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Physics Astrophysics Instrumentation and Methods for Astrophysics

astro-ph.IM Watch Instrumentation and Methods for Astrophysics

Monday 17 August

Instrumentation and Methods for Astrophysics

TomoSphero: Fast Differentiable Projector for Planetary and Solar Tomography on Spherical Grids

Evan Widloski and Lara Waldrop

Computational tomography is a tool for determining the internal structure of objects from a set of projections, typically taken along some regular path. In recent years, methods and GPU-accelerated libraries have emerged that allow for fast reconstruction from projections along more complicated paths. Most of these libraries rely on a Cartesian discretization of the object, which is not appropriate for all scenarios. We present TomoSphero, a differentiable tomographic projector over spherical grids which are often used in planetary and solar tomography. TomoSphero is designed to be used as a building block in reconstruction algorithms and includes common projection types such as cone-beam and parallel-beam, but is flexible enough to accommodate arbitrary projections. TomoSphero is implemented in PyTorch which allows for fast projection computation on GPUs, easy access to modern machine learning optimizers, and automatic differentiation for rapid prototyping of parametric models.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE

A Cross-Band (X-ray $\times$ Optical) Periodicity Search for Supermassive Black Hole Binaries: A Null Result and the First Completeness-Corrected Constraint

Karan Akbari

We present the first sample-level search for supermassive black hole binaries (SMBHBs) requiring coherent quasi-periodicity at a common period in the X-ray and optical bands, over 1194 Swift-BAT hard X-ray AGN (Stage 1) and 175 4XMM-DR14 AGN (Stage 2). No source is a co-periodic candidate. Each light curve is modelled as a damped random walk (DRW) and searched with a Lomb-Scargle periodogram and a look-elsewhere-corrected Monte-Carlo significance. Because DRW red noise is largely independent between corona and disc, we require both bands individually significant with periods coincident within 5%, and gate the survivors with the model-independent null-signal-template test of Robnik et al. (2024). Over $P=100$-$900$ d the completeness-corrected 95% upper limit on the co-periodic fraction is amplitude-dependent: $\lesssim 3\%$ for hard-X-ray fractional modulation $\gtrsim 0.3$, $\approx 15\%$ (precision-limited) at 0.2, and uninformative below $\sim 0.15$ (the $\epsilon=1$ floor is 0.25%). The sensitivity is set by the hard X-ray monitoring, not the optical photometry or the statistics, the opposite of the usual assumption. Daily MAXI and RXTE/ASM monitoring of the brightest AGN raises the X-ray completeness 5-8-fold, and the search remains null. Integrated over the BAT black-hole mass function, the expected all-amplitude co-periodic fraction is $\sim 3\times10^{-2}\, f_{\rm bin}\, \delta_{\rm mod}$ (modulo a factor $g<1$), with $f_{\rm bin}$ the sub-pc binary fraction, $\delta_{\rm mod}$ the modulating duty cycle, and $g$ the fraction reaching recoverable hard-X-ray amplitude, so a null is expected. We deliver a validated cross-band framework and the first completeness-corrected constraint on the co-periodic fraction, ready for the denser X-ray monitoring of Einstein Probe and eROSITA.
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Instrumentation and Methods for Astrophysics

Anti-windup PI controller for millimeter-wave adaptive optics: a Nobeyama 45 m radio telescope simulation

Ichiro Jikuya, Yoichi Tamura, Akio Taniguchi et al. (+8 more)

This work addresses the control problem for Millimeter-wave Adaptive Optics (MAO), which we define as compensating for the distance variation between the primary reflector (M1) and the receiver. We utilize a measurement system developed by Tamura et al. to track these variations. The challenge is formalized as an asymptotic constant disturbance suppression problem. We demonstrate that an anti-windup proportional-integral (AWPI) controller effectively solves this problem while respecting the physical movement constraints of the optical driving system. Simulation results, based on the Nobeyama 45-m Telescope with a two-axis translating sub-reflector (M2), validate the performance of the proposed AWPI approach.
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All authors Ichiro Jikuya, Yoichi Tamura, Akio Taniguchi, Masaki Sakakibara, Akinobu Miyake, Masato Hagimoto, Kianhong Lee, Chihiro Imamura, Shion Takeno, Sachiko S. Okumura, Nozomi Okada

Instrumentation and Methods for Astrophysics · Cross-listed from physics.space-ph

In-situ measurements of space plasma: recent progress and future challenges

Daniel Verscharen

Space plasmas like the solar wind or the Earth's space environment offer unique opportunities to observe fundamental plasma processes and their impact in situ. With modern space instrumentation, we measure the velocity distribution function of the plasma particles as well as the electromagnetic fields at high resolution and with minimal perturbation of the observed plasma systems. Plasma measurements like this are often not possible in laboratory settings on Earth. This review article focuses on modern diagnostic methods for the in-situ detection of plasma particles in space. It presents the detection principle of top-hat electrostatic analysers and highlights recent examples of scientific discoveries based on data from the heliospheric space missions Parker Solar Probe and Solar Orbiter. These examples demonstrate the capabilities of modern space plasma instrumentation. The article then discusses future directions in space plasma physics as well as the involved challenges in terms of the required plasma diagnostics. These new developments include, for example, upcoming and proposed space missions such as the operational space-weather mission Vigil, the multi-spacecraft mission HelioSwarm, the Mars mission M-MATISSE, and the electron-astrophysics mission Debye.
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Instrumentation and Methods for Astrophysics

Galaxy Morphology Classification: Uncertainty Modeling and Out of Distribution Detection

