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Physics Astrophysics Instrumentation and Methods for Astrophysics

astro-ph.IM Watch Instrumentation and Methods for Astrophysics

Tuesday 6 October

Instrumentation and Methods for Astrophysics

Optimizing Laguerre-Gaussian Mode Interferometry in Gravitational-Wave Detectors through Modal Degeneracy Breaking

Liu Tao, Eleonora Capocasa and Matteo Barsuglia

Higher-order Laguerre-Gaussian modes can reduce test-mass thermal noise in gravitational-wave interferometers, but their implementation is limited by degeneracy-induced coupling losses in realistic high-finesse cavities. We mitigate these losses by optimizing the mirror curvature to break modal degeneracy. We develop a general framework for designing an axisymmetric corrective test-mass surface profile that lifts the degeneracy of the sixth-order Laguerre-Gaussian subspace while preserving an injected donut-shaped $\mathrm{LG}_{0,6}$ mode. Expanded in a Fourier-Bessel basis, the profile is optimized to maximize the frequency splitting from the nearest unwanted mode while minimizing target-mode loss. For a Virgo-like Fabry-Perot arm cavity, the optimized profile separates the $\mathrm{LG}_{0,6}$ resonance from the nearest same-order resonance, $\mathrm{LG}_{1,4}$, by 2.04% of the free spectral range, reducing unwanted-mode gains below unity at the target-mode resonance and suppressing their resonant enhancement. The profile introduces negligible target-mode loss and improves robustness against astigmatism and realistic mirror surface distortions. Monte Carlo simulations with realistic mirror imperfections yield an average contrast defect of 368 ppm and an average reflected optical loss of 979 ppm, equivalent to a round-trip loss of approximately 3.5 ppm for the modeled cavity. These results substantially improve upon the central anti-reflective mirror mask approach based on selective loss engineering, bringing reflected optical loss within a factor of two of that obtained with the fundamental Gaussian mode under the same simulation conditions. This approach offers a route toward robust donut-shaped Laguerre-Gaussian modes in future precision interferometers with realistic imperfections.
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Instrumentation and Methods for Astrophysics

Very Long Baseline Interferometry with the SKA Observatory

J. F. Radcliffe, J. Yang, Z. Paragi et al. (+131 more)

Very Long Baseline Interferometry (VLBI) is a fundamental technique that combines signals from telescopes separated by thousands of kilometres to obtain some of the highest-resolution images in astronomy. The Square Kilometre Array Observatory (SKAO) will provide sensitive elements to current VLBI arrays, enabling deep VLBI observations (including the first low-frequency VLBI capability in the Southern Hemisphere). This summary chapter outlines the science that the SKAO, when participating in a VLBI array, will achieve (such as AGN physics, explosive transient localisation, Galactic structure, and gravitational waves), and the current understanding of how VLBI with the SKAO will operate. Given that VLBI requires partnerships with other instruments, the chapter concludes with outstanding issues and considerations for the community needed to maximise the scientific return on investment in SKA-VLBI.
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All authors J. F. Radcliffe, J. Yang, Z. Paragi, O. Bayandina, C. Reynolds, C. García-Miró, T. An, M. Abada-Simon, J. N. H. S. Aditya, I. Agudo, T. Akahori, A. Alberdi, S. Anton, P. Atri, A.-K. Baczko, S. Belladitta, E. K. Bempong-Manful, R. Beswick, M. Bhardwaj, E. Bonnassieux, A. Brunthaler, C.-S. Chang, P. Charlot, S. Chen, W. Chen, X. Cheng, A. Chhipa, J. O. Chibueze, I. Cho, J. B. Climent, L. Cui, S. Curiel, F. D'Ammando, J. R. Dawson, A. Deller, H. Ding, R. Dodson, J. Drevon, F. Eppel, S. Frey, M. Garrett, M. Gawroński, J. Geng, S. Giarratana, M. Giroletti, S. Gulyaev, L. I. Gurvits, C. Hao, T. Hirota, A. J. Hedge, H. Hu, H. Imai, P. Jiang, J. de Jong, M. Kadler, B. Karimi, P. Kharb, R. Khatun, J.-Y. Kim, J. Kim, J. Kim, F. Kirsten, H. R. Klöckner, H. Kobayashi, Y. Y. Kovalev, M. Kunert-Bajraszewska, A. Kutkin, H. J. van Langevelde, J. Li, Y. Li, Y. Li, Z. Lin, D. Liu, H. Liu, K. Liu, A. Lobanov, R.-S. Lu, V. Mahatma, B. Marcote, M. Mezcua, J. Moldón, L. K. Morabito, S. E. Motta, S. Murthy, I. Natarajan, A. Njeri, J. Oh, M. Orienti, A. Osetrova, M. Pandey-Pommier, F. Panessa, J. Park, M. Pérez-Torres, L. Petrov, J. C. S. Pierce, C. Phillips, L. Ricci, M. Rioja, H. Ro, J. Röder, E. Ros, M. Rupen, K. L. J. Rygl, R. Santra, S. Silpa, T. Savolainen, G. A. S. Sundaram, P. Shastri, X. Shu, A. Słowikowska, B. W. Sohn, C. Spingola, F. Sweijen, K. Takahashi, R. Timmerman, F. Ubertosi, L. Uscanga, E. Varenius, M. Verkouter, T. Vernstrom, S. Wagner, D. Williams-Baldwin, J. Wongphechauxsorn, X. Wu, M. Xu, Y. Xu, M. K. Y{\i}ld{\i}z, Z. Yan, A. Yang, X. Yang, S. Yao, W. Yu, B. Zhang, P. van Zyl

