arXiv subjects

Ewan S. Douglas

Publications and source records attributed to Ewan S. Douglas.

At least 19 recordsLinked to original sources

arXiv2026

The Lazuli Space Observatory: Architecture & 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' $\times$ 12' footprint with high-cadence photometry; an Integral Field Spectrograph (IFS) provides continuous 400-1700 nm spectroscopy at R $\sim$ 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. [Abstract abridged]

astro-ph.IM↗

arXiv2026

JWST/NIRCam Imaging of Young Stellar Objects. IV. Detailed Imaging of the Protoplanetary Disk around TW Hya

As the nearest protoplanetary disk to Earth ($d = 60.14$ pc), TW Hya is one of the most studied protoplanetary disks and a critical benchmark for testing planet formation theories. We present high-contrast coronagraphic imaging of the TW Hya disk from JWST/NIRCam across four filters (F187N, F200W, F356W, and F444W). We detect the disk's scattered-light emission in F200W, F356W, and F444W. An elliptical fit to the disk image yields an average inclination of $i = 8.74^{+1.03}_{-0.94}$ degrees and a position angle of $\mathrm{PA} = 75.62^{+7.86}_{-6.56}$ degrees. We find tentative evidence for radial variations in these parameters, a trend consistent with a disk warp. Our companion search yields no new detections, placing the lowest mass limits yet on companions that might be responsible for carving out the dust gap. Assuming no local extinction and a system age of 10 Myr, the F444W data are sensitive to masses down to $\sim 0.4\,M_{\rm Jup}$ at separations of $1$ arcsec ($\sim 60$ AU). Accounting for local disk extinction analogous to the AS 209 system, our limits reach sub-Jupiter masses beyond $2$ arcsec. Furthermore, our analysis provides a detailed view of a previously detected feature in the outer disk at $\sim 120$ AU, confirming its morphology as a distinct bifurcation structure. This feature may indicate the presence of complex substructures arising from dynamical planet-disk interactions. These results demonstrate JWST's ability to characterize the architecture of protoplanetary disks and constrain the properties of forming worlds.

astro-ph.EP↗

arXiv2026

Freezing the speckles: focal plane wavefront sensing with the spatially-clipped self-coherent camera

The next generation of Extremely Large Telescopes (ELTs) and the Habitable Worlds Observatory (HWO) require active speckle suppression to directly image exo-Earths. Focal plane wavefront sensing and control allows us to detect and remove time-varying speckles through measurements of the electric field. Wavefront sensing approaches include pairwise probing (PWP) and the self-coherent camera (SCC). However, the PWP technique is time-consuming, requiring at least 4 images and reducing the speed at which aberrations can be eliminated. The classical SCC modifies a standard coronagraph design, creating a reference electric field that interferes with speckles in the final focal plane, forming Fizeau fringes. However, this design only works over small spectral bandwidths and requires significantly oversized optics, limiting its effectiveness. We demonstrate a new SCC variant, the Spatially-Clipped SCC (SCSCC). The SCSCC utilizes a pinhole placed close to the Lyot stop, reducing the overall beam footprint and boosting the sensor's spectral bandwidth by factors of 3, respectively. A beamsplitter and knife edge downstream of the Lyot stop splits the light into 2 channels: fringed and unfringed, enabling wavefront sensing with a single exposure. Time-varying speckles are frozen in place, making them easy to remove. We present the SCSCC optical design combined with the photon resolving Hamamatsu Orca-Quest 2 camera. Furthermore, we demonstrate high speed wavefront control with the SCSCC, minimizing speckle intensity by 2x within a 5-11 lambda/D dark hole region on the Comprehensive Adaptive Optics and Coronagraph Test Instrument (CACTI) at the University of Arizona. These lab tests are in preparation for an on-sky demonstration of the SCSCC with the MagAO-X instrument. Our results make the SCSCC a valuable wavefront sensor for upcoming missions, including the Giant Magellan Telescope and HWO.