Prem Prakash, Shantanu Desai and P.K. Srijith

We present a comprehensive framework for galaxy morphology classification that combines enhanced “out-of-distribution (OOD)” detection with improved uncertainty quantification. Using “Galaxy Zoo DECaLS”, we trained a ResNet-34 architecture under three configurations: standard cross-entropy loss as a baseline, IsoMaxPlus loss function for OOD detection, and hybrid IsoMaxPlus+MonteCarlo Dropout for enhanced uncertainty quantification. IsoMaxPlus replaces the conventional SoftMax logits with distance-based class representations, preserving inter-class separability and enabling reliable OOD detection, without requiring additional architectural modifications or hyperparameter tuning. Coalescing IsoMaxPlus with MC Dropout provides a fast Bayesian approximation by performing multiple stochastic forward passes during inference. Our results show that IsoMaxPlus substantially improves OOD detection, increasing TNR@TPR95 by nearly $90\%$ relative to the cross-entropy baseline, while maintaining a competitive accuracy of 97% across nine morphological classes. Additionally, with MC Dropout, the model yields more stable predictions and a reduction in calibration error, providing more reliable uncertainty estimates. The Expected Calibration Error (ECE) is reduced from $0.0095$ to $0.0026$ ($\approx73\%$) for IsoMaxPlus and $0.0033$ ($\approx65\%$) when combined with MC Dropout, compared to the baseline. Misclassified or underconfident predictions exhibit higher predictive entropy and lower minimum distance scores, providing an interpretable metric for identifying unreliable predictions. These methods are well-suited for current and upcoming large-scale surveys, where reliable automated morphological classification and awareness of uncertainty are essential for identifying rare or previously unseen galaxy morphologies.
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Instrumentation and Methods for Astrophysics

Millimeter-wave adaptive optics: Demonstrating closed-loop correction for lowest Zernike modes

Yoichi Tamura, Akio Taniguchi, Kotaro Iwakami et al. (+15 more)

We report on a five-element prototype wavefront sensor for millimeter-wave adaptive optics (MAO), enabling closed-loop correction of tip-tilt and defocus via secondary mirror (M2) displacement. MAO is essential for large ground-based millimeter/submillimeter telescopes to maintain surface accuracy under wind and thermal distortions. Our sensor, based on radio interferometry, measures excess path lengths from the primary mirror to a focal-plane receiver. A previous two-element prototype achieved < 10 um accuracy at the Nobeyama 45 m telescope. The new five-element system, operating at 20 GHz, was installed on the same telescope. A “Moon-edge” experiment confirmed detection of wavefront gradients through strong correlation with continuum flux. Implementing a PI controller closed the sensor-M2 loop, stably suppressing the lowest Zernike modes. This approach establishes a foundation for metrology in future large-aperture submillimeter facilities such as AtLAST/LST.
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All authors Yoichi Tamura, Akio Taniguchi, Kotaro Iwakami, Ichiro Jikuya, Shion Takeno, Sachiko K. Okumura, Masaki Sakakibara, Akinobu Miyake, Masato Hagimoto, Kianhong Lee, Chihiro Imamura, Sho Fujisawa, Shutaro Inui, Masato Kato, Ryohei Kawabe, Mikio Kurita, Nozomi Okada, Juri Yamanaka

Instrumentation and Methods for Astrophysics

Tradeoff between segment density and IWA for high-contrast imaging of exoplanets with a large segmented space mission

Lucie Leboulleux, Raphaël Pourcelot, Laurent Pueyo et al. (+1 more)

Imaging Earth-like exoplanets with coronagraphs on future large segmented space telescopes such as the Habitable Worlds Observatory requires contrasts down to $10^{-10}$ at separations below 100 mas, imposing segment phasing control down to a few picometers. We evaluate how this constraint can be relaxed by optimizing telescope and instrument design, quantifying the impact on performance stability under segment phasing aberrations. We propose a system-level approach, adjusting the primary mirror segmentation and the focal-plane mask size (inner working angle). We compare the passive robustness to segment phasing errors across systems, and the ability of a Zernike low-order wavefront sensor to reconstruct aberrations and recover target performance. Increasing the focal-plane mask radius or decreasing segment count improves both passive robustness and sensor reconstruction: Increasing the mask radius from 3.5 to 6.5{\lambda}/D relaxes phasing constraints by up to a factor 4 near the IWA, and reducing the segment count from 85 (5 rings) to 7 (1 ring) relaxes them by up to a factor 2; The same mask radius increase also doubles, on average, the sensor's sensitivity to photon noise across segment piston, tip, and tilt modes. To conclude, jointly optimizing the segmentation scheme and mask size, so the low-order PSD envelope is blocked by the mask, can significantly relax phasing requirements, complementing active correction, with direct implications for HWO.
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All authors Lucie Leboulleux, Raphaël Pourcelot, Laurent Pueyo, Bryony Nickson

Instrumentation and Methods for Astrophysics

A NICE (Nulling Interferometry Cryogenic Experiment) update: Beyond 1e-5 and towards cryogenic operation

Jonah T. Hansen, Thomas Birbacher, Germain Garreau et al. (+10 more)

The Nulling Interferometry Cryogenic Experiment (NICE) is a mid-infrared laboratory testbed at ETH Zürich that aims to not only reproduce the deep ($<1\times10^{-5}$) broadband nulls of the nulling testbeds of the early 2000s, but also at the required sensitivity levels expected for the LIFE space mission. This sensitivity enforces the experiment to go cryogenic at temperatures around 15 K; an ambitious task for an ultra-precise interferometer. We share our results of the ambient precursor experiment, demonstrating repeatable $<1\times10^{-5}$ nulls at a single wavelength and high throughput, and investigations into the nulling performance across a broader bandpass and with dual polarisation states. We will also highlight the push towards cryogenic operation, with the instalment of a new 15 K test cryostat that will inform our choices of materials and optomechanical mounting techniques.
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All authors Jonah T. Hansen, Thomas Birbacher, Germain Garreau, Julio Pino-Jiménez, Emilie Bouzerand, Felix A. Dannert, David Eglin, Lee Feinberg, Adrian M. Glauser, Maximilian Kirchhoff, Oliver Pitz, Eckhart Spalding, Sascha P. Quanz

