The UDL contains the command values (i.e., the observation control table) for the current observation as well as some observation data produced by the flight software. These observation values include X/Y deflection offsets for the spectral calibration lamps, spectrum Y-balance offset, null deflection calibration correction, target coordinates prior to centering, flux measurement at end of target acquisition, and proportional deflection calibration corrections. The UDL files are identified by the extensions ``.ULH'' and ``.ULD''.