astro-ph.IM↗

arXiv2026

The eXtreme Wavefront Control Toolkit: High-Contrast Imaging Instrument Control for Ground and Space-Based Coronagraphs

We present the eXtreme Wavefront Control Toolkit (XWCTk) instrument control software system developed for the MagAO-X extreme adaptive optics (ExAO) instrument. The XWCTk is built on a foundation of the ImageStreamIO (ISIO) / MILK / CACAO low-latency image processing and high dimensional control tool chain. Instrument control is managed with the Instrument Neutral Distributed Interface (INDI). The application framework provides configuration, logging, and distributed IPC with INDI and low-latency IPC with ISIO. On MagAO-X, every detector is a potential wavefront sensor capable of sending commands to three separate DMs. MagAO-X utilizes a distributed control system, where multiple computers each manage low-latency wavefront control tasks but are capable of coordinated control. Implemented algorithms include neural networks for nonlinear reconstruction at over 3 kHz. We have incorporated distributed raspberry pis for accelerometer data acquisition with low-latency streaming to the real-time computers for sensor fusion control. A core design principle of the XWCTk is that all data can be saved all the time. This includes full-rate WFS images, DM commands, as well as science data. To facilitate this we have implemented a custom lossless compression system capable of sustaining high data rates to disk. A python interface for scripting and experimentation, as well as a python application framework is provided which can be used for non-real-time tasks. Remote operations (e.g. from Tucson Arizona when the instrument is at LCO in Chile) are routine. The XWCTk is under continuous development for the MagAO-X instrument, and will be adapted for GMagAO-X, the planned first-light ExAO coronagraph for the Giant Magellan Telescope. XWCTk is the baseline for a space high contrast imaging instrument, and as such ongoing development is focused on automation for robust operation in flight.

astro-ph.IM↗

arXiv2026

The Space Coronagraph Optical Bench (SCoOB): X. Dark zone maintenance

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.

astro-ph.IM↗

arXiv2026

The Space Coronagraph Optical Bench (SCoOB): 11. Modeling and correction of chromatic aberrations

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%-yield BMC Kilo-C deformable mirror, a black silicon pupil stop, and circular polarizers between wedged substrates. To assess the performance limits imposed by lateral chromatic aberration induced by refractive optical elements, we develop analytic and numerical tools to predict the broadband contrast. Additionally, we present the broadband contrast performance of the testbed using implicit electric field conjugation with multiple sensing bands for broadband control.

astro-ph.IM↗

arXiv2026

Tiny Observatory for Telescope Optimization (TOTO): testing algorithms for autonomous on-orbit alignment for space-based telescope systems

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.

astro-ph.IM↗

arXiv2026

Testing of machine learning wavefront sensing algorithms on the Tiny Observatory for Telescope Optimization (TOTO) testbed

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.

astro-ph.IM↗

arXiv2026

Low Thrust Electric Propulsion Mission Concepts For a 3-Meter Class Space Telescope

Space-based telescopes benefit from operating in stable orbital environments with reduced exposure to radiation and thermal fluctuations in order to minimize cost and maximize time for high-quality observations. Finding this ideal environment proves beneficial particularly for exoplanet discovery and characterization; direct imaging requires sub-nanometer wavefront stability and multi-hour observations, and transit detection requires parts-per-million photometric accuracy. Our team at University of Arizona's Steward Observatory and the Wyant College of Optical Sciences is evaluating various mission concepts for a 3-meter class telescope design, flying on a spacecraft bus equipped with a low thrust propulsion system. The presented mission analysis focuses on obtaining suitable transfer trajectories to the desired science orbit as well as understanding the radiation environment during the transfer, which is relevant for low thrust missions. The science analysis explores different operating orbits with the purpose of yielding maximum scientific return for detecting exoplanets. In this paper, we evaluate the use of a 2:1 lunar resonant orbit and a Sun-Earth L2 halo orbit for our mission.

