Digital spacecraft ionosondes

In cooperation with RCA, Astro-Electronics Division, a digital spacecraft ionosonde has been developed and its prototype built by ULCAR. On-board use of the Direct Discrete Fourier Transform for signal-to-noise enhancement, suppression of unwanted echoes and the identification of echo properties permit several applications. In ionospheric topside satellites (>800 km above ground) the ionospheric profile over all parts of the earth will be measured with simple and new data compression techniques on board of the satellite. Digital data preprocessing overcomes the breakthrough of ground-based man-made interference and analyzes auroral and equatorial echoes. Because the ionosonde measures amplitude, phase, Doppler, range and polarization of a radio wave simultaneously, it will be a very useful tool for the Waves in Space Plasma program of the NASA Space Shuttle, especially for a mother-daughter configuration. With a synchronized transmitter on the ground, such a Digisonde in a low-flying satellite (100–400 km) can receive signals from ducted radio waves launched into the ionosphere near natural or artificial ionization depletion areas for the study of large distance radiowave propagation.