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IMP-6 (IMP-I or Explorer 43, NSSDC ID: 71-019A) was a 16-sided drum-shaped spacecraft of dimensions: 1.8212 meter high and 1.3564 meter in diameter. Its mass was 635 kg. The spacecraft spin axis was perpendicular to the ecliptic plane with a spin rate of 5 rpm, giving it a spin period of 12 seconds. IMP-6 continued the study, begun by earlier IMPs, of the interplanetary and outer magnetospheric regions by measuring energetic particles, plasma, and electric and magnetic fields. A radio astronomy experiment was also included in the spacecraft payload. The initial apogee point was near the earth-sun line. The solar-cell and chemical- battery powered spacecraft carried two transmitters. One continuously transmitted PCM encoder data at a 1600-bps information bit rate. The second transmitter was used for transmission of VLF data and for ranging information. Three orthogonal pairs of dipole antennas were used for the electric fields experiments, and one of these pairs was also used for the radio astronomy experiment. The members of the antenna pair along the spacecraft spin axis extended 2.9 meter, the members of the antennal pair used in both the electric field and radio astronomy experiments extended 45.5 meter, and the members of the third pair were slightly unbalanced, extending 24.4 meter and 27.6 meter, respectively. All four elements perpendicular to the spin axis were to have extended 45.5 meter. The spacecraft reentered the earth's atmosphere on October 2, 1974, after a highly successful mission. The IMP (Interplanetary Monitoring Platform) spacecraft exploration program was carried out by the United States. _____________________________________________________________ Entry taken from: Hills, H. K., R. G. Littlefield, N. J. Schofield and J. I. Vette: 'Data Catalog Series for Space Science and Applications Flight Missions', Vol. 3A, NSSDC/WDC-A, NASA / Goddard Space Flight Center, September 1982. _________________________________________________________________ See also: Fairfield, D. H., Journal of Geophysical Research, 79, 1368, 1974. Frank, L. A. et al., Journal of Geophysical Research, 82, 129, 1977. Armstrong, T. and S. M. Krimigis, Journal of Geophysical Research, 81, 677, 1976. Williams, D. J., NOAA Technical Report, ERL 393-SEL 40, U.S. Department of Commerce, Boulder, Colorado, USA, October 1977.
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