HAUCHECORNE , Alain

Context. In 2015, the International Astronomical Union (IAU) passed Resolution B3, which defined a set of nominal conversion constants for stellar and planetary astronomy. Resolution B3 defined a new value of the nominal solar radius (R N = 695 700 km) that is different from the canonical value used until now (695 990 km). The nominal solar...

The European Space Agency's Aeolus satellite mission is designed to provide global information on the wind speed from the ground up to 30 km, which is highly demanded for weather forecasting. Aeolus satellite has been set into orbit in August 2018 and its payload consists of a sophisticated ALADIN lidar instrument measuring wind velocity by...

The PICARD spacecraft was launched on June 15, 2010 with one of its sci- entific objectives the study of the geometry of the Sun. The measure of the solar oblateness remains difficult because images are affected by optical distortions. Rolling the satellite as performed in previous space missions, allows determi- nation of the telescope...

The PICARD spacecraft was launched on June 15, 2010 with one of its sci- entific objectives the study of the geometry of the Sun. The measure of the solar oblateness remains difficult because images are affected by optical distortions. Rolling the satellite as performed in previous space missions, allows determi- nation of the telescope...

Knowledge of the Solar Diameter Imager and Surface Mapper (SODISM) plate scale is a fundamental parameter for obtaining the solar radius. We have determined the plate scale of the telescope on the ground and in flight onboard the Picard spacecraft. The results show significant differences; the main reason is that the conditions of observation...

The potential relationship between solar activity and changes in solar diameter remains the subject of debate and requires both models and measurements with sufficient precision over long periods of time. Using the PICARD instruments, we carried out precise measurements of variations in solar diameter during the rising phase of solar cycle 24....

PICARD is a mission dedicated to the simultaneous measurements of the solar total and spectral irradiances, its diameter and asphericity. It also probes seismically the solar interior by analysing its local intensity variation. PICARD contains a double program with in-space and on-ground measurements. Space observations are a priori most...

PICARD is an investigation dedicated to the simultaneous measurement of the absolute total and spectral solar irradiance, the diameter and solar shape, and to the Sun's interior probing by the helioseismology method. The spacecraft was successfully launched into a Sun-synchronous dawn-dusk orbit on 15 June 2010 by a DNEPR-1 launcher for a life...

The equator-to-pole radius difference (Δr=R eq−R pol) is a fundamental property of our star, and understanding it will enrich future solar and stellar dynamical models. The solar oblateness (Δ⊙) corresponds to the excess ratio of the equatorial solar radius (R eq) to the polar radius (R pol), which is of great interest for those working in...

PICARD is a CNES micro-satellite launched in June 2010 (Thuillier at al. 2006). Its main goal is to measure the solar shape, total and spectral irradiance during the ascending phase of the activity cycle. The SODISM telescope onboard PICARD also allows us to conduct a program for helioseismology in intensity at 535.7 nm (Corbard et al. 2008)....

For the past thirty years, modern ground-based time-series of the solar radius have shown different apparent variations according to different instruments. The origins of these variations may result from the observer, the instrument, the atmosphere, or the Sun. Solar radius measurements have been made for a very long time and in different ways....

Ground based solar observations are strongly affected by optical turbulence. The concept of a new instrument which allows to measure both spatial and temporal parameters of atmospheric turbulence has been proposed in the late 90s. The instrument MISOLFA (Moniteur d'Images Solaire Franco-Algérien) is based on this concept and has been developped...

PICARD SOL is the ground component of the PICARD mission and is operational since March 2011. A set of instruments including the replica of the space instrument and several atmospheric monitors was set up at Calern observatory in order to compare solar radius measured in space and on ground and to better understand and calibrate atmospheric...