Under cover of the SJ (Shijian) Chinese scientific research series, the government began launching pairs of satellites in 2006 that were believed to have a military ELINT mission.

The satellites were placed in sun-synchronous orbits at 600 km altitude. The second was separated about a minute after the first. The second pair was launched two years after the first. Chinese ELINT systems had been tested on earlier flights of the manned Shenzhou spacecraft's orbital module.

Typical orbit: 600 km circular, 98 deg inclinaton. Mass: 2,700 kg (5,900 lb).

• 2004 September 8 - SJ-6B - Launch Site: Taiyuan. Launch Complex: LC1. Launch Vehicle: CZ. Perigee: 593 km (368 mi). Apogee: 602 km (374 mi). Inclination: 97.70 deg. Period: 96.60 min.
  CAST968 platform. Released one minute after SJ-6A.

• 2004 September 8 - SJ-6A - Launch Site: Taiyuan. Launch Complex: LC1. Launch Vehicle: CZ. Perigee: 578 km (359 mi). Apogee: 593 km (368 mi). Inclination: 97.70 deg. Period: 96.40 min.
  It was announced that the two satellites had a design life of at least two years, and would be used to probe the space environment, radiation and its effects, record space physical environment parameters, and conduct other related space experiments. The two satellites were built by the Shanghai Academy of Space Flight Technology and Dongfanghong Satellite Company under subcontract to the China Aerospace Science and Technology Corporation. The scientific instruments aboard the satellites were mainly manufactured by the China Electronics Technology Corporation. Some Western observors believed the mission of the satellites included electronic intelligence technology tests.

• 2006 October 23 - SJ-6-2B SJ-6D - Launch Site: Taiyuan. Launch Complex: LC1. Launch Vehicle: CZ.
  

• 2006 October 23 - SJ-6-2A SJ-6C - Launch Site: Taiyuan. Launch Complex: LC1. Launch Vehicle: CZ.
  Replaced the SJ-6 Group 1 satellites A and B. Official purpose was to measure the space environment, but foreign analysts suspected a SIGINT role.