arXiv subjects

Tiffany Nguyen

Publications and source records attributed to Tiffany Nguyen.

6 recordsLinked to original sources

arXiv2026

Sub-diffraction-limited coronagraphic imaging with nano-printed PIAACMC phase masks

Imaging Earth-like exoplanets in the habitable zone of their host star is among the main science objectives of future ground-based and space-based observatories. However, the extreme contrast and small separations needed to image such planets cannot be reached with current technology. The Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) is a promising coronagraph to reach this goal. The PIAACMC uses a set of aspheric lenses to apodize the entrance pupil without throughput losses and a phase-shifting focal plane mask for starlight suppression. These allow us to maintain high throughput and achieve a small inner-working angle (IWA), unlocking the capability to observe exoplanets at the diffraction limit. The masks are manufactured in-house at Leiden University with Nanoscribe, a micro-3D-printer that uses two-photon polymerization to achieve sub-micron precision in height. We present the first scientific results with a focal plane mask for the PIAACMC on the Magellan Adaptive Optics eXtreme (MagAO-X) instrument for the 6.5-meter Magellan Clay telescope at Las Campanas Observatory, Chile. We show laboratory and on-sky contrast curves with a broadband z' filter centered at 908 nm with a 14% bandwidth. We use the PIAACMC to detect binary companions at separations ~0.8-5 lambda/D (~23-144 mas). This demonstrates the PIAACMC's capability to observe at the diffraction limit and below, with a sub-lambda/D IWA. Future work includes exploring new mask designs to improve the contrast in broadband light and performing active focal plane wavefront sensing and control.

astro-ph.IM↗

arXiv2026

On-sky demonstration of self-learning predictive control with MagAO-X

Direct imaging of exoplanets is very tricky and requires extremely well corrected wavefronts. Especially low-order order modes are detrimental to the performance of coronagraphs at their inner-working angle. However, that is precisely where conventional AO systems have the highest residuals that are caused by servo-lag errors. This servo-lag error can be reduced with predictive control where the control anticipates the future state of the atmospheric disturbance. We use a self-learning model predictive controller based on the concepts from sub-space predictive control (SPC). We present a novel implementation of the SPC by using an online QR-decomposition based recursive least squares approach. This approach has now been used for self-learning control of vibrations on the MagAO-X instrument. We see on average an Strehl increase of 15 percent and a decrease of the jitter to 0.9 mas. I will discuss how we have implemented the controller and its on-sky perfomance.

astro-ph.IM↗

arXiv2026

The Roman Coronagraph Community Participation Program: pre-launch reference star list and impact of reference star properties on post-processing performance

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 for both wavefront calibration and reference differential imaging post-processing. Reference star criteria for the most demanding coronagraph mode are restrictive, limiting the sample to only 40 candidates for which thorough observational vetting is needed to assess their suitability. Reference star properties such as resolved diameters, presence of circumstellar dust, and close point sources may also have more subtle impacts on post-processing efficacy that may inhibit final contrast performance. In this work, we describe the current progress of the CoronaGraph Instrument Reference stars for Exoplanets (CorGI-REx) observing campaign, a 300+-hour observing campaign that utilizes instruments from around the world to vet reference stars for high-order wavefront control suitability. We will present the pre-launch list of reference star candidates being utilized for the Roman Coronagraph Observation Phase constructed from a thorough analysis of high contrast and interferometric observations. We will also present the results of simulations investigating the impact of reference star resolved diameters and companions on post-processing performance. We conclude by discussing the importance of reference star selection for scheduling observations and optimizing contrast performance for the Roman Coronagraph along with implications for HWO coronagraph operations.

astro-ph.IM↗

arXiv2026

Sensor fusion on MagAO-X: real time vibration control using accelerometers

Mechanical vibrations are a significant source of residual wavefront error (WFE) in adaptive optics (AO) systems, limiting the performance of high-contrast imaging instruments. We present the design and on-sky deployment of a low-cost, modular accelerometer telemetry system for the MagAO-X extreme AO instrument on the 6.5 m Magellan Clay Telescope, consisting of piezoelectric accelerometers and a Raspberry Pi-based acquisition system that streams synchronized data to the real-time control computer with microsecond-level timing stability. The system is used to identify dominant telescope vibration sources and quantify their coupling to AO telemetry, revealing that several narrow-band modes originate from subsystems including the primary mirror glycol pump, secondary mirror actuation system, and telescope autofocus system. Coherence analysis between the synchronized accelerometer and wavefront sensor telemetry demonstrates that approximately one-third of the residual tip and tilt WFE is correlated with structural vibrations, indicating that accelerometer telemetry provides a promising foundation for future predictive control implementations. These results demonstrate that low-cost accelerometer telemetry provides a practical approach for vibration identification and a foundation for predictive control in current and future AO systems.

astro-ph.IM↗

arXiv2025

Macroscopic active matter under confinement: dynamical heterogeneity, bursts, and glassy behavior in a few-body system of self-propelling camphor surfers

We study a few-body system composed of self-propelling camphor surfers confined within a circular boundary. These millimeter-sized particles move in a regime where inertia and long-ranged interactions play a significant role, leading to surprisingly complex and subtle collective dynamics. These dynamics include self-organized bursts and glassy behavior at intermediate densities--phenomena not apparent from ensemble-averaged steady-state measures. By analyzing quantities like the overlap order parameter, we observe that the system exhibits dynamical slowing down as particle density increases. This slowdown is also reflected in the bursting activity, where both the amplitude and frequency of bursts decrease with increasing particle density. A minimal inertial active-particle model reproduces these dynamical steady states, revealing the importance of a new intermediate length scale--larger than the particle size. This intermediate scale is critical for the formation of structures resembling caging and plays a key role in the glass-like transition. Our results describe a macroscopic analog of an active glass with the additional phenomena of density-dependent bursting.

cond-mat.soft↗

arXiv2025

The Santa Cruz Extreme AO Lab (SEAL) 2.0: A reflective, multi-wavelength rebuild

The Santa cruz Extreme Adaptive optics Lab (SEAL) is a visible/near-infrared wavelength testbed designed to support technology development for high contrast imaging on large, segmented, ground-based telescopes. SEAL saw first light in 2021 as a transmissive, visible-wavelength AO testbed. In this paper, we present four major upgrades to SEAL: (1) the testbed has been rebuilt with custom off-axis parabolic mirrors, enabling operation in both near-infrared and visible wavelengths; (2) the suite of wavefront sensors now includes a Shack-Hartmann, transmissive four-sided pyramid, vector-Zernike, and, in the muirSEAL testbed, a photonic lantern; (3) the testbed includes a vector-vortex coronagraph and will soon include a hybrid astrophotonic coronagraph; (4) in addition to its original Keck-heritage RTC, SEAL now includes two additional control software packages: Catkit, originally developed for the HiCAT testbed at the Space Telescope Science Institute, and the RTC Compute And Control for Adaptive Optics (CACAO), originally designed for Subaru/SCExAO. We discuss the performance of the testbed after the reflective rebuild and on-going technology development work at SEAL.

astro-ph.IM↗