Instrumentation and Methods for Astrophysics

Cryogenic characterisation for the Nulling Interferometry Cryogenic Experiment (NICE)

Jonah T. Hansen, Emilie Bouzerand, Adrian M. Glauser et al. (+11 more)

The Nulling Interferometry Cryogenic Experiment (NICE) is an experimental testbed for the beam combiner of the Large Interferometer For Exoplanets (LIFE) space mission. Until now, progress on NICE has been confined to an ambient bench, where we have recorded progress in deep ($<10^{-5}$) nulls at wavelengths between 4 and 5 microns at 300 K. However, the ultimate goal and requirement of NICE is to repeat these measurements at the sensitivity levels expected for a planetary system, requiring deep cryogenic conditions at 15 K. Here, we describe the “Ice Cube” cryostat, a small version of the future NICE cryostat that is used for component and subsystem level cryogenic testing. This is interfaced with a measurement setup using a segmented aperture interferometer and a wavefront sensor. We will also describe the testing campaign for understanding the material and mounting challenges that will be faced when translating the warm bench to cryogenic operations.
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All authors Jonah T. Hansen, Emilie Bouzerand, Adrian M. Glauser, Bastien Rouzé, Noah Stocker, Walter Bachmann, Marcel Baer, Cindy Bellanger, Thomas Birbacher, Germain Garreau, Julio Pino-Jiménez, Jerome Primot, Eckhart Spalding, Sascha P. Quanz

Instrumentation and Methods for Astrophysics

Direct Imaging and Gradient-Based Analysis of the 12 August 2026 Partial Solar Eclipse from a Freely Rotating High-Altitude Balloon

Bjoern Poppe, Enno Gronewold, Matti Gehlen et al. (+7 more)

We report a proof-of-concept observation of the partial solar eclipse of 12 August 2026 using a freely rotating high-altitude balloon launched from Oldenburg, northern Germany. The payload carried two Insta360 ONE RS cameras equipped with 4K Boost wide-angle lenses; covered by filter material taken from a BRESSER eclipse viewing glass. Interval photographs were acquired every 10 s at ISO 800 and 1/1000 s. Of approximately 1,300 images, 21 contained a directly visible image of the eclipsed Sun, spanning 19:19:15-20:38:21 CEST and both sides of the local eclipse maximum. To test whether quantitative eclipse information could be recovered from these small, non-stabilized wide-angle images, the visible solar area was estimated using a two-dimensional gradient-based solar edge analysis and normalized to the first observation. The image-derived obscuration followed the independently calculated eclipse geometry with Pearson r = 0.959, a mean absolute difference of 9.5 percentage points, and an RMSE of 11.5 percentage points. Systematic deviations are consistent with the limitations of an uncalibrated action-camera system, including point-spread function, field-dependent lens response, filter geometry, and camera-to-camera differences. The results demonstrate that passive payload rotation can yield both visually useful and semi-quantitative direct eclipse observations without active solar pointing, and define a calibration strategy for future balloon-borne eclipse measurements.
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All authors Bjoern Poppe, Enno Gronewold, Matti Gehlen, Jona Schrader, Delia Gauk, Lisa Cordes, Maike I. Schmitz, Peter Schoenfeld, Simon Jaeger, Gerhard Drolshagen

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP

Optical-NIR Multi-band Photometric Analysis and Characterization of Giant Exoplanets with CPI-C

Yiming Zhu, Gang Zhao, Xi Zhang et al. (+4 more)

We present a multi-band photometric approach to characterize giant exoplanets, which represents one of the anticipated core scientific outcomes of Cool Planet Imaging Coronagraph (CPI-C). CPI-C operates with two observational channels covering visible and near-infrared wavelengths, each equipped with four broadband filters. The planet–star flux ratio integrated over each filter bandpass is calculated for photometric analysis. For cool planets observed in the visible bands, the data are primarily used to fit the overall spectral shape and methane-induced modulation, providing sensitivity to metallicity- and cloud-dependent spectral variations while constraining the reflected-light spectral shape and the combined scaling involving planet radius, orbital separation, and orbital phase. In the near-infrared bands, which probe thermal emission, the data help to better constrain fundamental planetary parameters including the effective temperature, radius, surface gravity and mass. For a synthetic giant planet with measurable reflected-light and thermal-emission components, the combined VIS4+NIR4 data provide tighter same-target constraints than either filter set alone, especially for the planet radius and cloud sedimentation parameter. Our simulations incorporate realistic instrument throughput, detector noise, and residual speckle noise. The results demonstrate that the eight-band design spanning visible to near-infrared wavelengths supports reflected-light diagnostics, thermal-emission characterization, and joint optical–NIR analysis of giant exoplanets within CPI-C science observations.
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All authors Yiming Zhu, Gang Zhao, Xi Zhang, Gang Wang, Bingli Niu, Zhonghua Lv, Jiangpei Dou

Instrumentation and Methods for Astrophysics

Exact spherical-wave forward model for radio reflection from stratified media and implications for the anomalous-polarity events observed by ANITA

