The SAPPHIRE auroral radar system

Abstract

This paper describes a new, 50 MHz auroral radar system, named SAPPHIRE, which observes at two locations in Canada: SAPPHIRE SOUTH, in the auroral zone and SAPPHIRE NORTH at nominal cusp latitudes in the vicinity of the polar cap – auroral zone boundary. SAPPHIRE was designed to offer superior time and frequency resolution for studies of the geophysical phenomena in the observing regions and to provide a better insight into the plasma processes responsible for the radio scattering. The radars are continuous-wave, dual bistatic systems with two transmitters and two receivers (both at a common receiver location) in each radar system. This configuration provides two-dimensional estimates of the phase velocities in the region of the scatterers. The systems were designed for unattended operation at remote sites and are controlled via modems using conventional telephone service. There are a number of innovative parts to the design of this radar. All frequencies used in the transmitter and receivers are generated using direct digital synthesis which gives independent and accurate control of both frequency and phase. The data collection system uses extensive parallel processing via a custom design of INMOS "transputers" in order to handle the large amount of data received per day. This data collection system only stores data for those times when the observed echoes fulfill some minimum threshold conditions. The most interesting aspects of the electronic design are described and some representative data from SAPPHIRE SOUTH are presented.