World / Opinion

Satellites show worth in search

(China Daily) Updated: 2014-03-28 06:57

China and other countries have employed satellites as well as aircraft and ships in the search for the missing Malaysia Airline plane. Some people have cast doubts on China's satellite technology because a United States' satellite first reported finding what was possibly the wreckage of the flight. Does China lag far behind in satellite technology? A column on gives detailed analysis. Excerpts:

The search for Flight MH370 is not the first time satellites have been used in such a disaster. When Air France Flight AF447 went missing, the United States used satellites to collect information about the weather and analyze the cause, although they were not used directly in the search.

Therefore China and other countries using satellites in the operations for the Malaysia Airlines plane is unprecedented. China has used about 20 of its satellites in all, which are of four types the Gaofen (high resolution), Yaogan (remote sensing), Fengyun (meteorology) and Haiyang (sea probing). The satellites have located floating objects, but so far all have proved not to be debris from the missing plane. The US satellite WorldView-2 made a breakthrough by finding signs of wreckages off Perth of Australia, and a French satellite found floating objects in the main search areas of the Indian Ocean.

That's why some are suggesting China's satellite technology lags behind that of US. It might be hard to compare different countries' satellite technology, but we can try to analyze from different aspects.

High-resolution satellites were first used as military reconnaissance satellites. The first reconnaissance satellite was the "Discoverer" of the US in the 1950s, which had imaging resolution of 15 meters; the technology was constantly improved and now the US' military "keyhole" KH-12 satellites have an imaging resolution of 0.1 meter, even 0.04 on a lowered orbit.

Gaofen-1, the first high-resolution satellite of China, has an imaging resolution of 1 meter; while the world record is held by DigitalGlobe, the precision of whose WorldView-2 that participated in the rescuing work is 0.5 meter, which will be improved in future models.

Thus it is obvious that China's Gaofen lags behind WorldView in resolution. But the floating objects found by both of them are more than 10 meters long; in that case, the resolution for both satellites is enough. Besides, higher resolution means a more limited view, which limits its use. The 16-meter resolution camera of the Gaofen-1 can cover 800 kilometers while a 2-meter resolution camera covers only 70 kilometers.

There are other indexes to judge a satellite's performance, such as time resolution. That for Gaofen-1 is four days, which means it can observe a certain area every four days; the same index for many other countries' satellites may be 20 days.

Besides the above-listed hardware, experienced analysts are also needed to read and interpret the photos shot by satellites; the higher the resolution, the more skill it takes. The fact that China released information about Gaofen-1 finding objects in a very short time implies hard work behind the scenes.

Above are pure technological comparisons of China and other countries' satellites. There are economic considerations, too. Gaofen-1 and other Chinese satellites started taking photos the day after the plane went missing, so it is possible that China changed the observation plans of the satellites in the search mission or even adjusted angles or orbits of some satellites, which is a very energy-consuming move that will shorten the satellites' lifespan. China's ability to maneuver the satellites in such a short time proves its ability to conduct such costly moves. China's satellites are doing a good job in the search for MH370.

The opinions expressed on this page do not necessarily reflect those of China Daily.

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