Status of the JWST optical telescope element

Abstract

Significant progress has been made in the development of the Optical Telescope Element (OTE) for the James Webb Space Telescope (JWST) Observatory. All of the mirror assemblies are complete and delivered. The composite Primary Mirror Backplane Support Structure (PMBSS) has completed assembly and in Static Load testing. All the deployment mechanisms have completed their qualification programs. This paper will discuss the current status of all the OTE components and the plan forward to completion.

James Webb Space Telescope (JWST) optical telescope element and integrated science instrument module (OTIS) cryogenic test program and results

“…With all segments deployed, iterative alignment of the PM took place using the PG and COCOA systemsa moving target during cooldown, but good practice for using all of the analysis tools with 18 segments for the first time, after the twosegment Pathfinder experience. In the latter stages of the cooldown, two important Thermal Distortion/Figure Drift tests were executed 27,28 tracking the PM figure vs. temperature against model predictions; results are described below.…”

“…The above were all pre-planned activities; there was also a significant period of ad hoc investigation, before and after the OTE thermal balance, of instabilities that had been observed in the PM figure 28 . These investigations are also discussed in the "Results" section below.…”

“…Besides the basic goal of returning the hardware to room temperature safely, numerous other test goals were accomplished during the warmup period. These included a Thermal Distortion/Alignment Drift test, in which PG measurements tracked the positions of the PM, SM, and AOS over a ~25K temperature range, to confirm the adequacy of the Model Uncertainty Factor applied to distortions of the large structural hardware 27,28 . The motors and heaters for the major deployment systems (the Deployable Tower Assembly, the hinge drives for the Secondary Mirror Support System, and the latch drives for the PM wings) also underwent assorted tests during the warmup period.…”

“…The Optical Telescope Element is comprised of the three-mirror anistigmat telescope (with its 18-segment Primary Mirror) and Fine Steering Mirror, along with the composite structures to support those optics and the mechanical and electrical systems required to deploy them (including the Secondary Mirror Support System, two 3-segment deployable wings for the Primary, and the actuators for deploying [from their launch restraints] and aligning the Primary Mirror segments and Secondary). Integration of the OTE was completed in 2016, as described by Atkinson et al (2016) 2 .…”

New method for characterizing the state of optical and opto-mechanical systems

“…Once completed the eighteen Primary Mirror Segment Assemblies (PMSAs) are mounted to the primary mirror backplane support structure, a graphite/epoxy composite truss structure. 4 All mirrors are coated with protected gold. The telescope will be assembled and instruments installed at NASA Goddard Space Flight Center clean room facility.…”