TIMED solar EUV experiment: pre-flight calibration results for the EUV grating spectrograph

The Solar EUV Experiment (SEE) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite will make measurements of the spectral irradiance of the Sun in the soft x-ray, extreme ultraviolet (EUV), and far ultraviolet (FUV) wavelength range. The EUV Grating Spectrograph (EGS) component of SEE is a 1/4 meter Rowland circle spectrograph with a mechanically-ruled concave grating and a microchannel plate detector with a two-dimensional 1024 x 64 coded anode (CODACON) readout. The EGS covers the wavelength range from approximately 26 to 197 nm. The primary calibration of the instrument was done at the NIST Synchrotron Ultraviolet Radiation Facility (SURF) III on their beam line #2. We will detail the calibration methods and results for the EGS, paying attention to the quantification of sensitivity variations over the instrument's large field of view (12.5degrees x 5.3degrees), plus scattered light, second-order, and linearity corrections.