astro-ph.IM↗

arXiv2026

Connecting Polarization to Exoplanet Yield Calculations for HWO

The Habitable Worlds Observatory (HWO) aims to enable the detection and characterization of Earth-like planets around Sun-like stars to search for possible signs of life elsewhere in our universe. This requires an incredibly sensitive coronagraph instrument that suppresses the light from the star by a factor of 10 billion, which must contend with error terms that have not previously limited high-contrast instrumentation at lower levels of starlight suppression. Polarization aberrations are one such source of error that is particularly problematic for coronagraphy on a large space telescope. Optical rays in large, compact astronomical observatories can have large changes in angle of incidence over the beam, which induce polarization aberrations that decrease sensitivities to faint signals at small angular separations. Limiting variation in angles of incidence along the optical path could lead to longer, less stable observatories. This could negatively impact the total number of exo-Earths HWO would be able to detect. This study links open-source physical optics modeling tools to an exoplanet yield optimizer to understand how polarization aberrations influence science return for HWO. We also explore how polarization aberrations scale with change in angle of incidence, which could drive the primary-secondary mirror distance and overall observatory stability. In the visible, we find that decreasing the EAC-1 barrel from 16m to 12m results in $\approx 10^{-10}$ contrast at the IWA where we expect exo-Earths to be. In the UV we appear to be less sensitive to polarization because exo-Earths are farther from the IWA. We also find a limited range over which the design reference mission of EAC-1 can be optimized to compensate for polarization aberrations using altruistic yield optimization. We then report on mitigation strategies to minimize the presence of polarization aberrations in HWO.

astro-ph.IM↗

arXiv2025

CoronaGraph Instrument Reference stars for Exoplanets (CorGI-REx) I. Preliminary Vetting and Implications for the Roman Coronagraph and Habitable Worlds Observatory

The upcoming Roman Coronagraph will be the first high-contrast instrument in space capable of high-order wavefront sensing and control technologies, a critical technology demonstration for the proposed Habitable Worlds Observatory (HWO) that aims to directly image and characterize habitable exoEarths. The nominal Roman Coronagraph observing plan involves alternating observations of a science target and a bright, nearby reference star. High contrast is achieved using wavefront sensing and control, also known as "digging a dark hole", where performance depends on the properties of the reference star, requiring V<3, a resolved stellar diameter <2 mas, and no stellar multiplicity. The imposed brightness and diameter criteria limit the sample of reference star candidates to high-mass main sequence and post-main sequence objects, where multiplicity rates are high. A future HWO coronagraph may have similarly restrictive criteria in reference star selection. From an exhaustive literature review of 95 stars, we identify an initial list of 40 primary and 18 reserve reference star candidates relevant to both the Roman Coronagraph and HWO. We present results from an initial survey of these candidates with high-resolution adaptive optics imaging and speckle interferometry and identify no new companions. We discuss the need for higher-contrast observations to sufficiently vet these reference star candidates prior to Roman Coronagraph observations along with the implications of reference star criteria on observation planning for Roman and HWO.

astro-ph.SR↗

arXiv2025

Progress toward a demonstration of high contrast imaging at ultraviolet wavelengths

NASA's Habitable Worlds Observatory (HWO) aims to achieve starlight suppression to the $10^{-10}$ level for the detection and spectral characterization of Earth-like exoplanets. Broadband ozone absorption features are key biosignatures that appear in the 200-400nm near-ultraviolet (UV) regime. Extending coronagraphy from visible wavelengths to the UV, however, brings with it a number of challenges, including tighter requirements on wavefront sensing and control, optical surface quality, scattered light, and polarization aberrations, among other things. We aim to partially quantify and address these challenges with a combination of modeling, high-resolution metrology to the scales required for UV coronagraphy, and ultimately a demonstration of UV coronagraphy on the Space Coronagraph Optical Bench (SCoOB) vacuum testbed. In these proceedings, we provide a status update on our modeling and contrast budgeting efforts, characterization efforts to understand performance limitations set by key optical components, and our plans to move toward a demonstration of UV coronagraphy.

