54 research outputs found
Compact Three Mirror Anastigmat Space Telescope Design using 6.5m Monolithic Primary Mirror
The utilization of a 6.5m monolithic primary mirror in a compact three-mirror
anastigmat (TMA) telescope design offers unprecedented capabilities to
accommodate various next generation science instruments. This design enables
the rapid and efficient development of a large aperture telescope without
segmented mirrors while maintaining a compact overall form factor. With its
exceptional photon collection area and diffraction-limited resolving power, the
TMA design is ideally suited for both the ground and space active/adaptive
optics concepts, which require the capture of natural guide stars within the
field of view for wavefront measurement to correct for misalignments and shape
deformation caused by thermal gradients. The wide field of view requirement is
based on a statistical analysis of bright natural guide stars available during
observation. The primary mirror clear aperture, compactness requirement, and
detector pixel sizes led to the choice of TMA over simpler two-mirror solutions
like Ritchey-Chretien (RC) telescopes, and the TMA design offers superior
diffraction-limited performance across the entire field of view. The standard
conic surfaces applied to all three mirrors (M1, M2, and M3) simplify the
optical fabrication, testing, and alignment process. Additionally, the TMA
design is more tolerant than RC telescopes. Stray light control is critical for
UV science instrumentation, and the field stop and Lyot stop are conveniently
located in the TMA design for this purpose.Comment: Presented at SPIE, Optics+Photonics 2023, Astronomical Optics:
Design, Manufacture, and Test of Space and Ground Systems IV in San Diego,
CA, US
Analysis of active optics correction for a large honeycomb mirror
In the development of space-based large telescope systems, having the
capability to perform active optics correction allows correcting wavefront
aberrations caused by thermal perturbations so as to achieve
diffraction-limited performance with relaxed stability requirements. We present
a method of active optics correction used for current ground-based telescopes
and simulate its effectiveness for a large honeycomb primary mirror in space.
We use a finite-element model of the telescope to predict misalignments of the
optics and primary mirror surface errors due to thermal gradients. These
predicted surface error data are plugged into a Zemax ray trace analysis to
produce wavefront error maps at the image plane. For our analysis, we assume
that tilt, focus and coma in the wavefront error are corrected by adjusting the
pointing of the telescope and moving the secondary mirror. Remaining mid- to
high-order errors are corrected through physically bending the primary mirror
with actuators. The influences of individual actuators are combined to form
bending modes that increase in stiffness from low-order to high-order
correction. The number of modes used is a variable that determines the accuracy
of correction and magnitude of forces. We explore the degree of correction that
can be made within limits on actuator force capacity and stress in the mirror.
While remaining within these physical limits, we are able to demonstrate sub-25
nm RMS surface error over 30 hours of simulated data. The results from this
simulation will be part of an end-to-end simulation of telescope optical
performance that includes dynamic perturbations, wavefront sensing, and active
control of alignment and mirror shape with realistic actuator performance.Comment: 8 pages, 6 figures, presented at SPIE Optics + Photonics 202
Approaches to developing tolerance and error budget for active three mirror anastigmat space telescopes
The size of the optics used in observatories is often limited by fabrication,
metrology, and handling technology, but having a large primary mirror provides
significant benefits for scientific research. The evolution of rocket launch
options enables heavy payload carrying on orbit and outstretching the
telescope's form-factor choices. Moreover, cost per launch is lower than the
traditional flight method, which is obviously advantageous for various novel
space observatory concepts. The University of Arizona has successfully
fabricated many large-scale primary optics for ground-based observatories
including the Large Binocular Telescope (LBT, 8.4 meter diameter two primary
mirrors), Large Synoptic Survey Telescope (now renamed to Vera C. Rubin
Observatory, 8.4 meter diameter monolithic primary and tertiary mirror), and
the Giant Magellan Telescope (GMT, 8.4 meter diameter primary mirror seven
segments). Launching a monolithic primary mirror into space could bypass many
of the difficulties encountered during the assembly and deployment of the
