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B. Mosser, J.P. Maillard (IAP), D. M\'ekarnia (OCA)
We report a new seismic observation of Jupiter in August 1996 with the Fourier transform spectrometer, based at the CFH telescope, used as an accelerometer. With this instrument, the Jovian velocity field could be measured for the first time with an absolute velocity calibration: the Doppler effect translates into a phase shift which is a fraction of a reference laser wavelength. The noise in the Fourier spectrum reaches 4~cm.s-1.\muHz-1/2.
A source of noise, identified as due to spurious velocity signal induced by the seeing effect on the rapidly rotating planet, as well as a poor window function, has precluded the possible direct identification of Jovian modes. However, there is a strong evidence in the data for an oscillation characteristic frequency \nu0, at 142±3\muHz, which confirms a low value of this parameter. Furthermore, the identification of the large splittings along the whole Fourier spectrum indicates a very small planetary core, if any. The modes amplitude is inferred not to exceed 0.6~m.s-1 in the [1-3~mHz] frequency range.