  The Low Wind Effect (LWE) refers to a phenomenon that occurs when the wind
speed inside a telescope dome drops below $3$m/s creating a temperature
gradient near the telescope spider. This produces phase discontinuities in the
pupil plane that are not detected by traditional Adaptive Optics (AO) systems
such as the pyramid wavefront sensor or the Shack-Hartmann. Considering the
pupil as divided in 4 quadrants by regular spiders, the phase discontinuities
correspond to piston, tip and tilt aberrations in each quadrant of the pupil.
Uncorrected, it strongly decreases the ability of high contrast imaging
instruments utilizing coronagraphy to detect exoplanets at small angular
separations. Multiple focal plane wavefront sensors are currently being
developed and tested on the Subaru Coronagraphic Extreme Adaptive Optics
(SCExAO) instrument at Subaru Telescope: Among them, the Zernike Asymmetric
Pupil (ZAP) wavefront sensor already showed on-sky that it could measure the
LWE induced aberrations in focal plane images. The Fast and Furious algorithm,
using previous deformable mirror commands as temporal phase diversity, showed
in simulations its efficiency to improve the wavefront quality in the presence
of LWE. A Neural Network algorithm trained with SCExAO telemetry showed
promising PSF prediction on-sky. The Linearized Analytic Phase Diversity (LAPD)
algorithm is a solution for multi-aperture cophasing and is studied to correct
for the LWE aberrations by considering the Subaru Telescope as a 4 sub-aperture
instrument. We present the different algorithms, show the latest results and
compare their implementation on SCExAO/SUBARU as real-time wavefront sensors
for the LWE compensation.
