A waveform diversity approach to mitigating ionosphere scintillation effects on wideband space radars

The results of a detailed study are presented which analyzed the impact of ionosphere plasma irregularities on wideband waveforms for low frequency space radar systems. The primary objective of this effort was to develop a systems engineering approach using waveform diversity to overcome the impact that the ionosphere has on the performance of a wideband waveform as it passes through the ionosphere. A secondary objective was to advance the physical understanding of mid- to low-latitude ionosphere plasmas at all local times, with special emphasis on post-sunset, as a basis for real-time determination of the impact of the ionosphere on VHF/UHF and L/S-Band space radar systems. Empirical data was collected over a three year period at multiple locations, including the Ronald Reagan Ballistic Missile Defense Test Site, Kwajalein Atoll, Marshall Islands. Radar targets included orbiting calibration spheres (at 900 km). For the first time, based on empirical data, the impact of the ionosphere on VHF/UHF and L/S-Band Space Radar as a function of time of day, time of year, frequency, and recurrent period was determined. For example, moderate ionosphere scintillation with a total electron content unit (TECU) of 25 resulted in a range error for UHF of about nine meters, and for L-Band four meters, and a variation in target RCS of +/-5 dB for UHF and +/- 1 dB for L-Band. These results are being used to develop ionosphere mitigation algorithms and perform validated system design trade studies for a sun-synchronous, wide area change detection space radar.