Doppler Shifts Measurements of the Zodiacal Light at the Pic Midi Observatory

At the Pic-du-Midi Observatory, we have started a program to observe the spectrum of the zodiacal light in the region of the b absorption lines of MgI. We use a 1 meter spectrograph with a holographic grating followed by a focal reducer to obtain a 19 A/mm dispersion over the micro-channel plate camera. Calibrated spectra obtained with an exposure time of 10 minutes systematically show earth atmospheric emission lines attributed to both NI and OH. The temporal variability of these emissions prevents an accurate determination of the line profiles. Our best processed measurements of Doppler shifts obtained during five nights do not allow to descriminate between circular and hyperbolic orbits of the interplanetary dust.