Shi Jian 1 (SJ-1) was the second Chinese satellite. It was designed and built by the Chinese Academy of Space Technology (CAST). The 221 kg SJ-1 spacecraft was based on the DFH-1 satellite, from which it inherited the 1 m pressurized spherical structure, but it was powered by Silicon solar cells, which were mounted on 14 trapezoidal planes on the upper and lower hemispherical shells. Batteries and transmitters were housed in the pressurized compartment. SJ-1 was spin-stabilized.