Ground solar radius survey in view of the Picard microsatellite mission
Abstract
A survey of the Solar radius has been initiated in 1975 by Francis Laclare, at the Calern site of the OCA (Observatoire de la Côte d'Azur), which have been chosen for hosting the ground segment of the CNES Microsatellite PICARD mission, to be launched in 2008. This reference series was obtained by Visual observations of the Sun with a Solar Astrolabe whose metrological character has to be stressed. We look into the Visual series and compare its variations with the Solar cycle, to find an opposing phase, globally and at the different times : maximum, minimum, raise and fall of the cycles. Parallel to that series, CCD measurements were made with the same instrument and gave results which are perfectly blended together, inside narrow error bars. Located next to the Astrolabe, DORAYSOL (Définition et Observation du Rayon Solaire) is a second generation instrument, keeping the strong points of its predecessor and designed to increase the number of CCD measurements and to be automated eventually. Since 1999, both series overlap beautifully and the number of radius data obtained give access to less-than-a-month radius variations, for the first time at the ground level. A few words are added to explain the pattern of the PICARD ground segment next to those instruments at Calern observatory, as well as the ground network intended to carry out the Sun's Radius ground survey (R2S3: Réseau de Suivi au Sol du Rayon Solaire).
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35.1047D