Paramita Dasgupta

Radio detection of ultra-high energy particles relies on the propagation and reflection of broadband radio pulses at boundaries between natural media. In the Sommerfeld–Weyl treatment, a spherical wave is decomposed into plane-wave components and their reflection from a single homogeneous interface is calculated exactly. We extend that treatment to an arbitrary number of laterally uniform spherical layers. Both the spherical-wave decomposition of the source and the spherical geometry of the boundary are retained, while the reflection and transmission coefficients of the plane-wave components are replaced by the exact characteristic-matrix coefficients of the layered medium, evaluated at the local incidence angle on the spherical boundary. When the layer contrast is removed, the formalism recovers the single-boundary result to machine precision, and it reproduces the published spherical-surface reflectivity calculation to better than $1.1\%$ at ten HiCal-2 elevation angles, with a mean deviation of $0.6\%$. We reproduce the measured HiCal-1 reflected pulses from their measured direct partners, with a best signed correlation of $0.83$ and a median of $0.70$ across $106$ pairs, of which $101$ show the expected polarity inversion. Applied to the six reported ANITA anomalous-polarity event geometries, the buried-layer refractive index required for a sign change of the reflection coefficient ranges from $1.68$ at the steepest event to $3.8$–$5.4$ at the four near-horizon events. The full waveform calculation gives no non-inverted reflected pulse at any of these angles, showing that shallow, laterally uniform firn layering does not account for the polarity of the anomalous ANITA events. Because the formalism depends only on the complex refractive index of the medium, it applies more generally to isotropic, nonmagnetic stratified media, including ice, lunar regolith, and conducting layers.
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Sunday 16 August

Instrumentation and Methods for Astrophysics

A Social Network Analysis of JWST General Observer Programs: The Emergence of a Decentralized Heterarchy

Christopher Williams

Developing proposals to execute programs on space telescopes involves networks of astronomers coalescing around ideas and plans for observations. When aggregated, these program level networks allow a collective structure of the overall social network of astronomers using a telescope to be created and analysed. We do this using program level investigator data over the first five cycles of accepted General Observer (GO) programs on the James Webb Space Telescope (JWST). The aggregate network contains 5252 unique astronomers with 144740 connections between them based on their program level participation. We apply a modularity class coefficient to visualize the sub communities that evolved within the aggregate network. Ten dominant sub communities emerge that are shown to correlate at various levels with the JWST scientific categories as defined by the Space Telescope Science Institute (STScI). These sub communities vary in size as well as diversity of countries and institutions represented. Analysis of the research interests of investigators within sub communities reveals that separation along the long axis of the graph is associated with the scale of science performed at community level (AU scale vs kpc Gpc scale). While the social network structures based on institutional affiliation and country of institution are highly centralized, the aggregate network at the investigator level is highly heterarchical and decentralized. It appears to be supportive of cross disciplinary interaction, and institutionalized integration between planetary system and cosmic structure science that is wide and redundant, rather than mediated by a small set of critical brokers. Results have implications for access policy (time allocation processes on telescopes leaving behind a legacy of heterarchical social networks) and access strategy (astronomer need to access networks before accessing telescopes).
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Saturday 15 August

Instrumentation and Methods for Astrophysics

Wide field Slitless Spectroscopy with JWST's MIRI

Andreea Petric, Sarah Kendrew, David Law et al. (+12 more)

We present a snapshot of the ongoing efforts to obtain background-subtracted, wavelength-, and flux-calibrated spectra taken with the new Wide-Field Slitless Spectroscopy (WFSS) mode for the MIRI instrument on the James Webb Space Telescope (JWST), offered for the first time in JWST Cycle 5 (starting July 2026). We describe here the capabilities of the new mode, the operational concept, and an overview of the calibration and pipeline development activities that are currently ongoing.
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All authors Andreea Petric, Sarah Kendrew, David Law, Alberto Noriega Crespo, Bryan Holler, Jane Morrison, Jonathan Aguilar, Misty Cracraft, Ian Wong, Stacey Alberts, Dean Hines, Kate Rowlands, Ned Molter, G. C. Sloan, Mike Engesser

Instrumentation and Methods for Astrophysics

Design and Realization of the LST Main Structure for the Cherenkov Telescope Array

T. Schweizer, J. Eder, H. Wetteskind et al. (+12 more)

The 23 m diameter Large Size Cherenkov Telescope (LST) for CTA, located at 2250 m a.s.l. on the Canary Island of La Palma, is the next-generation Cherenkov telescope following MAGIC, H.E.S.S., and VERITAS. To enable rapid repositioning (180{\deg} in 18 s) for gamma-ray burst observations, the mechanical structure was designed to be ultra- lightweight (110 tons). The space-frame structure consists of slender struts made of carbon fibre, aluminium (dish and camera mast), and steel. The telescope is designed to withstand extreme environmental conditions at the ORM observatory on La Palma, including wind speeds up to 200 km/h, uplift forces, and ice loads of up to 30 tons. We present the structural design developed to meet these functional and environmental requirements. MPP Munich is responsible for the telescope's mechanical structure together with partner institutes in France (LAPP) and Spain (IFAE). The prototype, LST-1, has been operational since 2019, and three additional LSTs are curre1ntly under construction.
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All authors T. Schweizer, J. Eder, H. Wetteskind, C. Jablonski, R. Stadler, R. Mirzoyan, D. Paneque, T. Masahiro, A. Fiasson, N. Geffroy, G. Deleglise, O. Blanch, J. Mundet, R. Garcia, A. J. Penuela Lopez

Instrumentation and Methods for Astrophysics

Adapting the 23m LST-North mechanical structure design for the strong Chile seismic environment

Thomas Schweizer, Josef Eder, Teshima Masahiro et al. (+2 more)

