The solar survey at Pic du Midi: calibrated data and improved images

• Published in: arXiv.org 2019-05
• Main Authors: Koechlin, Laurent, Dettwiller, Luc, Audejean, Maurice, Mael Valais, Arturo Lopez Ariste
• Format: Article
• Language: English
• Subjects: Angular resolution; Calibration; Channels; Chromosphere; Corona; Coronagraphs; Image contrast; Line spectra; Masks; Photosphere; Prominences; Solar cycle; Virtual observatories
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1902.06980

At Pic du Midi observatory we carry out a solar survey with images of the photosphere, prominences and corona. This survey, named CLIMSO (CLIchés Multiples du SOleil), is in the following spectral lines: Fe XIII corona (1.075 micron), H-alpha (656.3 nm) and He I (1.083 micron) prominences, H-alpha and Ca II (393.4 nm) photosphere. All frames cover 1.3 times the diameter of the Sun with an angular resolution approaching one arc second. The frame rate is one per minute per channel (weather permitting) for the prominences and chromosphere, and one per hour for the Fe XIII corona. This survey started in 2007 for the disk and prominences, and in 2015 for the corona. We have almost completed one solar cycle, and hope to cover several more, keeping the same wavelengths or adding others. Aims: Make the CLIMSO images easier to use and more profitable for the scientific community. Methods: Providing 'science-ready' data. We have improved the contrast capabilities of our coronagraphs, which now provide images of the Fe XIII corona, in addition to the previous spectral channels. We have also implemented an autoguiding system based on a diffractive Fresnel array for precise positioning of the Sun behind the coronagraphic masks. Results: The data (images and films) are publicly available and downloadable through virtual observatories and dedicated sites: e.g. http://climso.irap.omp.eu. For the H-alpha and and Ca II channels we calibrate the data into physical units, independent of atmospheric or instrumental conditions: we provide solar maps of spectral radiances inW m^-2 sr^-1 nm^-1. The instrumental improvements and the calibration process are presented in this paper.