Hypertelescopes are large optical interferometric arrays, employing many small mirrors and a miniature pupil-densifier before the focal camera, expected to produce direct images of celestial sources at high resolution. Their peculiar imaging properties, initially explored through analytical derivations, had been verified with simulations before testing a full-size testbed instrument. We describe several architectures and optical design solutions and present recent progress made on the Ubaye hypertelescope experiment. Arecibo-like versions with a fixed spherical primary meta-mirror, or an active aspheric one, have a suspended focal beam combiner equipped for pupil-drift accommodation, with a field-mosaic arrangement for observing multiple sources such as exoplanetary systems, globular clusters or active galactic nuclei. We have developed a cable suspension and drive system with tracking accuracy reaching a millimeter at 100m above ground.

The future large telescopes will be certainly equipped with Multi-Conjugate Adaptive Optics systems. The optimization of the performances of these techniques requires a precise specification of the different components of these systems. Major of these technical specifications are related to the atmospheric turbulence particularly the structure constante of the refractive index C2 n(h) and the outer scale L0(h). New techniques based on the moon limb observation for the monitoring of the C2 n(h) and L0(h) profiles with high vertical resolution will be presented. A new monitor PBL (Profileur Bord Lunaire) for the extraction of the C2 n(h) profile with high vertical resolution has been developed. This instrument uses an optical method based on observation of the moon limb with a DIMM configuration (Differential Image Motion Monitor). Indeed, in the PBL the lunar limb is observed through two sub-apertures of 6cm separated by a base of 30cm. The moon limb offers a continuum of stars at different angular separations allowing the scan the atmosphere with a very high resolution. The angular correlation along the lunar limb between of the differential distance between the two images of the lunar edge leads to the C2 n(h) profile. The other parameters of turbulence are also accessible from this instrument as the profile of outer scale, the seeing and isoplanatic & isopistonic domains. The PBL succeeded to our first moon limb profiler MOSP (Monitor of Outer Scale Profile) which was developed mainly for outer scale profile extraction. Several campaigns have been carried out with MOSP particularly at Mauna Kea Observatory (Hawaii) and Cerro Paranal in Chile. The PBL instrument has been installed at Dome C in Antarctica since January 2011. In addition to this winterized PBL for Dome C, a second copy of this instrument has been developed for mid-latitude sites. A first campaign with this light version of PBL, was carried out at the South African Large Telescope (SALT) Observatory in August 2011.

The Concordia Base in Dome C, Antarctica, is an extremely promising site for photometric astronomy due to the 3- month long night during the Antarctic winter, favorable weather conditions, and low scintillation. The ASTEP project (Antarctic Search for Transiting ExoPlanets) is a pilot project which seeks to identify transiting planets and understand the limits of visible photometry from this site. ASTEP 400 is an optical 40cm telescope with a field of view of 1° x 1°. The expected photometric sensitivity is 1E-3, per hour for at least 1,000 stars. The optical design guarantees high homogeneity of the PSF sizes in the field of view. The use of carbon fibers in the telescope structure guarantees high stability. The focal optics and the detectors are enclosed in a thermally regulated box which withstands extremely low temperatures. The telescope designed to run at -80°C (-110°F) was set up at Dome C during the southern summer 2009- 2010. It began its nightly observations in March 2010.

In order to prepare the future search for biosignatures on exo-Earths or exo-SuperEarths, we investigate the detection of life on the only planet known to shelter life to date, our Earth. We have to see the Earth as a dot, the way future exoEarths will appear to us. This is the case when we observe the Earthshine, using the Moon as a huge reflector to measure the whole Earth's albedo. Observations of the Earthshine made at the Haute-Provence Observatory and the European Southern Observatory showed biosignatures on Earth, including the Vegetation Red Edge (VRE) in the near infrared, which is due to chlorophyll absorption spectral properties. The VRE is only a few percents, and higher when continents instead of oceans are facing the Moon. At very high latitudes and some times of year, it is possible to observe the Earthshine during most of the day, which is not possible at lower latitudes. Throughout these long observing windows, Earth rotation brings various terrestrial "landscapes" in front of the Moon. So we planned to make observations at the French-Italian scientific Concordia Station located at the Dome C in Antarctica, and for this purpose we set up the LUCAS (LUmière Cendrée en Antarctique par Spectroscopie) experiment. A dedicated spectrograph was designed and built at the Haute-Provence and Meudon Observatories. The first observations began during the 2008 winterover campaign and go on.