Hypertelescopes are large optical interferometric arrays, employing many small mirrors and a miniature pupildensifier 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.
We present the concept of a new instrument dedicated to modeling turbulence inside the dome and in the surface
layer. It consists of using parallel laser beams separated by non redundant baselines between 0.1 and 2-3m and
measuring Angle-of-Arrival (AA) fluctuations from spots displacements on a CCD. We use weighted least-square
method to fit the measured AA longitudinal and transverse covariances with theoretical forms deduced from
the usual models of turbulence. Then, the whole parameters characterizing this turbulence are provided from a
complete spatio-temporal analysis of AA fluctuations. Thus, the surface layer turbulence energy in terms of C2N
constant is provided from the AA structure function as in the DIMM instrument.
This paper reviews the recent laboratory results we have obtained on the demonstration of a cophasing algorithm
based on the chromatic phase diversity method. The SIRIUS testbed was initially dedicated to the demonstration
of the direct imaging capabilities of arrays of telescope. We have developed and numerically modeled a piston
sensor based on the chromatic dependance of the spectral density phase. This method allows a global cophasing
of the array over a capture range of many wavelengths aiming at improving the robustness of the method.
The futures 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 C2n(h) and the outer scale L0(h). New techniques based on the moon limb observation for the monitoring of the C2n(h) and L0(h) profiles with high vertical resolution will be