astro-ph.IM↗

arXiv2025

Single-shot focal plane wavefront sensing with the spatially-clipped self-coherent camera

The Habitable Worlds Observatory requires active speckle suppression to directly image Earth-like exoplanets. Focal plane wavefront sensing and control allows us to detect, and subsequently remove, time-varying speckles through measurements of the electric field. Two measurement-based wavefront sensing approaches are pairwise probing (PWP) and the self-coherent camera (SCC). However, the PWP technique is time-consuming, requiring at least 4 images and reducing the speed at which aberrations can be eliminated. In the SCC, a coronagraph mask diffracts light outside of the Lyot stop, where it is filtered with a pinhole. The filtered light creates a reference beam, interfering with speckles that leak through the coronagraph. The classic implementation of the SCC only works over small spectral bandwidths and needs significantly oversized optics which limits its implementation. We propose a new variant, the Spatially-Clipped Self-Coherent Camera (SCSCC). The SCSCC utilizes a pinhole placed closer to the Lyot Stop, reducing the overall beam footprint and boosting the sensor resolution. A knife-edge beam splitter downstream of the Lyot Stop splits the light into two channels: fringed and unfringed. This allows us to sense the wavefront with a single exposure. Time-varying aberrations are effectively frozen in place, making them easy to remove. We present monochromatic simulation results of the SCSCC in a sensing and control loop, demonstrating a normalized intensity of ~ 4 * 10^-10 in a 5-20 lambda/D dark hole. We find that wavefront control paired with the SCSCC achieves ~ 50x deeper contrast than that achieved with PWP in a temporally evolving speckle field. Our results make the SCSCC a valuable wavefront sensor concept for the upcoming Habitable World Observatory mission.

astro-ph.IM↗

arXiv2025

Optical design and polarimetric performance of a SmallSat UV polarimeter to study interstellar dust: PUFFINS

The Polarimetry in the Ultraviolet to Find Features in INterStellar dust (PUFFINS) is a SmallSat mission concept designed to obtain ultraviolet (UV) spectropolarimetric observations to probe the interstellar dust grain properties and to understand wavelength-dependent extinction and star formation. PUFFINS plans to observe 70 UV bright target stars at varying distances within a 180-320 nm wavelength range with 0.02% polarimetric accuracy. PUFFINS uses a simple telescope design with all reflective optics coated with protected aluminum to enhance reflectivity in the UV. The telescope and the spectropolarimeter, which consists of a Wollaston prism and a half-wave retarder, have been carefully selected to be greater than Technology Readiness Level 6 (TRL6). The telescope is designed to exhibit negligible instrumental polarization and crosstalk, significantly reducing the time needed for polarimetric calibration in orbit. The optimum and careful selection of the target stars will enable PUFFINS to observe an expanded and well-defined sample to test the predictions by interstellar grain alignment theory in the observation phase of 9 months. This paper outlines the details of the optical and optomechanical design and evaluates the polarimetric performance of PUFFINS.

astro-ph.IM↗

arXiv2025

The Space Coronagraph Optical Bench (SCoOB): 6. demonstration of Lyot low order wavefront control combined with high order wavefront control using a vortex coronagraph

To reach and maintain high contrast levels, coronagraph instruments will require a combination of low-order and high-order wavefront control techniques to correct for dynamic wavefront error. Efficient low-order wavefront sensing and control (LOWFSC) schemes use the starlight rejected by the coronagraph such that LOWFSC can operate with a relatively bright signal to correct rapid disturbances. Meanwhile, a family of high-order wavefront sensing and control (HOWFSC) techniques utilizing the science camera have been developed to create regions of high contrast known as dark holes. These two control loops must operate simultaneously for dark holes to be maintained over long observation periods. Using a 952 actuator MEMS deformable mirror and a vector vortex coronagraph (VVC) on the Space Coronagraph Optical Bench (SCoOB), we demonstrate a Lyot-based LOWFSC loop operating in combination with a HOWFSC loop. For these experiments, implicit electric field conjugation (iEFC) is the chosen HOWFSC technique, and we demonstrate how this empirical method can be calibrated and deployed while the LOWFSC loop corrects for dynamic wavefront error. We show this combination of LOWFSC and iEFC maintained 1E-8 contrast levels in air.

