WFIRST Grism Characterization

We had presented the optical design and early test result of WFIRST grism spectrometer in previous SPIE conferences. This paper reports the follow-on activity of the spectral and radiometric calibrations, including the calibration methods, experiment designs, and test equipment calibration, such as the light source and detectors used in the test. The real grism calibration includes the throughput versus wavelength, which is largely determined by the diffraction efficiency of the two diffractive surfaces. It also includes spectral resolution, point spread function, and encircle energy measurements. The measured data are presented. The comparisons between the test data and the simulation from theory or optical model are also presented.