Picard, a solar mission dedicated to the study of the Sun: current results
Résumé
PICARD is a mission dedicated to the simultaneous measurements of the solar total and spectral irradiances, its diameter and asphericity. It also probes seismically the solar interior by analysing its local intensity variation. PICARD contains a double program with in-space and on-ground measurements. Space observations are a priori most favourable, however, space entails also technical challenges, a harsh environment, and a finite mission lifetime. The PICARD spacecraft, launched on June 15, 2010 will retire in April 2014. On ground, the instruments are less affected by in-space degradation and maintenance is easily provided so if the atmosphere is properly monitored and taken into account, they still represent an opportunity to generate the needed long-term time-series. That is why ground measurements have been carried out since May 2011-and will be pursued after the space program. In this talk, we describe both sets of instruments, and then present our current results. In particular, we show new estimates of the absolute values of the total solar irradiance, diameter and oblateness. We also report about helioseismic studies and about the apparent absence of mid-term trend in the measurement of the diameter.