e-POP RRI observations of the April 24, 2020 ARRL Frequency Measuring Test

One of the science objectives of the Radio Receiver Instrument (RRI) on the CAScade, Smallsat, and Ionospheric Polar Explorer/enhanced Polar Outflow Probe (CASSIOPE/e-POP) satellite is to study ionospheric influences on high frequency (HF) radio wave from low Earth orbit. RRI is made-up of 4, 3-m monopoles which can be electronically arranged into a crossed-dipole configuration.  On April 24, 2020, RRI tuned to measure the ARRL frequency measuring test (FMT) on 40 m, and successfully recorded part of the “call up” and all of the “key down” segments of the test.  The FMT provides a unique chance to study the effects of the ionospheric plasma on stable and reliable radio signals at frequencies that are close to the ionosphere’s critical frequency, a frequency regime in which the influence of the ionospheric plasma on radio wave propagation conditions is most pronounced.  In this presentation, we give preliminary results of our analysis of RRI’s FMT measurements which include an examination of the FMT’s Doppler characteristics, and the identification tell-tale signatures of ionospheric effects on the transmitted signal such as Faraday rotation and propagation mode delay.