Precise Astronomical Flux Calibration and its Impact on Studying the
  Nature of Dark Energy
  Measurements of the luminosity of type Ia supernovae vs. redshift provided
the original evidence for the accelerating expansion of the Universe and the
existence of dark energy. Despite substantial improvements in survey
methodology, systematic uncertainty in flux calibration dominates the error
budget for this technique, exceeding both statistics and other systematic
uncertainties. Consequently, any further collection of type Ia supernova data
will fail to refine the constraints on the nature of dark energy unless we also
improve the state of the art in astronomical flux calibration to the order of
1%. We describe how these systematic errors arise from calibration of
instrumental sensitivity, atmospheric transmission, and Galactic extinction,
and discuss ongoing efforts to meet the 1% precision challenge using white
dwarf stars as celestial standards, exquisitely calibrated detectors as
fundamental metrologic standards, and real-time atmospheric monitoring.
