ULTRAVIOLET AND VISIBLE IMAGING AND SPECTROGRAPHIC IMAGING INSTRUMENT

The Ultraviolet and Visible Imaging and Spectrographic Imaging experim ent consists of five spectrographic imagers and four imagers. These ni ne sensors provide spectrographic and imaging capabilities from 110 to 900 nm. The spectrographic imagers share an off-axis design in which selectable slits alternate fields of view (1.00-degrees x 0.10-degrees or 1.00-degrees x 0.05-degrees) and spectral resolutions between 0.5 and 4 nm. Image planes of the spectrographic imager have a programmabl e spectral dimension with 68, 136, or 272 pixels across each individua l spectral band, and a programmable spatial dimension with 5, 10, 20, or 40 pixels across the 1-degrees slit length. A scan mirror sweeps th e slit through a second spatial dimension to generate a 1-degrees x 1- degrees spectrographic image once every 5, 10, or 20 s, depending on t he scan rate. The four imagers provide narrow-field (1.28-degrees x 1. 59-degrees) and wide-field (10.5-degrees x 13.1-degrees) viewing. Each imager has a six-position filter wheal that selects various spectral regimes and neutral densities. The nine sensors utilize intensified CC D detectors that have an in intrascene dynamic range of approximately 10(3) and an interscene dynamic range of approximately 10(5); neutral- density filters provide an additional dynamic range of approximately 1 0(2-3). The detector uses an automatic gain control that permits the s ensors to adjust to scenes of varying intensity. The sensors have comm on boresights and can operate separately, simultaneously, or synchrono usly. To be launched aboard the Midcourse Space Experiment spacecraft in the mid-1990's, the ultraviolet and visible imaging and spectrograp hic imaging instrument will investigate a multitude of celestial, atmo spheric, and point sources during its planned 4-yr life.