This PDF file contains the front matter associated with SPIE Proceedings Volume 12677, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Replicated composite optics offer a route to manufacture precision mirrors for satellite applications in a fraction of time and with substantial cost and weight savings over conventional glass mirrors. However, the dimensional stability is a critical barrier to entry for utilizing these mirrors in UV/Vis space applications due to the organic nature of the optical surface and its susceptibly to environmentally-induced distortions that can cause deviations greater than SFE λ/20 (~32nm). Recently, advances in this technology have been achieved at The Aerospace Corporation by using UV cured replicating epoxy resins to produce replicated mirrors with relatively zero residual stress and high hygroscopic stability with RT processing. Elevated thermal stability, though, remains a critical issue as CTE mismatch between the composite and resin lead to residual stress formation which immediately degrades the optical quality and then causes further optical drift over time as stress relaxation occurs. In this paper, we demonstrate improved thermal stability of replicated mirrors by utilizing multiple replication layers where buried compliant layers accumulate residual stress and the top layer is an optimized high modulus resin that achieves a high-quality replication. As a result, thermal stresses incurred by elevated temperatures were reduced by more than 60% when measured via laser interferometry. Additionally, due to faster stress relaxation rates of the compliant layers, the CTE mismatch stress was removed in a matter of days versus years of a conventional single layer replication. This stack-up provides a route to mitigate stress and enhance replication stability.

NASA’s Roman Space Telescope’s Wide Field Instrument mosaic detector array of 18 H4RG-10 chips requires regular and uncommonly accurate calibrations to meet its science objectives. In addition to the quasi-Lambertian diffuser used for detector flat-fielding, a novel engineered diffuser is incorporated as part of seven cold stop masks on the science bandpass filters. These engineered diffusers are used to illuminate the focal plane concurrently with an exposure from the observatory, enabling signal-dependent nonlinearity corrections. This presentation demonstrates via experimental data how these diffusers can produce a spatially uniform and smooth illumination profile with increased flux compared to a Lambertian diffuser.

Additive manufacturing (AM; 3D Printing) is a process that fabricates objects layer-by-layer, unlocking previously unachievable geometrical freedom in design and manufacture. Its adoption for the manufacture of optical components for nanosats is challenging due to limited understanding of its inherent porosity and outgassing properties; however, AM has plenty of potential for lightweight space-based mirror structures as it enables the use of lattice structures and topology optimisation. AM is particularly relevant to nanosat deployable optics (DO) instrumentation, where a segmented mirror needs to be packed within a limited volume and mass budget. This paper describes the design, analysis, manufacture and metrology of AM mirror petal prototypes for a 6U nanosat DO payload. The objective of the prototypes was to reduce the mass and the part count relative to the conventional design. From the available 33 volumetric lattices including graph, triply periodic minimal surface and stochastic lattices within the AM design software used, two were downselected by using finite element analysis and manufacturability experiments. Prototypes were designed using these lattices, and the geometric and interface requirements of the conventional petal. These were printed, using laser powder bed fusion, in the aluminium alloy AlSi10Mg and post-processed using single point diamond turning. The internal (porosity) and external geometrical properties of the manufactured prototypes were measured using X-ray computed tomography and the optical properties of the reflective surface evaluated using interferometry. By utilising AM, a mass reduction of 44 % and the consolidation of nine parts into one was achieved.

Outpost Technologies designed, manufactured, and tested a 0.305-meter aluminum-silicon carbide metal matrix composite (Al-SiC MMC) mirror for infrared balloon gondola observatory application. Al-SiC MMCs, such as Materion’s SupremEX®, have high specific stiffness, excellent thermal conductivity, and lower CTE than most conventional metals. Furthermore, recent research and development efforts support a brand-new material for investigation: AyontEX™ 13 aluminum-silicon (Al-Si) alloy. Outpost identified significant cost and capability gaps in mirror substrate design trades between ultra-premium beryllium and SiC and conventional aerospace materials and proposes new materials for consideration. The Al-SiC MMC and Al-Si alloy programmatic and technical value proposition combines considerable improvements in specific stiffness and thermal performance at minimal costs increases over aluminum substrates. Assuming congruent geometry, SupremEX® 640XA Al-SiC MMCs reduce gravity sag errors by 47% and increases mirror and structural modes by 35% versus aluminum 5000 and 6000 series without affecting system mass. AyontEX™ 13 also exhibits higher specific strength and stiffness compared to aluminum and shows promise as an uncoated mirror substrate with optical surface finish properties achieved during diamond turning. Outpost presents study results, manufacturability assessments, and ground test concepts for TRL-advancing activities to bring the SupremEX® and AyontEXTM materials before future optics programs as highly capable and low-cost mirror substrates. Lastly, a discussion of ongoing and future work for ultraviolet (UV) and large (> 1.25-meter) Al-SiC MMC and Al-Si alloy applications.

