Vela-5B operated until 19 June 1979, although telemetry tracking was poor after mid-1976. The X-ray detectors on Vela 5A failed on 24 July 1970, leading to it's abandonment in 1976.
Owner(s).
U.S. Department of Defense and the U.S. Atomic Energy Commission.
Major contractor(s).
TRW.
Is it still in orbit.
Yes.
Launch mass.
N\A, but large for it's time and class.
Nationality(s).
Mostly American, but with some Dutch technical and manufacturing help. The Dutch also had some usage rights, but most stayed in American hands.
Satellite type.
Special reconnaissance satellite made to detect nuclear initiations and detonations in space.
It was part of a major series of 12 unmanned American reconnaissance satellites developed to detect radiation from nuclear explosions in the Earth’s atmosphere, that were lunched from 1963 to 1970.