(From Popular Science)
By Jeffrey Lin and P.W. Singer
On December 28, 2015, a Long March 3B/G2 rocket launched from Xichang and lofted into space the 4.6 ton Gaofen-4 imaging satellite.
Billed as a disaster relief satellite, the Gaofen 4 was placed in Geosynchronous Orbit (GEO). GEO satellites constantly stay above a patch of Earth, thus providing constant 24 hour surveillance of a geographic area. By contrast, low earth orbit (LEO) satellites such as the U.S. KH-11 spy satellites are closer to the Earth, so their speed exceeds that of the Earth’s rotation (meaning that they cannot maintain continuous surveillance over specific locations). In the Gaofen 4’s case, its range of view is a 7,000km by 7,000km box of 49 million square kilometers of Asian land and water in and around China.
The Gaofen 4 is the world’s most powerful GEO spy satellite. It has a color image resolution of slightly less than 50 meters (which is enough to track aircraft carriers by their wake at sea) and a thermal imaging resolution of 400m (good for spotting forest fires). It may also have a lower resolution video streaming capacity. Because of its round-the-clock coverage of Chinese territory and near aboard, Gaofen 4 can provide instant coverage of earthquake or typhoon hit areas to support humanitarian relief. It will also allow China to monitor strategic foreign sites such as WMD facilities and naval bases inside its observation box. Read more