Vela 2B 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
Vela 3A 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 3B and ERS 17 s