SCANDI – an all-sky Doppler imager for studies of thermospheric spatial structure

摘要

A new all-sky Fabry-Perot Interferometer called the Scanning Doppler Imager(SCANDI) was built and installed at Longyearbyen in December 2006.Observations have been made of the Doppler shifts and Doppler broadening ofthe 630 nm airglow and aurora, from which upper thermospheric winds andtemperatures are calculated. SCANDI allows measurements over a field-of-view(FOV) with a horizontal radius of nearly 600 km for observations at analtitude of 250 km using a time resolution of 8 min. The instrumentprovides the ability to observe thermospheric spatial structure within a FOVwhich overlaps that of the EISCAT Svalbard radar and CUTLASS SuperDARNradars. Coordinating with these instruments provides an importantopportunity for studying ion-neutral coupling. The all-sky image is dividedinto several sectors to provide a horizontal spatial resolution ofbetween 100–300 km. This is a powerful extension in observational capabilitybut requires careful calibration and data analysis, as described here. Twoobservation modes were used: a fixed and a scanning etalon gap. SCANDIresults are corroborated using the Longyearbyen single look direction FPI,and ESR measurements of the ion temperatures. The data show thermospherictemperature gradients of a few Kelvins per kilometre, and a great deal ofmeso-scale variability on spatial scales of several tens of kilometres.