GUVI: a hyperspectral imager for geospace

The Global Ultraviolet Imager (GUVI) is an imaging spectrometer on the NASA TIMED spacecraft which was launched on December 7, 2001. This instrument produces a far ultraviolet (FUV) data cube of spatial and spectral information at each step of a scan mirror - that scan mirror covers 140 deg in the cross track direction - a span that includes on limb. GUVI produces simultaneous monochromatic images at five "colors" (121.6 nm, 130.4 nm, 135.6 nm, and in broader bands at 140-150 nm and 165-180 nm) as its field of view is scanned from horizon to horizon. The instrument consists of a scan mirror feeding a parabolic telescope and Rowland circle spectrometer, with a wedge-and-strip detector at the focal plane. We describe the design, and give an overview of the environmental parameters that will be measured. GUVI is a modified version of the Special Sensor Ultraviolet Spectrographic Imager (SSUSI), which was launched on the DMSP Block 5D3 F16 satellite on October 18, 2003 and is slated to fly on DMSP satellites F17 through F20, as well. We present some results the science analysis of the GUVI data to demonstrate its relevance to the space weather community.