LAM). In addition to this, the fourth and final trajectory-correction manoeuvre will also be conducted on Monday. As on Monday, the 475 kg (dry mass) spacecraft is 13 million km away from Mars, having cruised 98 percent (201 million km) of the radio distance from the earth and 653 million km of the sun's 666 million km orbit. "The course correction has been postponed to Sep 22 from Sunday (Sep 14) to conserve the precious liquid fuel weighing (852 kg) and ensure the orbital insertion takes place when the spacecraft is closer to Mars for smooth transition from the sun's orbit," Rao said. On Wednesday, the orbit insertion will take place when the spacecraft will be 423 km from the Martian surface and 215 million km away (radio distance) from the earth. The ambitious Rs.450-crore ($70 million) Mars Orbiter Mission (MOM) was launched Nov 5, 2013 on board a polar rocket from the spaceport Sriharikota off the Bay of Bengal, about 80 km north-east of Chennai. "India will be the first country in the world to insert a spacecraft into the Martian orbit in its maiden attempt if the operation succeeds and also the first Asian country to reach the red planet's sphere," Indian Space Research Organisation (ISRO) scientific secretary V. Koteswara Rao said. The state-run ISRO will be the fourth space agency after National Aeronautics and Space Administration (NASA) of the US, Russian Federal Space Agency (RFSA) and European Space Agency (ESA) to have undertaken a mission to Mars. Scientists at the spacecraft's control centre have started uploading commands since Sunday and will verify them late Monday. During the Orbiter's long journey, mid-course correction was carried twice - Dec 11 and June 11 - but skipped in April and August as it was cruising in the solar orbit as intended. "The liquid apogee motor (LAM) or fuel engine at the bottom of the spacecraft will be fired Sep 22 for four seconds to enter the Martian sphere of influence and the course correction will consume about 500gm of fuel," Rao said. The speed of the spacecraft will also be reduced to 2.14 metre per second from 22.2 km per second for enabling smooth transition into the Martian orbit from the sun's orbit Sep 24. The insertion operation will begin at 4.17 a.m. by first activating the spacecraft's three antennas for receiving and transmitting signals between earth and Mars. At 6.56 a.m., the spacecraft will be rotated towards Mars and five minutes later when sunlight is not falling on the Martian surface causing eclipse, the thrusters beneath the engine will give the Orbiter altitude control. "The liquid engine will start firing at 7.17 a.m. and at 7.21 a.m., Mars occult begins. A minute later at 7.22 a.m., telemetry (radio signals) will be off or out of receiving radars on the earth," Rao pointed out. Scientists at the space agency's deep space network at Byalalu, about 40 km from Bangalore, NASA's Earth station at Goldstone on the US west coast, the ESA's Earth station at Madrid will confirm the insertion into the Martian orbit 24 minutes later at 7.54 a.m. "Telemetry signals resume and Doppler measurements will provide first signals about the successful insertion of the spacecraft into the Martian orbit," Rao added. The spacecraft, with five scientific instruments, will be placed in an elliptical orbit, with the nearest distance from the Martian surface being 423 km and the furthest 80,000 km, to rotate around it in a duration equivalent to 3.2 earth days.
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