Deformable mirrors (DMs) are a critical enabling technology for many astrophysics mission concepts currently in development. Unfortunately, generating the control signals required by DMs is difficult, and historically there have been few options for controlling a DM on a spacecraft. In this work, electronics suitable for controlling a 952 actuator MEMS DM have been developed and their performance has been characterized. The driver electronics deliver 16 bits of resolution with a least significant bit increment of 2.75 milliVolts and RMS electronic noise of less than 1.2 milliVolts over the range of 0 to 170 Volts. These electronics have been built to be compatible with the needs of missions that are cost-constrained and risk-tolerant. To that end, the driver electronics use widely available parts with a total expected unit cost of approximately $30,000. Although the driver electronics do not use radiation hardened parts, testing data indicates a 2 year lifetime in a TESS-like orbit with 90 percent confidence when shielded by 6 millimeters of aluminum.

For accurate optical testing of large mirrors with long radii of curvature, multiple measurements using single-shot phaseshifting interferometers are typically required to reduce the impact of air turbulence on air stratification prevention. This paper proposes a new technique that utilizes hierarchical clustering to classify acquired wrapped phases into similar pattern clusters, eliminating the influence of unknown noises by excluding minority patterns. For each cluster, the circular mean is used to calculate denoised wrapped phases, and the surface figure is obtained from the unwrapped phases. Since the number of phase-unwrapping algorithm runs equals the number of chosen clusters, the proposed technique is significantly faster than conventional procedures. In 500 measurements on a 1.5 m diameter spherical mirror, the proposed technique reduced measurement time and the root-mean-square error's standard deviation of the surface figure by approximately 23% and 15%, respectively, compared to conventional procedures.

High-accuracy metrology is vitally important in manufacturing ultra-high-quality free-form mirrors designed to manipulate X-ray light with nanometer-scale wavelengths. However, surface topography measurements are instrument dependent, and without the knowledge of how the instrument performs under the practical usage conditions, the measured data contain some degree of uncertainty. Binary Pseudo Random Array (BPRA) “white noise” artifact are effective and useful for characterizing the Instrument Transfer Function (ITF) of surface topography metrology tools and wavefront measurement instrument. BPRA artifact contains features with all spatial frequencies in the instrument bandpass with equal weight. As a result, power spectral density of the patterns has a deterministic white-noise-like character that allows direct determination of the ITF with uniform sensitivity over the entire spatial frequency range. The application examples include electron microscopes, x-ray microscopes, interferometric microscopes, and large field-of-view Fizeau Interferometers. Furthermore, we will introduce the application of BPRA method to characterizing the ITF of Cylindrical Wavefront Interferometry (CWI), by developing the BPRA artifact which matches the radius of curvature of the cylindrical wavefront. The data acquisition and analysis procedures for different applications of the ITF calibration technique developed are also discussed.

We introduce a modifying deflectometry method to reduce parasitic ghost signal noises in transparent optical testing. The proposed approach shows adjusting the screen distance and displayed screen pattern to shrink the light from undesired surfaces’ reflection. The flexibility of deflectometry optical layout allows huge adjustment availability while keeping the optical testing capability and suppressing the parasite signal. Moreover, the customized fringe pattern could shine the desired surface only effectively. Ray tracing simulation shows the best system formation, and the modified experimental setup confirms the proposed method for various types of optics testing. Lastly, we discuss the limitations of the method.

MOIS is a multi-object configurable slit spectrograph designed to be used with the 3.6 Devasthal Optical Telescope (DOT). It will cover the near-infrared wavelength band of 0.97 - 2.37 microns and have a spectroscopic field of view of 9.1′×3.1′ and an imaging field of view of 9.6′ diameter. MOIS is being designed as a precursor to a future multi-object spectrograph for the planned National Large Optical Telescope (NLOT) in India. MOIS is currently designed with a modular configurable slit unit of 5 slits created by 10 bars moving pair-wise in opposition. The slit unit can be upgraded independently to increase the multiplexing capability. The design has unique challenges of operating the configurable slits in cryo temperatures and developing the wide-field imager and spectrograph optical design for the input f/9 beam from the telescope. Many unique design optimizations have been used following several trade studies to allow better mechanical tolerances and flexibility in the design for position of coldstop and thermal performance. We will discuss the detailed design and modeling for MOIS that has been completed as part of the preliminary design.

