Solar Ecartometry Sensor with 1 arcsec resolution for the Picard satellite.




A result of French multi-institutional and international cooperation, Picard is a CNES solar-terrestrial microsatellite mission of the Myriade series. Its overall objective consists in monitoring the solar diameter, differential rotation, and constant (simultaneous measurement of the absolute total and spectral solar irradiance), and in studying the long-term nature of their interrelations. Subcontracting for the CNES, Lambda-X developed the PSES with Belgium’s Coretec (mechanical design) and IASB (electronics).

Technical challenge

The Picard Sun Ecartometry Sensor (PSES) is the fine solar pointer aligning the Picard satellite instruments with the sun and boasting an accuracy higher than 5 arcsec (~0.001 deg). The device is made up of two parts: an optical front and an electronic back. The former, a narrow bandwidth filter at 782 nm in the solar continuum, allows eliminating the disturbance caused by the presence of sunspots. The filtered Sun image is projected on the four quadrants detector of the electronic back part. Each photodiode of the detector provides a voltage output proportional to the received light intensity. The two parts of the SES are directly mounted on the SODISM instrument to minimize the misalignments.

Key technical characteristics

Field of view 2000 arcsec (0.55°)
Absolute accuracy 5 arcsec
Resolution 1 arcsec


Launched in June 2010 and initially designed for a 2-year mission, the Picard satellite’s operation has been extended until 2015.