2610.07743 · 6 Oct · Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366) Report-no:AASKAII/Radcliffe01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopes

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

Discovery of 2 km ultra-fast rotating asteroid in Rubin DP2 catalog via varying Fourier order method

Dmitrii E. Vavilov, Siegfried Eggl and Sarah Greenstreet

Time-resolved photometry from large surveys can yield rotation periods for huge numbers of asteroids, but only if the reliability of each period is assessed automatically, since sparse and irregular sampling produces many false periodogram minima. We present an improved method that determines asteroid rotation periods with a Fourier series whose order is chosen for each object individually. This has substantial advantages over lower order methods, especially when unique solutions for the spin period cannot be reliably determined. In such cases, the method reports the set of alternative periods together with the corresponding probability estimates. We apply the improved spin period determination method to the NSF-DOE Vera C. Rubin Observatory Data Preview 2 (DP2) catalog of solar system objects and determine reliable periods for a large sample of asteroids. Among them we find 66 super-fast rotators, which spin faster than the classical 2.2 h spin barrier. Two of them are remarkable: asteroids 491384 and 566130 are both larger than 2 km, yet they complete a full rotation in only about five minutes. To survive such a fast spin, they must have significant internal cohesion. At a diameter of about 2.5 km, asteroid 491384 is the largest ultra-fast rotator known so far.
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Monday 5 October

Instrumentation and Methods for Astrophysics

The First Decade of Breakthrough Listen

David H.E. MacMahon and Daniel J Czech

Breakthrough Listen (BL), launched in July 2015 with a 10-year, \$100M commitment from the Breakthrough Prize Foundation, is the most comprehensive search for technosignatures ever conducted. This paper reviews the program's first decade from the facilities and instrumentation perspective: the digital backends and data recorders, the signal-processing pipelines, the data archive, and the observatory partnerships that made the science possible. We organize the decade into three architectural eras. In Generation 1 (2016--2019), BL deployed packetized raw-voltage wideband recorders on the 100-m Green Bank Telescope and the 64-m Parkes telescope, enabling targeted surveys of thousands of nearby stars across $\sim$0.7--8 GHz. In a network-expansion phase (2020--2023), BL extended its instrumentation to partner facilities including the Sardinia Radio Telescope and international LOFAR stations, and developed verification frameworks that proved essential when the program's highest-profile signal candidates emerged. Since 2023, BL has operated in a fully commensal era: Ethernet-based, commodity-GPU backends riding on routine observatory operations: COSMIC at the Karl G. Jansky VLA, a revived Allen Telescope Array with deployed real-time deep-learning pipelines, and an autonomous multi-beam commensal survey at MeerKAT (BLUSE; $>$1.2 million pointings since mid-2022). Over the decade, capturing data at ever higher rates forced a systematic approach to compression and archiving; the storage estate grew to $\sim$42 PB of capacity ($\sim$31 PB in use) across seven systems on four continents by March 2026. We conclude with engineering lessons (commodity hardware over bespoke hardware, open data as a first-class requirement, commensal science as backend validation, and verification frameworks built before they are needed) and with the outlook for SKA-era commensal technosignature science.
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2610.07482 · 5 Oct · Keynote paper (Rudolf Pesek Lecture), 55th IAA Symposium on the Search for Extraterrestrial Intelligence (SETI), Session A4.1 "SETI Science and Technology". Presented at the 77th International Astronautical Congress (IAC 2026), Antalya, Türkiye, 5-9 Oct 2026; to appear in the IAC proceedings. 11 pages, 2 figures, 2 tables

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

Adaptive proposals for nonparametric equation-of-state inference with RIFT: iterative Gaussian-process refinement in a compressed sequence representation

R. O'Shaughnessy and Z. Zhu

Nonparametric equation-of-state (EOS) inference evaluates the likelihood on a finite ensemble drawn from a prescribed functional prior. Reweighting that ensemble suffices for the binary neutron stars detected so far, and loses effective sample size only once the likelihood concentrates — which needs third-generation catalogues, or extra electromagnetic and nuclear-theory information folded into the same target. We develop and validate an adaptive-proposal procedure that leaves the base prior fixed: data-informed generations are combined by multiple importance sampling and, where that degenerates at large catalogue size, by a calibrated Gaussian projection. We implement it in two representations — a compressed principal-component parametrization of the neutron-star sequence, whose draws need no stellar-structure solve, and a sound-speed parametrization with a differentiable Tolman–Oppenheimer–Volkoff solver — both on a constrained low-density-to-pQCD bridge. Because that anchor, and not the bridge, fixes the low-density prior, we rebuild the ensemble with a crust-plus-chiral-EFT anchor in place of the wide nuclear metamodel: the maximum-mass prior is unmoved, the radius gains a hard prior ceiling at the measured NICER value. GW170817 with the specified NICER and radio factors gives the calibration-conditional $R(1.4\,M_\odot)=11.7\pm0.4$km; in a synthetic $1000$-event catalogue it reproduces the mean fixed-prior $\Lambda(1.4\,M_\odot)$ to $0.4$%, $1.5$ times wider, as the fixed archive's effective sample size falls from $\sim\!470$ to 22.
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Instrumentation and Methods for Astrophysics

SPECULATE: A synthetic spectral library, emulator and fitting package for accretion disc winds – Infrastructure and application to CVs

Austen G. W. Wallis, Christian Knigge, James H. Matthews et al. (+6 more)

