According to reports by Chinese state-owned Xinhua news agency, China has launched three more Yaogan-30 remote-sensing satellites from the Xichang Satellite Launch Centre in southwestern China on 26 July.
The report states that the satellites, which were placed into orbit by a Long March-2C carrier rocket, are primarily functioned for electromagnetic detection and “related technological tests”.
Analysts contend that the Yaogan-30 satellites are mainly designed for military signals intelligence (SIGINT) purposes and can geo-locate military platforms, particularly warships, by intercepting electromagnetic transmissions such as radar.
The satellites are operated as triplets, positioned in relatively close proximity, that can measure the angular or time difference of arrival of intercepted signals, from which the position of the source can be determined. The satellites have been positioned in a low-Earth orbit with an altitude of 600 km and inclination of 35°.
Shortly after the launch, all three satellites were reported to have reached the intended orbit. The first four groups of Yaogan-30 triplets were launched over a four-month period, from September 2017 to January 2018. The launch of the latest group increases the number of satellites in the constellation to 15.
The previous launch of a Yaogan satellite, on 22 May was unsuccessful because of a malfunction of the carrier rocket’s third stage. Yaogan-33 is thought to have been configured as a synthetic aperture radar satellite.
The increasing number of Chinese military surveillance satellites will provide shorter refresh intervals for areas of critical interest, such as the East and South China Seas.
Near-real time updates of target position from remote sensors may be required by anti-ship ballistic missiles (ASBMs) if the high terminal velocity creates a plasma shield that adversely affects the performance of the missile’s homing radar.
The ability of SIGINT satellites to geo-locate ships at sea is clearly dependent upon those ships making transmissions that can be intercepted. While transmissions can be minimised to reduce the risk of detection by SIGINT satellites, radar will be required to detect incoming ASBMs.