The 23-meter-diameter Large-Sized Telescope (LST) is the largest size telescope of the next generation Cherenkov Telescope Array (CTA). The first telescope, LST-1, was installed at the Roque de los Muchachos Observatory (ORM) on La Palma at an altitude of 2,250 m in 2018 and has been in operation since 2019. Its ultra-lightweight structure (110 tons) enables extremely rapid repositioning (180{\deg} in 18 seconds) and has been designed to withstand extreme environmental conditions, including storms and winds exceeding speed up to 200 km/h. To deploy the same solid telescope design at the CTA Southern Observatory in Chile, the structure must be adapted to the significantly higher seismic demands of the site. To address this challenge, the Max Planck Institute for Physics (MPP) has proposed the integration of a seismic isolation system with the proven LST-1 structural design. This approach substantially reduces seismic loads and dynamic amplification, thereby avoiding extensive structural modifications and enabling the existing telescope design to be transferred to the Chilean site with only minor adaptations. In this contribution, we present the proposed seismic isolation concept and its feasibility studies. MPP is responsible for the mechanical structure of the LST and has validated the concept through detailed finite-element analyses and long-term structural lifetime assessments.
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All authors Thomas Schweizer, Josef Eder, Teshima Masahiro, Holger Wetteskind, Razmik Mirzoyan

Instrumentation and Methods for Astrophysics

Stress-Testing DANTE under Detector Domain Shift: a Representation-Coherent Reanalysis of LIGO O4a

Luca Cirfeta

This sixth version of the Domain-Adaptive Network for Transient Evaluation (DANTE) preprint stress-tests an unsupervised transient-noise pipeline under representation mismatch and observing-run adaptation. We reanalyse 10,429 detector-time strain candidates from 42 LIGO O4a sessions using frozen DINOv2 patch embeddings and a Top-k multiple-instance score. Candidate and native-background Q-transforms share Q in [4,64], and detector-specific thresholds are calibrated from 5,000 run-native windows by temporal-block bootstrap. The coherent analysis yields 6,365 ROBUST, 1,275 AMBIGUOUS, and 2,789 BACKGROUND statistical dispositions; 4,676 of 10,372 paired historical dispositions differ from the cross-representation v5 analysis. Direct controls resolve an O3b-O4a score shift and reduction after native adaptation for H1, but not L1, while known-glitch separation is detector- and morphology-dependent. Replicated studies quantify population-dependent sensitivity to background draw, clustering seed, dictionary size, and whitening, demonstrate native-index absorption, and identify conditional low-Q blindness. A conservative H1-L1 max-shift screen yields 13/8,806 values above threshold, but its on-source values and pooled per-event null maxima are not exchangeable. The primary two-null PEM endpoint shows no resolved ROBUST-BACKGROUND enrichment (p=1.000), and two catalogue overlaps are consistent with a circular-shift coverage proxy (p=0.651). Simulation-only compact-binary controls show detector- and distance-dependent disagreement between novelty, native disposition, and physical coincidence. We withdraw the v5 discovery, rate-limit, catalogue-recall, and survey-wide stability interpretations. The supported result is a measured set of failure modes and validity conditions for unsupervised detector characterization, not a new glitch class or an astrophysical search.
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2608.15166 · 15 Aug · 12 pages, 10 figures, 1 table. Sixth version: representation-coherent O4a reanalysis, detector-aware catalogue reconstruction, replicated robustness and failure-mode validation, physical and catalogue null controls, and withdrawal of unsupported v5 discovery, rate-limit, catalogue-recall, and survey-wide stability interpretations

Abstract PDF $EMBD ×1

Instrumentation and Methods for Astrophysics

Parameter estimation in differential equations: Mathematical foundations for satellite gravimetry, review and perspectives

Peiliang Xu

Satellite gravimetry has become essential in many areas of earth science. However, the resolution of satellite gravitational models remains low at scales of a few hundreds km and no gravity recovery methods can take full advantages of unprecedented high accuracy of satellite tracking measurements. We first provide a unified theoretical framework of parameter estimation in differential equations for satellite gravimetry and then briefly review the mathematical methods to compute the gravity field of the Earth from satellite tracking. We focus on the collocation method, Kaula linear perturbations, two-point boundary value problems and orbit-energy-based methods. The numerical integration method is also included in this review, though it has been proved to be mathematically incorrect and physically not permitted. The reason is that it has become the standard method to routinely produce global gravitational models from satellite tracking data, which have been widely applied in many different areas of earth science. Because it is not clear how the incorrect foundation would affect gravity products from satellite tracking, we do not review any applications of these products. We then present a measurement-based perturbation theory to estimate the gravity field of the Earth, which can fully utilize both precise satellite orbits of arbitrary length and unprecedented high accuracy of satellite and inter-satellite tracking. The method is theoretically free of modeling errors, is capable of extracting any small forces from satellite and inter-satellite tracking data and provides a guarantee for high-precision and high-resolution global gravity models. Finally, we assume a reference gravity model and derive local solutions to the Newton's nonlinear governing differential equations of satellite motion for scattered tracking data that can still be important in some applications.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP

Scaling of microcraters with molten rims derived from laser-induced cratering experiments

S. Sato, H. Shibayama, K. Nagai et al. (+1 more)

Microcraters with molten rims are widely observed in returned samples from the Moon and asteroids. These features reflect the conditions of small-scale impact events, but the impact velocities required for their formation are not well understood. In this study, we use well-controlled laser irradiation on rock surfaces as an experimental analog to investigate the formation of these molten-rim craters. Specifically, we derive a scaling relation between crater volume, total irradiation energy, and energy loss associated with thermal diffusion. The experimental results indicate that molten-rim structures of microcraters can be formed in the range of $10^2$–$10^3$~m/s impact velocity. This value is consistent with some previous studies which suggested that the origin of microcraters is secondary impact events. These findings provide experimental constraints on the formation mechanisms of molten-rim microcraters and offer a new perspective on impact processes recorded on planetary surfaces. The estimated result is also consistent with the impact velocity required to produce the observed wavy rim protrusions due to a Rayleigh-Taylor hydrodynamic instability ($\sim 10^2$~m/s).
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All authors S. Sato, H. Shibayama, K. Nagai, H. Katsuragi

