  The Picard solar satellite has been launched on June 15, 2010. This mission
is dedicated to the measurement of the solar diameter with an expected accuracy
of milliarcseconds of arc. The radiometer onboard is to measure the total solar
irradiance. The final goal is the evaluation of the W, the logarithmic ratio of
radius and luminosity. This parameter will help the climatologists to recover
past values of the solar luminosity when the radius is available from ancient
eclipses data.
