NASA’s Habitable Worlds Observatory will consist of a segmented telescope and high contrast coronagraph to characterize exoplanets for habitability. Achieving this objective requires an ultra-stable telescope with wavefront stability of picometers in certain critical modes. The NASA funded Ultra-Stable Large Telescope Research and Analysis – Technology Maturation program has matured key component-level technologies in 10 areas spanning an “ultra-stable” architecture, including active components like segment edge sensors, actuators and thermal hardware, passive components like low distortion mirrors and stable structures, and supporting capabilities like precision metrology. This paper will summarize the final results from the four-year ULTRA-TM program, including advancements in performance and/or path-to-flight readiness, TRL/MRL maturation, and recommendations for future work.
NASA / MSFC has been preparing for X-ray calibration of the large
optic for the future ESA Athena mission at the 500 meter XRCF
beamline. Improvements include new facility X-ray detectors (Six
Amptek C2 window SDDs and a PI-MTE3 4k CCD camera), stages, and
verification of the facility's operation to the level reached for the
ground calibration of the Chandra X-ray telescope. The XRCF 1.5
meter beam size requires that a flight Athena optic be calibrated by
combining measurements from the six individual sub-sectors of the full
optic. New XRCF capabilities for the Athena measurement include the
ability to measure 12 meter focal length optics with the focal point
not co-linear with the facility optical axis.
As part of these preparations, in January 2023 we tested an SPO module
at the XRCF, aligning the optic in the facility and measuring the
point spread function and effective area at two separate energies.
Our results agree well with previous measurements of this module taken
at the MPE PANTER X-ray beamline. We present a synopsis of the
XRCF facility and its X-ray testing equipment, results from the
XRT#4 testing campaign in January 2023, and show that the XRCF is
currently capable of testing and calibrating large optics for the next
generation of flagship and probe class X-ray observatories.
The X-Ray and Cryogenic Facility (XRCF) at Marshall Space Flight Center is the world’s largest x-ray optic calibration facility and NASA’s premier cryogenic optical test facility. Built specifically to calibrate the Chandra telescope, the facility contributed to several other x-ray missions until 2005 when it became dedicated to normal incidence optical testing at cryogenic temperatures. Recently the facility’s x-ray test capability has been returned to service and updated. New beam monitors, focal plane detectors, and test article and instrument positioning systems have been added. The x-ray data acquisition system has been updated. A real-time position monitoring metrology system is being developed that will enable calibration of large diameter optics via partial illumination in a diverging beam. The newly expanded x-ray test capabilities of the facility will be discussed.
NASA’s Habitable Worlds Observatory will consist of a segmented telescope and high contrast coronagraph to characterize exoplanets for habitability. Achieving this objective requires an ultra-stable telescope with wavefront stability of picometers in certain critical modes. The NASA funded Ultra-Stable Large Telescope Research and Analysis – Technology Maturation program continues to mature key component-level technologies for this new regime of “ultra-stable optical systems,” including active components like segment edge sensors, actuators and thermal hardware, passive components like low distortion mirrors and stable structures, and supporting capabilities like precision metrology. This paper will present an update to the latest results from hardware testbeds and simulations in the areas listed above. It will also contain a correction to previously published results of Ball’s Integrated Demo, which consists of a capacitive sensor and three actuators operating in closed loop.
The recently released Astro2020 Decadal Survey recommends a large IR/O/UV space telescope that can observe potentially habitable exoplanets. Achieving this goal requires a telescope with wavefront stability on the order of picometers in some modes. The Ultra-Stable Large Telescope Research and Analysis – Technology Maturation (ULTRATM) program has matured key component-level technologies for this new regime of “ultra-stable optical systems,” including active components like segment edge sensors, actuators and thermal sensing and control hardware, as well as passive components like low distortion mirror mounts and stable composites for structures. Hardware testbeds have demonstrated component performance in the desired regime and with path-to-flight properties and simulations have applied those results to the flight system. These component level demonstrations are a critical step to enable subsequent subsystem and system level demonstrations of an ultra-stable telescope.
The X-ray and Cryogenic Facility (XRCF) at the NASA Marshall Space
Flight Center (MSFC) is the baselined facility for X-ray testing of
the Athena X-ray optics. Here we give an overview of the planned
testing, including the XRCF facility and its 500-meter X-ray
beamline, the required facility X-ray sources and detectors,
testing requirements, and the GSE required for X-ray testing and
calibration of the Athena mirror assembly module demonstrator (MAMD),
the qualification model mirror (QM), and the flight model mirror (FM).
Of special interest is the metrology system needed for the
calibration: because the large Athena optic (the Mirror Assembly
Module, or MAM) is too large for full illumination in the XRCF 1.5m
diameter X-ray beam, the six sectors of the MAM will be tested
separately, requiring precise knowledge of the optic and detector
positions during the calibration to enable the stitching together of
the full MAM point spread function from measurements of the individual
sectors.
To achieve the ambitious science goal of performing direct imaging of earth-like exoplanets with a high contrast coronagraph, future space-based astronomical telescopes will require wavefront stability several orders of magnitude beyond state-of-the-art. The Ultra-Stable Large Telescope Research and Analysis – Technology Maturation (ULTRA-TM) program is maturing key component-level technologies for this new regime of “ultra-stable optical systems” through hardware testbeds that demonstrate component performance in the desired picometer regime and with path-to-flight properties. This paper describes the initial results from these testbeds – which address key capabilities across the ultrastable architecture and include active components like segment edge sensors, actuators and thermal sensing and control hardware, as well as passive components like low distortion mirror mounts and stable composites for structures. These promising experimental results are the first steps in our team’s technical maturation plan to credibly enable a large, ultrastable telescope in space. The resulting component, sub-system and system roadmaps are meant to support planning for technology development efforts for future NASA missions.
