The Solar Diameter Imager and Surface Mapper (SODISM) on board the PICARD space mission provides wide-field images of the photosphere and chromosphere of the Sun in five narrow pass bands (centered at 215.0, 393.37, 535.7, 607.1, and 782.2 nm). PICARD is a space mission, which was successfully launched on 15 June 2010 into a Sun synchronous dawn-dusk orbit. It represents a European asset aiming at collecting solar observations that can serve to estimate some of the inputs to Earth climate models. The scientific payload consists of the SODISM imager and of two radiometers, SOVAP (SOlar VAriability PICARD) and PREMOS (PREcision MOnitor Sensor), which carry out measurements that allow estimating the Total Solar Irradiance (TSI) and the Solar Spectral Irradiance (SSI) from the middle ultraviolet to the red. The SODISM telescope monitors solar activity continuously. It thus produces images that can also feed SSI reconstruction models. Further, the objectives of SODISM encompass the probing of the interior of the Sun via helioseismic analysis of observations in intensity (on the solar disc and at the limb), and via astrometric investigations at the limb. The latter addresses especially the spectral dependence of the radial limb shape, and the temporal evolution of the solar diameter and asphericity. After a brief review of its original science objectives, this paper presents the detailed design of the SODISM instrument, its expected performance, and the scheme of its flight operations. Some observations with SODISM are presented and discussed.

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 as well as some simulations on how to correct observations. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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 atmosphere and/or in the sun. Astrometric satellites scheduled at the end of this decade will perform non ambiguous diameter measurements.A survey of the Solar radius has been initiated in 1975 by Francis Laclare, at the Calern site of the Observatoire de la Cote d'Azur, which have been chosen for hosting the ground segment of the Centre National d'Etudes Spatiales (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. Considering the Visual series results, we have compared the solar diameter variations with the solar activity cycle, and we found an opposite phase, for the whole series and at the different times of the cycles. Parallel to that series, CCD measurements were made with the same instrument and gave results which are perfectly blended together, within our quoted uncertainties.Located next to the Solar Astrolabe, DORA YSOL (Definition et Observation du Rayon Solaire) is a second generation instrument, which keeps the major features of the design of its predecessor and, which is designed to increase the number of CCD measurements and to be eventually automated. Since 1999, both series overlap correctly within our quoted uncertainties.Some information is added to explain the pattern of the PICARD mission ground segment, next to those instruments at Calern Observatory, as well as the international network intended to carry out the Sun's Radius ground survey (R2S3: Reseau de Suivi an Sol du Rayon Solaire). (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

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 needed. In addition to the Hg-mask, a variation on the theme is proposed by a diameter and wavelength adaptive phase mask made of a gas bubble in immersion oil between two optical windows. The instrument concept offers a good versatility to test other mask type and pupil apodization techniques.

In order to optimize the occulting process of a Lyot coronagraph and to provide a high dynamic range imaging, a new kind of occulting disk has been developed at the National Observatory of Rio de Janeiro. A mercury (Hg) drop glued onto an optical window by molecular cohesion and compressed by a pellicle film is used as the occulting disk. The minimum of the superficial tension potential function provides an optical precision (lambda/100) of the toric free surface of the mercury. This process provides a size control for the adaptation to the seeing conditions and to the apparent diameter of a resolved object, and in the case of adaptive optics, to the Airy diameter fraction needed. The occultation is a three dimensional process rear the focal plane on the toric free surface that provides an apodization of the occultation. The Hg-Mask coronagraph has been projected for astrometric observations of faint satellites near to Jovian planets and works since 2000 at the 1.6 m telescope of the Pico dos Dias Observatory (OPD - Brazil).

Earth based observations of Proteus are made highly difficult by the magnitude difference with Neptune, and the closeness to the planet. To overcome these difficulties, observation campaigns using a Hg-mask coronograph developed for astrometry are being pursued at the Laboratorio Nacional de Astrofisica, Brazil. The observations are made at visible light wavelengths with the 1.6 m reflector telescope. The large 4' x 4' field of view of the camera makes it possible to image a sufficient number of background stars that are used to carry out the astrometric analysis of these data.The first results of the campaigns are presented in this paper. They include 45 independent observations made over 2 nights in 2002. The positions are referred to the Hipparcos/Tycho2 frame. The mean offsets relative to the JPL ephemeris are -0."083 (sigma = (0."148) in the x = Deltaalpha cos delta direction, and -0."051 (sigma = 0."115) in the y = Deltadelta direction. Additional astrometric data need to be collected in order to investigate further the possible offset of Proteus with respect to the Voyager ephemerides. For the sake of completeness the early 2000 and 2001 campaigns, although less accurate, are also discussed.

In order to optimize the occulting process of a classical Lyot coronagraph for imaging faint satellites next to Jovian planets, we designed a coronagraph with a variable‐diameter occulting disk (Hg mask). We present the description of the Hg‐mask coronagraph developed at the Observatório Nacional, Rio de Janeiro, and the imaging test on Neptune’s satellite Proteus.