Multi-field merit-function-based regression method for Wide Field Infrared Survey Telescope grism system alignment.

The grating prism (grism), slitless spectrometer aboard the Wide Field Infrared Survey Telescope enables a survey of emission-line galaxies. To facilitate its opto-mechanical alignment, a six-degree-of-freedom element was fabricated using alignment fiducials and integral flats and used to measure a wavefront by using an infrared interferometer placed at various field points over a 20×14  deg field of view in the grism coordinate frame. Modeling identified E2 to be the most sensitive element to the grism wavefront error and was used to efficiently align the system.