Disc winds are critical components of accreting astrophysical systems and their observations can yield a wide variety of spectral line profiles. Yet, inferring disc wind parameters remains challenging: the underlying parameter spaces are high-dimensional and degenerate, while the radiative-transfer simulations are imperfect and computationally expensive. This paper tackles bridging this gap. Here, we present 'Speculate', an open-source framework for rapidly emulating and fitting observations with synthetic accretion disc wind spectra, generated from the Monte Carlo radiative-transfer code Sirocco. Speculate includes the release of our cataclysmic variable (CV) training data, a library of 88,680 sparsely gridded Sirocco spectra spanning the ultraviolet and optical wave bands, a suite of pre-trained emulators, and its interactive Marimo user interface. Speculate compresses spectral grids using principal component analysis and then provides three approaches to interpolate the resulting latent representation: with a regular-grid interpolation, a neural network, or a Gaussian process. All three architectures enable Speculate to generate a Sirocco spectrum between $1-40\,\mathrm{ms}$, thereby enabling efficient inference. The first two support rapid $\chi^2$ optimisation. The Gaussian process utilises a Bayesian inference engine coupled with a covariance-aware, flexible likelihood function, adapted and accelerated from the Starfish framework. This function helps absorb correlated discrepancies between simulations and data. Tests show all architectures reproduce unseen Sirocco spectra with broadly comparable accuracy and can recover their physical parameters. Subsequently, we apply Speculate to 5 representative nova-like CV spectra, reproducing several observed line features while also exposing mismatches where the current model grid omits relevant physics.
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All authors Austen G. W. Wallis, Christian Knigge, James H. Matthews, Knox S. Long, Madeleine-Mai Ward, Stuart A. Sim, Adam B. Hill, Amin Mosallanezhad, Nicolas Scepi

Instrumentation and Methods for Astrophysics

A Classifier Framework for ALMA Bandpass Calibration Anomalies

Ci Xue, Brian S. Mason, Gazi A. Rakib et al. (+8 more)

Bandpass calibration corrects instrumental responses across observing frequencies in interferometric radio observations, so the measured calibration solutions inherently contain spectral variation that varies with instrumental configurations and noise conditions. However, some signals contain anomalies, which if not caught can lead to poorly constructed science products. Observatory pipelines often use scalar metrics with individual, linear decision boundaries. Constructing a simple parametric model can be effective for observations with a relatively limited parameter space, but it becomes progressively less accurate as the parameter space expands. To address this challenge, we design a machine learning framework that treats anomaly identification as a supervised classification task and learns complex, non-linear decision boundaries across multiple features optimized for predictive performance. In particular, we use an XGBoost model that sits on top of several features and specialized scan statistic models to classify anomalies in amplitude solutions from ALMA bandpass calibrations. Trained on an extensive, quality-controlled ALMA dataset, this classifier framework leverages features derived from kernel-based scan statistics to characterize deviating spectral intervals, while remaining extensible to additional feature sets. This method substantially reduces misclassifications in bandpass anomaly detection compared to the current pipeline heuristics. By improving flagging decisions and calibration quality, this classifier framework provides a scalable supplement for observatory operations and is generalizable to next-generation radio facilities.
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All authors Ci Xue, Brian S. Mason, Gazi A. Rakib, Tristan Ashton, Jeff M. Phillips, Ignacio Toledo, Ryan A. Loomis, Ilsang Yoon, John E. Hibbard, Omkar Bait, Eric J. Murphy

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

Chana: A GPU-Accelerated AMR GRRMHD Code

Tianshu Wang

This paper presents Chana, a GPU-accelerated, block-structured adaptive-mesh code for general relativistic magnetohydrodynamics, multigroup M1 neutrino transport, and dynamical spacetime evolution using the Z4c formulation. Each physical module uses independently selected spatial discretizations and ghost-zone widths to balance accuracy and computational cost. Stiff radiation-matter interactions are treated implicitly, with Jacobians calculated analytically from the chain-rules. The code is written in C++20 and it uses MPI and Kokkos 5 for distributed-memory and performance-portable parallelism. The code is validated through a number of GRMHD, radiation transport, and dynamic spacetime tests. For a representative core-collapse supernova configuration with three neutrino species and 12 energy groups per species, the code achieves approximately $1.1 \times 10^6$ cell updates per GPU second on NVIDIA A100 GPUs using four-stage RK4 integration. Weak-scaling efficiency remains above 85% up to 256 GPUs on Perlmutter.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP

Enhancing the Interpretability of Radial Velocity Analysis Using Leave-one-out Cross-validation

Matthew C. Nixon, Ritvik Basant, Rafael Luque et al. (+2 more)

Radial velocity (RV) observations are reaching increasingly high precision, enabling the targeting of low-amplitude signals. Assessing results obtained at the limits of our capabilities requires understanding the relationship between data, models and inference. Leave-one-out cross-validation (LOO-CV) has become an increasingly popular tool for interpretable model criticism in astronomical data analysis. In this work, we demonstrate how LOO-CV can provide insight into the RV analysis of exoplanetary systems through three case studies. We first investigate the anomalously high mass of HD 119130 b inferred from CARMENES RVs, later revised significantly downward after follow-up observations with other instruments. We show that this high mass was strongly driven by two individual measurements, whose removal significantly reduces the tension between data sets. Next, we use LOO-CV as a model selection tool for the GJ 4276 system. Here, LOO-CV prefers an eccentric single-planet model over a two-planet model, and identifies the orbital phases at which follow-up observations would best discriminate between them. Finally, we extend LOO-CV to models with correlated noise, applying it to the GJ 357 system, whose RVs are modeled with a Gaussian process. We find no predictive support for a fourth planetary signal that is moderately favored by the Bayesian evidence, strengthening the interpretation of a three-planet architecture previously reported in the literature. We provide practical guidance for implementing LOO-CV in RV analysis, together with an online tutorial. Such methods will become ever more important as future RV surveys push the limits of planet detection and characterization.
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All authors Matthew C. Nixon, Ritvik Basant, Rafael Luque, Luis Welbanks, Pierrot Lamontagne

