The various scientific objectives of the mission PICARD are explained in the following paragraphs:
 

Periodic variations of the climate
Measurements of the solar diameter
The shape of the Sun
The modelling of the Sun's functioning
The energy received by the Earth and its climate
The Climate during the XVII^th century
The long-term variability of the Sun
The modelling of the climate
The physics of the atmosphere
The space weather

The PICARD mission using three instruments will implement the following observations and programs:

SOVAP measures the total solar radiance.
PREMOS measures the solar spectral radiance in some spectral domains in infrared, visible and UV relevant of the ozone photochemistry which are essential measurements for the physics of the atmosphere and the climate of the Earth.
SODISM measures the diameter, the shape of the sun, the activity, the differential rotation in several spectral domains, and carries out a major survey of the solar interior structure by use of the heliosismology method.

All these measurements will make possible to understand their relation by using solar and climate modelling as well as their variations. The combined use of absolute spectral measurements by PREMOS with the total solar radiance by SOVAP as well as the images by SODISM will make possible to check and refine our current theoretical understanding of the variations of solar radiance, by identifying the characteristics responsible for these variability. With regard to the Earth, they will be used as inputs to GCM simulations with aim to study the response of the Earth's atmosphere to the variations of spectral and total solar radiance.

This table shows the scientific objectives, the measurements and the instruments which will carry them out. SODISM I and II are two identical instruments dedicated to the measurement of the solar diameter, the first being placed in orbit, and the second operated on the ground.

References for the whole PICARD site