Alignment and Test of the Wide Field Infrared Survey Telescope (WFIRST) Engineering Design Unit (EDU) Grism

Hagopian, John ; Berrier, Josh ; Chambers, John ; Content, David ; Dominguez, Margaret ; Gong, Qian ; Krom, Jason ; Marx, Catherine ; McMann, Joseph ; Pasquale, Bert(NASA Goddard Space Flight Center, Greenbelt, MD, United States)

关键词: AMBIENT TEMPERATURE;    CORONAGRAPHS;    DEGREES OF FREEDOM;    DESIGN ANALYSIS;    ERROR ANALYSIS;    FIELD OF VIEW;    IMAGING TECHNIQUES;    INFRARED TELESCOPES;    MECHANICAL ENGINEERING;    OPERATING TEMPERATURE;    PRISMS;    SPECTROSCOPY;    WAVE FRONTS;    WIDE-FIELD INFRARED SURVEY TELESCOPE (WFIRST);    COMPENSATORS;    INFRARED INTERFEROMETERS;    SPECTROMETERS;    THEODOLITES;   

RP-ID  :  GSFC-E-DAA-TN71604-1

学科分类：地球科学(综合)

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

The WFIRST wide field instrument (WFI) includes a slitless spectrometer, which plays an important role in the WFIRST mission for the survey of emission-line galaxies. WFI is building engineering design and environmental test (EDU and ETU) units to reduce risk for the flight grism unit. We report here on successful build and test of the EDU grism. The four-element EDU grism consists of two prism elements and two diffractive elements that provide R700 dispersion. The elements were fabricated with alignment fiducials and integral flats to allow opto-mechanical alignment in six-degrees of freedom. Each element in turn, was installed onto a hexapod and positioned to its nominal orientation relative to the grism deck, then bonded into individual cells. Alignment measurements were performed in situ using theodolites to set tip/tilt and a Micro-vu non-contact Multisensor Measurement System was used to set despace, decenter and clocking of each element using the hexapod. After opto-mechanical alignment, the grism wavefront was measured using an Infrared ZYGO interferometer at various field points extending over a 20 by 14- degree (local) field of view. Using modeled alignment sensitivities, we determined the alignment correction required on our Element 2 prism compensator and successfully minimized the field dependent wavefront error and confocality. This paper details the alignment and testing of the EDU grism at ambient and cold operating temperatures.