The search for artificial and natural objects in both cis-lunar and trans-lunar space has grown increasingly important. To accurately detect and track small objects, stray light mitigation is a necessity. Observations conducted in 2022 from a ground-based telescope intended to track such objects have been hampered by excess lunar stray light. In this paper, we present work done to resolve this problem by applying black pigments to the optical tube and thus suppressing its surface scattering. A non-sequential ray tracing model was created to analyze the telescope’s final focal plane irradiance. This model was used to identify critical and illuminated surfaces to determine the stray light paths that have affected observations. We conducted experimental tests to measure the Bidirectional Reflectance Distribution Function (BRDF) of various practical, readily available, and robust black coatings, including paints such as Black 3.0 and Musou. After application on the actual telescope tube, the new surface coating reduced the photon count on the detector from a variable-angle off-axis point source by 76% over all angles measured.

Earth observation and greenhouse gas sensing from space provides vital information for climate and climate change monitoring, indicating the importance of novel spaceborne telescopes and spectrometers. We present a novel freeform pushbroom imaging spectrometer enabling the sensing of water vapor, carbon dioxide and methane in the atmosphere, while fitting within 2 CubeSats Units. The design comprises a 2-mirror freeform telescope, combined with a near-infrared (1100 – 1700 nm) spectrometer featuring 3 freeform mirrors and a reflective grating, providing both spatial and spectral information using a 2D detector. All mirrors are described and optimized using XY polynomials, enabling a nearly diffraction-limited performance. The novel design is exceeding the state-of-the-art, by showing a full FOV of 120°, a spatial resolution of 2.6 km, and a spectral resolution of 13 nm. According to our knowledge, our novel design shows the widest field-of-view that has ever been realized for space-based telescopes, nearly reaching Earth observation from limb to limb from an altitude of about 700 km. The freeform telescope mirrors were manufactured in-house using high-precision 5-axis milling and 5-axis ultraprecision diamond tooling. Finally, a laboratory proof-of-concept demonstrator was realized validating the field-of-view and focusing spot sizes, paving the way for future space missions that target wide field-ofview imaging and/or an enhanced climate monitoring.

New development approaches, including launch vehicles and advances in sensors, computing, and software, have lowered the cost of entry into space, and have enabled a revolution in low-cost, high-risk Small Satellite (SmallSat) missions. To bring about a similar transformation in larger space telescopes, it is necessary to reconsider the full paradigm of space observatories. Here we will review the history of space telescope development and cost drivers, and describe an example conceptual design for a low cost 6.5 m optical telescope to enable new science when operated in space at room temperature. It uses a monolithic primary mirror of borosilicate glass, drawing on lessons and tools from decades of experience with ground-based observatories and instruments, as well as flagship space missions. It takes advantage, as do large launch vehicles, of increased computing power and space-worthy commercial electronics in low-cost active predictive control systems to maintain stability. We will describe an approach that incorporates science and trade study results that address driving requirements such as integration and testing costs, reliability, spacecraft jitter, and wavefront stability in this new risk-tolerant “LargeSat” context.

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 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.

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.

Continuous wavefront sensing on future space telescopes allows relaxation of stability requirements while still allowing on-orbit diffraction-limited optical performance. We consider the suitability of phase retrieval to continuously reconstruct the phase of a wavefront from on-orbit irradiance measurements or point spread function (PSF) images. As phase retrieval algorithms do not require reference optics or complicated calibrations, it is a preferable technique for space observatories, such as the Hubble Space Telescope or the James Webb Space Telescope. To increase the robustness and dynamic range of the phase retrieval algorithm, multiple PSF images with known amount of defocus can be utilized. In this study, we describe a recently constructed testbed including a 97 actuator deformable mirror, changeable entrance pupil stops, and a light source. The aligned system wavefront error is below ≈ 30 nm. We applied various methods to generate a known wavefront error, such as defocus and/or other aberrations, and found the accuracy and precision of the root mean squared error of the reconstructed wavefronts to be less than ≈ 10 nm and ≈ 2 nm, respectively. Further, we discuss the signal-to-noise ratios required for continuous dynamic wavefront sensing. We also simulate the case of spacecraft drifting and verify the performance of the phase retrieval algorithm for continuous wavefront sensing in the presence of realistic disturbances.

