WIVERN, a laboratory experiment for testing novel laser-based wavefront sensing techniques

WIVERN is a testbed for laboratory experiments in laser-based wavefront sensing. It emulates laser uplink from a 4 m telescope with 1.6 arcsec seeing and laser back-scattering from up to 20 km. Currently there are three current wavefront sensing capabilities. The first two are from a wide-field of view (1.0 arcmin) Shack Hartmann wavefront sensor observing a constellation of point sources at infinity (reference targets, star-oriented wavefront sensing), or an image from emulated back-scattering (wide-field correlation wavefront sensing). The third is based on the PPPP concept. Other sub-systems are laser projection replicating a pupil launch, a 7x7 pupil-conjugate deformable mirror (DM), and a wide-field camera for PSF analysis. A 500 Hz rate accumulates sufficient data for statistical and machine-learning analysis over hour timescales. It is a compact design (2.1 m(2)) with mostly commercial dioptric components. The sub-system optical interfaces are identical: a flat focal plane for easy bench reconfiguration. The end-to-end design is diffraction-limited with <= 1% pupil distortion for wavelengths lambda=633-750 nm.