Precision alignment mechanisms for the Roman Coronagraph Instrument

The Nancy Grace Roman Space Telescope, National Aeronautics and Space Administration’s (NASA) next flagship mission in astrophysics, is due for launch in May 2027 with an onboard Coronagraph Instrument (CGI) which will serve as a technology demonstrator for exoplanet direct imaging. The Roman Coronagraph will be capable of detecting and characterizing exoplanets and circumstellar disks in visible light at an unprecedented contrast level of ∼108 or better at small angular separations 3 to 9 λ/D. The instrument is equipped with six precision alignment mechanisms (PAMs) which enable ultra-stable, sub-micrometer positioning of optical elements such as coronagraphic masks, optical filters, and polarizers. To achieve contrast level, which are two to three orders of magnitude better than state-of-the-art visible or near-infrared coronagraphs, the mechanisms need to be stable at sub-microradian levels during a typically 10-h-long science observation. We report here about the development of these mechanisms and present their performance test results from the qualification/flight acceptance test program. All PAM flight models were delivered in the year 2022 and integrated into the CGI flight instrument. Meanwhile, CGI has successfully completed all testing at the Jet Propulsion Laboratory and was shipped to NASA’s Goddard Space Flight Center in May 2024 for the final integration into the Roman spacecraft.