US-A (Upravlenniye Sputnik Aktivny) were active radar satellites for ocean surveillance. The high power consumtion of the active radar required a nuclear reactor as power source. The satellites were known as RORSAT in the west. The US-AO series consisted of satellites, which tested all the system components but the nuclear reactor. They were battery powered.
Low Earth OrbitThe Transit-O series of satellites that closely followed the design of Transit 5C-1 were also called “Oscars” (Oscar is the phonetic alphabet for “O”, i. e., operational). They were also called NNS (Navy Navigation Satellite) or shortened NavSat.
Polar OrbitThe OV2 (Orbiting Vehicle 2) series satellites were originally built for project ARENTS (Advanced Research Environmental Test Satellite), which was intended to obtain supporting data for the Vela program. After the cancellation of the ARENTS program, the already built hardware was reused for OV2, a low-cost series of experimental satellites, which were to be launched for free on Titan-3C test flights to very different orbits.
Elliptical Orbit