Since April 2006, China has launched a number of reconnaissance satellites known as Yaogan Weixng (遥感卫星), or “Remote Sensing Satellite” (RSS) in its English translation. While Chinese official media briefly described these satellites as “intended for scientific experiments, land survey, crop yield assessment, and disaster monitoring”, it is understood that these satellites are actually operated by the People’s Liberation Army (PLA) to provide high-resolution imagery intelligence capability for both military and civil missions.

So far two types of RSS satellites have been identified: the electro-optical digital imaging variant developed by CASC 5th Academy and synthetic aperture radar imaging variant developed by CASC 8th Academy. The former was launched from the Jiuquan Satellite Launch Centre (JSLC) aboard CZ-2C/D rockets, while the latter was launched from the Taiyuan Satellite Launch Centre (TSLC) aboard CZ-4B/C rockets.

Synthetic Aperture Radar Imaging Variant

The launch of Yaogan 1 and Yaogan 3 from the Taiyuan Satellite Launch Centre (Chinese Internet)

China state-run Xinhua new agency announced on 27 April 2006 that a new satellite named YaoGan WeiXing 1 (Remote Sensing Satellite 1, or RSS-1) was successfully launched by a CZ-4B (Batch-02) launch vehicle from Taiyuan. According to the Chinese media reports, the Remote Sensing Satellite-1 launched on 27 April 2006 weights 2,700kg. The satellite housed in an enlarged fairing (length 10m; diameter 3.8m) on top of the three-stage CZ-4B launch vehicle, which lifted off at 18:48 Beijing Time (10:48 GMT). The payload was released into a near-polar sun-synchronous orbit some 603km high. This was also the first flight using the improved CZ-4B Batch-02 launch vehicle.

Another report confirmed that the Remote Sensing Satellite-1 was fitted with a electronic motor-powered solar panel which expanded under the command from the ground control station. The onboard radar It is not known which band the JB-5’s radar is working, and what kind of resolution the radar image can achieve. An additional three satellites have been launched from Tianyuan since then. The latest launch took place on on 22 April 2009, with Yaogan Weixing 6 (JianBing 10) being launched from from Taiyuan aboard a CZ-2C SLV.

Space-Based SAR Programme

Synthetic aperture radar (SAR) is an active microwave instrument producing high-resolution imagery of the Earth’s surface in all-weather, day/night conditions. A SAR instrument can measure both intensity and phase of the reflected microwave radiation, resulting not only in a high sensitivity to texture, but also in some three-dimensional capabilities. While conventional optical imagery intelligence systems are less effective in night and bad weather (e.g. cloudy) conditions, the SAR generates its own microwave radiation that can penetrate cloud, haze, shallow water, or even ground surface to obtain high-resolution images of the Earth surface as well as underwater and underground.

China first began to develop the SAR technology in the late 1970s, with the first operational airborne X-band mono-polarisation SAR system introduced in 1981 by the Electronic Research Institute of the China Academy of Science (CAS). The multi-polarisation SAR system was introduced in the early 1990s for flood monitoring. The first operational real-time airborne SAR system which can analyse the images using onboard equipment and transmit the image data to ground stations via datalink communication was introduced in 1994.

Yaogan 3/Jianbing 7 being transported to the launch pad onboard a trailer (Chinese Internet)

For over a decade China had been planning to put a high-resolution SAR satellite in orbit for all-weather targeting applications, particularly the location of naval forces in the Taiwan Strait. China has also taken an interest in the potential civil applications of such a system in the aftermath of the flooding, landslides, and typhoon damage in 1994. While China has used optical imaging space-based remote-sensing systems, there is particular interest in active microwave imagery that can penetrate southern China's constant cloud cover. It is believed that China’s space-based SAR system development has benefited from its co-operation with Russia and Europe in this field.

The PLA views SAR satellite imagery as vital in its ability to achieve information dominance in future warfare. Unlike the conventional passive optical imagery satellites, the space-based SAR system can see through clouds, rain, fog and dust in order to detect targets on the ground or underground, and in or under the ocean. In addition, SAR satellites are extremely useful in tracking moving targets, and can be useful in satisfying military mapping requirements. Chinese engineers have been examining SAR satellites as a means to track enemy submarines in shallow waters.

Preliminary research and development on China’s first-generation space-based SAR system was initiated in the late 1980s, and the model R&D began in 1991. In May 1995, the State Science & Technology Committee (SSTC) and COSTIND approved the finalised design and work on associated high speed data transmission. A ground simulation system for the SAR satellite was developed by CAS and BUAA in the late 1990s. Even before the launch of the first-generation SAR satellite, preliminary research had already began on the second-generation SAR satellite system. According to a BUAA report, the second-generation SAR satellite programme had been listed in China’s 11th Five-Year Development Plan (2006~2010).

Yaogan 3/Jianbing 7 inside an enlarged fairing of the CZ-4C launch vehicle (Chinese Internet)

The main contractors for the SAR satellite system include China Academy of Science’s Institute of Electronics (SAR instruments), Shanghai Academy of Spaceflight Technology (spacecraft general design and CZ-4B launch vehicle), 501 and 504 Institutes of China Academy of Space Technology, Nanjing Research Institute of Electronic Technology (also known as CETC 14 Institute) and Southwest Institute of Electronic Equipment (SWIEE, also known as CETC 29 Institute), and Beijing University of Aeronautics & Astronautics (BUAA).

Radar

The CAS Electronic Research Institute has been tasked under “Project 863”—China’s high-tech development plan—to develop an indigenous satellite-based SAR system since the late 1980s. Little details are available regarding the SAR system carried by the JianBing-5, but a CAS leaflet has revealed some information on a prototype system introduced in the late 1990s for ground simulation. The system later formed the core technology of the SAR carried by the Remote Sensing Satellite series.

According to the leaflet, the SAR prototype works in L-band and has two resolution options. In the high-resolution mode the system has a resolution of 5m and a field of view of 40km. In the low-resolution mode the system has a resolution of 20m and a filed of view of 100km. The prototype system was tested onboard a plane and its result was said to be satisfactory.

Electro-Optical Digital Imaging Variant

Yaogan 4/Jianbing 8 launched from the Jiuquan Satellite Launch Centre by a CZ-2D launcher (Chinese Internet)

Chinese media briefly reported on 25 May 2007 that the ChangZheng family of space launch vehicles had successfully conducted its 99th flight, sending two satellites into space. The CZ-2D launch vehicle, which was launched from Jiuquan at 15:12 local time (07:12 GMT) on 25 May 2007, carried the YaoGan WeiXing 2 (Remote Sensing Satellite 2, RSS2) designed by China Academy of Space Technology (CAST, also known as 5th Space Academy), as well as a pico-satellite designed by Zhejiang University for scientific experiment.

It is understood that the satellite was actually a new-generation digital imaging reconnaissance satellite known as JianBing 6 in its military designation. It replaced the older FSW-4 film return type reconnaissance satellites to provide imagery intelligence capability for both military and civil users, with an estimated ground resolution of 0.6~1 metre. A second satellite Yaogan Weixing 4 (RSS-4/Jianbing 8) was launched from Jiuquan on 1 December 2008.

Launch Records