Pioneer 7

Description

Pioneer 7 was the second in a series of solar-orbiting, spin-stabilized, solar-cell and battery-powered satellites designed to obtain measurements of interplanetary phenomena from widely separated points in space on a continuing basis. The spacecraft carried experiments to study positive ions and electrons in the solar wind, the interplanetary electron density (radio propagation experiment), solar and galactic cosmic rays, and the interplanetary magnetic field. Its main antenna was a high-gain directional antenna. The spacecraft was spin-stabilized at about 60 rpm, and the spin axis was perpendicular to the ecliptic plane and pointed approximately toward the south ecliptic pole. By ground command, one of five bit rates, one of four data formats, and one of four operating modes could be selected. The five bit rates were 512, 256, 64, 16, and 8 bps. Three of the four data formats contained primarily scientific data and consisted of 32 seven-bit words per frame. One scientific data format was used for the two highest bit rates. Another was used for the three lowest bit rates. The third contained data from only the radio propagation experiment. The fourth data format contained mainly engineering data. The four operating modes were (1) real time, (2) telemetry store, (3) duty cycle store, and (4) memory readout. In the real-time mode, data were sampled and transmitted directly (without storage) as specified by the data format and bit rate selected. In the telemetry store mode, data were stored and transmitted simultaneously in the format and at the bit rate selected. In the duty cycle store mode, a single frame of scientific data was collected and stored at a rate of 512 bps. The time period between which successive frames were collected and stored could be varied by ground command between 2 and 17 min to provide partial data coverage for periods up to 19 h, as limited by the bit storage capacity. In the memory readout mode, data were read out at whatever bit rate was appropriate to the satellite distance from the Earth.

Pioneer 7 was launched on 17 August 1966 into a solar orbit with a mean radius of 1.1 AU. The spacecraft was last tracked successfully in March 1995, there are no further plans to track or attempt communication with Pioneer 7.