Explanation:

• Picard is a CNES solar-terrestrial microsatellite mission of the Myriade series with French multi-institutional and international cooperation.
• The overall objective is to monitor the solar diameter, the differential rotation, the solar constant (simultaneous measurement of the absolute total and spectral solar irradiance), and to study the long-term nature of their interrelations.
• The mission was named in honor of the 17th century French astronomer Jean Picard (1620-1682), who made the first long-term measurements of the solar diameter, observed sunspots, and determined the rotational velocity of the sun.
• Picard was also the first who accurately measured the length of a degree of a meridian (longitude line) and from that result estimated the size of the Earth.
• Beyond the determination of the Earth orbit eccentricity, the diameter measurements brought important information about the particular state of the sun during the so-called Maunder Minimum [named after E. W. Maunder (1851-1928), an English astronomer who studied solar records of the period 1645-1715], a period showing a quasi absence of sunspots as compared to the early 17th century.

Source: ForumIAS