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

Detecting multiple planets in Gaia data using Bayesian model selection

Emmanuel J. Greenfield and James E. Owen

Gaia will soon provide a census of cold giant planets. However, an astrometric signal contains the superimposed reflex motion of all companions, so planetary signals cannot be treated individually. We therefore investigate Gaia's planet-detection capabilities for 1-planet and 2-planet systems, with special attention to systems near 2:1 mean-motion resonance. Gaia can detect 2-planet systems, although the lower-S/N planet requires a higher S/N threshold, especially when the outer planet is more massive and near 2:1 commensurability. When fitting a 1-planet model to a circular 2-planet resonant system, the resulting fit shows biases in eccentricity (up to e = 0.8), mass (up to 100%), and inclination (up to 50 deg). The bias is maximised when the planets' astrometric signatures are similar, since the combined orbital signal deviates most from a single Keplerian orbit. Many of these systems can be identified as having 2 planets using Bayesian model selection. Still, in some cases the second planet is hidden and undetectable due to its S/N, leading to these biases for the outer planet's orbital parameters. When the outer planet is roughly over three times as massive as the inner planet, orbital approximations allow us to recover the astrometric resoeccentric degeneracy from the bias. When the planets are in dynamical resonance, apsidal precession observed over a long enough baseline (e.g. DR5) can contribute to breaking the degeneracy at short orbital periods. Overall, these biases might significantly affect constraints on planet formation, migration, and evolution models from Gaia population-wide demographics.
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Instrumentation and Methods for Astrophysics

Optimal Photon Counting with Fast, Low Noise Astronomical Imagers

Jack T. Dinsmore, Christopher Layden, Roger W. Romani et al. (+9 more)

Measuring rapid astrophysical phenomena requires many short exposures, which suffer from repeated read noise. A variety of recent technologies are achieving sub-electron read noise, which enable rapid time-domain studies of faint sources. These data can be analyzed with traditional methods, but the ability to resolve individual electrons enables a new class of more precise, photon-counting techniques. We present a photon-counting method for sub-electron read noise detectors which delivers optimal statistical uncertainties. We focus on Complementary Metal-Oxide-Semiconductor (CMOS) detectors and demonstrate our method on optical data collected by CMOS instrument "proto-Lightspeed," recently commissioned at the Magellan Clay telescope at Las Campanas Observatory. The method can be applied to non-CMOS detectors as well, such as skipper CCDs and linear-mode avalanche photodiodes. The method substantially improves analysis of faint sources, increasing signal to noise ratios by up to $\sim 130\%$, which would require 5.3$\times$ more observing time to accomplish with data alone. As an example we show detections of four normal rotation-powered pulsars with confirmed optical pulses, achieved in under two hours of total exposure. We provide the lightspeedpy pipeline for reducing proto-Lightspeed data with both photon counting and standard techniques.
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All authors Jack T. Dinsmore, Christopher Layden, Roger W. Romani, Vera L. Berger, Kevin B. Burdge, Geoffrey Mo, Deepto Chakrabarty, Emma T. Chickles, Gabor Furesz, Juliana García-Mejía, Dave Osip, Jack Piotrowski

Instrumentation and Methods for Astrophysics

Armillary: A Label-Free Coordinate System for Stellar Spectra

Yuan-Sen Ting and Serat Saad

A stellar spectrum is determined by a few parameters, so a set of spectra lies on a low-dimensional manifold with those parameters as its coordinates. We introduce Armillary, which generalises the Sequencer of Baron and Ménard from an ordering to multidimensional coordinates, constructed from the spectra alone. Two stars are compared by the Wasserstein distance between their signed absorption profiles. Shortest paths through a nearest-neighbour graph measure distance along the manifold and give the coordinates, and the same graph transfers the labels of a few stars to all the others. The coordinates are more nearly linear in $T_{\rm eff}$ and $\log g$ than principal components, t-SNE, UMAP or an autoencoder. The label transfer, without deep learning, is more precise than the first three and comparable to the autoencoder. On 202,932 APOGEE DR17 stars, an illustrative draw of 32 training stars recovers the ASPCAP $T_{\rm eff}$, $\log g$ and [M/H] of held-out dwarfs and giants, with $1\sigma$ errors of 100 K, 0.18 and 0.083 dex. Resolving the two $\alpha$ sequences of the disc in [$\alpha$/M] for giants takes 128 training stars, and with 2048 the four errors improve to 33 K, 0.06, 0.026 and 0.022 dex. On 104,799 DESI stars, 32 training labels from APOGEE recover the stellar parameters to 129 K, 0.25 and 0.203 dex, even for spectra degraded to a signal-to-noise of about 20. At a signal-to-noise of about 100, 2048 training labels resolve the two $\alpha$ sequences of the disc in DESI giants, with errors against APOGEE of 51 K, 0.07, 0.047 and 0.026 dex. The code is public at https://github.com/tingyuansen/armillary.
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Instrumentation and Methods for Astrophysics · Cross-listed from hep-ph

Lunar radio emission from dark photon dark matter

Ariel Arza

The dielectric surface of the Moon provides an efficient interface for the conversion of dark matter dark photons into radio waves. This work explores a novel detection strategy that aims to capture this radio emission using standard radio telescope antennas. Detailed sensitivity projections are presented that demonstrate the power of this technique. It is found that both current and future radio observatories, including large arrays such as the Atacama Large Millimeter/submillimeter Array (ALMA) and the Square Kilometer Array (SKA), as well as large single dishes like the Five-hundred-meter Aperture Spherical Telescope (FAST) and the Green Bank Telescope (GBT), can explore a substantial and previously inaccessible parameter space for these dark matter candidates.
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Instrumentation and Methods for Astrophysics

