Despite glitches, ISRO confident of Chandrayaan-I
Monday, 20 July 2009, 14:09 IST   |    7 Comments
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Chennai: The Indian Space Research Organisation's (ISRO) first lunar mission Chandrayaan-I may have suffered technical setbacks within a year of its launch, but the organisation is confident that the spacecraft will complete its mission. "The failure of electronic components within a year of a satellite's launch is one of the risks that a mission faces. Once the satellite crosses one year, then one can expect stable operation for several years to come," M. Annadurai, project director of Chandrayaan-I and II, told IANS from Bangalore on phone. Chandrayaan-I's onboard star sensor -- a critical component that guides the spacecraft -- failed May 16 owing to heat around the moon. What compounded the problem was that the standby unit also failed. Though another component on the spacecraft -- the Bus Management Unit -- also failed, the satellite was able to switch on the standby unit. To manage the situation, ISRO hit upon an innovate technique. It used the redundant sensors-gyroscopes -- along with antenna pointing information and images of specific location on the surface of the moon -- for determining the spacecraft's orientation. Curiously on May 20, ISRO raised the spacecraft that was orbiting the moon at a height of 100 km (originally intended orbital height) since November last year to 200 km stating that it would now be imaging the lunar surface with a wider swath. According to Annadurai, the satellite will function normally provided no other component fails. His confidence stems from the fact that a similar critical situation arose when India's communication satellite Insat-2E was launched in 1999. "Couple of years after its launch Insat 2E encountered a critical problem as its main and standby earth sensors failed," recalled Annadurai, who was also the mission director for that satellite launch. According to him, the communication satellite mission was saved by out of box thinking to use alternate components to perform the functions of the failed ones. "Insat 2E is even now functioning very well, much beyond its projected life span. The satellite's transponders are now transmitting several television channels," he remarked. The other satellite that is being partly utilised as it didn't reach its intended orbit is the GSAT-1 launched in 2001 by the first geosynchronous satellite launch vehicle (GSLV), the second rocket of ISRO. "Though GSAT-1 drifted, as we had some experimental instruments in that we used other means to make the satellite functional to get the required data," he remarked. According to him, India's lunar satellite has already visited and photographed all the spots it had to visit till date. "Prior to the launch we thought of downloading the data sent by Chandrayaan-I only from India. The effective download time was 12 hours. However a satellite observation centre in the US agreed to download the data at its end so that there is a continuous data download for 24 hours. As such scientific data required has already been acquired," Annadurai explained. ISRO's Polar Satellite Launch Vehicle (PSLV) put into orbit Chandrayaan-I Oct 22, 2008 from its launch centre at Sriharikota around 80 km from here. Revolving around the moon around 3,000 times during the last eight months, Chandrayaan-I has sent more than 70,000 images of the surface including the lunar mountains and craters, including those in the permanently shadowed regions. The spacecraft is also collecting valuable data pertaining to the chemical and mineral content of the moon. Though Chandrayaan-I has six foreign payloads, Annadurai said ISRO is not liable to pay any compensation if the mission does not complete its full life term. Annadurai also refuted the claim that ISRO had given up on the moon mission. "We have not given up the mission." Annadurai said the learning from this first mission was immense. "We launched the spacecraft with the information gathered from others. Now we have first hand data and experience."
Source: IANS
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