WINDI – THE WIND INTERFEROMETER

M. Martin-Neira¹, F. Scala¹, A. Strangfeld¹

¹European Space Agency

The WINDI concept aims at exploring the possibility of measuring the horizontal components of the wind vector over a wide swath of a few hundreds of kilometres, from the planetary boundary to a height of 20 km, with a height resolution of 2 km, through the use of a distributed interferometric radiometer with an observation frequency centred at the water vapour resonant rotational line at 22.235 GHz.

The emission of the water vapour molecules can be received by two receivers forming a baseline and cross-correlated. By filtering the signals with a filter shape similar to that of the line spectrum, it is possible to obtain fringes at the output of the cross-correlator. These fringes move in the delay axis (fringe-rotation) at a rate proportional to the wind velocity parallel to the baseline. By setting two baselines at an angle the two components of the wind velocity vector can be obtained. In order to get the vertical (and horizontal) resolution, antennas with a number of parallel pencil beams are used on both ends of the baseline, intersecting with each other in the atmospheric volume of interest.

This contribution aims at presenting at the conference the basic preliminary analysis that has been carried out showing the formation of fringes with a rotation proportional to the Doppler shift, hence the wind velocity. However, a full sensitivity analysis of this idea is still to be carried out and is work in progress. If once completed the theoretical analysis remains positive, the WINDI concept could be verified with a ground demonstration experiment which will also be introduced at the conference.