A Technosignature Survey Of The Anti-Solar Point: The SETI Institute's Largest-Ever Campaign With The Allen Telescope Array

Isabel Gerrard and Sofia Z. Sheikh

The ATA-ASP campaign is a radio technosignature survey of the Anti-Solar Point as a "Schelling point", using the Allen Telescope Array (ATA) in the Search for Extraterrestrial Intelligence (SETI). We borrow from game theory the concept of Schelling points to hypothesize spacetime coordinates where both we and an extraterrestrial agent might send and search for a signal. From the perspective opposite the Sun, an extraterrestrial agent could detect Earth transiting within the habitable zone, thus this Anti-Solar Point (ASP) poses a shared and salient Schelling point. This campaign uses the ATA, tuned to 2356-3700 MHz, to observe Earth's ecliptic, and searches for sky-localized, narrowband, Doppler-drifting signals. Analysis is conducted using the Allen Telescope Survey Agnostic Technosignature pipeline (ATSAT), which integrates software packages bliss and NBeamAnalysis with radio frequency interference removal and outputs spectrograms. Narrowband signals and their Doppler-drift rates indicate technological and distant origin, while comparing beamformed beams localizes signals to the ASP. The plots are visually inspected and cataloged into six signal morphologies to distinguish potential signals-of-interest and radio frequency interference. To date, the survey has observed approximately 12% of the projected coordinate coverage over 126 observations; 67% of sessions have been analyzed, producing more than 11,000 plots, all of which have been inspected and 75% labeled. 25 of these labeled spectrograms contain narrowband drifting signals sky-localized to the ASP, and the 10 corresponding coordinates will be re-observed. Although SETI literature has long proposed searching for beacons at the ASP, this campaign provides the first observational coverage. Observing Earth's ecliptic will require a multi-year effort and produce over 11 petabytes of data, making it the ATA's largest survey ever.
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Instrumentation and Methods for Astrophysics

XuYi Interferometer Observation Simulator

M. Hadjara, T. Xu, Y. Sun et al. (+21 more)

The XuYi Interferometer is the first Chinese long-baseline optical interferometer currently under development by the National Institute of Astronomical Optics and Technology (NIAOT) of the Chinese Academy of Sciences. In preparation for future scientific operations, we developed the XuYi Interferometer Observation Simulator (XIOS), a lightweight MATLAB-based software package designed to assist observers in planning interferometric observations. The simulator combines target observability calculations, interferometric baseline geometry, delay-line constraints, (u,v)-coverage prediction, and visibility estimation into a single graphical user interface. It incorporates astronomical routines from the MAAT toolbox and adopts visualization concepts inspired by ASPRO2. The software allows users to evaluate observing opportunities, predict interferometric performances, and generate realistic observing configurations before telescope operations. We present the architecture of the simulator, its principal modules, and representative simulation results obtained for the current three-telescope XuYi interferometric configuration operating in the near-infrared H band.
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All authors M. Hadjara, T. Xu, Y. Sun, W. Wei, C. Liu, H. Zhang, J. Huang, C. Zeng, J. Yuan, J. Perdigon, A. Boskri, S. Lagarde, R. Petrov, R. Ligi, B. Lopez, F. Millour, J. Dejonghe, F. Baron, J. Wang, X. Wu, H. Zhao, Y. Hou, Z. Hua, X. Cui

Instrumentation and Methods for Astrophysics

BRICS Southern Observatory (BRICS-SO) Project: Invitation to African countries to invest in Chile

Massinissa Hadjara, Amokrane Berdja, Swagat R. Das et al. (+6 more)

Recently, the BRICS countries created a promising astronomy consortium (https://www.bricsastronomy.org/), which was joined last year by some emerging countries, including two African countries, namely: Egypt and Ethiopia. Certainly, other African countries will join BRICS+ in the years to come. Thus, by pooling their efforts, emerging countries (BRICS+) are sure to quickly catch up with their technological delay in the field of astronomy, particularly through ambitious and large-scale projects. Chile, due to the exceptional climatic conditions of its North, is recognized as the world capital of astronomy where all the largest consortia have settled there and applied all their know-how. The official launch of BRICS (and then its expansion to other countries; BRICS+) is welcomed as an excellent opportunity to think big in the development of astronomy. China has shown great determination in being the first country in the South to establish astronomical facilities in Chile, thus opening a possible opportunity for BRICS+ astronomers. Ambitious astronomical instrumentation is essential for the future of Astronomy and Astrophysics. Access to existing facilities is becoming more and more difficult because of saturation. Existing programs like the VLT-I/ELT and their instruments necessitated decades of collaboration between international institutions. It is therefore necessary for the BRICS+ astronomical community to collaborate together on ambitious projects without wasting time in order to offer a new pole with new opportunities for the researchers. This pole (BRICS-SO), in addition to attracting highly qualified people, will also help train new generations in all our countries, and encourage exchanges and collaborations.
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All authors Massinissa Hadjara, Amokrane Berdja, Swagat R. Das, Elisson S. G. de Almeida, Slobodan Jankov, Vladmir Lukin, Abdelkarim Boskri, Zouhair Benkhaldoun, Jinghui Zheng

Instrumentation and Methods for Astrophysics

Towards a GPU-Accelerated Real-Time Imaging Pipeline for SETI at the Allen Telescope Array

Karen I. Perez, Joe S. Bright, Vishal Gajjar et al. (+1 more)

