Explorer 43

Explorer 43, also called as IMP-I and IMP-6, was a NASA satellite launched as part of Explorer program. Explorer 43 was launched on 13 March 1971 from Cape Canaveral Air Force Station (CCAFS) (restored to its old name of Cape Canaveral in 1974), with a Thor-Delta M6 launch vehicle. Explorer 43 was the sixth satellite of the Interplanetary Monitoring Platform. Explorer 43 continued the study, begun by earlier IMPs, of the interplanetary and outer magnetospheric regions by measuring energetic particles, plasma, electric fields and magnetic fields. Its orbit took it to cislunar space during a period of decreasing solar activity. A Radio astronomy experiment was also included in the spacecraft payload. The 16-sided spacecraft was high by in diameter. The spacecraft spin axis was normal to the ecliptic plane, and its spin rate was 5 rpm, with propulsion Star-17A. The initial apogee point lay near the Earth-Sun line. The solar-cell and chemical-battery powered spacecraft carried 2 transmitters. One continuously transmitted PCM encoder data at a 1600 bit/s information bit rate. The second transmitter was used for transmission of Very low frequency (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 , the members of the pair used in both the electric field and radio astronomy experiments extended , and the members of the third pair were slightly unbalanced, extending , respectively. All four elements perpendicular to the spin axis were to have extended . Two dipole antennas were mounted orthogonally in the spin plane of the spacecraft while a third dipole antenna was mounted along the spacecraft spin axis. Antenna element lengths were -X, ; +X, ; -Y and +Y, ; -Z and +Z (spin axis), . Electrometers measured the analog potential difference between the elements in each pair of antennas simultaneously every 5.