The quality of this shared calibration, however, depends in any particular time period on the quality of our knowledge of the spectral energy distributions (SEDs) of the reference stars observed. Work at ISR has focused on progressively refining and updating knowledge of the visible-through-infrared spectra of commonly observed standard stars using all available strands of information. 

This effort brings together and cross-correlates theoretical modeling, data from various calibration experiments, exo-atmospheric spectrometry (ESA’s ISO SWS & CVF, HST’s STIS &NICMOS) and relative photometry (DIRBE, MSX, Hipparcos, IRAC) taken from satellite observatories, as well as the large ground databases of relative magnitude comparisons between types of stars. 

These data are culled, reanalyzed and reconsidered in light of subsequent information, such as evidence of variability in primary standard Vega.  The results are built into synthetic continuous spectra/SEDs (stored as computer files) which constitute the best available estimate of each standard star’s absolute spectral calibration. 

These absolutely calibrated spectra of stars of varying temperature are then used to find a best-fit function of temperature at each catalogued wavelength which generates the mean predicted template spectral shape for a star of any temperature in the range covered by the original standard stars. 

These can be used to represent stars which have had no direct continuous spectrometry performed on them, greatly expanding range of stars which can become calibrators in the sky.

Point of Contact for this project is Charles Engelke.