This study presents a computational vector fiducial deflectometry method for aligning multi-mirror telescopes. The method is demonstrated on both a Cassegrain and a three-mirror off-axis system, with experimental validation performed for the Cassegrain case. Computational vector fiducial patterns are customized for each telescope configuration, and misalignments are interpreted using Zernike gradient vector polynomials. Component sensitivities of the degree of freedom are analyzed, and suitable polynomial bases are identified to characterize misalignment. Simulations with arbitrary misalignments confirm that the method is applicable to both the Cassegrain and the three-mirror off-axis systems, improving the wavefront error from PV = 271 to PV = 0.451 for the LAF-TMS case. An experimental alignment of the Cassegrain telescope further verifies the feasibility of the approach, yielding a successful result in obtaining wavefront errors with PV = 0.841 and MS = 0.181. These results highlight the feasibility of the vector fiducial deflectometry and reverse optimization as a systematic method for multi-mirror alignment. (c) 2026 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

The proposed Habitable Worlds Observatory (HWO) aims to detect and characterize Earth-like planets around Sun-like stars from the ultraviolet to the infrared using high-contrast imaging. A dichroic mirror is a natural choice for splitting light between multiple wavelength channels in such a system, but the coating must introduce minimal polarization aberrations and chromatic wavefront errors (WFE) to avoid limiting contrast. We present the design of a long-pass dichroic mirror operated at a 7^∘ angle of incidence that provides high reflection in the short-wavelength band, high transmission in the long-wavelength band, and a sharp cut-on near 550 nm. A multilayer thin-film design process was used to meet these spectral requirements while reducing polarization aberrations and chromatic WFE sensitivity. Reflected phase optimization was also incorporated to reduce sensitivity to manufacturing-induced layer-thickness variations, which can produce wavelength-dependent WFE and degrade coronagraph performance. The resulting coating-induced WFE was propagated through simulations of a vector vortex coronagraph to assess contrast performance. Simulations predict dark-hole contrast residuals at the 10^-12 level, indicating that the optimized dichroic mirror does not limit coronagraph performance.

We present a baseline, cost-effective upgrade solution for the 61" Kuiper Telescope that enhances its capabilities for a wide-field-of-view survey mission. The proposed solution features a prime focus corrector operating at f/4.5, which achieves a diagonal field of view of approximately 0.94∘. The optical design emphasizes simplicity and efficiency, offering three key advantages. First, it is cost-effective because all lenses are composed of planar or spherical surfaces, significantly reducing manufacturing and testing complexity and costs. Second, the design employs a single optical material, streamlining material requirements. Third, it offers exceptional achromatic performance over a wide field of view, enabling high-fidelity survey imaging. The upgraded system will host a 10 µm-pixel detector, ensuring high-resolution imaging capabilities. Baseline analyses, including sensitivity and Monte Carlo simulations, demonstrate the robustness of our design. This upgrade aims to enhance the telescope's performance and integrate seamlessly into the broader telescope network for the Catalina Sky Survey Mission, thereby advancing survey throughput, cost-efficiency, and imaging capabilities.

The Lazuli Space Observatory is a 3-meter aperture astronomical facility designed for rapid-response observations and precision astrophysics across visible to near-infrared wavelengths (400-1700 nm bandpass). An off-axis, freeform telescope delivers diffraction-limited image quality (Strehl >0.8 at 633 nm) to three instruments across a wide, flat focal plane. The three instruments provide complementary capabilities: a Wide-field Context Camera (WCC) delivers multi-band imaging over a 35' × 12' footprint with high-cadence photometry; an Integral Field Spectrograph (IFS) provides continuous 400-1700 nm spectroscopy at R ∼ 100-500 for stable spectrophotometry; and an ExtraSolar Coronagraph (ESC) enables high-contrast imaging expected to reach raw contrasts of 10^-8 and post-processed contrasts approaching 10^-9. Operating from a 3:1 lunar-resonant orbit, Lazuli will respond to targets of opportunity in under four hours–a programmatic requirement designed to enable routine temporal responsiveness that is unprecedented for a space telescope of this size. Lazuli's technical capabilities are shaped around three broad science areas: (1) time-domain and multi-messenger astronomy, (2) stars and planets, and (3) cosmology. These capabilities enable a potent mix of science spanning gravitational wave counterpart characterization, fast-evolving transients, Type Ia supernova cosmology, high-contrast exoplanet imaging, and spectroscopy of exoplanet atmospheres. While these areas guide the observatory design, Lazuli is conceived as a general-purpose facility capable of supporting a wide range of astrophysical investigations, with open time for the global community. We describe the observatory architecture and capabilities in the preliminary design phase, with science operations anticipated following a rapid development cycle from concept to launch.

