THE EISCAT SVALBARD RADAR - A CASE-STUDY IN MODERN INCOHERENT-SCATTERRADAR SYSTEM-DESIGN

The EISCAT (European incoherent scatter) Svalbard radar (ESR) was offi cially inaugurated on August 22, 1996. This event marked the successfu l completion on schedule of the first phase of the EISCAT Svalbard rad ar project. In contrast to previous incoherent scatter radars, the ESR system design was adapted to make use of commercial off-the-shelf TV transmitter hardware, thereby reducing design risk, lead times, and co st to a minimum. Commercial hardware is also used in the digital signa l processing system. Control and monitoring are performed by distribut ed, networked VME systems. Thanks to modern reflector antenna design m ethods and extreme efforts to reduce the receiver noise contribution, the system noise temperature is only 70 K, thus making the ESR about 3 0% faster than the much more powerful EISCAT UHF radar in F region exp eriments! Once the transmitter power is increased to 1 MW, it will bec ome about 2-3 times faster than the UHF radar. State-of-the-art excite r and receiver hardware has been developed inhouse to accommodate the special requirements introduced by operating the radar at the exceptio nally high duty cycle of 25%. The RF waveform is generated by a system based on four switchable direct digital synthesizers. Continuous moni toring of the transmitted RF waveform by the receiver system allows re moval of klystron-induced spurious Doppler effects from the data. Inte rmediate-frequency sampling at 7.5 MHz is employed, followed by fully digital channel separation, signal detection, and postdetection filter ing in six parallel receiver channels. Radar codes for both E and F la yer observation have been designed and perfected. So far, more than 40 hours of good quality ionospheric data have been collected and analyz ed in terms of plasma parameters. While the tragic loss of the Cluster mission suddenly changed the plans and dispositions of a majority of the ESR user community, the radar has still been in high demand since its inauguration. It is now being operated by EISCAT staff on a campai gn basis, to provide ground-based support data for a number of other m agnetospheric satellites, notably Polar and FAST, and will be opened t o the EISCAT user community for special program operations later in 19 97.