From Goddard Resources :
"The Diffraction Grating Evaluation Facility (DGEF) is a world-class, advanced resource that was developed at Goddard to evaluate optical components such as diffraction gratings, mirrors, and filters as well as detection systems used in space instrumentation. The DGEF has the ability to measure imaging performance, scattered light, and spectral efficiency at the sub-arcsecond level over a spectral range of 30 to 1100 nm. The facility can accommodate optical systems up to 1 meter in diameter. The DGEF has been used to determine the performance of diffraction gratings, mirrors, filters, polarizers, telescopes, and imaging camera systems, such as the 16 grating types of the Space Telescope Imaging Spectrograph (STIS) that was installed into the Hubble Space Telescope (HST) in 1997."
At the DGEF, the properties of the ACS filters are characterized with several instruments, such as FIRM (Facility for Index of Refraction Measurements) for measurements of the index of refraction of the filter materials, WOMBAT (Wildly and Openly Modified Broadband Achromatic Twyman Green Interferometer) for the transmitted wavefronts from the UV to the near-IR, and TUT (Transmittance Uniformity Tester) for the in-band (IB) and out-of-band (OOB) spectral and spatial transmittances of the filters.
Leviton, D.B., Boucarut, R.A., Bush, F.D., Content, D.A., Keski-Kuha, R.A., Kral, C., Krebs, C.A., Madison, T.J., Mehalick, K.I., Miner, L.A., Norton, T.A., Petrone, P., Puc, B.P., Standley, C., Tsvetanov, Z., & Varosi, F. 1998, in Space Telescopes and Instruments V, eds. P.Y. Bely and J.B. Breckinridge, SPIE Vol. 3356, 350
Boucarut, R.A., & Leviton, D.B. 1998, in Space Telescopes and Instruments, eds. P.Y. Bely and J.B. Breckinridge, SPIE Vol. 3356, 377