physics.optics↗

arXiv2025

The Space Coronagraph Optical Bench (SCoOB): 7. design, fabrication, and first light for a self-coherent camera

The 2020 Decadal Survey on Astronomy and Astrophysics tasked future space observatories with the goal of detecting and characterizing a large sample of Earth-like exoplanets. To achieve this, these observatories will require coronagraphs and wavefront control algorithms in order to achieve $10^{-10}$ or better starlight suppression. The Space Coronagraph Optical Bench (SCoOB) is a vacuum compatible testbed at the University of Arizona which aims to advance and mature starlight suppression technologies in a space-like environment. In its current configuration, SCoOB is a charge-6 vector vortex coronagraph outfitted with a Kilo-C microelectromechanical systems deformable mirror capable of achieving sub-$10^{-8}$ dark hole contrast at visible wavelengths using implicit electric field conjugation (iEFC). In this work, we demonstrate the use of a self-coherent camera (SCC) for dark hole digging and maintenance on SCoOB. The SCC introduces a small off-axis pinhole in the Lyot plane which allows some starlight to reach the focal plane and interfere with residual speckles. This enables high-order focal-plane wavefront sensing which can be combined with active wavefront control to null the speckles in a specified region of high contrast known as the dark hole. We discuss considerations for implementation, potential limitations, and provide a performance comparison with iEFC. We also discuss the design optimization and fabrication process for our SCC Lyot stops.

astro-ph.IM↗

arXiv2025

Stray and Scattered Light Considerations in a Non-contiguous Array of Commercial CMOS Sensors in a Space Mission

Recent advances in CMOS technology have potential to significantly increase the performance, at low-cost, of an astronomical space telescope. Arrays of sensors in space missions are typically contiguous and act as a monolithic detector. A non-contiguous array, with gaps between individual commercial CMOS detectors, offers potential cost and schedule benefits but poses a unique challenge for stray/scattered light mitigation due to complexities in the optomechanics. For example, if the array of detectors is being fed a large field of view, then each detector will have a different angle of incidence. Any individual bandpass filters need to be held perpendicular to the incoming beam so as not to create variances of central wavelength transmission from detector to detector. It naturally follows that the optical design can force filter ghosts to fall between detectors. When dealing with well-focused, high-intensity beams, first and second order stray light path analyses must be conducted to determine scattered light from glints off of individual optics/opto-mechanics or detector specific vane structures. More mechanical structures are necessary for imaging with non-contiguous arrays, all of which have potential to increase scattered light. This proceeding will document various stray light mitigation strategies for a non-contiguous array of sensors in a space telescope.

astro-ph.IM↗

arXiv2025

Stages of commissioning alignment for three-mirror anastigmat (TMA) telescopes

Reliable, autonomously, deployment of telescopes enables a wide range of possible science cases. In this paper, we present a method for multi-stage telescope alignment with a simple commercial imaging sensor. For these studies, we use a design of an example three mirror anastigmat telescope and consider how the average spot size across the detector changes as a function of primary and secondary mirror positioning. This multi-stage alignment procedure will consist of three subprocesses, starting with a coarse alignment and converging down to a finer alignment before moving on to a stage where the telescope will refine its misalignments for data acquisition. This alignment strategy has been tested and meets diffraction limited requirements on a subset of misalignment cases from a statistical Monte Carlo simulation given misalignment tolerances on the telescope.

astro-ph.IM↗