Traditional technosignature and transient searches commonly operate on beamformed time–frequency products. Interferometric imaging adds spatial context and allows time-domain searches to be performed across many image pixels simultaneously. We report the development and testing of a GPU-accelerated interferometric imaging and image-domain dispersion-measure (DM) search pipeline for Allen Telescope Array (ATA) post-correlation UVH5 visibility data, integrated with the CyberEther streaming framework to replay recorded visibility data and work toward real-time operation. The pipeline forms Stokes-I dirty images from correlated visibilities, incorporates Inter-Quartile Range Mitigation (IQRM) flags into the imaging weights, images 48 frequency subbands spanning 287.5\,MHz, subtracts a temporal mean over the full observation from each subband and pixel, applies IQRM-informed subband masking, and performs a blind trial-DM search using a short-history image ring buffer. On a controlled 10-minute three-spectral-window test observation containing a periodic dispersed pulsed injection (DM\,$\approx$\,150\,pc\,cm$^{-3}$), the pipeline recovers the injected source at the phase centre with a best-fit DM\,$=$\,150\,pc\,cm$^{-3}$, with individual dispersed pulses reaching a median image-plane S/N of $\approx$52. When integrated into CyberEther, the core processing requires approximately 63\,ms per integration compared with a native integration time of approximately 98\,ms, demonstrating that the core science-processing operations can be completed within the available integration time. The present implementation operates on recorded visibility data and relies on a temporal mean and MAD noise estimate precomputed over the full observation. For live operation, these quantities will instead need to be estimated from data available up to the current integration.
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All authors Karen I. Perez, Joe S. Bright, Vishal Gajjar, Luigi F. Cruz

Instrumentation and Methods for Astrophysics

Sub 35-ps Single-Photon Stellar Intensity Interferometry of Vega

Verena G. Leopold, Sebastian Karl, Stefan Richter et al. (+7 more)

SII enables measurements of stellar photospheres by correlating intensity fluctuations, offering a robust alternative to amplitude-based techniques. With the advent of modern single-photon counting detectors, this method has re-emerged as a powerful technique in stellar interferometry exploiting their ultra-high timing resolution. We determine the stellar diameter of Vega at 405 nm using spatial intensity correlations measured at the C2PU facility, part of the Observatoire de la Cote d'Azur. We employed a setup identical to Leopold et al. (2025). The two campaigns in April and August 2024 used hybrid photodetectors (HPDs; 22.7 ps resolution) and new PhotonPix detectors (34.8 ps resolution). A Photonscore TDC integrated photon arrival times and IRIG-B timestamps for synchronization. Our analysis consisted of calculating auto- and cross-correlation histograms from the recorded data, which were then normalized and corrected for optical path differences. The temporal auto-correlations yield a consistent coherence time of 0.21 ps. This confirms the effectiveness of the PhotonPix detectors despite a slight degradation in timing resolution relative to the HPDs. Combining the data from the two measurement campaigns yields a uniform disk diameter of Vega of 2.97 +/- 0.23 mas. This agrees with the 3.047 mas diameter predicted by the stellar atmosphere model at our observation wavelength, validating our technique and the new PhotonPix detectors for precision SII at sub-35 ps resolution. The integration of advanced single-photon detectors like the PhotonPix into existing IACT SII instruments promises substantial enhancements in signal-to-noise ratio and observational capabilities, particularly with CTA LSTs. Although challenges such as night sky background saturation and precise positioning and guiding remain, SII observations at apparent magnitudes up to 7.8 are within reach.
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All authors Verena G. Leopold, Sebastian Karl, Stefan Richter, Jean-Pierre Rivet, Yury Prokazov, Evgeny Turbin, Gennady Sintotskiy, Iurii Datii, Jason Aufdenberg, Joachim von Zanthier

Instrumentation and Methods for Astrophysics

Design and development of the PRIMAger instrument for PRIMA

Anne Costille, Fabrice Madec, Johan Floriot et al. (+11 more)

PRIMA (PRobe far-Infrared Mission for Astrophysics) is an infrared space observatory designed to operate over the next decade. Equipped with a 1.8 m telescope actively cooled to 4.5 K, the project is currently in the concept study phase as part of the NASA Probe Explorers program. PRIMA will carry two instruments: FIRESS and PRIMAger. PRIMAger will offer two observation modes: hyperspectral imaging and polarimetric imaging. Both channels will use ultra-sensitive kinetic inductance detector (KID) arrays, covering wavelengths from mid-infrared to far-infrared. A European consortium will develop the cold unit of the PRIMAger instrument while the Readout Electronics and Continuous Adiabatic Demagnetization Refrigerator (CADR) will be provided by Goddard Space Flight Center (GSFC) and shared between the 2 instruments. The hyperspectral mode will cover the 24-84 $\mu$m range with a spectral resolution of R $\ge$ 8, ensured by a linear variable filter placed in front of the detector. The polarimetric mode will provide polarimetric imaging in four broad bands from 92 to 235 $\mu$m, using KIDs with three polarization orientations. The main structure of the instrument is the optomechanical assembly, cooled at 1K. It supports at first the two focal plane array assemblies incorporating 0.125K detector stages. In addition, the main structure is providing the interfaces for the 0.125K thermal link, the readout cables and the filters. This paper presents the technical requirements and expected performance of the instrument, as well as the associated design of the sub-systems ensuring compliance. A major challenge will be in-flight performance verification. We will also detail the development strategy, including the planned verification and test program.
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All authors Anne Costille, Fabrice Madec, Johan Floriot, Tony Pamplona, Thomas Prouvé, Laure Ciesla, Marc Sauvage, Willem Jellema, Lorenza Ferrari, Jochem Baselmans, Florent Canourgues, Renaud Goullioud, Carole Tucker, C. Darren Dowell