We describe testing and analysis conducted to demonstrate in-space thermoelastic shape stability of starshade structures. Thermoelastic deformation testing was conducted on key starshade structural components. These components were constructed at relevant scales and at relevant fidelity to flight-like structures. Results from thermoelastic deformation testing were used to calibrate high-fidelity finite element structural analysis techniques; these finite element tools were then used to predict the in-space thermoelastic distortions of a 26 m-diameter starshade. The in-space temperatures for these structures were predicted using a separate radiative-thermal finite element simulations, and were meant to envelope temperatures that a starshade would experience during periods of telescope shading. The predicted in-plane thermoelastic deformations of this 26 m-diameter starshade were found to be sufficient to fit into an overall error budget to enable instrument contrast better than 1e-10.
To achieve the ambitious goal of directly imaging exo-Earths with a coronagraph, future space-based astronomical telescopes will require wavefront stability several orders of magnitude beyond state-of-the-art. The Ultra-Stable Large Telescope Research and Analysis – Technology Maturation (ULTRA-TM) program will mature critical technologies for this new regime of “ultra-stable optical systems” through component-level hardware demonstrations.
This paper describes the progress towards demonstrating performance of these technologies in the picometer regime and with flight-like properties – including active systems like segment sensing and actuation and thermal sensing and control, as well as passive systems like low distortion mirror mounts and composite structures. Raising the TRL of these technologies will address the most difficult parts of the stability problem with the longest lead times and provide significant risk reduction for their inclusion in future mission concepts.
KEYWORDS: Composites, James Webb Space Telescope, Mirrors, Mirror structures, Stochastic processes, Metrology, Control systems, Process control, Temperature metrology, Statistical analysis
Composite materials are applied in precision optical metering structures because of their low thermal expansion properties in concert with high specific stiffness. Twisting and bending of long composite tubes, such as the secondary mirror support structure for the JWST telescope, requires control and verification. A stochastic modeling method was applied that simulates the manufacturing process variability and estimates ranges for expected twist and bend over the tube length from ambient to cryogenic temperatures. A development strut for the JWST secondary mirror support structure was fabricated and a metrology system was designed and implemented that measured the bend and twist response from ambient to 30 K. Modeling methods and predictions are outlined. The test metrology and results are summarized, along with a comparison between test and prediction.
KEYWORDS: Composites, James Webb Space Telescope, Manufacturing, Space telescopes, Precision measurement, Temperature metrology, Tolerancing, Mirrors, Telescopes, Structural design
Composite materials often carry the reputation of demonstrating high variability in critical material properties. The JWST telescope metering structure is fabricated of several thousand separate composite piece parts. The stringent dimensional stability requirements on the metering structure require the critical thermal strain response of every composite piece be verified either at the billet or piece part level. JWST is a unique composite space structure in that it has required the manufacturing of several hundred composite billets that cover many lots of prepreg and many years of fabrication. The flight billet thermal expansion acceptance criteria limits the coefficient of thermal expansion (CTE) to a tolerance ranging between ±0.014 ppm/K to ±0.04 ppm/K around a prescribed nominal when measured from 293 K down to 40 K. The different tolerance values represent different material forms including flat plates and different tube cross-section dimensions. A precision measurement facility was developed that could measure at the required accuracy and at a pace that supported the composite part fabrication rate. The test method and facility is discussed and the results of a statistical process analysis of the flight composite billets are surveyed.
KEYWORDS: Curium, James Webb Space Telescope, Cryogenics, Composites, Temperature metrology, Space telescopes, Mirrors, Manufacturing, Metrology, Analytical research
The need for JWST's metering structure to be stable over time while at cryogenic temperatures is derived from its
scientific objectives. The operational scenario planned for JWST provides for the optical system to be adjusted on
regular intervals based upon image quality measurements. There can only be a limited amount of optical
degradation between the optical system adjustments in order to meet the scientific objectives. As the JWST primary
mirror is segmented, the structure supporting the mirror segments must be very stable to preclude degradation of the
optical quality. The design, development and, ultimately, the verification of that supporting structure's stability rely
on the availability of analysis tools that are credibly capable of accurately estimating the response of a large
structure in cryogenic environments to the nanometer level. Validating the accuracy of the analysis tools was a
significant technology demonstration accomplishment. As the culmination of a series of development efforts, a
thermal stability test was performed on the Backplane Stability Test Article (BSTA), demonstrating TRL-6 status
for the design, analysis, and testing of Large Precision Cryogenic Structures. This paper describes the incremental
development efforts and the test results that were generated as part of the BSTA testing and the associated TRL-6
demonstration.
KEYWORDS: Distortion, James Webb Space Telescope, Manufacturing, Magnetism, Temperature metrology, Composites, 3D modeling, Aluminum, Space telescopes, Metrology
The unprecedented stability requirements of JWST structures can only be conclusively
verified by a combination of analysis and ground test. Given the order of magnitude of the
expected motions of the backplane due to thermal distortion and the high level of confidence
required on such a large and important project, the demonstration of the ability to verify the
thermal distortion analysis to the levels required is a critical need for the program. The
demonstration of these analysis tools, in process metrology and manufacturing processes
increases the technology readiness level of the backplane to required levels. To develop this
critical technology, the Backplane Stability Test Article (BSTA) was added to the JWST
program. The BSTA is a representative substructure for the full flight backplane, manufactured
using the same resources, materials and processes. The BSTA will be subject to environmental
testing and its deformation and damping properties measured. The thermally induced
deformation will be compared with predicted deformations to demonstrate the ability to predict
thermal deformation to the levels required. This paper will review the key features and
requirements of the BSTA and its analysis, the test, measurement and data collection plans.
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