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R. Moreno, S. Guilloteau (IRAM), E. Lellouch, T. Encrenaz (DESPA), F. Forget, E. Chassefiere, F. Jegou, F. Hourdin (LMD)
On July 16,17,18 2001, we observed Mars with the IRAM Plateau de Bure Interferometer (PdBI). Observations were obtained in the CO(2--1) and CO(1--0) rotational lines at 230.538 and 115.271 GHz respectively, with a spectral resolution up to 40 kHz. Mars' average angular size was equal to 19\arcsec ~and the spatial resolution in our CO(2--1) and CO(1--0) maps is about 2.5\arcsec ~and 5\arcsec, respectively. The observations sampled the period just after Northern Vernal Equinox (Ls ~ 196\circ). The high spectral resolution will allow us to determine and map Doppler shifts -- especially in the (1--0) line where the signal-to-noise is much higher than in the CO(2--1) line -- and therefore to directly investigate Mars' middle atmosphere (near 50 km) circulation. We already obtained such wind measurements on Mars with the PdBI (Moreno et al 1999, BAAS, 31, 1149), and found a strong retrograde flow for a similar season (Ls ~ 140\circ), which was at odds with Mars General Circulation Models (GCMs) which rather predict a weak prograde flow for this season. These new measurements will therefore provide additionals constraints to Mars GCMs in the poorly characterized middle--atmosphere. Preliminary wind results will be presented.