Instrumentation and Methods for Astrophysics · Cross-listed from eess.SY

Fast and Stable Nonlinear Emulation of TIEGCM Using an Autoregressive SINDy Framework

Daniele Sicoli, Sriram Narayanan and Piyush M. Mehta

The ever-growing number of satellites and resident space objects in low Earth orbit keeps increasing the risk of collision between these objects. To mitigate this risk, the development of new space situational awareness tools and a new generation of probabilistic emulators of the thermosphere is increasingly felt by the community of operators and scientists. We previously built a Reduced Order Probabilistic Emulator based on 3 steps: dimensionality reduction, dynamic modeling, and uncertainty quantification. Here we further develop the dynamic modeling side within ROPE using a class of stable and autoregressive nonlinear models inspired by SINDy, a framework for the identification of the nonlinear dynamics. We use this framework, which we call SINDy-AR, to emulate the thermospheric density simulated by TIEGCM. This is also the first time a SINDy-AR framework is applied to such a high dimensional system as the thermospheric emulation because of its complexity. The dynamical emulators are selected on stability and accuracy criteria, so that they can be relied on in operations and space situational awareness applications. Building surrogate models with SINDy-AR can show dynamical differences between the learned emulations. The state-dependent structure of the TIEGCM emulation shows compatibility with the presence of terdiurnal, 27-day linked to solar rotation, semiannual, and annual tidal waves. The execution speedup of the whole SINDy-AR pipeline with respect to TIEGCM 2.0 is about 90,000 times, which makes the new framework capable of being deployed on board a satellite given the low computational constraints it would be subjected to.
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Instrumentation and Methods for Astrophysics

Technological maturation of a Gigapixels Astrometry instrument for the Habitable World Observatory.

Florence Ardellier-Desages, Jerôme Amiaux, Jérôme Bobin et al. (+12 more)

This paper presents the development strategy for HWO-AGATE (Accurate Guiding and Astrometry Targeting Exoearths), a high-precision relative astrometry instrument concept designed for the future Habitable Worlds Observatory (HWO). The instrument is based on a gigapixel-class focal plane that incorporates the new generation of large-format GigaPyx CMOS sensors developed by Pyxalis. The proposed architecture relies on four 220-megapixel sensors assembled into a focal plane array and coupled with a dedicated calibration system to achieve the astrometric precision required for exoplanet detection and characterization. Preliminary study identified three major technological challenges. First, the performance of the 220-MP detectors must be validated against HWO's astrometric requirements. Second, the development of space-qualified packaging and integration solutions is required for a multi-sensor focal plane, while addressing the electrical and thermal constraints associated with the fast readout of large-format CMOS detectors. Third, an onboard calibration data-processing architecture must be implemented to reduce the raw data volume by approximately two orders of magnitude, enabling efficient operation within spacecraft resource limits. To address these challenges, we propose a comprehensive technology maturation program based on the construction of a representative end-to-end detection chain. The demonstration setup will include a partial focal plane equipped with 220-MP sensors, front-end electronics, a dedicated processing unit, and the calibration subsystem. The objective is to demonstrate compliance with HWO-AGATE requirements and to raise the maturity of large-format CMOS detector technology to Technology Readiness Level 5 (TRL 5). Detector validation and space-qualified packaging activities are already supported through institutional funding and the French national PEPR ORIGINS program in the RETINA (Researching Exoplanets Through Imaging for Narrow-angle Astrometry) project.
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All authors Florence Ardellier-Desages, Jerôme Amiaux, Jérôme Bobin, Stéphane Chevobbe, Eric Doumayrou, Pierre-Antoine Frugier, Pierre-Olivier Lagage, Manon Lizzana, Fabien Malbet, Jerôme Martignac, Julien Michelot, Fabrice Pancher, Pichon Thibault, Samuel Ronayette, Hugo Rousset

Instrumentation and Methods for Astrophysics

Not just a phase: detecting nanohertz gravitational waves from phase alone

Kathrin Grunthal, Eric Thrane, Rutger van Haasteren et al. (+2 more)

Unambiguously detecting a gravitational-wave background (GWB) in pulsar-timing data requires a robust detection statistic. The pulsar timing community currently relies heavily on the cross-correlation-based "optimal statistic." Its design was motivated to avoid false-positive detections from unmodeled pulsar red noise. However, recent work by van Haasteren (2025) suggests that the optimal statistic is not, in fact, optimal. Moreover, the optimal statistic is still susceptible to false positives from misspecified noise. To guard against this, analysts employ quasi-resampling methods such as phase shifts, in which complex phases are randomly assigned to each pulsar strain measurement, thereby destroying any gravitational-wave-induced correlations. Inspired by the concept of phase shifts, we introduce a formalism in which the GWB is measured entirely from phase measurements. We argue that this approach is robust against false positive detections without the need for ad hoc quasi-resampling methods. We demonstrate the feasibility of this formalism by measuring the amplitude and spectral index of a simulated GWB, injected to a simplified mock representation of a pulsar timing array data set. For this example, we use simulation-based-inference and model the phase-based likelihood using a neural circular spline flow. We show that it is possible to adequately recover the spectral parameters of the gravitational wave background signal using the phase-based likelihood. By comparing our results to ones obtained with the optimal statistic, we show how much resolving power comes from amplitude versus phase.
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All authors Kathrin Grunthal, Eric Thrane, Rutger van Haasteren, David J. Champion, Michael Kramer

Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det

Investigating Optical Coupling Material Candidates in NaI(Tl) Detectors for the SABRE-North Dark Matter Experiment

