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Chandrayaan falters as ‘star sensors’ fail

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G. Madhavan Nair.
G. Madhavan Nair.

Divya Gandhi

A handicap, but 90-95% of objectives accomplished: Madhavan Nair

Bangalore: Less than nine months after India’s first lunar satellite Chandrayaan-I was launched in the glare of media flash bulbs, the chairman of the Indian Space Research Organisation announced that the satellite’s ‘star sensors’ – vital in determining the orientation – had failed.

Describing the failure a “handicap,” Madhavan Nair told journalists at the ISRO headquarters on Friday, that Chandrayaan’s orientation had been set right by activating contingency “gyroscopes” on board.

Being an electro-mechanical device, however, the life-span of the gyroscopes cannot be predicted, said S. Satish, ISRO spokesperson. He added that on May 19 Chandrayaan’s orbit was raised from 100 km to 200 km from the lunar surface to “save fuel” after the gyroscopes were activated.

According to an ISRO press release, one of Chandrayaan’s bus management units, which performs crucial control functions on the spacecraft, has failed. This would imply that the spacecraft is running on the backup unit.

The technical snag, which occurred on April 26, was detected on May 16, according to ISRO sources. Mr. Nair attributed it to “excessive radiation from the sun” that “can degrade devices in the star sensors.” The sensors cannot be recovered at this stage and the remaining part of the two-year mission would be completed in the “gyro mode,” he said, adding that “the orientation accuracy has been quite satisfactory.”

Asked if the sensors’ failure would compromise the expected two-year life-span of the satellite, the ISRO chairman said: “The life [of the spacecraft] is not dependent on this instrument. This instrument is used only for orientation of the spacecraft.” A large number of other factors including fuel and telemetry would also contribute to a successful mission, he said.

He added that “90 to 95 per cent” of the objectives of the lunar mission had been accomplished, including reaching the satellite to a 3.84 lakh km orbit around the moon; capturing images of its terrain and ascertaining its mineral content; and placing the Indian tri-colour on its surface.

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