Friday 14 August

Instrumentation and Methods for Astrophysics

Sub-Pixel Calibration of CMOS Sensors for Precision Astrometry

M. Shao and I. Hahn

Many sources of systematic error are important to centroid the position of a star below the level of $10^{-4}$ of the FWHM of the stellar image. One of the more important sources of centroiding error is the imperfect position of the pixels in a focal plane array. In this paper, we discuss the calibration of pixel position of multiple commercial CMOS detectors. Focal plane arrays are semiconductor devices fabricated with 10's nanometer precision. However, the effective location of a pixel can be biased if there's a QE gradient across the pixel. We typically see pixel position variations of 1–3% of a pixel in most CMOS imagers. This paper describes how we measure the position of each pixel below the $10^{-3}$ pixel level. We also describe how this information might be used in a least square fitting of an airy spot to obtain a higher accuracy position of the centroid of the PSF.
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Instrumentation and Methods for Astrophysics

Enabling Quantitative Polarimetry for Keck/NIRC2: Preliminary Mueller Matrix Model Calibration

Manxuan Zhang, Briley L. Lewis, Maxwell A. Millar-Blanchaer et al. (+27 more)

The Keck/NIRC2 infrared imager was upgraded in 2025 with dual-beam polarimetric observing modes spanning approximately 1.1–4.1 microns (JHKL' bands). We present a preliminary JHK calibration of NIRC2 Polarimetry using a wavelength-dependent Mueller matrix model of the Keck tertiary mirror (M3), half-wave plate (HWP), image rotator (IMR), downstream optics, and Wollaston prism. We constrain the model downstream of M3 using dome flat sequences spanning ten HWP and nine IMR angles in each band. Although the model reproduces the dominant modulation, the residuals show structure dependent on HWP and IMR angle. Measurement matrix inversion of unpolarized standard star observations gives M3 diattenuations of 0.0119+/-0.0009, 0.0098+/-0.0004, and 0.0068+/-0.0005 in J, H, and Kp, substantially closer to Fresnel predictions for aluminum than the values derived from dome flats. The larger dome flat modulation may indicate polarization in the incident dome illumination or Mueller matrix model inaccuracies. These results establish an initial calibration framework while motivating improved input polarization constraints, fixed HWP parameters from previous laboratory measurements, model validation with polarized standard stars, and extension to L'.
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All authors Manxuan Zhang, Briley L. Lewis, Maxwell A. Millar-Blanchaer, Eduardo Marin, Jayke S. Nguyen, William Melby, Carlos Alvarez, Jaren N. Ashcraft, Mahawa Cisse, Charles-Antoine Claveau, Jacques-Robert Delorme, Greg Doppmann, Michael P. Fitzgerald, Matthew Freeman, Percy Gomez, Trisha Hammen, Ryan Hersey, Nemanja Jovanovic, Marc Kassis, Scott Lilley, Jessica Lu, James E. Lyke, Keith Matthews, Dimitri Mawet, Thomas McIntosh, Max Service, Lauren Simmons, Jacob Taylor, Rob G. van Holstein, Ed Wetherell

Instrumentation and Methods for Astrophysics

An open-source data processing pipeline for Keck / NIRC2-Polarimetry

Briley L. Lewis, Maxwell A. Millar-Blanchaer, Rebecca Zhang et al. (+3 more)

The Keck/NIRC2 infrared imager was recently upgraded with a new suite of polarimetric observing modes. This polarimetry upgrade (referred to as NIRC2-Pol) will open up a wide range of new astronomical studies, including investigations of exoplanets, the Galactic center, active galactic nuclei and the solar system. Astronomical polarimeters require sophisticated data reduction, especially for quantitative polarimetry requiring the use of a Mueller Matrix model for instrumental polarization calibration. This work presents the design of a flexible, user-friendly, open-source data processing pipeline intended for use with NIRC2-Pol, summarizing its key steps and details of its ongoing implementation.
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All authors Briley L. Lewis, Maxwell A. Millar-Blanchaer, Rebecca Zhang, Jayke Nguyen, Max Brodheim, Ashish Uhlmann

Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE

The Evolution of the ACIS Contamination Layer on the Chandra X-ray Observatory from 2010 to 2026

Paul P. Plucinsky, Peter W. Ratzlaff, Akos Bogdan et al. (+1 more)

The Chandra X-ray Observatory (CXO) was launched over 27 years ago and has been delivering spectacular science over the course of its mission. The Advanced CCD Imaging Spectrometer (ACIS) is the prime instrument on the satellite, conducting over 90% of the observations. The CCDs operate at a temperature of $-$120$^\circ$C and the optical blocking filter (OBF) in front of the CCDs is at a temperature of approximately $-$60$^\circ$C. The surface of the OBF has accumulated a layer of contamination over the course of the mission, as it is the coldest surface exposed to the interior to the spacecraft. We have been characterizing the thickness, chemical composition, and spatial distribution of the contamination layer as a function of time over the mission. The contamination model has required several revisions over the course of the mission as the properties of the contamination layer have changed and our understanding of the layer has improved. In this paper, we evaluate the performance of the current contamination model (N0016 released in CalDB 4.12.3 on 16 December 2025) using the most recent calibration observations conducted from 2023 to 2026 by using the standard model spectrum for the supernova remnant 1E 0102.2-7219 (E0102) developed by the International Astronomical Consortium for High Energy (IACHEC), spectral data from the cluster of galaxies known as Abell 1795, and high resolution X-ray spectra of Mrk 421. This evaluation has been complicated by the decreasing observed counts at low energies, especially the O VII He$\alpha$ line complex and the O VIII Ly$\alpha$ line from E0102 which are no longer useful for this purpose. The analyses of the E0102, Abell 1795, and Mrk 421 data show that the current model of the contamination adequately predicts the additional absorption through mid-2026.
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All authors Paul P. Plucinsky, Peter W. Ratzlaff, Akos Bogdan, Herman L. Marshall

