28 July 2010
6 receiving stations
The SODISM instrument is operating perfectly.
The French-developed 11-cm-diameter telescope, the nerve centre of the Picard observation system, has returned a 1st image of the Sun, dated 22 July, just 1 month after the satellite was placed in orbit.
“This allows us to check the instrument is working properly and make a few adjustments for data processing on the ground,” explains François Buisson, Picard project leader at CNES.
Images from the satellite do not arrive in a ready-to-use format.
“SODISM digital data are constructed from light captured by the telescope and sent via radio link to 1 of the 6 Picard receiving stations on the ground,” continues François Buisson. “They are then relayed to the CNES control centre in Toulouse before being delivered to the Picard mission centre in Brussels, which decodes and decompresses the data and constructs the image.”
The 11-year cycle
The wheels of this machine need to be well oiled, because SODISM will be acquiring 1 image of the Sun every minute for the next 2 years at least.
“Picard’s real strength is its ability to continuously observe the Sun for several years,” explains François Buisson. “It will obtain ultra-precise measurements of the Sun’s diameter as well as the radiant energy it emits to provide a better understanding of the relationships between these parameters over the course of the 11-year solar cycle.”
The image of 22 July was acquired at a wavelength of 607 nm, but SODISM can also operate at 5 other wavelengths to observe such details as sunspots and faculae* as well as the Sun’s internal structure.
Besides SODISM, Picard also carries 2 radiometers to measure solar irradiance.
The mission scientists are thus hoping to unravel the mysteries of the “day star”.
*Small bright spots visible on the Sun’s surface.