| Vela 3B | |
| Operator: | USAF |
| Cospar Id: | 1965-058B[1] |
| Satcat: | 1459 |
| Manufacturer: | TRW |
| Launch Mass: | 235kg (518lb) |
| Launch Date: | UTC |
| Launch Rocket: | Atlas Agena D 2A |
| Launch Site: | Cape Canaveral LC-13 |
| Orbit Epoch: | [2] |
| Orbit Reference: | Geocentric |
| Orbit Regime: | Highly Elliptical |
| Orbit Periapsis: | 5310.8km (3,300miles) |
| Orbit Apoapsis: | 169892.3km (105,566.2miles) |
| Orbit Inclination: | 23.7° |
| Orbit Semimajor: | 117972km (73,304miles) |
| Orbit Period: | 6,721 minutes |
| Apsis: | gee |
| Programme: | Vela |
| Previous Mission: | Vela 3A |
| Next Mission: | Vela 4A |
Vela 3B (also known Vela 6, Vela Hotel 6 and OPS 6564[3]) was a U.S. reconnaissance satellite to detect explosions and nuclear tests on land and in space; the first of the third pair of Vela series satellites; taken together with Vela 3A and ERS 17 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. About 1 transmission was received every 4 hours. The second mode was used until the next pair of Vela satellites were launched.
The ship remains in orbit around Earth.