Despite glitches, ISRO confident of Chandrayaan-I completing mission

CHENNAI: The Indian Space Research Organisation's (ISRO) first lunar mission Chandrayaan-I may have suffered technical setbacks within a year of
its launch, butthe 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. link....