Chandrayaan's performance deeply affected, says Nair

It is still not clear how much the failure of the star sensor on board has cut into the two-year journey of Chandrayaan. However, ISRO officials say the gyroscopes are prone to early failure compared with the star sensors. If the present gyroscopes fail on Chandrayaan, then “we will have to look for ways to salvage the mission,” says the official.

Drifts

As announced by Nair himself, the electro-mechanical gyroscopes have drifts. To determine attitude, they require antenna and additional information in the form of images taken of the Moon’s surface as reference. When the gyroscope took over on April 26, the not-so-precise element of it resulted in more manoeuvres for the spacecraft, resulting in the loss of more fuel for course correction.

To counter this problem, the orbit of Chandrayaan was raised from 100 km from the lunar surface to 200 km on May 19. The thermal environment at this altitude was benign, resulting in less number of manoeuvres for the spacecraft, besides saving on fuel.

Even with this move, the fuel might not be sufficient for the two-year journey. But ISRO officials argue the greatest danger comes from the failure of the gyroscope itself rather than the fuel being exhausted.

The ISRO chief also declared that 90-95 per cent of the data had already been collected, accomplishing majority of the objectives specified under the mission.

It has been a mere eight months, since the payloads have been functional. It is not yet known if these mission objectives were reworked in view of the orbit being raised to 200 km, following the failure of the sensor.

ISRO spokesperson S Satish said the duration of the mission was kept longer, as it was not certain whether all the payloads would be functional concurrently.

Only two payloads, the Moon Mineralogy Mapper, which provides information about the types, quantity and location of minerals present on the lunar surface and the Hyperspectral Imager, which takes pictures of the moon’s surface by recording the visible and infrared light, are pending.

The remaining payloads, according to the ISRO, have completed all the mission objectives.

Though the ISRO chief declared that the mission would not be cut short, the stage seems to be set for a sooner-than-expected death of the country’s maiden moon mission.

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