Modern observational astronomy makes extensive use of deep, wide-field imaging and large spectroscopic surveys, defining telescope design spaces in which angular resolution, achievable depth, and survey efficiency are considered jointly rather than independently. Conventional étendue alone does not fully capture the efficiency with which resolved and deblended information can be acquired. We introduce a resolution-weighted étendue metric that provides a quantitative basis for comparing information throughput across different facilities. Applying this metric, we illustrate how accounting for angular resolution reshapes the relative placement of existing telescopes in design parameter space, with a representative space telescope design serving as an example of this shift. We consider two distinct reflective space telescope designs utilizing a variation of the three-mirror anastigmat configuration. The strategic placement of the tertiary mirror significantly influences the telescope’s form factor, enabling compact architectures for very large aperture systems. These designs achieve large resolution-weighted étendue and imaging throughput, making them well-suited for precision cosmological and astrophysical measurements.

Phase retrieval techniques are utilized to correct low order wavefront aberrations originating from misalignments of the optical system in space based telescope concepts. Traditional phase retrieval involves observation of the Point Spread Function (PSF) and a diversity measurement, usually focus diversity although other measures are possible, to reconstruct the incident wavefront at the science detector. We consider a Machine Learning model trained originally on simulated data, and then augmented with real focus diversity data from the Tiny Observatory for Telescope Optimization (TOTO) testbed at the University of Arizona. We then compare the wavefront sensing performance of the Machine Learning model with known truth values of the generated dataset. The model predictions for low order Zernikes on TOTO data after training and validation show a reasonable agreement with the true Zernike coefficients.

The space coronagraph optical bench (SCoOB) is a high contrast imaging testbed designed to demonstrate starlight suppression techniques at visible wavelengths in a space-like vacuum environment. Since the previous proceedings, the testbed has undergone major component upgrades, including a 100

The Tiny Observatory for Telescope Optimization (TOTO) is an optical testbed designed to evaluate the efficacy of autonomously driven alignment algorithms for space-based telescope systems. For space-based missions, active control of the telescope alignment on-orbit offers potential to relax passive alignment requirements and reduce on-ground verification activities. TOTO is used to evaluate and verify simulation work of two primary alignment algorithms, Stochastic Parallel Gradient Descent (SPGD) and focus-diverse phase retrieval (FDPR). Previous simulation work has confirmed that by using SPGD for coarse alignment followed by focus-diverse phase retrieval for fine alignment, we can reach diffraction-limited performance on-orbit. This paper presents the results of the autonomous alignment algorithm of a Cassegrain telescope using TOTO. We report the current status of TOTO as well as preliminary results from SPGD and phase retrieval on the testbed using monochromatic light source to simulate an on-axis point source.

The Space Coronagraph Optical Bench (SCoOB) is a vacuum high contrast imaging testbed designed to demonstrate starlight suppression at optical wavelengths and obtain contrasts better than 10^-8 in a one-sided dark hole from 3 to 10 λ/D using a vector vortex coronagraph (VVC) mask. Some of the recent efforts have been in testing dark zone maintenance (DZM) algorithms which are used to stabilize the contrast in the presence of wavefront drifts and allow for the long integration times required by exoplanet observations. In this work, we discuss the results from simulations with two DZM algorithms - linear dark field control (LDFC) and extended Kalman Filter-based (EKF) DZM. We also report preliminary results from the testbed with LDFC.

Low-surface-brightness (LSB) structures play a crucial role in understanding galaxy evolution by providing significant insights into galaxy interactions, the histories of mass assembly, and the distribution of dark matter. Nevertheless, their inherently faint nature, coupled with observational difficulties such as stray light interference and variations in the sky background, has significantly impeded comprehensive studies of LSB features. The KASI Deep Rolling Imaging Fast Telescope (K-DRIFT) project aims to address these observational challenges by developing off-axis freeform three-mirror telescopes and observational strategies specifically designed for LSB imaging surveys. The first generation of K-DRIFT (G1) has been successfully completed, and the forthcoming survey, scheduled to commence shortly, is expected to yield novel insights into the LSB universe. This paper outlines the scientific motivations of the project, discusses the technical challenges encountered, highlights the innovative solutions devised, and describes the future trajectory of the K-DRIFT.

This paper describes the design and experimental validation of a heliostat metrology system in which a large mirror's shape is obtained from measurements of its reflection of a fixed fine-scale regular pattern. A detailed map of the surface is obtained from measurements of distortion in the reflected image, using new code to correlate reflected rays with incident rays, and then deriving the surface shape by integrating the slopes obtained from the ray deviations. The method was developed to enable metrology of focusing heliostats whose reflector shape is actively altered to correct the large changes in astigmatism that arise as the solar angle of incidence (AOI) changes through the day. It was used to set and test such a reflector, made from a single 2.4 m & times; 3.3 m -sheet flat float glass, and bent into shape using self-twisting axes and 58 support actuators on the steel frame to focus disc images of the sun at 113 m distance for a 60(O) AOI. The accuracy of this method was verified by subsequent field tests directly measuring the actual solar concentration performance, which is the ultimate evaluation criterion. The heliostat formed a concentrated solar disc with a measured diameter of 1.14 m, compared to the ideal value of 1.04 m. This close agreement confirms the measured float glass surface shape error of 0.66 mrad and 0.41 mrad root-mean-square (RMS) in the x and y directions, with corresponding residual metrology uncertainties of approximately 0.37 mrad and 0.23 mrad RMS representing all unidentified error sources of the outdoor field test.