NSSDCA ID: 1963-046A-07
Mission Name: IMP-AA five-element, split-collector Faraday cup was used to measure solar wind particles in the following sequence: positive ions from 45 to 105 eV, positive ions from 95 to 235 eV, positive ions from 220 to 640 eV, positive ions from 560 to 1800 eV, electrons from 65 to 210 eV, and positive ions from 1700 to 5400 eV. The split plane of the collector was in the spin equatorial plane of the spacecraft. Measurements consisted of 22 instantaneous current samples, each separated by 0.16 s (spanning more than one satellite rotation). These measurements represented the sum of the current to the split collector, the maximum difference in current encountered during spacecraft rotation, and an identification of which half of the collector was maximum. The entire sequence required 2.8 min and was repeated every 5.5 min. The entrance cone for this Faraday cup had a half-angle of about 80 deg. Interference was encountered from refracted particles (with the most pronounced effect at about 70 deg incidence to cup normal), from secondary electrons, and from ultraviolet radiation. For further details, see E. F. Lyon, "Explorer-18 plasma measurements," The Solar Wind, edited by Mackin and Neugebauer, Pergamon Press, 1966.
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Name | Role | Original Affiliation | |
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Prof. Herbert S. Bridge | Principal Investigator | Massachusetts Institute of Technology |