Chandrayaan Unveiled

Bangalore, Sep 18: It looked like a colourful wrapped candy as the spacecraft that will launch India`s maiden odyssey to the moon was on Thursday unveiled here.

The spacecraft, lodged at `Checkout 2` room at the centre is all decked up with golden multilayer insulated foils covering a major part of its body with the highly sophisticated components sitting snugly inside.

The integrated lunar spacecraft has successfully passed the thermal vaccuum test where the spacecraft was inserted into a huge simulator akin to a well and its chambers closed.

The temperature of the chamber using infra red rays was raised to maximum of 120 degrees and lowered to minimum of over minus 100 degrees to test its mechanical and system integrity, an ISRO official said.

"The test, carried over 20 days, simulated conditions akin to the harsh environment in the moon where temperature ranges from high to very low. The test ensured that all the components and packages integrated were working and there was no mechanical or system defect, the official told the media team.

The spacecraft built by ISRO in collaboration with other partners like HAL will carry 11 payloads, including five instruments developed by ISRO. These include a Terrain Mapping Stereo Camera which could capture images having five m spatial resolutions (size of the smallest object that can be seen) and 20 km swath (width of the picture). This would help in topographic mapping of moon.

The spacecraft would have a hyper spectral camera (for mineral mapping), a laser-ranging instrument (for topography), Xray Fluorescence spectorometer (for chemical mapping), Higher Energy Xray spectrometer for identifying and understanding the transport of volatiles on the moon.

It will carry a moon impact probe (which will detach itself on arrival on the moon`s orbit), having three instruments, a mass spectrometeter, a C-band Altimeter and a video camera, which will capture information within 20 minutes during its slow falling motion on the moon`s surface, Srikumar, Chief Scientist, said.

Apart from the above five pay load, it would carry additional instruments of other countries; a Miniature Imaging Radar Instrument from NASA (for detection of polar ice and soil topography, altimetery) Sub KeV Atom Reflecting Analyser (from IRF, Sweden, JAXA, Japan, supported by ESA and VSSC and ISRO) for detection of atmospheric neutrals composition, magnetic anomalies).

It would also have a Moon Mineralogy Mapper from US, Infra-Red Spectrometer-2 from Germany and Radiation Dose Monitor from Bulgaria for studying radiation.

"We received 26 offers to carry payloads and brought the number down after debating", an ISRO official said.

The spacecraft carries a bipropellant propulsion system for carrying fuel for two years in orbit.

After separation from the launcher, the spacecraft will be raised to moon rendezvous orbit by three consecutive "in-lane manoeuvres at the perigee (closest location to earth) to achieve the required 386,000 km apogee", M Annadurai, Project Director, said.

"After third perigee `burn`, the achieved lunar transfer trajectory orbit is computed using tracking data received by the Deep Space Network and midcourse correction if required is done.

"The spacecraft will coast for about five days in the trajectory prior to the lunar encounter," the official said.

"The major manoeuvre of the mission is called the lunar orbit insertion leading to lunar capture. The manoeuvre ensures successful lunar capture in a polar, near circular 500 kms altitude orbit around the moon," he said.

"After successful capture and health checks, the latitude will be lowered through a series of in-plane corrections to 100 km near circular orbit," Annadurai said.

"Everything has been planned to ensure that the satellite moves at a position when the moon was closest and could be captured by the Moon`s orbit. The satellite will rotate around the earth`s orbit twice before it is fired into the lunar orbit," he said.

The travel from the earth to moon`s orbit is expected to take around 20 days in all including five days during the last lap of the journey.

The nearly 1,400 kgs Chandrayaan will be launched by PSLV-XL, a variant of flight proven PSLV from Satish Dhawan Space Centre and tracked and commanded by a 32 metre antenna at Byalalu near Bangalore.

The mission would provide insights into the chemical composition of the moon, detect, if any, the presence of water, study solar winds, map minerals and attempts to answer questions on moon`s composition. It will study far and near side of the moon and provide a three-dimensional picture.

While India prepares for its maiden unmanned mission, the Chandrayaan Mission two is already on the drawing board, he said, adding that the second mission would have Rover landing on the moon and collect samples.