Explorer 36 (also called GEOS 2 or GEOS B, acronym for Geodetic Earth Orbiting Satellite) was a NASA satellite launched as part of the Explorer program, being the second of the two satellites GEOS. Explorer 36 was launched on 11 January 1968 from Vandenberg Air Force Base, with Thor-Delta E1 launch vehicle. Explorer 36 was a gravity-gradient stabilized, solar cell powered spacecraft that carried electronic and geodetic instrumentation.