Rocket astrophysical observatories K-2, k-3 and K-4 were launched in Soviet Union in the 1960s and early 1970s under the direction of Grigor Gurzadyan of Byurakan Observatory in Armenia, for the study of the Solar ultraviolet and X-ray emission. R-5 Pobeda ballistic rockets were used, launched from Kapustin Yar military base. The 500 km altitude flights, after the first 120 km of active regime, were performing 8–9 minutes of observations, with further parachute landing of the payload.