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The Optical Research Section at the Goddard Space Flight Center is establishing the diffraction grating evaluation facility (DGEF) to evaluate the performance of new technology diffraction gratings for future space flight instrumentation. Performance is most accurately evaluated with the grating in the optical configuration for which it is designed. For this reason the DGEF has been devised to evaluate gratings in an optical breadboard scheme that emulates design concepts or design options. The working volume of the DGEF was sized to accommodate proposed spectrographic designs for future missions, e.g. Lyman or the Far Ultraviolet Spectroscopic Explorer (FUSE)1, and second generation Space Telescope instruments such as the Space Telescope Imaging Spectrograph (STIS)2. Space was also allocated to set up supporting equipment, including stimulus sources and diagnostic systems. The spectral range which we propose to eventually cover extends from the extreme ultraviolet into the infrared. The facility, designed and built by Baker Manufacturing Co. in Evansville, Wisconsin, consists of a large, vibration isolated granite slab, 3m wide, 6.7m long, and 0.6m thick, with an aluminum surface plate 7.6cm thick for the optical set-up surface and vacuum sealing3. Vacuum capability is provided by a stainless steel vacuum cover and collar that will provide a working height of roughly 1.2m. The vacuum chamber will be pumped with four cryopumps to a pressure of one microtorr or less. Electrical, cooling water, and cryogenic interfaces to devices inside the chamber will be provided through the vacuum collar. Internal motions for mirrors, detectors, etc. will be implemented by means of computer controlled precision optical stages with stepper motors and encoded read-outs. The granite slab, aluminum surface plate, and vibration isolation system, have been delivered and installed on a temporary basis until construction of the permanent laboratory is completed in late 1988. Test results for several STIS new technology gratings, including an ion etched cross disperser are presented.
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