From what I gathered, these were special spy stuff that used the highly elliptical orbit to stay over a spot on the ground for an extended time. OTOH, the flew low and fast on the back side of the orbit, which may have had tactical reasons. They also were not transmitting on the usual frequencies bands.
They were useful moving frequencies sources to test tracking function. Tracking the sun or Cassiopeia became somewhat mundane after a while. Satellites were much more fun as you could watch the antenna follow them.