THUILLIER , Gérard

A large volume of data (temperatures, densities, concentrations, winds, etc.) has been accumulated showing that in addition to seasonal changes in the thermosphere, annual variations are present and have a component that is a function of latitude. It appears that the helium concentrations have much larger variations in the southern hemisphere...

The PICARD satellite is dedicated to the monitoring of solar activity. It carries several imaging and radiometric instruments. One of them, SODISM, is a high-resolution radio-imaging telescope measuring the Sun diameter and total flux in near UV and visible wavelengths. Along with mirrors, SODISM includes highly reflective filters and...

For the last 25 years, ground time series of the solar radius have shown (different) apparent variations according to different instruments. The origin of these variations may search in the observer, the instrument, the atmosphere and up to the sun. Ground instruments are automated to reduce the "personnal equation" and place that origin in the...

The PICARD space mission is scheduled for a launch in 2010. Its payload consists in 3 instruments: SODISM from LATMOS, SOVAP from IRMB (Belgium) and PREMOS from PMOD (Switzerland). SODISM key objective is to measure the diameter and shape of the Sun with an accuracy of a few milliarcseconds (mas), and their potential change during the...

PICARD is a French space scientific mission. Its objectives are the study of the origin of the solar variability and the study of the relations between the Sun and the Earth's climate. The launch is foreseen by the end of 2009 on a Sun Synchronous Orbit at 725 km altitude. The mission life time is two years, however to be extended to three...

PICARD is a scientific space mission dedicated to the study of the solar variability origin. A French micro-satellite will carry an imaging telescope for measuring the solar diameter, limb shape and solar oscillations, and two radiometers for measuring the total solar irradiance and the irradiance in five spectral domains, from ultraviolet to...

PICARD is a scientific space mission dedicated to the study of the solar variability origin. A French micro-satellite will carry an imaging telescope for measuring the solar diameter, limb shape and solar oscillations, and two radiometers for measuring the total solar irradiance and the irradiance in five spectral domains, from ultraviolet to...

PICARD is a scientific space mission dedicated to the study of the solar variability origin. A French micro-satellite will carry an imaging telescope for measuring the solar diameter, limb shape and solar oscillations, and two radiometers for measuring the total solar irradiance and the irradiance in five spectral domains, from ultraviolet to...

PICARD is a French space scientific mission. Its objectives are the study of the origin of the solar variability and the study of the relations between the Sun and the Earth's climate. The launch is scheduled for 2010 on a Sun Synchronous Orbit at 725 km altitude. The mission lifetime is two years, however that can be extended to three years....

PICARD is a space mission launched in June 2010 to study mainly the geometry of the Sun. The PICARD mission has a ground program consisting mostly in four instruments based at the Calern Observatory (Obser-vatoire de la Côte d'Azur). They allow recording simultaneous solar images and various atmospheric data from ground. The ground instruments...

For the last thirty years, ground time series of the solar radius have shown different variations according to different instruments. The origin of these variations may be found in the observer, the instrument, the atmosphere and the Sun. These time series show inconsistencies and conflicting results, which likely originate from instrumental...