ONERA, funded by the French Ministry of Defence has conducted the realization and experimentations of the Doppler Skywave OTH Radar called NOSTRADAMUS. One of the main characteristics of Skywave OTH Radar is the dependence to the ionosphere for successful operation. The use of the HF band allows Skywave OTH Radar to bounce radio waves from the ionosphere, receiving tiny signals back from reflecting surfaces as the sea, islands, ships and aircraft. The knowledge of the behavior of the ionosphere in a real time configuration is of primary importance because it influences on the choice of frequencies. Radars systems require developing a real-time frequency management system (FMS) using prediction program or measurements supplied by vertical or oblique sounders. The French OTH Radar concept has been developed and implemented so that the radar could be completely autonomous with respect to others "ionospheric information providers." This paper presents the NOSTRADAMUS system, the frequency management system, and shows some results obtained during the past years.

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<div>With the start of the Spanish PAZ system, another earth observation satellite has become available to the scientific community. Following the launch of the PAZ science phase, we performed a number of ground experiments using different modes of the satellites SAR instrument, measuring the transmitted radar signal as well as its ground reflections using the HITCHHIKER receiver. The data acquired in these experiments is analyzed and used in collaboration with the PAZ calibration team at INTA to characterize the PAZ instrument and thus verify the system calibration. Further we obtained bistatic radar images from the data of the HITCHHIKER ground receiver.</div>