Instrumentation and Methods for Astrophysics

$\texttt{Aether.jl}$ : A High-Performance 3D MHD and Multifluid Dust Code Written in a Dynamic Language with an Interactive Human-AI Development Framework

Ka Wai Ho

We present $\texttt{Aether}$, a new finite-volume code for compressible hydrodynamics and magnetohydrodynamics, written in Julia and primarily designed for GPU systems. The code solves the MHD equations with constrained transport in Cartesian, cylindrical, and spherical-polar coordinates, using standard high-order Godunov methods. An arbitrary number of dust fluids can be coupled to the gas through stiff mutual drag. It was developed from scratch with interactive Human-coding agent workflow; the paper documents the framework of this workflow alongside the numerical methods. Performance-critical kernel is written through $\texttt{KernelAbstractions}$, and supports runs on CPUs and GPUs from multiple vendors. $\texttt{Aether}$ can be ran either from an interactive notebook or batch scripts, keeping prototyping, production runs, and analysis in a single language. We verify the implementation through a series of hydrodynamic, MHD, and dust tests. Although written in a dynamic language, $\texttt{Aether}$ achieves comparable or even higher single-GPU throughput than C++ code on the same hardware. In weak scaling on Frontier, parallel efficiency stays above $93\%$S on 4096 GCDs. These results show that a dynamic language now supports production astrophysical MHD simulations on exascale systems. $\texttt{Aether}$ and its Jupyter notebook example suite are publicly available.
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Instrumentation and Methods for Astrophysics

On the Acceleration of Pulsar Timing computations using Normalising Flows and Parallelisation

Churchil Dwivedi, Hiya Shah and Hemanga Tahbildar

Single-Pulsar Noise Analysis (SPNA) and Gravitational Wave (GW) searches done on Pulsar Timing Array (PTA) datasets have everlastingly suffered from the computational bottleneck arising due to high dimensionality and multi-modality of the PTA likelihood landscape, along with strong correlations amongst various single-pulsar noises and ensemble-level common noise processes. We addressed this outstanding issue by employing a Normalising Flow-based Preconditioned Monte-Carlo sampling technique implemented in the POCOMC package, for the first time on PTA-specific computations, and comparing the achieved acceleration with the widely used PTMCMCSAMPLER and DYNESTY packages. We further investigated the acceleration achieved via parallelisation over an increasing array of communicating nodes on a high-performance computing (HPC) resource, by employing the PARALLEL_BILBY architecture with DYNESTY. We tested the acceleration on realistic long baseline simulated datasets with SPNA and Common Red Noise (CRN) analysis. We found PARALLEL_BILBY to be the most efficient in parallelisation, achieving a runtime of ~10min and ~100min with 16 nodes for spatially uncorrelated and Hellings and Downs-correlated CRN searches, respectively. POCOMC outperforms in single node performance requiring only ~10h for correlated search. PTMCMCSAMPLER was found to be the least efficient. We envisage POCOMC to be of great importance for PTA analyses, without requiring any GPU or HPC support, while also performing ensemble-level GW searches within a manageable time span. These results have everlasting implications with increasing data volumes and need to incorporate more complicated models, which were otherwise beyond reach due to the associated computational costs.
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Instrumentation and Methods for Astrophysics

Enhancing the performance and capabilities of the MIRI instrument on JWST

S. Kendrew, M. Engesser, K. Rowlands et al. (+23 more)

MIRI, the Mid-Infrared Instrument on the James Webb Space Telescope, is the only instrument sensitive to wavelengths longward of 5 um on the observatory. In this regime, MIRI brings order-of-magnitude improvements over past instruments and missions in a wavelength range that is challenging or impossible to access from the ground. As such, MIRI occupies a unique parameter space, offering unparalleled capabilities in all areas of astrophysics, from the Solar System to the most distant galaxies in the Universe. We continue to make operational improvements to MIRI, four years into its operational lifetime, to create new observing opportunities, improve performance, and enhance its scientific return. In this paper we will describe several such improvements, and their anticipated impact on MIRI and JWST science.
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All authors S. Kendrew, M. Engesser, K. Rowlands, A. Noriega-Crespo, M. Decleir, H. Diamond-Lowe, M. Regan, J. Aguilar, S. Alberts, T. Bell, M. Cracraft, A. Dyrek, K. Gordon, D. Hines, B.J. Holler, K. Larson, D. Law, K. Murray, B. Nickson, B. O'Sullivan, A. Petric, B. Sargent, S. Shenoy, G.C. Sloan, B. Trahin, I. Wong

Instrumentation and Methods for Astrophysics

CCAT: a two-octave 1.024 GHz KID readout featuring an overlap-channel polyphase synthesis filter bank on RFSoC

Ruixuan Xie, Adrian K. Sinclair, James Burgoyne et al. (+6 more)

