IRBAH , Abdanour

Anisoplanatism in Adaptive Optics or Differential Astrometry as in ground-based solar diameter measurement needs the knowledge of atmospheric turbulence profiles. MISolFA is a monitor dedicated to statistically estimate daytime turbulence profiles C-{n}**{2}(h) from solar limb agitation measurements. In order to understand the statistics of the...

The results here discussed were produced by a program of visual observations carried out at the Calern Observatory from 1975 to 1998. The sun radius data collected display some variability, in particular an oscillation of 0.2″amplitude and 11.8 years period which seems anticorrelated with the sunspot cycle. These apparent variations might also...

Seeing monitoring in astronomy is widely based on the statistical analysis of angle-of-arrival (AA) fluctuations, which are usually modelled in the framework of the near-field approximation where diffraction through turbulence is ignored. They are consequently believed to be completely independent of wavelength. We discuss in this paper the...

The theoretical expression of the transverse angular covariance of angle-of-arrival fluctuations of the incoming wave-fronts integrated all over the telescope pupil has been established in the case of one-layer model and using the Von Kàrmàn theory. This model depends on three atmospheric parameters: the spatial coherence outer scale ${\cal...

PICARD is a French space scientific mission. Its objectives are the study of the origin of the solar variability and the study of the relationship between the Sun and the Earth's climate. PICARD was launched on June 15, 2010 on a Dnepr-1 launcher. SODISM (SOlar Diameter Imager and Surface Mapper), an instrument of the PICARD payload, is a high...

In order to deduce significant astrophysical results from solar diameter measurements it is necessary to take an accurate account of instrumental and atmospheric effects. This paper presents a comparison between visual and charge coupled device (CCD) camera measurements performed by means of the Calern Observatory solar astrolabe during the...

High angular resolution observations of the sun are limited by atmospheric turbulence. The MISOLFA seeing monitor (still under construction) is developed to obtain spatial and temporal statistical properties of optical turbulence by analyzing local motions observed on solar edge images. The solar flying shadows used for angle-of-arrival...

The MISOLFA seeing monitor is developed to analyze spatial and temporal statistical properties of daytime optical turbulence. It is based on Angle-of-Arrival (AA) statistical properties. The MISOLFA optical de- vice measures AA-fluctuations observed as intensity variations in the pupil plane image formed through a thin slit positioned in the...

A method is presented allowing one to estimate, in the case of daytime observations, the angle-of-arrival isoplanatic patch size from the measurement of the differential image motion of the solar limb. The experimental results have been obtained using the solar astrolabe of Calern Observatory (CERGA-France). Performing a modelization as...

High angular resolution observations of the sun are limited by atmospheric turbulence. The MISOLFA seeing monitor (still under construction) is developed to obtain spatial and temporal statistical properties of optical turbulence by analyzing local motions observed on solar edge images. The solar flying shadows used for angle-of-arrival...

Atmospheric turbulence is responsible of the spatio-temporal fluctuations in astronomical object images obtained by means of ground-based telescopes. They are due to wave-front degradations present at the entrance of the instrument pupil plane. We first establish in this paper the formulation of the angle-of-arrival angular structure function...

Atmospheric turbulence is responsible of spatio-temporal fluctuations of astronomical object images obtained by means of ground-based telescopes. The image motion is due to the angle formed by the pupil plane with the wave-front slope all over the pupil. This defines an averaged angle of arrival which may be also considered at each point of the...

As a consequence of an astrometry program, conducted since 1975 on a solar astrolabe at the Calern Observatory (Observatoire de la Côte d'Azur), we have obtained a data set of apparent solar diameters which encompasses periods greater than one solar cycle. From a set of more than 5000 visual observations, made by the same observer between 1975...

The one dimensional point spread function for long exposure frames of the whole system atmosphere-instrument is deduced from solar limb observations using data recorded at Calern Observatory (France). It is then compared to the theoretical one deduced from the Von Karman model. Good agreement is found allowing to deduce the spatial coherence...

Daily observation conditions are needed when observing the Sun at high angular resolution. MISOLFA is a daytime seeing monitor developed for this purpose that allows the estimation of the spatial and temporal parameters of atmospheric turbulence. This information is necessary, for instance, for astrometric measurements of the solar radius...

The one-dimensional point spread function for long-exposure frames of the whole system atmosphere - instrument is calculated from solar limb observations using data recorded at OCA Observatory (France). It is then compared to the theoretical one deduced from the Von Karman model and various wave-front structure functions. Good agreement is...

By applying the theory of slowly rotating stars to the Sun, the solar quadrupole and octopole moments J2 and J4 were computed using a solar model obtained from CESAM stellar evolution code (Morel, 1997) combined with a recent model of solar differential rotation deduced from helioseismology (Corbard et al., 2002). This model takes into account...

The SODISM Telescope of the PICARD Space mission will perform diameter measurements by directly imaging the Sun on a CCD camera. An internal calibration system allows us to follow scale factor variations induced by instrument deformations resulting from temperature fluctuations on orbit or from others causes. We present this calibration system...

In this paper, the new coronagraph that will be mounted at the Pic du Midi Observatory (IMCCE - T1m telescope) is presented. To optimize the occulting process of a Lyot coronagraph, a compressed mercury (Hg) drop is used as an occulting disk and its size control offers an adaptation to the seeing conditions or to the Airy diameter fraction...

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...

Diameter measurements performed with the solar astrolabe are affected by instrumental and atmospheric effects. The problem is to know how these effects contribute to the error on diameter measurements. Thus, a numerical simulation is developed to bring some responses to this problem. For this purpose, synthetic images of the Sun similar to the...

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 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...

The series of measurements of the Solar radius at CALERN site of the observatoire de la Côte d'Azur (OCA) spans about 30 years. Measurements of the Sun were first achieved visually by the same single observer, then gradually grew more man-independent with the use of CCD acquisitions. The DORAYSOL instrument was designed and built up to keep...