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.

Extreme wavefront correction is required for coronagraphs on future space telescopes to reach 10^-8 or better starlight suppression for the direct imaging and characterization of exoplanets in reflected light. Thus, a suite of wavefront sensors working in tandem with active and adaptive optics are used to achieve stable, nanometerlevel wavefront control over long observations. In order to verify wavefront control systems, comprehensive and accurate integrated models are needed. These should account for any sources of on-orbit error that may degrade performance past the limit imposed by photon noise. An integrated model of wavefront sensing and control for a space-based coronagraph was created using geometrical raytracing and physical optics propagation methods. Our model concept consists of an active telescope front end in addition to a charge-6 vector vortex coronagraph instrument. The telescope uses phase retrieval to guide primary mirror bending modes and secondary mirror position to control the wavefront error within tens of nanometers. The telescope model is dependent on raytracing to simulate these active optics corrections for compensating the wavefront errors caused by misalignments and thermal gradients in optical components. Entering the coronagraph, a self-coherent camera is used for focal plane wavefront sensing and digging the dark hole. We utilize physical optics propagation to model the coronagraphy’s sensitivity to mid and high-order wavefront errors caused by optical surface errors and pointing jitter. We use our integrated models to quantify expected starlight suppression versus wavefront sensor signal-to-noise ratio.

Large-scale radio telescope projects will be important in answering modern astronomical questions like those of the National Academies' Astro2020 survey. We propose an efficient and cost-effective thermoforming process with fringe projection metrology (FPM) as an alternative to current panel fabrication methods. In our thermoforming process, we use a flexure plate with actuated tiles to create an adjustable mold inside an oven. Unshaped panels are placed on the adjustable mold and heat is applied, thermoforming the panel to the mold shape. This process allows for the rapid prototyping and production of many panel shapes with sufficient accuracy and reduced recurring costs. We apply FPM to evaluate the mold and panel shapes. FPM applies phase-shifted fiducial patterns, camera stereo vision, and triangulation to measure the thermoformed panel. We applied these technologies in beginning the construction of the Public Outreach Radio Telescope (PORT) and its off-axis dish of 26, 0.5 m², 1/8" thick panels. The PORT is designed for 30dB of gain at λ = 21 cm wavelength, and the dish was toleranced to λ = 3 cm wavelength for future observations. In this proof of concept, we have installed thermoformed panels measured with FPM on a radio telescope.

Because of its extremely low thermal expansion glass ceramic ZERODUR® is widely used as mirror substrate material in earth-bound and space-borne astronomy or as structural parts in integrated-circuit and flat panel display lithography (to name only some of its wide applications). In all its applications it needs to be mounted in some way to a support structure to enable its functionality. Common examples used in astronomical telescopes are epoxy bonding of invar pads to the ZERODUR® mirror blanks or epoxy-free mechanical clamping of ZERODUR® parts to support frames. The mounting should not influence the functionality by inducing thermo-mechanical deformation on the ZERODUR® part. But even more important the bonding procedure should prevent inducing high stresses to the mounting interface that potentially reduces the lifetime of the mount. The achievable strength of ZERODUR® strongly depends on its surface treatment. Generally, mechanical strengths of around 100 MPa are achieved on fine ground and acid etched ZERODUR® surfaces. When becoming interfaces, the reliability of the mount is not only influenced by the initial strength of these surfaces but also on the choice of the epoxy, the mounting material and even the geometrical configuration of the bonding. This paper gives a guideline on the “dos” and “don’ts” in mounting ZERODUR® supplemented by practical examples from literature.

