  The limits for adaptive-optics (AO) imaging at high contrast and high
resolution are determined by residual phase errors from non-common-path
aberrations not sensed by the wavefront sensor, especially for integral field
spectrographs, where phase diversity techniques are complicated by the image
slicer. We present the first application of kernel phase-based wavefront
sensing to ground-based AO, where an asymmetric pupil mask and a single image
are sufficient to map aberrations up to high order. We push toward internally
diffraction-limited performance with the Oxford-SWIFT integral field
spectrograph coupled with the PALM-3000 extreme AO system on the Palomar
200-inch telescope. This represents the first observation in which the
PALM-3000 + SWIFT internal point-spread-function has closely approached the
Airy pattern. While this can only be used on SWIFT with an internal stimulus
source, as at short wavelengths the uncorrected atmospheric wavefront errors
are still > 1 radian, this nevertheless demonstrates the feasibility of
detecting non-common-path errors with this method as an active optics paradigm
for near-infrared, AO-corrected instruments at Palomar. We note that this is a
particularly promising approach for correcting integral field spectrographs, as
the diversity of many narrowband images provides strong constraints on the
wavefront error estimate, and the average of reconstructions from many narrow
bands can be used to improve overall reconstruction quality.
