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Chandrayaan’s orbit raised again

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Alert eyes: Scientists manning the monitoring consoles on October 25 at the Indian Deep Space Network Control Centre at Byalalu village near Bangalore, where two huge bowl-shaped antennae have been set up to track and communicate with Chandrayaan-1.
Alert eyes: Scientists manning the monitoring consoles on October 25 at the Indian Deep Space Network Control Centre at Byalalu village near Bangalore, where two huge bowl-shaped antennae have been set up to track and communicate with Chandrayaan-1.

Special Correspondent

CHENNAI: “An air of professionalism and cool-headedness” prevailed at the Spacecraft Control Centre (SCC) at the ISRO Telemetry Command, Control and Tracking Network (ISTRAC), headed by S.K. Shivakumar at Bangalore, where radio frequency specialists radioed commands on Sunday morning to the engine on board Chandrayaan-1 to fire, an ISRO official said.

The engine fired for about nine-and-a-half minutes from 7.08 a.m. on Sunday. This successful firing lifted the spacecraft’s orbit from an apogee of 74,715 km and a perigee of 336 km on Saturday to its present apogee of 1.64 lakh km and a perigee of 348 km. The spacecraft has almost reached half the distance to the moon, which is 3,84,000 km away from the earth. In this orbit, Chandrayaan-1 takes about 73 hours to go round the earth once.

At this distance from the earth, the electric transmitter power with which Chandrayaan-1 “whispers” is so low that the signals received from it are very feeble and they have to be amplified, the official explained. “So it is quite a big challenge to communicate with the spacecraft when it is travelling deep in space,” he added.

The two antennae with a diameter of 32 metres and 18 metres that belong to the Indian Deep Space Network (IDSN) of ISRO at Byalalu village, near Bangalore, were playing a crucial role in tracking and communicating with Chandrayaan-1 in such a high orbit. When the spacecraft becomes operational, these huge bowl-shaped antennae will also receive scientific information from the 11 instruments on board Chandrayaan-1.

If three more firings of the liquid apogee motor on Chandrayaan-1 are successfully accomplished on October 29, November 3 and November 8, the spacecraft will reach its final abode of 100 km around the moon on November 14th or 15th. Commands will then be radioed from the Spacecraft Control Centre to Chandrayaan-1 to eject the Moon Impact Probe (MIP) which “sits like a hat on top of it.”

The MIP, which will crashland on the moon’s surface, will be a technological forerunner to India landing a rover in the moon around 2012-2013 as part of Chandrayaan-2 mission with Russia.

After the MIP is ejected, the remaining 10 scientific instruments on the spacecraft will be switched on, one after the other.


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