Flat field of UVCS detectors for early part of SOHO mission

Abstract

The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) comprises two telescopes and two spectrometer channels for spatially resolved ultraviolet spectral diagnostics of the solar corona. The principal lines for which the two channels are optimized are the H I 'Lyman-(alpha) ' line at 121.5 nm and the O VI (O5+) doublet at 103.2 and 103.7 nm. An 'in-flight' method, using observations of stars and scattered solar disk light, has been devised to determine the flat field function, i.e., the relative detection efficiency of the detector pixels. We present the details and results of this process. Local pixel-to-pixel efficiency variation is found to be, typically, about plus or minus 9% to plus or minus 17% (1 (sigma) ) for the H I Lyman-(alpha) channel and plus or minus 9% for the O VI channel.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.