Chandrayaan set right after sensor malfunction

Friday, 17 July 2009, 22:25 IST
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Chandrayaan set right after sensor malfunction
Bangalore: Indian space scientists have corrected the orientation of the country's first lunar spacecraft Chandrayaan-1 after one of its sensors malfunctioned, a senior official said Friday. "We have overcome the snag and the spacecraft is again able to look at the lunar surface while orbiting at about 200 km above the moon," Indian Space Research Organisation (ISRO) director S. Satish told IANS. The defect in the star sensor was detected over a month ago. Scientists at the satellite control centre of ISRO telemetry, tracking and command network (ISTRAC) here overcame the disorientation, using the antenna-pointing mechanism and gyroscope on board the spacecraft. "We have succeeded in veering the spacecraft towards the moon without affecting its multiple functions and all its scientific instruments are working satisfactorily. The mission is safe," Satish said. The space agency's deep space network (DSN) at Byalalu, about 40 km from here, is able to receive the orientation information from the spacecraft regularly. "Orientation of the spacecraft towards the lunar surface is critical for conducting the experiments. If it's away or disoriented, data collection will be difficult," Satish noted. The malfunction occurred about three weeks after Chandrayaan's orbit was raised to 200 km from 100 km with a wider swath May 19 for further studies on orbit perturbations and gravitational field variation of the moon. "The orbit-raising exercise has enabled us to minimise the number of manoeuvres. The spacecraft has completed about 3,000 orbits around the moon, with 12 orbits a day," Satish pointed out. The 518 kg Chandrayaan-1 was launched Oct 22, 2008 from India's only spaceport Sriharikota, about 90 km north-east of Chennai, on board the 316-tonne polar satellite launch vehicle (PSLV-C11) and inserted into the lunar orbit Nov 8. During the last nine months, all the 11 scientific payloads on board the spacecraft were started and the space network has been receiving excellent quality data about the moon. Of the 11 scientific instruments (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 near and far side of the moon, with a high spatial and altitude resolution of 5-10 metres. "Specific instruments will conduct chemical and mineralogical mapping of the entire lunar surface for collecting data on the distribution of elements such as magnesium, aluminium, silicon, calcium, iron and titanium, with a spatial resolution of about 25 km and high atomic number elements such as radon, uranium and thorium, with a spatial resolution of about 20 km," the ISRO official said. Of the five Indian payloads, the 34 kg moon impact probe (MIP) was landed on the lunar surface Nov 14 last year from a distance of 100 km after the spacecraft was inserted into the lunar orbit Nov 8. During the 25-minute descent of the probe, its mass spectrometer measured the constituents of the thin lunar atmosphere. The spectrometer also analysed the chemicals and minerals of the moon and relayed the data to the ground station after the probe crashed into the lunar surface. The probe, carrying three instruments and with the Indian flag painted on its outer panes, settled in a crater in the moon's south pole.
Source: IANS
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