Lightweight optical manufacture is no longer confined to the conventional subtractive (mill and drill), formative (casting and forging) and fabricative (bonding and fixing) manufacturing methods. Additive manufacturing (AM; 3D printing), creating a part layer-by-layer, provides new opportunities to reduce mass and combine multiple parts into one structure. Frequently, modern astronomical telescopes and instruments, ground- and space-based, are limited in mass and volume, and are complex to assemble, which are limitations that can benefit from AM. However, there are challenges to overcome before AM is considered a conventional method of manufacture, for example, upskilling engineers, increasing the technology readiness level via AM case studies, and understanding the AM build process to deliver the required material properties. This paper describes current progress within a four-year research programme that has the goal to explore these challenges towards creating a strategy for AM adoption within astronomical hardware. Working with early-career engineers, case studies have been undertaken which focus on lightweight AM aluminium mirror manufacture and optical mountings. In parallel, the aluminium AM build parameters have been investigated to understand which combination of parameters results in AM parts with consistent material properties and low defects. Metrology results from two AM case studies will be summarised: the optical characteristics of a lightweighted aluminium mirror intended for in-orbit deployment from a nanosat; and the AM build quality of wire arc additive manufacture for use in an optomechanical housing. Finally, an analysis of how surface roughness from AM mirror samples and build parameters are linked will be discussed.

In this paper, we investigate several bonding methods for attaching lateral flexures to the side of a mirror in order to mitigate the potential long-term instability caused by thermal stress. To analyze the behavior of the mirror, bonding, and flexures under different mechanical and thermal loads, we utilize finite element models and examine three key aspects of the flexure bonding: the bonding area, the use of an additional block for bonding, and the choice of flexure material. Our study utilizes the primary mirror of the GEMINI telescope as a sample application and for validation purposes. Through our simulations and analysis, we aim to address various options for the flexure-bonding design and optimization.

In this paper, we propose a noncontact, high-precision method for measuring the flat surface of large-scale optics using laser trackers and spherically mounted reflectors (SMRs) placed on motorized stages. Accurate measurement of surface flatness is critical for the development of optical systems, especially for aligning large-scale astronomical telescopes and space-based instruments. The proposed method can capture high-resolution surface figure of large flat areas, generating dense spatial point clouds. The measurement system consists of laser trackers, SMRs on two-dimensional motorized stages, and a flat mirror. The laser tracker directly measures the position of an SMR and captures an image of the SMR through the reflection from a flat mirror. The motorized stage enables precise and repeatable movement of the optics, allowing for the measurement of the local slope and complete surface figure of the flat mirror. To demonstrate the effectiveness of the proposed method, we conducted a series of measurements using a large flat mirror. The results show that the proposed method can measure the surface figure of a flat mirror with six-degrees-of-freedom, accuracy, and precision. The measurement data obtained from the laser tracker and SMR were compared with those obtained using an interferometer-based measurement system with a parabolic mirror, and the results were found to be in excellent agreement. The proposed method offers a noncontact, high-precision solution for measuring the surface figure of large flat areas and has the potential to significantly improve the manufacturing and testing of large optical systems for astronomy and space-based applications.

We are developing the KASI-Deep Rolling Imaging Fast Telescope Generation 1 (K-DRIFT G1) based on the on-site performance assessment of the K-DRIFT pathfinder. The telescope is a confocal off-axis freeform three-mirror system designed for the detection of extremely low surface brightness structures in the sky. The optical specifications of the K-DRIFT G1 are as follows: the entrance pupil diameter is 300 mm, the focal ratio is 3.5, the field of view is 4.43° × 4.43°, and the image area is 81.2 mm × 81.2 mm with 10 μm pixels. We performed sensitivity analysis and tolerance simulations to integrate and align the system. We present the analysis results and development plan of the K-DRIFT G1.

We have developed the KASI-Deep Rolling Imaging Fast Telescope (K-DRIFT), adopting a 300 mm aperture off-axis freeform three-mirror design to detect faint and diffuse low-surface-brightness structures. By conducting the on-sky test observations and performing a series of simulations to analyze the performance of the K-DRIFT, we confirmed three main error sources causing optical performance degradation. The imaging performance of the K-DRIFT has successfully improved by correcting low-to-mid spatial frequency wavefront errors based on performance analysis results. This paper presents the K-DRIFT’s optical performance analysis algorithm and the optical performance improvement.

Highly multiplexed spectroscopic surveys have changed the astronomy landscape in recent years. However, these surveys are limited to low and medium spectral resolution. High spectral resolution spectroscopy is often photon starved and will benefit from a large telescope aperture. Multiplexed high-resolution surveys require a wide field of view and a large aperture for a suitable large number of bright targets. This requirement introduces several practical difficulties, especially for large telescopes, such as the future ELTs. Some of the challenges are the need for a wide field atmospheric dispersion corrector and to deal with the curved non-telecentric focal plane. Here we present a concept of Multi-Object Spectroscopy (MOS) mode for TMT High-Resolution Optical Spectrograph (HROS), where we have designed an atmospheric dispersion corrector for individual objects that fit inside a fiber positioner. We present the ZEMAX design and the performance of the atmospheric dispersion corrector for all elevations accessible by TMT.

