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Remote sensing gets smaller, sharper, high-tech

As remote-sensing technologies go, the hyperspectral Earth imagery technology that ISRO is testing on the just-launched 83-kg mini satellite IMS-1 is apparently the next thing to watch out for.

Early birds
ISRO wants to be among the early birds in that uncharted band in the coming years. Hyperspectral imagery is not fully in the global market and only a couple of other space agencies are still testing it out.

While ISRO plans to share IMS-1 imageries selectively with research agencies and third world countries, it could be putting a satellite offering hyperspectral data on commercial basis in 2-3 years’ time.

The hyperspectral applications range from mineral exploration and crop health monitoring to national security and surveillance – all of which need a high level of clarity and differentiation of the object. A similar ‘hyspex’ camera is being put on the Chandrayaan-1 mission slated for the third quarter this year. The Moon orbiter aims to map the lunar surface and explore its minerals.

Cartosat data
“We (ISRO) are working on all (hyperspectral aspects such as) advanced technologies, devices, electronic processing, onboard data handling and data compression on ground,” said Dr V. Jayaraman, Director, Earth Observation Systems at ISRO. All the innovations would have major social, strategic and commercial spinoffs.

The two satellites are already beaming good pictures but the Cartosat data is to be assessed fully in the coming 3-6 months before it is given out to users, according to Mr K.R. Sreedhara Murthi, Executive Director of Antrix Corporation, ISRO’s export arm. Cartosat-2A data look finer and along with predecessor Cartosat-2, would halve the time taken to cover a region.

Hyperspectral images
As for hyperspectral imageries from IMS-1, Mr Murthi said, “We still need to experiment on a few applications before the operational applications can evolve. Globally, too, this area is not commercially established.”

Hyperspectral images are as lucid as the technology is complex and the design is challenging. Such pictures give 64 differentiated colours compared to the present four primary (multispectral) colours from the ‘vanilla’ IRS (Indian remote sensing) satellites. Processing the overlapping colours also will be difficult.

The extremely high level of colour differentiation, however, reduces the fine view or resolution that a remote-sensing satellite camera can give. Dr Jayaraman told Business Line that in the coming years, ISRO was trying to fuse the two advantages – colour and clear view – on to one platform from an upcoming satellite, perhaps Cartosat-3.

This could go as fine as a resolution of 30 cm – the stupendously small size that can be picked up from a distance of 600 km above Earth. The best global offer today is around 40-50 cm by a US commercial satellite while Cartosat-2A that was launched on Monday can give up to 80-100 cm. ISRO will be offering 1-m imageries from Cartosat-2A, Dr Jayaraman said.

Small satellites
The budget for remote-sensing remains at 12-15 per cent of the overall outlay for Department of Space projects – which this year has increased 24 per cent to Rs 4,074 crore. ISRO’s future remote sensing technology is getting smaller, sharper and specific. Starting with IMS-1, “We are going towards small satellites. Where the 1990s twin-cameras on an IRS weighed 120 kg and beamed 5-6 km resolution pictures, today’s IMS has a single camera of 5.5 kg. Our resolution is less than 1 metre (on Cartosat-2A),” he said. The next IRSs fall into three themes: Resourcesats 2 and 3 along with microwave or RISAT will be the workhorses for land and resources observation; mapping will be done with a series of Cartosats (three are up now); and sea and atmosphere monitors like Oceansats and the Indo-French Megha Tropiques, among many others. “We have to have a series of satellites for a variety of uses, along with new sensors and new technologies,” Dr Jayaraman said.