Radio Science at IAP plays an important role on the studies of the MLT region, from using both radar as well as radio techniques. Although many observations can be done with commercial radar/radio instruments, the quality, precision, as well as spatial and temporal resolutions can be considerably improved with radio science techniques. This is particularly true for existing unique IAP instruments like MAARSY and Saura radars, as well as for the reengineering of existing instruments, like the MMARIA concept on specular meteor radars. Radio science activities at IAP involve among other:

• antenna design and testing using numerical electromagnetic codes as well as passive and active experiments,
• design and development of acquisition radio/radar systems (like SANDRA),
• implementation of pulse compression, multi-pulse, and multi-frequency schemes,
• use of magnetoionic theory to derived parameters from Faraday rotation radar and/or riometer observations (e.g., D region electron densities),
• spatial as well as frequency domain radar imaging techniques, etc.

Given that advances of technology, where one can sample almost continuously in time and at different receiving antennas, and pulses can be changed arbitrarily, both in phase and amplitude, the radio science techniques must be accompanied by robust inverse theory, either via backward or forward scattering model approaches (e.g., Maximum Entropy in radar imaging).

Measured spectral width of radar echoes is often used as an indicator for turbulence. Especially for MF radars the echoes are often received from multiple directions, given the comparably small antenna structure or imperfect sidelobe suppression in the radiation pattern. The return from multiple directions each having different Doppler shift superimpose to a broad spectrum.

For a more reliable analysis and interpretation of the data the scattering positions can be calculated for each spectral bin and the spectra are cleaned for near zenith return.