Gardner, L. D.; Smith, P. L.; Kohl, J. L.; Atkins, N.; Ciaravella, A.; Miralles, M. P.; Panasyuk, A.; Raymond, J. C.; Strachan, L., Jr.; Suleiman, R. M.; Romoli, M.; Fineschi, S.

The Radiometric Calibration of SOHO (ESA SR-002). Edited by A. Pauluhn, M.C.E. Huber and R. von Steiger, p.161, 2002

Abstract

The Ultraviolet Coronagraph Spectrometer (UVCS) was characterized and radiometrically calibrated in the laboratory as a system at the Harvard-Smithsonian Center for Astrophysics in June of 1995. Component level calibrations of optical components and detectors were also performed. After launch, an in-flight calibration activity was carried out that extended the laboratory calibration, compared UVCS measurements of stars to those of other instruments and monitored the radiometric stability of UVCS through repeated measurements of stars that are believed to have nearly constant ultraviolet irradiance. In-flight measurements have, in general, confirmed the laboratory radiometric calibration. Comparisons to Spartan 201 observations of the same coronal structures agree within 10 %. The system responsivity, although it has changed somewhat during the six years of operation, is well behaved and characterizable. This paper describes the UVCS calibration and its results.