In a new type of radio propagation experiment, radio waves of both magnetoionic modes are radiated from a pair of ground‐based transmitters to a Nike Apache rocket. A power ratio of 10 db at the rocket is maintained by a servoloop that includes the transmitters, the rocket‐borne receiver, and the telemetry system. The frequencies of the two modes are controlled by crystals that differ in frequency by 500 hz. The central frequency is 3385 khz. This technique facilitates measurement of ionospheric Faraday rotation and differential absorption by well‐calibrated instrumentation located on the ground. A method of analyzing Faraday and absorption data, based on the generalized magnetoionic theory, is developed and applied to rocket data to obtain electron concentration and collision frequency, and to calibrate a Langmuir‐type electron current probe that measures the fine structure of the electron concentration profile. Results of a typical flight are shown in which electron concentrations are determined in the altitude range 55–105 km and collision frequencies in the range 85–105 km.

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The characteristics of midlatitude sporadic‐E layers are observed using rocket payloads incorporating a probe and a propagation experiment.Layers below 120 km show evidence of preferred altitudes. The slopes of layers are within 1° of horizontal. The horizontal dimensions are deduced to be several hundred kilometers. Individual profiles of daytime layers show a range of shapes ranging from triangular to rectangular. The plasma frequency derived from the peak electron density in the layer is found to agree with the blanketing frequency given by the local ionosphere sounder.

Measurements of electron concentration taken at the same time and at the same place in the lower ionosphere by independent instrumentation mounted on the same rocket are described. The technique utilizes Faraday rotation and differential absorption of radio waves propagating from the ground to the rocket at two different frequencies. Agreement near 90 km within ___7%, _--+-6%, ___8%, and ___3% is demonstrated by the four available cases of coincidence in time and altitude. Maximum dispersion at o.ther altitudes is calculated from known random errors. Stronger variation of electron collision frequency with altitude than with season is indicated by 34 measurements between 75 and 100 km. Insensitivity of electron concentration determinations at 72 km to errors in extrapolated collision frequency models is demonstra'ted. Partial reflection data are compared with rocket results in the one case of commonality in time and place.

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