Next-generation submillimeter instruments require gigahertz-scale readout bandwidths to support the growing detector counts of large microwave kinetic inductance detector (KID) arrays. Designed to meet the readout bandwidth and tone-capacity requirements of the CCAT Prime-Cam 850 GHz and 410 GHz instrument modules, we developed our second-generation (Gen2) KID readout system on a Xilinx ZCU111 radio frequency system-on-chip (RFSoC), based on a parallelized overlap-channel polyphase synthesis filter bank and a companion wideband receiving channelizer. This two-octave architecture reads out four independent RF networks, each with 1.024 GHz instantaneous bandwidth and up to 2048 detectors. The polyphase synthesis doubles the baseline channel count and bandwidth, and enables on-the-fly control of individual tone frequency, amplitude and phase, facilitating optimized KID biasing and providing a gateway to tone tracking. These capabilities may also be useful more broadly across Prime-Cam and in similar frequency-division multiplexed (FDM) readout systems. We present the design in DSP simulation, and measurements in RF loopback as well as with two KID test chips, one spanning the full two-octave band. Loopback measurements demonstrate comparable noise performance between the first-generation (Gen1) baseline and Gen2; preliminary on/off-resonance measurements indicate detector-noise-limited operation for the majority of channels; and the digital channel crosstalk is measured and discussed. We report FPGA resource and power utilization and assess scalability toward future large-format KID instruments.
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All authors Ruixuan Xie, Adrian K. Sinclair, James Burgoyne, Maxwell Chapman, Scott Chapman, Steve K. Choi, Anthony I. Huber, Ben Keller, Michael D. Niemack

Thursday 13 August

Instrumentation and Methods for Astrophysics

Performance Analysis of the Asgard/NOTT Nulling Interferometer: Optimizing Observing Modes for High-contrast Detection

J. P. Scott, S. Ertel, T. A. Stuber et al. (+21 more)

We evaluate the performance of three beam-combination schemes, single-Bracewell, asymmetric dual-Bracewell, and symmetric dual-Bracewell, for the forthcoming Asgard/NOTT nulling interferometer at the Very Large Telescope Interferometer. Utilizing the SCIFYsim end-to-end simulator, we assess the instrument's performance by deriving the precision of calibrated null measurements as a function of stellar magnitude and simulating observations of varying hot exozodiacal dust (HEZD) distributions and a hot Jupiter. The study reveals distinct trade-offs for each observing mode. The single-Bracewell mode provides high throughput and preserves spatial information but suffers from poor error suppression. The asymmetric dual-Bracewell mode offers the strongest error suppression for detecting point-like sources, but it inherently suppresses symmetric astrophysical signals such as expected from HEZD. The symmetric dual-Bracewell mode provides a middle ground with modest error suppression while being sensitive to symmetric emission. We conclude that utilizing a combination of all three observing modes provides a robust strategy for detecting HEZD, constraining the structure of its distribution, and identifying false positives from stellar companions.
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All authors J. P. Scott, S. Ertel, T. A. Stuber, D. Defrère, R. Laugier, J. C. Augereau, P. Chingaipe, G. Garreau, X. Haubois, M. Ireland, F. Kirchschlager, S. Kraus, F. Martinache, M-A. Martinod, K. Missiaen, S. Morel, J. Morren, K. Ollmann, P. Priolet, G. Raskin, M. Salman, N. Schuhler, W. Verstraeten, S. Wolf

Instrumentation and Methods for Astrophysics

MORFEO control strategy

Guido Agapito, Lorenzo Busoni, Cédric Plantet et al. (+7 more)

The ESO Extremely Large Telescope (ELT) will offer unprecedented sensitivity and resolution in the near-infrared, marking a new era for ground-based astronomy. Among its key imaging instruments is MORFEO coupled with MICADO. MORFEO (Multi-conjugate adaptive Optics Relay For ELT Observations), formerly known as MAORY, is the largest astronomical adaptive optics system ever designed. It features 12 wavefront sensors and three deformable mirrors, for a total of over 20,000 subapertures and over 6,000 actuators. MORFEO represents one of the greatest upcoming challenges in the field of astronomical adaptive optics. While the design builds upon the heritage of previous AO systems, several architectural choices are entirely new, driven by the unique scale and requirements of this instrument. One of the main challenges is delivering high and uniform wavefront correction across the MICADO field of view. To meet this goal, the MORFEO control strategy adopts a specific approach: sodium laser guide stars are used to sense modes above focus only, since differences in beacon altitude can introduce significant aberrations. Natural guide stars are instead employed to measure and correct for tip, tilt, plate scale variations, and field-averaged focus. In this work, we present the MORFEO control strategy and provide performance estimates across different observing scenarios.
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All authors Guido Agapito, Lorenzo Busoni, Cédric Plantet, Giulia Carlà, Alfio Puglisi, Jean-Pierre Véran, Marco Falotico, Gabriele Umbriaco, Edoardo Redaelli, Paolo Ciliegi

Instrumentation and Methods for Astrophysics

Laser Metrology for Precision Alignment of Transmission Gratings in the REDSoX Soft X-ray Polarimeter

Swati Ravi, Alan Garner, Jill Juneau et al. (+4 more)

The Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX) is a NASA sounding-rocket mission designed to perform the first astrophysical spectropolarimetry in the 0.2-0.4 keV energy band. The instrument uses critical-angle transmission (CAT) gratings to disperse incident X-rays onto laterally graded multilayer (LGML) mirrors, requiring 48 individual gratings to be co-aligned to within 6 arcminutes in yaw, pitch, and roll. To support the systematic assembly of the grating array, we adapted a scanning laser-reflection metrology technique in which normal-reflected, angled-reflected, and diffracted ultraviolet laser beams are measured using three position-sensitive detectors (PSDs). Changes in the measured beam positions are used to reconstruct the local yaw, pitch, and roll of each grating and provide real-time feedback during mechanical adjustment. We demonstrate the system using a prototype miniature grating structure containing two gratings. Following co-alignment, the assembly underwent a flight-level random-vibration test followed by a qualification-level sine sweep. Measurements obtained before and after testing showed that the relative grating orientations were retained to within 1 arcminute, less than 17% of the REDSoX co-alignment tolerance. This work establishes a reproducible and scalable approach to the assembly and verification of large transmission-grating arrays for REDSoX and future X-ray spectroscopic instruments.
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All authors Swati Ravi, Alan Garner, Jill Juneau, F. Elio Angile, Ralf K. Heilmann, Herman L. Marshall, Sarah N.T. Heine