Measurement of picometer-scale mirror dynamics

A high-speed interferometer has been designed and built to measure the dynamics of the James Webb Space Telescope primary mirror system currently under testing. This interferometer is capable of tracking large absolute motion (i.e., piston) of the mirror's entire surface over orders of magnitudes of wavelengths displacement. Preliminary tests have shown it to be capable of measuring dynamic effects on the level of tens of picometers reliably. This paper reports the details of test setup to do so, the data system used to collect and process the data, and the algorithms to distill the dynamics motions detected. The results that were obtained are presented and followed by a discussion of the conclusions and potential applications of this measurement technique.