segmented primary mirrors. However, it might bring up unprecedented challenges
and hurdles, also. We explore and foresee the expected challenges and evaluate
them. To estimate the tolerance and optical error budget of a large optical
system in space such as three mirror anastigmat telescope, we have developed a
methodology that considers various errors from design, fabrication, assembly,
and environmental factors.Comment: 6 pages, presented August 2023 at SPIE Optics+Photonics, San Diego,
CA, US
Topological pupil segmentation and point spread function analysis for large aperture imaging systems
Future large aperture telescopes and high contrast imaging systems will often include segment gaps, structural obscurations, along with outer edges which produce diffraction effects that are disadvantageous to high contrast imaging (e.g., for exoplanet detection) or continuous wavefront control across the optical aperture. We present an optimization strategy for several pupil segment topologies for next-generation telescope concepts. Wave propagation results based on diffraction-limited point spread function analyses using Fraunhofer diffraction theory are presented using the Python-based POPPY simulation tool
Generalized large optics fabrication multiplexing
High precision astronomical optics are manufactured through deterministic computer controlled optical surfacing processes, such as subaperture small tool polishing, magnetorheological finishing, bonnet tool polishing, and ion beam figuring. Due to the small tool size and the corresponding tool influence function, large optics fabrication is a highly time-consuming process. The framework of multiplexed figuring runs for the simultaneous use of two or more tools is presented. This multiplexing process increases the manufacturing efficiency and reduces the overall cost using parallelized subaperture tools
The space coronagraph optical bench (SCoOB): 2. wavefront sensing and control in a vacuum-compatible coronagraph testbed for spaceborne high-contrast imaging technology
The 2020 Decadal Survey on Astronomy and Astrophysics endorsed space-based
high contrast imaging for the detection and characterization of habitable
exoplanets as a key priority for the upcoming decade. To advance the maturity
of starlight suppression techniques in a space-like environment, we are
developing the Space Coronagraph Optical Bench (SCoOB) at the University of
Arizona, a new thermal vacuum (TVAC) testbed based on the Coronagraphic Debris
Exoplanet Exploring Payload (CDEEP), a SmallSat mission concept for high
contrast imaging of circumstellar disks in scattered light. When completed, the
testbed will combine a vector vortex coronagraph (VVC) with a Kilo-C
microelectromechanical systems (MEMS) deformable mirror from Boston
Micromachines Corp (BMC) and a self-coherent camera (SCC) with a goal of raw
contrast surpassing at visible wavelengths. In this proceedings, we
report on our wavefront sensing and control efforts on this testbed in air,
including the as-built performance of the optical system and the implementation
of algorithms for focal-plane wavefront control and digging dark holes (regions
of high contrast in the focal plane) using electric field conjugation (EFC) and
related algorithms.Comment: 7 pages, 5 figures, SPIE Astronomical Telescopes and Instrumentation
202
The Space Coronagraph Optical Bench (SCoOB): 1. Design and Assembly of a Vacuum-compatible Coronagraph Testbed for Spaceborne High-Contrast Imaging Technology
The development of spaceborne coronagraphic technology is of paramount
importance to the detection of habitable exoplanets in visible light. In space,
coronagraphs are able to bypass the limitations imposed by the atmosphere to
reach deeper contrasts and detect faint companions close to their host star. To
effectively test this technology in a flight-like environment, a high-contrast
imaging testbed must be designed for operation in a thermal vacuum (TVAC)
chamber. A TVAC-compatible high-contrast imaging testbed is undergoing
development at the University of Arizona inspired by a previous mission
concept: The Coronagraphic Debris and Exoplanet Exploring Payload (CDEEP). The
testbed currently operates at visible wavelengths and features a Boston
Micromachines Kilo-C DM for wavefront control. Both a vector vortex coronagraph
and a knife-edge Lyot coronagraph operating mode are under test. The optics
will be mounted to a 1 x 2 meter pneumatically isolated optical bench designed
to operate at 10^-8 torr and achieve raw contrasts of 10^-8 or better. The
validation of our optical surface quality, alignment procedure, and first light
results are presented. We also report on the status of the testbed's
integration in the vaccum chamber.Comment: 14 pages, 9 figure
Instantaneous phase shifting deflectometry
