The James Webb Space Telescope (JWST) is an on axis three mirror anastigmat telescope with a primary mirror, a
secondary mirror, and a tertiary mirror. The JWST mirrors are constructed from lightweight beryllium substrates and the
primary mirror consists of 18 hexagonal mirror segments each approximately 1.5 meters point to point. Ball Aerospace
and Technologies Corporation leads the mirror manufacturing team and the team utilizes facilities at six locations across
the United States. The fabrication process for each individual mirror assembly takes approximately six years due to
limitations dealing with the number of segments and manufacturing & test facilities. The primary mirror Engineering
Development Unit (EDU) recently completed the manufacturing process with the final cryogenic performance test of the
mirror segment assembly. The 18 flight primary mirrors segments, the secondary mirror, and the tertiary mirror are all
advanced in the mirror production process with many segments through the final polishing process, coating process, final
assembly, vibration testing, and final acceptance testing. Presented here is a status of the progress through the
manufacturing process for all of the flight mirrors.
The JWST (James Webb Space Telescope) primary mirror consists of 18 hexagonal mirror segments each approximately
1.5 meters point to point. The mirror segments are constructed from a lightweight beryllium substrate with both a
radius-of-curvature actuation system and a six degree-of-freedom hexapod actuation system. The manufacturing process
for each individual mirror assembly takes approximately six years due to limitations dealing with the number of
segments and manufacturing & test facilities. In order to catch any manufacturing or technology roadblocks, as well as
to streamline specific processes, an Engineering Development Unit (EDU) was built to lead the mirror manufacturing
flow. This development unit has all of the same requirements as the flight units and is actually considered to be one of
the flight spare mirrors. The EDU was manufactured with a lead time of approximately six months over the other mirrors
to assure adequate time to optimize each step in the manufacturing process. Manufacturing and tests occurred at six
locations across the U.S. with multiple trips between each. The EDU recently completed this arduous process with the
final cryogenic performance test of the mirror assembly taking place at Marshall Space Flight Center's (MSFC) X-Ray
& Cryogenic Facility (XRCF). Testing included survivability tests to 25 Kelvin, hexapod & radius-of-curvature
actuation systems testing, and cryogenic figure & prescription testing. Presented here is a summary of the tests
performed along with the results of that testing.
The James Webb Space Telescope (JWST) is a large space based astronomical telescope that will operate at
cryogenic temperatures. The telescope by virtue of its size must be stowed in an inoperable configuration for launch
and remotely reconfigured in space to meet the operational requirements using active Wave Front Sensing and
Control (WFSC). This paper will report on the optical budgeting process used to manage the performance of the
active system. The current status of the design and verification of the optical hardware, the WFSC processes, and
the total system verification modeling will be presented. More detailed discussions of the system verification by
analysis will be presented in separate accompanying papers.
The JWST (James Webb Space Telescope) primary mirror consists of 18 hexagonal mirror segments. Each segment is approximately 1.5 meters point to point and is constructed from a lightweight beryllium substrate. In order for the 18 segments to act as a single 6.5 meter diameter mirror each one must be capable of 6 degrees of freedom motion relative to the mirror backplane and be able to change its radius of curvature to closely match those of the other segments. As it would be nearly impossible to manufacture the 18 individual
segments with the same radius, a RoC (radius of curvature) actuation mechanism is attached to each mirror allowing RoC fine tuning post manufacturing. The RoC actuation system consists of a single actuator and six struts attached to the back of the mirror. The radius of curvature is matched by closely manufacturing the
radius of each segment relative to the nominal value and then, during cryogenic testing, actuating the RoC of each mirror. This cryogenic actuation reduces polishing times and allows for compensation of radius changes measured during other manufacturing steps. Presented here is a high-level overview of the method used to
set the mirror's radius of curvature at cryogenic temperature, disassemble the mirror system for additional polishing and processing, and perform final cryogenic verification.
With a planned launch of 2013, NASA's James Webb Space Telescope (JWST) will be the premier space observatory
for astronomers worldwide. This infrared space telescope will be passively cooled to cryogenic temperatures in its solar
L2 orbit. The JWST Optical Telescope Element (OTE) features a 6.5 meter, segmented Primary Mirror, which focuses
light onto a Secondary Mirror and finally redirected into and through the Aft Optics Subsystem (AOS). The AOS
consists of an optical bench which aligns and supports the telescope's Tertiary Mirror and Fine Steering Mirror
Assemblies. This paper describes the unique cryogenic requirements and design of the JWST Beryllium AOS optical
bench. Key performance requirements are reviewed including: launch environment, the cryogenic operating environment
(nominally 39K), and optical alignment stability at cryogenic temperatures. The mechanical design approach utilizing
Beryllium as the structural material for the AOS Bench is described relative to meeting the driving requirements.
Material property verification, low and predictable material variability, and low thermal gradients across the structure are
also discussed.
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