Spectral irradiance calibration in the infrared.: XII.: Radiometric measurements from the Midcourse Space Experiment

We describe the series of absolute stellar irradiance calibration experiments conducted by the Mid-course Space Experiment (MSX). These experiments validate the published absolute irradiances of our primary and secondary standards, namely, alpha CMa and a set of bright K-M giant stars, and confirm their radiometric "closure" (relative irradiances). We also validate the absolute spectra of 29 of the fainter calibrators that have been previously published using MSX data. This work underpins the absolute calibrators provided for DIRBE, IRTS, ISO, our all-sky network of 422 fainter calibration stars (Paper X), and the MSX Point Source Catalog, and it is now being extended to accommodate calibrators for SIRTF.