| Vela 2B | |
| Operator: | USAF |
| Cospar Id: | 1964-040B[1] |
| Satcat: | 837 |
| Manufacturer: | TRW |
| Launch Mass: | 135kg (298lb) |
| Launch Date: | UTC |
| Launch Rocket: | Atlas LV-3A Agena-D |
| Launch Site: | Cape Canaveral LC-13 |
| Orbit Reference: | Geocentric |
| Orbit Regime: | Highly Elliptical |
| Orbit Periapsis: | 94436km (58,680miles) |
| Orbit Apoapsis: | 11775km (7,317miles) |
| Orbit Inclination: | 40.8° |
| Orbit Period: | 100,12 hours |
| Apsis: | gee |
| Programme: | Vela |
| Previous Mission: | Vela 2A |
| Next Mission: | Vela 3A |
Vela 2B (also known Vela 4, Vela Hotel 4 and OPS 3674[2]) 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.