THE ASIAN TSUNAMI
An eye in the sky
Despite natural disasters striking the country each year, focus among official agencies is often sadly lacking. That deficiency may need more than just an infusion of technology to rectify, says N. GOPAL RAJ.
Satellite imagery of the southwestern coast of Sri Lanka just after the killer waves struck.
SINCE the earliest times, man has gazed skyward, hoping to discern signs of good or ill fortune in the patterns of the stars. These days, the heavens provide a very different sort of help and one born of human ingenuity spacecraft that can watch over us. Circling just a few hundred kilometres above the earth, remote sensing satellites can monitor all that is happening in the skies and on the ground below them. From this vantage point in space, the spacecraft's cameras can cover vast areas. With the advance of technology, the cameras can also capture startling close-up pictures. Other satellites act as space-based relay stations for all sorts of communications, be it telephone conversations or data being passed on from one computer to another.
Together, the remote sensing and communication satellites are powerful tools in coping with any natural disaster. The first gives the ability to quickly assess the extent of the damage that has been wrought and the places most badly affected, information that is essential for making sure that aid reaches the right places. The latter restores communication links that are likely to have been disrupted as a result of the disaster.
Satellites and relief work
India has several remote sensing and communication satellites of its own. The Indian Space Research Organisation (ISRO) has established the Disaster Management Support programme to ensure the effective utilisation of these space assets. Unfortunately, much of India is vulnerable to natural disasters of one kind or the other: coastal places can be ravaged by cyclones, major rivers can burst their banks and flood surrounding areas and the hilly regions can witness dangerous landslides. If this litany of woes was not enough, recent events have shown that tsunamis too can pose a terrifying threat, even though they may happen only once or twice in a century.
At present, satellites cannot be used to detect tsunamis. But ISRO has been using its satellites to assist the massive relief effort under way to help the victims of the tsunami of December 26. ISRO has supplemented satellites imageries by also deploying an aircraft equipped with high-resolution imaging systems. This aircraft has been used to obtain pictures of the tsunami-affected areas in Tamil Nadu and in the Andaman and Nicobar islands. In addition, ISRO has sent many hand-held satellite phones to the Andaman and Nicobar islands. It has repaired the satellite communication terminals there that were damaged by the tsunami, including one at a Car Nicobar hospital that was being used for telemedicine, according to a spokesperson for ISRO.
Floods are a yearly event. During the 2003-2004 financial year alone, ISRO helped Central and State agencies monitor 17 major floods, using satellite imageries to establish the extent of inundation. With remote sensing data, it is possible to map areas where there is standing water, those from which the flood waters have receded, areas with submerged standing crops, places where the floods have deposited sand on agricultural land, locate breaches in the embankments, and identify marooned towns and villages. By comparing images taken before and after the flood, the extent of damage to crops and infrastructure can be readily estimated.
A digital database
ISRO is creating a detailed digital database of disaster-prone districts in the country. Terrain information, data on land use patterns, infrastructure such as roads and buildings and the location of inhabited areas will be among the details recorded. When a natural calamity strikes, the affected areas can be delineated and the database will reveal how many people live in those places, where they live and what the probable extent of the losses will be.
Such information is required both to aid immediate rescue and relief efforts as well as to plan recovery from the disaster. "We need to understand the needs of government officials and present the information to them in a form that they can understand and act upon," remarked one ISRO oficial. It is understood that the database will cover some 60 districts in the first phase and will later be extended to cover over 150 districts.
An illustration from the National Oceanic and Atmospheric Administration that shows, from left, the sequence of the tsunami.
But satellites have their limitations too. ISRO's current remote sensing satellites' cameras depend on sunlight reflected back into space from the ground. So if clouds obscure the ground, the satellite
will not pick up any useful imagery. That is especially a problem during the monsoon when floods occur, but has reportedly also been an issue in taking images of tsunami-hit areas. One alternative is to deploy satellites equipped with radar, which can penetrate clouds and also provide pictures at night. Such satellites are bigger, heavier, more complex and much costlier than conventional remote sensing satellites. India is already using data from Canada's Radarsat satellite and plans to have its own radar satellite, Radar Imaging Satellite (RISAT), in orbit next year.
Images at the right time
There is also the issue of getting satellite images when needed. With the current Indian remote sensing satellites in orbit, images of any place can be secured within 11/2 days (assuming there is no cloud cover), say ISRO officials. But a rescue effort may need information about the affected areas in hours. The aircraft operated by the ISRO's National Remote Sensing Agency at Hyderabad, which is the nodal agency for receiving and processing remote sensing data, has been able to secure images in such a situation. When fitted with an airborne radar, the aircraft can take images even in conditions of low visibility and at night. The aircraft has been used in this mode for flood-mapping in Bihar. As an offshoot of the RISAT development, ISRO is planning a compact and more advanced airborne radar than the experimental set that it is currently using.
Another way to improve the availability of satellite imageries is to have more satellites in orbit. The Surrey Satellite Technology Limited (SSTL), a British company that has specialised in small satellites, has created a "Disaster Monitoring Constellation" consisting of four remote sensing satellites, with each satellite owned by a different country. ISRO is also looking at a similar concept. India is a signatory to the "charter on cooperation to achieve the coordinated use of space facilities in the event of natural or technological disasters", and the Indian satellites can be a part of a global constellation of satellites.
In the end, remote sensing data and better communications are only tools to help mount a properly coordinated and well-focused relief effort. Despite natural disasters striking the country each year, such coordination and focus among Central and State agencies is often sadly lacking. That deficiency may need more than just an infusion of technology to rectify.
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