Bangalore (PTI) India's maiden moon probe Chandrayaan-I developed a technical malfunction and came close to failure but space scientists salvaged the Rs 400 crore satellite which is now operational though crippled.

ISRO on Friday said the mission has achieved more than 90 per cent of the mission' scientific objectives.

The star sensor, a critical instrument on board India's only satellite orbiting the moon, failed on May 16 due to overheating and hurting the two-year mission launched on October 22 last and putting some experiments in jeopardy.

Space scientists got over the "anomaly" (star sensor failure) within a week by activating the satellite's gyroscope and put the spacecraft back into normal operation, Indian Space Research Organisation Chairman G. Madhavan Nair said.

Mr. Nair however said more than 90 per cent of the scientific and mission objectives had already been achieved, and dismissed suggestions that the sensor failure might reduce the lifespan of the spacecraft.

He said space scientists had tried to work around the problem and patched two other instruments to help manoeuvre the spacecraft to the desired locations.

"We are not sure how long we will be able to sustain it.

The life of Chandrayaan-I designed for two years may be reduced," ISRO spokesman S. Satish said.

Mr. Nair said the star sensor, one of the prime sensors, was used for determining the spacecraft's altitude. Looking at the stars, this sensor can determine the orientation of the moon spacecraft accurately.

ISRO is now using gyroscopes, electro-mechanical devices used for Indian Remote Sensing class of satellites, which gives the orientation accuracy quite satisfactorily, he said.

Mr. Nair dismissed suggestions that the ISRO kept that "handicap" under wraps and said the space agency is faced with one problem or other involving its fleet of 20 spacecraft everyday.

He, however, indicated that the Chandrayaan-1 odyssey might be curtailed earlier than the planned duration of the mission -- not because of the sensor failure but due to the likely completion of its mission objectives much ahead of schedule.

"Life (of the spacecraft) is not dependent on this instrument (star sensor). This instrument is used only for orienting the spacecraft", he said.

"The sensor cannot be recovered at this stage and we hope that the remaining part of this mission will be completed in the gyro mode as expected".

"...we will not be unhappy after completing the mission objectives, we have to close down the spacecraft (ahead of schedule", he said, adding, ISRO would meet the scientific community during August-September and decide "what needs to be done further (in regard to the moon mission)".

Mr. Nair said the star sensor is suspected to have failed because of "excessive radiation" from the Sun. He said gyroscopes are not susceptible for the kind of radiation that the sensor was subjected to. "So, we hope it will survive the remaining mission duration".

The sensor failure has given ISRO a "valuable input" for its Chandrayaan-II mission, slated for 2013 -- that electronic systems to be flown for deep space missions (unlike those in low earth orbits) need to be improved and hardened, he said.

The lunar probe launched from the spaceport of Sriharikota in Andhra Pradesh had put India in the elite club along with the US, Russia, the European Space Agency, Japan and China which have launched such missions.

Chandrayaan 1: In-depth

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