GrainCams is a lunar rover payload designed to explore lunar dust. It is a suite of two light field cameras: SurfCam and LevCam. The main goal of SurfCam is to provide 3D imaging of fairy castle structures believed to exist on the lunar surface. LevCam’s objective is to understand dust speed and track the trail of lofting dust on the lunar surface. The mechanical stiffness of the camera is capable of enduring the vibration and shock conditions of the launcher. Thus, we conducted the opto-mechanical design for Surfam and analyzed the safety through theoretical estimation. The safety of whole structure is also reviewed from structural analysis such as linear static analysis and modal analysis. These cameras will operate in the extreme temperature of the moon. To achieve a viable thermal design despite the extreme lunar thermal environment and uncertainty of the payload interface with the rover, we assumed a thermal adiabatic payload interface and employed passive (e.g., thermal insulation blankets (MLIs), surface control of thermal radiation, specially designed radiators with an inclination angle of 36.5° to effectively avoid Solar flux and maximize unobstructed view of space relative to the lunar surface in hot cases) and active (e.g., heaters) thermal control techniques. Each camera should weigh no more than 5 kg and consume no more than 20 W of power. In this paper, we present the preliminary results of the structure design of GrainCams.

This paper presents a new method called ZernikeNet for accurately calculating Zernike coefficients in aspheric optical components. Surface figure error (SFE) measurements obtained using interferometer often include alignment errors and low-order aberrations, such as piston, tip, tilt, and defocus, which need to be removed to effectively analyze high-order aberrations. The traditional method for removing low-order aberrations involves Zernike polynomial fitting to the SFE, but this assumes that the optical component is circular and can be decomposed into an orthogonal basis set of Zernike polynomials. However, for aspheric optical components, the orthogonality of Zernike polynomials may not hold, making it challenging to accurately represent the SFE. To address this challenge, ZernikeNet employs a deep learning-based approach, where interferometer map of the optical component is fed into a multi-layer neural network structure to output a set of 36 Zernike coefficients. The proposed deep learning network is trained using a single-shot metrology approach, where a single input interferometer map is used to generate high-accuracy Zernike coefficients through intentional overfitting. Experimental results using data from aspheric mirror show that ZernikeNet can effectively remove low-order aberrations, leaving only high-order aberrations, resulting in a low residual SFE RMS value. This method offers a significant advantage over traditional Zernike polynomial fitting approaches for optical components with complex shapes, making it a promising tool for the design and analysis of advanced optical systems.

The quality of mirror surface is a crucial factor in enhancing the optical performance of space telescopes, and the Tool Influence Function (TIF) is an important parameter that determines the surface quality by measuring the unit removal volume. Although TIF studies have traditionally been performed under static conditions, there is a growing interest in studying dynamic TIF using a moving polishing head. In this presentation, we report on initial dynamic TIF patterns on SiC mirror surfaces for Space Optical Telescopes using the Orthogonal Velocity Tool (OVT) at KASI.

An innovative polarization-holographic imaging Stokes spectropolarimeter is presented. The main analyzing unit of such a polarimeter is the integral polarization-holographic diffraction element, which enables the complete analysis of the polarization state of incoming light to be carried out in real-time. It decomposes the incoming light into diffraction orders, the intensities of which vary depending on the polarization state of the light source. After the simultaneous diffraction order intensity measurements of the corresponding points or areas in the diffraction orders, we get the real-time Stokes images of the light source, which allows determining the entire polarization state of a point or extended space object for different spectral regions and variable polarization. A working aperture can be from 0.5 cm up to 5 cm in diameter. The results of studies on improving the stability and diffraction efficiency of the element are presented. Measurements of the polarization state by the standard star were carried out to calibrate the spectropolarimeter. Polarimetric measurements of some astronomical objects have been carried out. The resulting errors are better than 10^-2. The polarization-holographic imaging Stokes spectropolarimeter has no mechanically moving or electrically tunable optical elements, has no internal reflections, and is universal, compact, cost-effective, and lightweight.