Implications for contrast as a result of the wind vector and non-stationary turbulence

In an adaptive optics (AO) system, finite time delays contribute a relatively large amount to the overall wavefront error. The temporal error, due to the time delays, adds to the speckle halo which is visible in the science plane of a high contrast imaging (HCI) instrument. The halo limits the inner working angle, preventing HCI from probing...

Optimization of contrast in adaptive optics for exoplanet imaging

Direct imaging of exoplanets requires overcoming the enormous contrast between the exoplanet and its host star, to distinguish the reflected light from the exoplanet, from the diffracted light of the star. Direct optimization of contrast, using nonlinear optimization techniques of the Adaptive Optics (AO) system coupled with coronagraphy, shows...

Modelling and prediction of non-stationary optical turbulence behaviour

There is a strong need to model the temporal fluctuations in turbulence parameters, for instance for scheduling, simulation and prediction purposes. This paper aims at modelling the dynamic behaviour of the turbulence coherence length r0, utilising measurement data from the Stereo-SCIDAR instrument installed at the Isaac Newton Telescope at La...

Focal-plane wavefront sensing with high-order adaptive optics systems

We investigate methods to calibrate the non-common path aberrations at an adaptive optics system having a wavefront-correcting device working with an extremely high resolution (larger than 150x150 correcting elements). We use focal-plane images collected successively, the corresponding phase-diversity information and numerically efficient...