Image: Prepping the last Vela satellite

The Vela series of satellites, which spanned 1963-1984, carried Los Alamos-designed-and-built sensors for detecting x-rays, gamma rays, neutrons, and the natural background of radiation in space. 

In addition to their function as "watchdogs" for possible clandestine nuclear testing in the atmosphere and in space (velar means "to watch over" in Spanish), these satellites also contributed significantly to astrophysics, interplanetary physics, and our understanding of the Earth's magnetosphere. This photo shows the last of the Vela Twin-Satellites, designated Vela V-B, during final checkout at Los Alamos National Laboratory before its launch on April 8, 1970.