The SCExAO NIR speckle lifetime experiment

Abstract

We describe in this paper an experiment to predict the performance of a real-time speckle nulling loop using high frame rate speckle images collected using a SAPHIRA detector on the SCExAO instrument. Even after extreme adaptive optics corrections, a halo of speckles surrounds the PSF core, and these speckles must be mitigated in order to detect faint structures such as disks or extrasolar planets. Several post-processing techniques such as ADI, PDI, and SDI enable the differentiation between speckles and intrinsic features in the science target, but their ability to improve contrast is limited. In order to detect faint objects such as reflected-light exoplanets, additional techniques need to be implemented. A promising technique is speckle nulling, whereby artificial speckles are generated on top of speckles in the halo in order to destructively interfere them away. If such a loop is implemented with high temporal bandwidth on-sky, then both static and rapidly-changing speckles could be reduced, enabling greatly improved contrasts. We collected 1.7 kHz H-band images and are in the process of analyzing them to simulate the performance of such a loop.