Absolute calibration of astronomical flux standards

Abstract

The goal of astronomical data calibration is to convert measurements recorded in some particular instrumental units into physical quantities, such as erg cm−2 s−1 Hz−1, removing as much as possible all instrumental signatures. In principle, photometric calibration is a solved problem – laboratory reference standards such as blackbody furnaces achieve precisions well in excess of those needed for astrophysics. In practice, however, transferring the calibration from these laboratory standards to astronomical objects of interest is far from trivial – the transfer must reach outside the atmosphere, extend over 4π steradian of sky, cover a wide range of wavelengths, and span an enormous dynamic range in intensity.