Double floating probe measurements on S³-A

S3-A (Explorer 45) was launched into an eccentric equatorial orbit with a 5.2-RE apogee and 3° inclination on November 15, 1971 (see Longanecker and Hoffman [1973] for a description of the spacecraft and its experiment complement). The spacecraft carried a pair of symmetrical floating probes designed to measure dc electric fields in regions well inside the plasmapause. The sensors are 5.5-inch diameter spheres on fiberglass foldout booms separated by a distance of 5.08 meters. The plasma sheath surrounding the spacecraft is asymmetrical because only one side of the satellite is photoemitting and the sunlit surface is nonconducting.