Satel­lites show worth in search

China Daily (Canada) - - COMMENT -

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 guan­ 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 sug­gest­ingChina’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 0.1me­ter, even 0.04 on a low­ered or­bit.

Gaofen-1, the first high-res­o­lu­tion satel­lite of China, has an imag­ing res­o­lu­tion of 1me­ter; 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 be­hindWorldView 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 Gaofe­nis 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 en­er­gy­con­sum­ing 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.

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