An incremental verification approach will be used to reduce risks. Performance parameters are tested incrementally as the observatory is integrated to increase the confidence in the final verification.

The figure of each segment of the primary mirror will be individually tested at cryogenic temperatures in the X-ray Calibration Facility (XRCF) at Marshall Space Flight Center (MSFC). Using center-of-curvature and partial-aperture tests, the operation of the entire telescope optics will be verified at Chamber A at Johnson Space Center (JSC). This huge chamber will be outfitted with helium shrouds to simulate the thermal environment at L2. A test stand will hold JWST right-side up and provide gravity compensation of the telescope structure. Test equipment at the center of curvature will measure the phasing of the mirrors before and during the thermal vacuum tests. ITT, a Northrop Grumman corporate partner, will oversee the testing. The STScI is supporting the tests and the development and testing of the multi-wave interferometer used at the center of curvature.