Vela 2B

Vela 2B (also known Vela 4, Vela Hotel 4 and OPS 3674 ) was a U.S. reconnaissance satellite for detecting explosions and nuclear tests on land and in space, the first of the second pair of Vela series satellites, taken together with Vela 2A and ERS 13 satellites. The secondary task of the ship was space research (X-rays, gamma rays, neutrons, magnetic field and charged particles).

The satellite was rotationally stabilized (2 rps). The ship could work in real time mode (one data frame per second) or in data recording mode (one frame every 256 seconds). The first mode was used for the first 40% of the mission's duration. The second one was used until the next pair of Vela satellites were launched.

The ship remains in orbit around Earth.

Instruments

 * X-ray and charged particle detector
 * Gamma ray detector and charged particles
 * Neutron detector
 * Electron and proton spectrometer
 * Background radiation detector
 * Solid state detector
 * Geiger-Muller counters
 * Magnetometer