An instantaneous phase shifting deflectometry measurement method is presented and implemented by measuring a time varying deformable mirror with an iPhone (R) 6. The instantaneous method is based on multiplexing phase shifted fringe patterns with color, and decomposing them in x and y using Fourier techniques. Along with experimental data showing the capabilities of the instantaneous deflectometry system, a quantitative comparison with the Fourier transform profilometry method, which is a distinct phase measuring method from the phase shifting approach, is presented. Sources of error, nonlinear color-multiplexing induced error correction, and hardware limitations are discussed. (C) 2016 Optical Society of AmericaCollege of Optical Sciences at the University of Arizona (Technology Research Initiative Fund (TIRF) Optics/Imaging Program); Korea Basic Science Institute; Friends of Tucson Optics (FoTO) (Endowed Scholarships in Optical Sciences)Open Access Journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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Alignment of Multi-Order Diffractive Engineered (MODE) lens segments using the Kinematically-Engaged Yoke System
With the continued development of multi-order diffractive engineered (MODE) lenses that consist of both multi-order diffractive surfaces and a diffractive Fresnel lens surface, it is becoming more realistic that these components may be used as an ultralight large aperture primary for space telescopes. As conceptual designs for these large primaries push the size limits of optics manufactured by compression molding, it becomes necessary to make a segmented MODE lens primary rather than a monolithic one. We use the Kinematically-Engaged Yoke System (KEYS) to align the segments of a 0.24-m, PMMA, monochromatic, MODE-like lens (having no diffractive Fresnel lens features). The KEYS alignment system consists of modified ultra-fine alignment screws with ball bearings on the end that kinematically engage with the step-like features of the MODE lens surface (similar to a Fresnel lens) to constrain the segments in 5 degrees of freedom, leaving rotation about the optical axis unconstrained. The alignment of the segments is verified using multiple methods including a scanning white light interferometer and deflectometry. Such an alignment system has the capability of fixing the segments together in order to bond them with adhesive while aligned. These tests offer a proof of concept for a system that can be used for an eventual 0.24-m, compression molded, glass, segmented MODE lens.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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Instantaneous phase mapping deflectometry for dynamic deformable mirror characterization
We present an instantaneous phase mapping deflectometry (PMD) system in the context of measuring a continuous surface deformable mirror (DM). Deflectometry has a high dynamic range, enabling the full range of surfaces generated by the DM to be measured. The recent development of an instantaneous PMD system leverages the simple setup of the PMD system to measure dynamic objects with accuracy similar to an interferometer. To demonstrate the capabilities of this technology, we perform a linearity measurement of the actuator motion in a continuous surface DM, which is critical for closed loop control in adaptive optics applications. We measure the entire set of actuators across the DM as they traverse their full range of motion with a Shack-Hartman wavefront sensor, thereby obtaining the influence function. Given the influence function of each actuator, the DM can produce specific Zernike terms on its surface. We then measure the linearity of the Zernike modes available in the DM software using the instantaneous PMD system. By obtaining the relationship between modes, we can more accurately generate surface profiles composed of Zernike terms. This ability is useful for other dynamic freeform metrology applications that utilize the DM as a null component.LOFT group; Korea Basic Science Institute; II-VI Foundation Block-Gift ProgramSPIE grants to authors of papers published in an SPIE Journal or Proceedings the right to post an author-prepared version or an official version (preferred version) of the published paper on an internal or external server controlled exclusively by the author/employer, provided that (a) such posting is noncommercial in nature and the paper is made available to users without charge; (b) an appropriate copyright notice and full citation appear with the paper, and (c) a link to SPIE's official online version of the abstract is provided using the DOI (Document Object Identifier) link.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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