China's LEOs Work With Its Undersea Surveillance System

KQN made interesting comments on December 5, 2017 on China's undersea surveillance system, islands and missiles. This Chinese surveillance system relies on hydrophones and other undersea sensors backed up by confirmation and weaponised patrols by Chinese submarines, surface ships and aircraft. 

I will first refer to the low earth orbiting (LEO) portion of China's undersea surveillance system. Hydrophones can "cue" LEOs, that is "alert" LEOs that a potential target has been detected by hydrophones and the target's approximate location. The latest Chinese LEOs are probably the Chinese Yaogan-30 reconnaissance / "spy" satellites - the subject of today's post below.

Drawing on: Satellite Observation December 3, 2017 and N2YO .

China launched (see coverage paths above courtesy Satellite Observation):

-  3 Yaogan-30s on September 29, 2017 (dubbed the green Yaogan-30-01 triplet)  

-  3 more Yaogan-30s on November 24, 2017  (the red "Yaogan-30-02" triplet), and 

-  3 more Yaogan-30s are expected to be launched soon (dubbed the future blue Yaogan-30-03"
   triplet).

All 6 satellites (and 3 later) will have a 600km low earth orbit (LEO) with a 35° inclination. 

Satellite Observation has an interesting analysis: 

-  each triplet is not flying in close formation so this suggests they are not used for signal intelligence
   triangulation to pinpoint the source of an electromagnetic signal (eg. a surface ship).
-  Each of the 3 satellites in each triplet are too far away for triangulating signals, since the satellites
   are not even in line of sight of each other.
-  also at 600 km this is below the 1000km optimal orbit for signal intelligence satellites
-  instead each satellite of each triplet have been phased 120° apart, providing maximum revisiting
-  3 x 3 revisits means a high revisit rate (almost constant) 
-  high revisits from a 600km orbit suggests small optical [Comment also perhaps including infra-red
   for night and synthetic aperture radar (SAR)) satellites to see through rain and shallow water].

The observation is made: "...the satellites have a good coverage of the Pacific, India, China, North Korea and even Japan, but the most northern and southern parts of the globe are not covered: the satellites spend their time in the band of latitudes relevant to Chinese national security concerns...In conclusion, the Chinese are building a high-revisit constellation, in all likelihood for tactical use."

See MORE TEXT AND DIAGRAMS ON THIS AT SATELLITE OBSERVATION

COMMENT

Perhaps likely optical/infra-red naval viewing targets include surface ships, surfaced submarines and even snorkels. Other sensors including SAR might be useful detecting shallow running submarines including submarine wakes. 

Technical advances in China's reconnaissance satellites may one day make (non-AIP) conventional submarines, like Australia's, that need to regularly snort, unviable. 

Other viewing targets may be stealth aircraft, SLBMs and SLCMs being launched and in flight. 

Pete