Bangalore, July 17 (Inditop.com) The failure of a critical sensor onboard India’s maiden lunar spacecraft Chandrayaan-1 will not impact its mission life and space scientists have overcome the snag with an innovative technique, a top space official said here Friday.
“The star sensor used to determine the orientation of the spacecraft towards the lunar surface started malfunctioning from April 26 due to excessive radiation of the sun while orbiting 100 km away from the moon,” Indian Space Research Organisation (ISRO) chairman G. Madhavan Nair told reporters here.
“We have used redundant sensors (gyroscopes) along with antenna-pointing information to overcome the anomaly,” he added.
Claiming that the snag would not curtail the mission’s life, which lasts two years, Nair said that scientists had corrected the orientation to enable the 514 kg spacecraft look at the lunar surface from its raised orbit of 200 km away from the moon.
“We have overcome the failure of the star sensor and brought the mooncraft back into normal operation using gyroscopes and electro-mechanical devices used for remote sensing satellites to determine orientation accurately,” Nair asserted.
Chandrayaan was launched amid fanfare Oct 22, 2008, from spaceport Sriharikota, about 90 km north-east of Chennai, onboard the 316-tonne polar satellite launch vehicle (PSLV-C11). It was inserted into the lunar orbit Nov 8. A week later, its moon impact probe (MIP) landed on the lunar surface Nov 16.
“Other than the failure of the star sensor and one of the bus management units, the health of the spacecraft is normal. A review of its activities confirmed that all primary mission objectives have been met during the eight months of its operation,” Nair pointed out.
The 11 scientific payloads onboard the mooncraft continue to send high quality data as per planned sequence to its ground station – the space agency’s Deep Space Network (DSN) at Byalalu, about 40 km from this tech hub.
“We will take a detailed review of the scientific objectives and the performance results of the mission in the next three months. Further operational procedures will be worked out accordingly,” Nair noted.
“Chandrayaan faced hostile environment around the moon, especially in terms of thermal cycling as well as radiation. The first encounter was when it was put in the 100 km orbit. The spacecraft reached a stage of thermal runaway about a month after it was inserted into the lunar orbit. The entire spacecraft would have been baked. We would have lost it,” Nair recalled.
Nair admitted that the mission had reached a stage where many of the electronics have failed and some of the power supply instruments have malfunctioned.
“We were, however, able to energise the redundant units and keep them alive,” he added.
The mooncraft has orbited around the moon 3,000 times during the last eight months and its high-resolution cameras relayed about 70,000 digital images of the lunar surface, providing breathtaking views of mountains and craters, including those in the permanently shadowed area of the moon’s polar region.
“The spacecraft is also collecting valuable data pertaining to the chemical and mineral content of the moon, the earth’s only natural satellite,” the space agency said in a statement later.
Scientists at the satellite control centre of the ISRO telemetry, tracking and command network (ISTRAC), raised the spacecraft’s circular orbit May 19 to 200 km away from the lunar surface to reduce the resolution of the imagery but widen the swath for gathering good quality data.
Of the 11 scientific payloads, five are Indian. Of the other six, three are from the European Space Agency (ESA), two from the National Aeronautics and Space Administration (NASA) of the US and one from Bulgaria.
The scientific objectives of the spacecraft are remote sensing of the moon in visible, near infrared, low energy x-ray and high-energy x-ray regions.
During the two-year expedition, some of the payloads will prepare a three-dimensional atlas of both the near and far side of the moon, with a high spatial and altitude resolution of 5-10 metres.
Referring to the problems encountered by the mission after its launch, Nair said space missions were very, very complex and there were instances of problems onboard.
