FIRST MESOSPHERIC OBSERVATIONS USING AN IMAGING DOPPLER INTERFEROMETER ADAPTATION OF THE DYNASONDE AT HALLEY, ANTARCTICA

The digital ionospheric sounder, or dynasonde, located at the British Antarctic Survey's research station at Halley, Antarctica, has recentl y been operated as an imaging Doppler interferometer (IDI). The implem entation of this mode of operation does not require any changes to the system hardware but involves a specially written sounding configurati on and newly designed data analysis software. Using four independent a ntennas and two receivers, the signals returned from mesospheric altit udes are range-gated and processed using Doppler sorting and spatial i nterferometry. A three-dimensional (3-D) image of the scattering locat ions can then be built up for a region stretching to over 30 degrees f rom the zenith. The sky map locations and Doppler velocities of the in dividual scattering points are used to fit a 3-D velocity vector repre senting the motion of the neutral wind in the mesosphere. In this pape r the radar hardware, sounding configuration, and data processing are described, and the relative merits of the IDI technique as applied at Halley are discussed. The characteristics of the scattering points are outlined, and initial neutral wind measurements are presented.