title: Measurement of large cryogenic structures using a spatially phase-shifted digital speckle pattern interferometer.
abstract: The James Webb Space Telescope (JWST) Backplane Stability Test Article (BSTA) was developed to demonstrate large precision cryogenic structures' technology readiness for use in the JWST. The thermal stability of the BSTA was measured at cryogenic temperatures at the Marshall Space Flight Center (MSFC) X-Ray Calibration Facility (XRCF) and included nearly continuous measurements over a six-week period in the summer of 2006 covering the temperature range from ambient down to 30 Kusing a spatially phase-shifted digital speckle pattern interferometer (SPS-DSPI). The BSTA is a full size, one-sixth section of the JWST primary mirror backplane assembly (PMBA). The BSTA, measuring almost 3 m across, contains most of the prominent structural elements of the backplane and is to our knowledge the largest structure ever measured with SPS-DSPI at cryogenic conditions. The SPS-DSPI measured rigid body motion and deformations of BSTA to nanometer-level accuracy. The SPS-DSPI was developed specifically for the purposes of this test and other tests of large cryogenic structures for JWST.
authors.affiliation: Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA.
authors.forename: Babak
authors.initials: B
authors.lastname: Saif
authors.forename: Marcel
authors.initials: M
authors.lastname: Bluth
authors.forename: Perry
authors.initials: P
authors.lastname: Greenfield
authors.forename: Warren
authors.initials: W
authors.lastname: Hack
authors.forename: Bente Hoffmann
authors.initials: BH
authors.lastname: Eegholm
authors.forename: Peter
authors.initials: P
authors.lastname: Blake
authors.forename: Ritva
authors.initials: R
authors.lastname: Keski-Kuha
authors.forename: Lee
authors.initials: L
authors.lastname: Feinberg
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Arenberg