Accession Number : ADA458662
Title : Absolute Infrared Calibration of Standard Stars by the Midcourse Space Experiment
Descriptive Note : Technical rept.
Corporate Author : AIR FORCE RESEARCH LAB HANSCOM AFB MA SPACE VEHICLES DIRECTORATE
Personal Author(s) : Price, S D ; Paxson, C ; Engelke, E ; Murdock, T L ; Kraemer, K E
Report Date : Apr 2004
Pagination or Media Count : 240
Abstract : Calibration experiments were conducted with the SPIRIT III infrared instrument on the Midcourse Space Experiment (MSX) against a number of infrared standard stars and five emissive reference spheres that were ejected at various times during the mission. The physical properties of the 2 cm diameter aluminum spheres, such as the Bond albedo and thermal emissivity of the Martin Black coating, were measured in the laboratory. The thermal balance equation between total flux absorbed and that emitted by the sphere was solved to obtain the time dependent temperature of the sphere under the assumption that the sphere radiates as a blackbody at this temperature with a mean infrared emissivity. The estimated uncertainties in the modeling of the sphere are estimated to be about 1K in the thermal component and 3% for the geometry contribution. MSX also measured more than 150 averaged fluxes on eight standard infrared calibration stars during the 10-month mission. The photometric spectral energy distributions of the stars are measured to be within the uncertainties assigned to absolute fluxes adopted for these stars, with a few exceptions. However, the small MSX measurement uncertainties did reveal statistically significant deviations from the recommended values. Beta Peg was the only calibrations star that was found to be variable. MSX also observed excess fluxes for Vega in the 12.1, 14.7 and 21.3 um spectral bands; the excesses in the latter two bands are consistent with the published thermal model for the dust ring around this star. The absolute calibration of the fluxes of the stellar standards based on the average of the measurements of the spheres over all MSX bands and the five experiments agrees with the predictions to within the uncertainties. The zero magnitude absolute fluxes proposed by Cohen et al (1992) are validated if the flux from Sirius is increased by 1%.
Descriptors : *SPACE ENVIRONMENTS , *CALIBRATION , *INFRARED STARS , DATA PROCESSING , TEMPERATURE , PREDICTIONS , MODELS , SPHERES , EMITTANCE , ALUMINUM , COATINGS , PHYSICAL PROPERTIES , TIME DEPENDENCE , UNCERTAINTY , EXPERIMENTAL DATA
Subject Categories : Astronomy
Coatings, Colorants and Finishes
Distribution Statement : APPROVED FOR PUBLIC RELEASE