The Hindu : Moon mission in five years

Online edition of India's National Newspaper
Sunday, Aug 17, 2003

National

National

Moon mission in five years

By N.Gopal Raj

THIRUVANANTHAPURAM Aug. 16. India's Moon mission, Chandrayan-1, which was formally announced by the Prime Minister, Atal Behari Vajpayee, in his Independence day address, will pave the way for more planetary exploration, according to the Indian Space Research Organisation (ISRO)

The Chandrayan-1 is expected to be the forerunner of more ambitious planetary missions in the coming decades, including landing robots on the Moon and visits to other planets in the solar system, an ISRO press release issued today said. The Chandrayan-1 is to be launched in five years' time.

The Indian Moon mission will be unique in many respects, says George Joseph, former director of the Space Applications Centre at Ahmedabad, who headed the task force, which examined how best to carry out the Moon mission. Dr. Joseph holds the ISRO's Satish Dhawan Distinguished Professorship.

The satellite, weighing over 1,000 kg at launch, will map the entire surface of the Moon and also carry instruments to study its composition. A single high-resolution camera, using a unique arrangement of light detectors, will provide the stereoscopic capability necessary for three-dimensional mapping of the Moon. Most of the Moon will be mapped at a resolution of five metres. But towards the polar regions, where light will be less, the resolution would be 15 to 20 metres.

The satellite will also carry an X-ray and gamma ray spectrometer, as well as an imaging camera, which can distinguish visible and infrared light in up to 32 frequency bands. Both instruments will be used to study the Moon's composition and provide insights into its origins. Provision has also been made to accommodate instruments from other countries.

An updated version of the Polar Satellite Launch Vehicle (PSLV) will place the lunar spacecraft in an elliptical Geostationary Transfer Orbit (GTO). This is the temporary orbit occupied by communication satellites before moving to their final orbital positions. The PSLV has already been used once for a GTO launch, when it successfully lofted the country's first dedicated meteorological satellite, Kalpana-1, a year back.

The satellite will then fire its own onboard rocket engine to acquire the velocity needed to break free of the Earth's gravitational pull and head for the Moon. The satellite will weigh 525 kg when it enters into orbit around the Moon.

Initially, the spacecraft will circle the Moon several hundred kilometres above its surface. During this phase, the spacecraft's orbit will be closely monitored. The perturbations to its orbit will serve to accurately map the Moon's gravitational anomalies. The satellite will then be brought down to a height of just 100 km.

A large diameter deep space antenna will have to be set up to receive radio signals from the spacecraft. While it is circling the Moon, the spacecraft will be about 380,000 km from Earth and its radio signals will be faint. These signals make it possible to track the spacecraft, monitor the health of its onboard systems and also provide the channel for sending back the voluminous data gathered by its scientific instruments.

The satellite will be designed for a life of two years. ``It will be one of the longest missions to the Moon,'' says Dr. Joseph.

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