KH-4B 10 (Corona 138) & Tripos 4

The KH-4B (Keyhole-4B) marked the sixth iteration within the Corona program for optical reconnaissance satellites. It was equipped with two J-3 panoramic cameras, each with a focal length of 61 cm, providing a ground resolution of 1.8 meters and a ground swath of 16 km × 217 km. Additionally, the KH-4B featured the DISIC (Dual Improved Stellar Index) camera, offering superior mapping capabilities compared to the KH-5 Argon system. The DISIC camera had a focal length of 91 cm, providing a ground resolution of 30 meters, with a frame coverage of 260 km × 260 km.

The Tripos Sousea satellites were part of a series of so called Program 11 or P-11 "Subsatellite Ferrets", low orbit ELINT/SIGINT satellites to pinpoint and characterize different Radar emitters in the Soviet Union and Warsaw pact states.