First on-sky results, performance and future of the HiCIBaS - LOWFS

HiCIBaS-LOWFS is a spatially modulated pyramid wavefront sensor to be used on the HiCIBaS project, a high-contrast imaging balloon borne telescope, as a fine pointing and atmospheric turbulence sensor. Since the project will be using a relatively small telescope on a limited budget, creative solutions must be developed to respond to the requirements for such systems. For example, we need a linear response to large error in order to be able to correct for pointing error in a photon-limited regime caused by the telescope small size. Most solutions arent well suited for the optical design in HiCIBaS since the high-contrast coronagraph and the Low-Order Wavefront Sensor (LOWFS) both run as separate instruments. The design is centered around the modification of existing pyramid wavefront sensor by adding static, spatial modulation to an otherwise unmodulated system. The spatial modulation is achieved by adding an axicon (a conical optical element) at an imaged telescope pupil plane. This has for effect to add a very large non-common path aberration between the imaging plane and the wavefront sensor. This has for effect to shape the point-spread function incident on the pyramid to a ring shape, which minimize diffraction effect on the apex of imperfect pyramids. We present the first lab results involving the wavefront sensor and its performances for wavefront reconstruction and pointing accuracy. We also discuss the first on-sky results that were recorded with the 1.6-m telescope at the Observatoire du Mont-Megantic in Qubec, Canada using Universite Lavals optical AO test-bench. These results pave the way to the design and integration of the wavefront sensor in the context of the HiCIBaS project.