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.
The satellite is part of the dual use China High-Resolution Earth
Observation System (CHEOS), which already has five other satellites
(Gaofen 1, 2, 3, 5 and 8). This fits within a larger program of radar,
imaging, hyperspectral and atmosphere monitoring satellites that will
support Chinese civilian missions like agriculture, construction,
disaster relief and climate change monitoring. Of course, the Chinese
Aerospace Force (a new branch of the PLA following its December 2015
reorganization) could easily make use of such satellites during Chinese
military operations. Also of interest is the Jilin LEO imaging
satellites (sponsored by the Jilin Provincial government); the first
four Jilin satellites launched in October 2015 and already have 80cm
imaging resolution. By 2030, the Jilin constellation will have 138
imaging, high-resolution small satellites that provide all weather
coverage of any point on Earth, at 10 minute intervals.
xyz via China Defense Forum
GEO Spy Satellite
This scientific article by Beijing Institute of Space Mechanics
and Electricity's Zhang Yue, Wang Chao, Su Yuan and Jiao Jianchao,
describes temperature control on a 20+ meter diameter mirror made of
optical membrane foil (a smaller satellite can unfold the optical
membrane foil to create a larger lens to enable higher resolution).
DARPA is also looking at similar concepts to meet American IMINT needs.
With a lifespan of 8 years, the Gaofen 4 will likely be superseded by
future GEO observation satellites with higher resolution imaging
capabilities. One intriguing possibility is revealed in a study from a
Chinese engineering journal. Enterprising scientists propose that a
future GEO spy satellite could deploy a foldable telescope lens of over
20 meters diameter, which could be powerful enough provide sub 1-meter
resolution (similar to Ball Aerospace and DARPA's Membrane Optics
program). Such a futuristic GEO spy satellite wouldn't just be able to
find interesting targets like aircraft carriers and missile launcher
trucks, it could beam back real time video streams of enemy forces
underway.
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