Explorer 33

Description

Explorer 33 was a spin-stabilized (spin axis parallel to the ecliptic plane, spin period varying between 2.2 and 3.6 s) spacecraft instrumented for studies of interplanetary plasma, energetic charged particles (electrons, protons, and alphas), magnetic fields, and solar X rays at lunar distances. The spacecraft failed to achieve lunar orbit but did achieve mission objectives. The initial apogee occurred at about 1600 h local time. Over the first 3-yr period, perigee varied between 6 and 44 earth radii. Apogee varied between 70 and 135 earth radii, and the inclination with respect to the equator of the earth varied between 7 and 60 deg. Periods of principal data coverage (essentially 100%) are July 1, 1966 (launch), to January 14, 1970; February 21, 1970, to March 6, 1970; July 31, 1970, to September 14, 1970; January 15, 1971, to February 28, 1971; March 23, 1971, to May 31, 1971; and August 23, 1971, to September 15, 1971. No data were obtained after September 21, 1971.