Chandrayaan 1 snippets

The reasons for early termination of the Chandrayaan-I mission are now tumbling out and they reveal that Isro had kept the moon orbiter’s problems tightly under wraps. Contrary to the space agency’s explanation that Chandrayaan’s orbit around the moon had been raised from 100 km to 200 km in May this year for a better view of the lunar surface, it is now known that this was because of a miscalculation of the moon’s temperature that had led to faulty thermal protection. Admitting this, Dr T K Alex, director, Isro Satellite Centre, Bangalore, said, ‘We assumed that the temperature at 100 km above the moon’s surface would be around 75 degrees Celsius.However,it was more than 75 degrees and problems started to surface. We had to raise the orbit to 200 km.’’ On May 19, Isro said it had raised Chandrayaan’s orbit to “enable further studies on orbit perturbations, gravitational field variation of the moon and also to enable imaging of a wider swathe of the lunar surface’’. It now transpires that heating problems on the craft had begun as early as November 25, forcing Isro to deactivate some of the payloads—there were 11 in all. As a result, some experiments could not be carried out which raised questions on whether the pre-launch thermal vacuum test done on the spacecraft was adequate. In early 2009, the situation improved and Chandrayaan-1 started operating normally. However, the snags resurfaced—this time with the two star sensors because of high temperature. The sensors are crucial in determining the orientation of the craft in space.
What Went Wrong?
Problems began because Isro miscalculated temperature at 100 km above the moon’s surface, Chandrayaan’s scheduled orbit. Craft was built to withstand 75°C but encountered higher temperatures
November 25, 2008 : Heating problems emerge, forcing Isro to deactivate some payloads. A few experiments have to be aborted
April 26, 2009 : Chandrayaan’s star sensor packs up. Back-up sensor too fails in 2nd week of May
May 19 : Spacecraft’s orbit raised to 200km to avoid the heat. Isro says this was done to enable ‘‘further studies’’ of the Moon Isro engineers use ingenious ways to restore spacecraft but ‘‘it was like repairing a car’s broken steering wheel with Scotch tape,’’ admits an official
August 29 : Communication with craft snaps all of a sudden. Isro chairman says onboard computers got affected by heat. Acknowledges that heat-related problems weren’t anticipated August 30 : Mission formally called off
Despite the failure of the star sensors, Chandrayaan-1 transmitted excellent images, including that of the solar eclipse on July 22. Also at 12.30 am on August 21, it flew along with a Nasa craft to detect ice on the moon’s north pole. “Chandrayaan-2’s thermal design will be strengthened to withstand more than 100°C,’’ T K Alex, director of Isro Satellite Centre, Bangalore, said on the sidelines of the eighth international conference on low cost planetary mission conducted by the International Academy of Astronautics in Goa. Barc is collaborating with Isro to strengthen the radiation shield of Chandrayaan-2, slated for lift-off in 2013. The average day temperature on the moon’s surface is 107°C, while the mean night temperature is -153°C. Though Isro claims 95% of its planned experiments have been completed, it remains to be known whether payloads designed to operate at a 100-km orbit completed their missions. The issue has triggered a fierce debate on whether Isro should have declared it a one-year mission right at the beginning rather than an ambitious two-year programme.

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