The KH-4, or Keyhole-4, represented the fourth iteration within the Corona program. This version introduced stereoscopic imaging capabilities with the Corona-M or Mural camera, consisting of two C''' (Corona triple-prime) cameras mounted with a 30-degree separation angle for forward and rear-looking perspectives. Additionally, a 4 cm index camera was included for specific imaging tasks. The Mural camera offered a ground resolution of 7.5 meters. Operating atop the Agena-D upper stage, the satellite facilitated attitude control during its mission, with film return managed by a single General Electric return vehicle (SRV). Upon mission completion, the film return capsule utilized its own solid-fuel retro motor for deorbiting, enabling mid-air recovery by specially equipped aircraft.

In 1962, the US Air Force launched ERS (Environmental Research Satellites), small technology satellites built by TRW Systems Group. These satellites, also known as Tetrahedral Research Satellites (TRS) or Octahedral Research Satellites (ORS), varied in shape. TRS Mk.1 satellites were tetrahedrons with solar cells for power. TRS 2 (ERS 2) aimed to study changes in Earth's radiation belt post-nuclear tests but failed to separate from its primary payload, the KH-4 12 military reconnaissance satellite.