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High throughput, low inner working angle (IWA) phase masks coronagraphs areessential to directly image and characterize (via spectroscopy) earth-likeplanets. However, the performance of low-IWA coronagraphs is limited byresidual pointing errors and other low-order modes. The extent to whichwavefront aberrations upstream of the coronagraph are corrected and calibrateddrives coronagraphic performance. Addressing this issue is essential forpreventing coronagraphic leaks, thus we have developed a Lyot-based low orderwave front sensor (LLOWFS) to control the wavefront aberrations in acoronagraph. The LLOWFS monitors the starlight rejected by the coronagraphicmask using a reflective Lyot stop in the downstream pupil plane. The earlyimplementation of LLOWFS at LESIA, Observatoire de Paris demonstrated an openloop measurement accuracy of 0.01 lambda/D for tip-tilt at 638 nm when used inconjunction with a four quadrant phase mask (FQPM) in the laboratory. Tofurther demonstrate our concept, we have installed the reflective Lyot stops onthe Subaru Coronagraphic Extreme AO (SCExAO) system at the Subaru Telescope andmodified the system to support small IWA phase mask coronagraphs (< 1 lambda/D)on-sky such as FQPM, eight octant phase mask, vector vortex coronagraph and thephase induced amplitude apodization complex phase mask coronagraph with a goalof obtaining milli arc-second pointing accuracy. Laboratory results have shownthe measurement of tip, tilt, focus, oblique and right astigmatism at 1.55 umfor the vector vortex coronagraph. Our initial on-sky result demonstrate theclosed loop accuracy of < 7 x 10-3 lambda/D at 1.6 um for tip, tilt and focusaberrations with the vector vortex coronagraph.

Lyot-based Low Order Wavefront Sensor: Implementation on the Subaru Coronagraphic Extreme Adaptive Optics System and its Laboratory Performance