Electron temperature in the upper F -region

Abstract

The Ariel I satellite, which was launched on 26 April 1962, carried two Langmuir probes to measure the density and temperature of the ionospheric electrons. The experimental technique and the physical arrangement of the probes have been described in detail in the preceding paper (Bowen, Boyd, Henderson & Willmore 1964) and only further details relevant to the measurements presented in this paper will be discussed here. The properties of the ionosphere are deduced from the first and second derivatives with respect to probe voltage of the probe current/voltage characteristic, these two quantities being transmitted in real time by the satellite telemetry system. In addition, some information from each voltage sweep of each of the probes was processed by a low-speed encoder and recorded on the satellite tape recorder for subsequent transmission when within range of a telemetry station. In this way data recorded over an entire orbit were obtained irrespective of the distribution of the telemetry stations. This paper describes the analysis of electron temperature data from the low-speed system. 2. The Storage and Processing of the Probe Measurements The low-speed encoder sampled each of two information channels from each probe during a period of 30.72 s. Since the probe sweep period was 55 s each channel was sampled once or twice during the sweep. One of the channels was used to determine the maximum modulation depth reached in the sweep of the probe curve, while the other was used to record the maximum value of the first derivative of the probe current characteristic. These quantities were determined by diode peak-reading circuits and retained in capacitor memories whose storage time was much greater than the sweep period. Temporary local storage of the information was necessary both because the presentation of the maximum value of the two parameters could not be synchronized with the encoder sampling, and because the information was sampled continuously for an interval of 0.48 s, during which time a large change in modulation depth could occur. Thus the capacitor store was required to retain the information for a time which could be as large as the interval between encoder samples.