  One of the principal challenges of 21 cm cosmology experiments is overcoming
calibration error. Established calibration approaches in the field require an
exquisitely accurate sky model, and low-level sky model errors introduce
calibration errors that corrupt the cosmological signal. We present a novel
calibration approach called Delay-Weighted Calibration, or DWCal, that enables
precise calibration even in the presence of sky model error. Sky model error
does not affect all power spectrum modes equally, and DWCal fits calibration
solutions preferentially from error-free modes. We apply this technique to
simulated data, showing that it substantially reduces calibration error in the
presence of realistic levels of sky model error and can improve 21 cm power
spectrum sensitivity by approximately 2 orders of magnitude.
