The James Webb Space Telescope (JWST) is a large, infrared space telescope that has recently started its science program which will enable breakthroughs in astrophysics and planetary science. Notably, JWST will provide the very first observations of the earliest luminous objects in the universe and start a new era of exoplanet atmospheric characterization. This transformative science is enabled by a 6.6 m telescope that is passively cooled with a 5 layer sunshield. The primary mirror is comprised of 18 controllable, low areal density hexagonal segments, that were aligned and phased relative to each other in orbit using innovative image-based wave front sensing and control algorithms. This revolutionary telescope took more than two decades to develop with a widely distributed team across engineering disciplines. We present an overview of the telescope requirements, architecture, development, superb on-orbit performance, and lessons learned. JWST successfully demonstrates a segmented aperture space telescope and establishes a path to building even larger space telescopes.

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It is imperative that we have high confidence that the optical performance capability of JWST is well-understood before launch. With the telescope operating at cryogenic temperatures and sporting a 6.6 meter primary mirror diameter, the optical metrology equipment required to measure the optical performance can be quite complex. The JWST Test team undertook an effort to greatly simplify the optical metrology approach, while retaining the key measurements and verification methodology. The result is a cryogenic optical test configuration and implementation using Chamber A at NASA's Johnson Space Center that uses the science instruments to help understand JWST's optical performance.

Abstract:With the delivery of its flight scientific instruments and the completion of all telescope optics both scheduled to occur later this year, the James Webb Space Telescope (JWST) will enter into a challengin g integration and test (I&T) program. Highlights of that program include cryo-vacuum tests of the Integrated Science Instrument Module (ISIM) at Goddard Space Flight Center, ambient integration of the ISIM and the Optical Telescope Element (OTE) at Goddard, and an end-to-end cryo-vacuum test of the OTE + ISIM system at Johnson Space Center. We review the overall flow of the I&T program, highlighting the key activities and the critical verifications to be.performed at each step.