The Solar Oblateness Measured On Board The PICARD Spacecraft, and The Solar Disk Sextant Instrument
Résumé
The PICARD Spacecraft was launched on 15 June 2010. It carries four instruments. One of them, SODISM is an imaging telescope with a 2K x 2K CCD detector, dedicated to the measurement of the solar diameter and the limb shape. Although the data processing is still in a validation phase, we can already present some preliminary results concerning the solar oblateness. These measurements are obtained during a special operation in which the spacecraft turns around the Sun direction. The rotation, made by 300 angular increments, allows us to determine the instrument optical distortion and the solar oblateness. The method used to extract this information will be described. We shall present the preliminary results as a function of wavelength, and compare them with measurements obtained with the SDS instrument, and with the predictions from theoretical modeling.