Lincoln Experimental Satellite 4, also known as LES-4, was a communications satellite, the fourth of nine in the Lincoln Experimental Satellite, and the first of the series designed for operations at geosynchronous altitudes. Launched by the United States Air Force (USAF) on 21 December 1965, it demonstrated many then-advanced technologies including active use of the military's SHF band to service hundreds of users.

Orbiting Vehicle 2-3, the second satellite of the second series of the United States Air Force's Orbiting Vehicle program, was an American solar astronomy, geomagnetic and particle science research satellite. Launched 22 December 1965 along with three other satellites, the mission resulted in failure when the spacecraft failed to separate from the upper stage of its Titan IIIC.