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SJ 2


SJ 2 (Shi Jian 2) was a Chinese satellite mission to measure and study the micrometeoroids and debris environment and to conduct electromagnetic background experiments.

the satellite featured a spin-stabilized octahedral prism shaped structure and and was sun-pointing with a total mass of 250 kg. The satellite structure had a length of 1.2 m and an outer diameter of 0.615 m. Four deployable solar wings are attached to the top of the satellite.

The satellite carried instruments for measuring space debris:

  • MMW (Millimeter Wave) Radar. The objective is to detect debris of size 3-10 cm or larger by remote sensing methods in the altitude range of 600 to 1300 km. The instrument provides measurements with a velocity resolution of <50 m/s; a direction resolution of <1 arcsec; the time resolution is <1 s;
  • IP (Impact Detector). The objective is to collect particles and impacting radiation (light) signals. The instrument consists of a charge detector and a light detector, each with different collecting apertures and different viewing directions. The charge detector collects particles in the mass range of 10-7 to 10-15 g, a size range of 0.05 to 50 m, and a velocity resolution of <10 km/s. The instrument mass is 6 kg (6 W power). - The light detector collects particles in the mass range of 10-3 to 10-7 g, a size range of 50 m to 0.5 mm, and a velocity resolution of <10 km/s.
  • Large Sensitive Array (located at the back of the solar panel). The objective is to detect the total impact effect by measuring the change of the resistance.
  • Optical Monitor. The objective is to monitor the surface change of the two solar panels (caused by debris impacts). The instrument uses four CCD cameras which are located inside the spacecraft.

SJ 2 was launched as one of three payloads on a FB-1 rocket in September 1981. An earlier launch failure in July 1979 reportedly carried the same payloads.

Nation: China
Type / Application: Technology
Power: 4 deployable fixed solar arrays, batteries
Mass: 250 kg
Orbit: 232 km × 1598 km, 59.4
Satellite COSPAR Date LS Launch Vehicle Remarks
SJ (2) 1979-F02 27.07.1979 Jq LC-2/138 F FB-1 with SJ (2A), SJ (2B)
SJ 2 1981-093D 19.09.1981 Jq LC-2/138 FB-1 with SJ 2A, SJ 2B


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