Some Thoughts on Cross-calibration in the Mid-Infrared

I provide some examples of the cross-calibration between the instruments aboard the Spitzer Space Telescope. Current cross-calibration accuracy between the Spitzer instruments is better than 5% and consistent with the calibration uncertainties of the instruments and the current uncertainties in the absolute calibration of infrared zero-points. Utility of cross-calibration extends beyond reconciling measured fluxes; examples are given of how cross-calibration can be used to identify/mitigate instrumental signatures. The Spitzer cross-calibration efforts are placed in context by a brief review of the current state of absolute calibration in the infrared. The current accuracy of calibration is limited by knowledge of the fundamental zero points to about 2%. Rapid progress in the field is being made which suggests that the 1% absolute photometric accuracy requirement of some future dark energy probes can be met.