Fields and Particles Data from Explorers 33 and 35

Explorer 35 achieved a 5 Rm lunar orbit, but Explorer 33 went into a moderately eccentric, geocentric orbit of about 15 day period, 70 Earth radii apogee for most of its life. Their principal periods of coverage were 7/1/66-1/14/70 and 7/19/67-2/23/72.

Intermittent Explorer 33 data were acquired up to 5/31/71; Explorer 35 coverage declined during the last two years of its principal period. The spacecraft carried instruments to measure in situ magnetic fields (Ness and Sonett), plasmas (Bridge), and energetic particles (Anderson and Van Allen). In addition, Van Allen's Geiger tubes measured 2-12 Angstrom solar X-rays.