Pre-Flight Resolution and Performance of the Far Ultraviolet Spectroscopic Explorer (FUSE)

Spectroscopic data obtained from the spectrograph of the Far Ultraviolet Spectroscopic Explorer (FUSE) during the integration and test phase of development has been acquired and analyzed. We present the most current measurement of the resolution of FUSE as a function of wavelength over the entire bandpass of 905 - 1187 Angstroms. The FUSE instrument outputs spectra through four channels. Both H₂ and PtNe emission line spectra were studied using an automated routine to determine the full width at half maximum (FWHM) of more than 100 spectral lines per channel. The resolution of the instrument has been characterized using a subset of the emission lines of both H₂ and PtNe. The spectral lines chosen were determined to be unblended, and were identified as arising from only single molecular transitions. Using resolution as a diagnostic tool, we have performed a self consistency check to assure that different channels of the spectrograph image identical wavelength regions with comparable resolutions. In addition, we have studied the effects of focal plane motion on the resolution of FUSE. The results of these studies provide a prediction of the instrument's performance after launch.