Data flow

Figure 11.3 illustrates, in a greatly simplified form, the path by which the low-power data from Explorers I and III and the high-power data from Explorer I passed from the sensors in space to produce human-readable tables and graphs in our Iowa laboratory. The Explorer III high-power data were handled quite differently, as described later.

Pulse rates registered by the GM counter and the micrometeorite impact micro­phone were scaled on the satellite, that is, reduced by factors of 32 and 4, respectively, to produce more manageable rates for telemetry. The sensor signals modulated the frequencies of audio oscillators, and the tones were combined to form composite signals, which, in turn, modulated the satellite transmitters.

At the ground receiving stations, the receiver outputs were recorded on magnetic tapes, and the tapes were shipped to JPL. There the data were examined to ascertain their quality, and the satellite temperatures were computed. Initially, magnetic-tape copies of appropriate data channels were sent to SUI and the Air Force Cambridge Research Center (AFCRC). Somewhat later, the original tapes were sent to Iowa.

In our laboratory, the tapes were played back and the signals were passed through a bank of filters that separated the four original audio tones. The filters were followed by discriminators that converted the audio tones to the relatively slowly varying signals like those that had originated in the satellite. Thus, the outputs of the four

OPENING SPACE RESEARCH

discriminators were identical with the inputs to the satellite multiplexer (except for the addition of noise). Those four signals drove moving-pen galvanometers to produce ink traces on continuously moving paper strip-charts.