Chandrayaan's moon impact photos to be released soon

Tuesday, 30 December 2008, 09:22 Hrs
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New Delhi: It is a set of pictures that is among the most anticipated in India - around 3,200 frames tracking the descent of the first-ever Indian-built device to the moon's surface.

But the Indian public may have to wait for some more time to take a peek at that journey.

The images were taken by the 35-kg Moon Impact Probe (MIP) as it hurtled down for nearly 25 minutes after detaching from India's maiden lunar probe Chandrayaan-I and landed on the lunar surface at 8.31 p.m. Nov 14.

That day, the Indian Space Research Organisation (ISRO) had released two photos of the pockmarked surface taken from MIP. Nothing after that.

According to a key Chandrayaan scientist, it is now a matter of waiting a bit more - though he still could not specify the date.

"While we have released some sample images already, the full set of 3,200 pictures will also be made public after some more time," A.S. Kiran Kumar, deputy director, sensor development area in ISRO's Ahmedabad-based Space Applications Centre, told IANS.

Kumar headed the team which built the Terrain Mapping Camera (TMC), one of India's key payloads on Chandrayaan.

The pictures are currently being analysed at ISRO's Physical Research Laboratory. "We could be releasing it in a couple of months," Kumar said, adding that the last photograph on the set was from a height of two to three kilometres from the surface.

One of the several activities involved in getting the pictures ready for public release is to identify the surface features. "Since the pictures are of very high resolution, the features are not listed on any current moon atlas," he said.

The TMC has meanwhile been mapping the South Pole at a resolution of five metres, through lens capable of capturing images at three angles simultaneously.

Recently, China unveiled a three-dimensional map of the lunar surface with data from its Chang'e-1 mission, while Japan has been frequently releasing imagery from its lunar orbiter, Kaguya, including that of the landing site of the Apollo 17 spacecraft.

But, Kumar insisted, photographs collected by the Indian orbiter would be better due to higher resolution and lower orbit height at 100 km.

"The Chinese camera is three-dimensional but only has a resolution of 200 metres compared to our five-metre resolution. The Japanese one has 10-metre resolution, but they have only stereo doublet - we have a stereo triplet," he said.

By stereo triplet, the senior ISRO scientist referred to TMC's capability to take images from three angles - frontal, nadir and rear views. "The advantage is that no portion (of the surface) will be blocked. Occlusion will not be a problem," he said.

In optics, 'occlusion' refers to the method in which a close object masks or covers an object that is further away.

While Chandrayaan goes around the moon approximately 12 times each day - the camera is operational for two to three orbits.

"We have to balance every activity on the satellite, take note of the operating condition and find the optimal time to transmit to the ground station," Kumar said.

The time slot also gets limited as the camera has to factor in the solar illumination angle, which changes with the orbit of the moon. The scientists have decided to limit the solar angle to 30 degrees on both sides of the equator to take consistently well-lit images.

During the 20-minute photographing in each orbit, TMC captures images over an area 1,700 km long and 20 km wide, which translates into 1.4 km per second.

"Every second of data recorded takes about two and a half seconds to be transmitted to the ground station," said Kumar. The latest photograph released is of a lunar impact crater on the far side of the moon.

The senior ISRO scientist said several images have also been provided to academic institutions for analyses.

NASA's Moon Mineralogy Mapper payload team has also sought information from TMC. "They are interested in particularly looking at the terrain data," Kumar added.
Source: IANS
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