James Webb Space Telescope Optical Simulation Testbed I: overview and first results

Abstract

The James Webb Space Telescope (JWST) Optical Simulation Testbed (JOST) is a tabletop workbench to study aspects of wavefront sensing and control for a segmented space telescope, including both commissioning and maintenance activities. JOST is complementary to existing optomechanical testbeds for JWST (e.g. the Ball Aerospace Testbed Telescope, TBT) given its compact scale and flexibility, ease of use, and colocation at the JWST Science & Operations Center. We have developed an optical design that reproduces the physics of JWST's three-mirror anastigmat using three aspheric lenses; it provides similar image quality as JWST (80% Strehl ratio) over a field equivalent to a NIRCam module, but at HeNe wavelength. A segmented deformable mirror stands in for the segmented primary mirror and allows control of the 18 segments in piston, tip, and tilt, while the secondary can be controlled in tip, tilt and x, y, z position. This will be sufficient to model many commissioning activities, to investigate field dependence and multiple field point sensing & control, to evaluate alternate sensing algorithms, and develop contingency plans. Testbed data will also be usable for cross-checking of the WFS&C Software Subsystem, and for staff training and development during JWST's five-to ten-year mission.

Extended-image-based correction of aberrations using a deformable mirror with hysteresis

“…With a view to the next generation of large space telescopes, we designed and built a highresolution imaging system as testbed for image-based aberration correction. Image-based aberration correction could be an alternative or a complement to wavefront sensing via phase diversity as used by JWST and demonstrated on its testbeds [33,34].…”

Scientific discovery with the James Webb Space Telescope

“…The optics are designed to deliver diffraction limited performance at λ > 2 microns, and therefore Webb will have excellent image quality over most of its wavelength range [19,42]. More information on the image quality across all Webb instruments is described in [43].…”

Making good use of JWST's coronagraphs: tools and strategies from a user's perspective

“…We do not present any performance assessment or predictions as this has been largely covered by passed Perrin et al contributions [11][12][13][14] but rather focus on the building blocks and tools for the user community and on how people can find relevant information and how the blocks are associated to each other. We start by presenting shortly the coronagraphic modes and capabilities as well as the baseline PSF subtraction strategies.…”