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Last modified 11 June 2003
Instrumentation
EISCAT includes elements which bring together a wide range of skills from engineering, in the construction and operation of the antennas and transmitters, through the design and construction of highly-sensitive receivers, to the development of advanced pulse coding and decoding algorithms used to extract the maximum information from the returned, scattered signals.
The EISCAT VHF and UHF radars share a single high voltage capacitor bank which provides about 90 kV for the klystron amplifiers during normal operation. The UHF transmitter operates with peak powers in excess of 1.7 MW, while the VHF transmitter operates at about 3 MW using two klystrons.
The UHF radar uses three, fully steerable parabolic antennas and the VHF radar uses a 120 m by 40 m parabolic cylinder antenna mechanically steerable in the geographic meridian plane. At ESR there are two antennas, one steerable 32m dish and one fixed 40m dish, aligned with the magnetic field.
The radars are controlled by two radar controllers; each of which can hold up to 32000 instructions and issue them with microsecond precision. This timing accuracy is maintained between the sites using cesium time standards.
The scattered signals are received using cryogenically cooled (at Kiruna and Sodankylä), very low noise pre-amplifiers and distributed between up to eight independent channels on each radar. The analogue signals are digitized at rates up to 10 MHz and the resulting 8-bit complex samples processed by high-speed correlators to produce 32-bit complex auto-correlation functions in real time. The data are temporarily recorded to large disk files, from which a real-time analysis provides on-line estimates of ionospheric parameters, before being finally stored on high density magnetic tape.
EISCAT's specially designed real-time operating system (EROS) provides a variety of system control and diagnostic information allow scientists to monitor data quality and make real-time decisions on experimental operations.
EISCAT engineers are currently engaged in designing, building and testing several components which will allow the radar to evolve into a third generation system over the next few years. This approach is exemplified by a special signal pre-processor (called MUFFIN) whose block diagram appears opposite. This will pre-process the digital outputs of the EISCAT receivers, before passing the results to existing and planned computing hardware.
The development of such systems is paralleled by related projects at several of the other Incoherent Scatter radar sites, where the same bus architecture has been adopted, and ensures that EISCAT, and its staff, remain at the forefront of technological development in these areas.
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