A data acquisition and processing system for mass producing topside ionograms

Data telemetered from the Alouette I and II swept-frequency topside sounder ionospheric satellites are collected by a worldwide network of 22 ground stations. To acquire data, each spacecraft is commanded, and its telemetry signals received and recorded, on magnetic tape. The telemetry tapes are then forwarded to processing centers where the ionospheric data are converted into ionograms and stored on 35-mm film. Because telemetry tapes are often contaminated with noise and spurious signals, and because of the nature of the sounder signals, considerable difficulty has been experienced in mass producing suitably coded high-quality ionograms, These problems are described and an outline is given of how they have been solved or minimized. Essential features of the design and performance of the spacecraft and the telemetry and command ground stations are included as pert of a unified description of a system for generating ionograms. For purposes of illustration the telemetry and command ground station and the ionogram processing system currently in use at Ottawa are described. This system has proved highly successful and has evolved over a period of six years of topside operations involving 18 000 hours of processing time and the production of approximately 2.3×10⁶ionograms. In conclusion a brief description of an improved processor for the ISIS-I satellite is given, along with some comments on future developments.