Addressing the photometric calibration challenge: explicit determination of the instrumental response and atmospheric transmission functions
I will present an overview of our ongoing efforts to ascertain (through direct measurement) the both instrumental response function and the variable aspects of atmospheric transmission, in the context of surveys such as PanSTARRS and LSST. We have now gained experience with the use of tunable lasers and NIST-calibrated photodiodes to ascertain the instrumental response function from multiple telescopes, and have obtained interesting results on stray and scattered light. We have also been operating a spectrophotometric sky transmission monitor for PanSTARRS, and I will present initial results from that system. I will close with some thoughts on next steps in this process.