Satellite images for big picture

S'pore's Crisp research centre relies on seven satellites to keep track of environmental goings-on in the region

YOU need the big picture when trying to detect sea pollution, forest fires and other environmental problems.

And Singapore's Centre for Remote Imaging, Sensing and Processing (Crisp) is there to provide it.

Seven satellites, circling the earth twice every three hours, send a continuous supply of pictures of the region to Crisp's satellite ground station at the National University of Singapore (NUS).

Crisp helped the Maritime and Port Authority of Singapore nail the oil tanker Song San for polluting Singapore waters in August 1996. It has also helped monitor haze and forest fires daily since 1998.

Other projects include surveying rice cropping systems in Vietnam, monitoring toxic red-tide plankton and looking at the health of trees in forests hit by fires.

Crisp captures 400 to 500 scenes daily from five commercial satellites - the French Spot satellites, Europe's ERS and Canada's Radarsat. It charges about US$2,000 (S$3,600) per image.

Director Kwoh Leong Keong told The Straits Times that the centre also provides other services.

For instance, it has developed software able to combine more than one image taken of the same area.

'In this region you can wait for a year to get a cloud-free image,' he said. 'So we combine many images to get a cloud-free result.'

Crisp, which began operations in 1995, is an NUS research centre.

Its two antennae - with diameters of 13 m and 6 m - receive satellite images of a 3,000-km-radius area.

CHANGES

Get a bird's-eye view of Singapore, past and present, in these images from the Centre for Remote Imaging, Sensing and Processing (Crisp). The centre uses satellites hurtling over the region to take photographs. CHANG AI-LIEN marvels at these pictures.

THE PRESENT

-- CNES

THIS is a computer-processed picture of Singapore corresponding to the one on the facing page, which is in natural colour. It was taken by the French Spot 2 satellite, which 'sees' in three colours - red, green and infrared. Because it does not detect blue, anything green is made blue here, and anything red is made green. Infrared, which the satellite camera can see but the human eye cannot, is represented by red. The trees and vegetation appear red because they reflect near-infrared bands - between red and infrared - more strongly than they reflect the green bands which we see in real life. In the image on the facing page, Crisp has used a computer program to predict the blue areas, and so it can reproduce the image in natural colour.

THE PAST

This 1973 picture of Singapore shows how much the country has changed. It is clear that many areas have been built up and developed. And how the nation has grown. Singapore's land area increased from 580 sq km in the 1960s to 660 sq km in 1999, mainly due to land reclamation. Future reclamation could make up an additional 100 sq km.

How they do it: The satellites sail 600 km to 800 km above the earth, circling the globe about 16 times daily at tremendous speeds of about 25,000 kmh. Pictures are sent via microwaves to the the centre's ground station. Crisp can produce full-resolution images a mere 10 minutes after the satellite has passed.