Chemseddine Ananna, Gabriella Cataldi, Davide D'Angelo et al. (+21 more)

Direct dark matter detection with NaI(Tl) scintillators requires ultra-low-background materials. Silicone optical pads can couple NaI(Tl) crystals to photomultiplier tubes (PMTs) if they provide adequate optical transmission and radiopurity. We characterize four candidate materials for the SABRE-North experiment: commercial EJ-560, used as a reference, and three materials produced at the University of Salento (SYLGARD 184, EGel 3002 A/B, and a hybrid formulation) using different catalyst ratios and curing conditions, yielding ten samples in total. Optical transmittance was measured from 310 to 850 nm by UV/Vis/NIR spectrophotometry. Radiopurity was assessed at the STELLA facility at LNGS using high-purity germanium (HPGe) $\gamma$-ray spectrometry and, for EJ-560, high-resolution ICP-MS. At the 410 nm NaI(Tl) emission peak, EJ-560 shows an absorbance coefficient of $0.064\pm0.017$ mm$^{-1}$. The best locally produced samples reach $0.097\pm0.015$ and $0.093\pm0.014$ mm$^{-1}$ for SYLGARD 184 with a 10:2 base-to-catalyst ratio cured at room temperature and at $40^\circ$C, respectively, $0.125\pm0.015$ mm$^{-1}$ for EGel 3002 with a 2B:A ratio cured at $40^\circ$C, and $0.106\pm0.014$ mm$^{-1}$ for the hybrid 10:1 EGel A:CataSYL formulation cured at room temperature. EJ-560 exhibits detectable $^{232}$Th-chain activity at about 1.8 mBq/kg and the highest $^{40}$K activity, $(120\pm20)$ mBq/kg. The locally produced materials show no detectable Th-chain contamination but exhibit $^{226}$Ra activities of about 2.3 mBq/kg and lower $^{40}$K levels. No single material is optimal across all criteria. Additional ICP-MS screening, HPGe measurements of cured pads, and direct NaI(Tl)-PMT light-yield tests are required for a conclusive SABRE-North material selection.
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All authors Chemseddine Ananna, Gabriella Cataldi, Davide D'Angelo, Giulia D'Imperio, Maria Luisa De Giorgi, Giuseppe Di Carlo, Attilio Di Giacinto, Marcella Diemoz, Aldo Ianni, Sana Gul Khattak, Edoardo Martinenghi, Alessandro Miccoli, Marcin Misiaszek, Daniele Montanino, Valerio Pettinacci, Lidio Pietrofaccia, Shahram Rahatlou, Krzysztof Szczepaniec, Claudia Tomei, Valerio Toso, Chiara Vignoli, Samina Zuhra, Francesco Ferella, Stefano Nisi

Sunday 4 October

Instrumentation and Methods for Astrophysics · Cross-listed from cs.AI

A Framework for Automated Multi-Source Satellite Data Analytics and LLM-Based Report Generation

Hind Yousif Alhammadi and Isam Mashhour Al Jawarneh

This paper presents the workflow for building an automated ArcGIS Pro tool using ArcPy to extract the Land Surface Temperature (LST) from Landsat 7, 8 and 9 datasets. The tool eliminates the need for manual band selection and repetitive raster computations by automating the multi-step workflow of radiometric calibration, NDVI-based emissivity correction, and thermal conversion. In addition to supporting batch and single-scene processing, the tool has an optional Large Language Model (LLM) for statistical result interpretation and reporting. Depending on batch size, the tool reduced the processing time from around 11-58 minutes when done manually to around 4-11 minutes using the tool. We tested the tool with data from Ras Al Khaimah (RAK) in the UAE, and the LST obtained for Ras Al Khaimah ranged from approximately 25C to 50C, demonstrating an accurate LST mapping compatible with the weather conditions of RAK. In summary, our tool reduces human errors and improves processing accuracy and efficiency for thermal and environmental remote sensing applications, in addition to providing an interactive LLM-based interface for result interpretation.
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Instrumentation and Methods for Astrophysics

Grid Optimization for Wide Field Modulation Collimators

Steven E. Boggs

Wide-field localization of transient sources such as gamma-ray bursts (GRBs) places new demands on the grid design of modulation collimators, whose usable field of view (FOV) is normally limited by self-vignetting. A grid slat thick enough to be opaque at the energies of interest also clips off-axis rays, shrinking the effective slit width and ultimately defining the FOV itself. Historical bigrid or rotating-modulation-collimator (RMC) designs have been designed with this trade-off as an unavoidable consequence of geometric optics. We explore whether the cross-sectional shape of the grid slats can be optimized for wide FOV applications. We derive a general transmission-function framework for a bigrid pair in terms of an effective slit width that depends on slat geometry and use it to compare four slat cross sections: the conventional rectangular slat, an idealized diamond profile, a hexagonal profile that approximates photochemical etching, and the circular wire grids of early X-ray astronomy. We show that for the same bigrid pitch and thickness, a diamond profile extends the FOV and eliminates clipping throughout most of the field. We also demonstrate that a hexagonal profile achievable with standard tungsten etching factors captures many of the benefits of the idealized diamond profile. Extending the analysis to the four-phase demodulation, we show that slat shape directly sets the extent of the resulting phase-space blind spots, and that the diamond profile removes them entirely across a target FOV where the rectangular baseline cannot. We further show that finite grid opacity is a largely separable effect. Leakage through the grid leaves the geometric blind-spot boundaries unchanged. These results identify slat cross-sectional shape as a design parameter that can substantially increase throughput and widen the blind-spot-free field of view of a wide-field modulation collimator.
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Instrumentation and Methods for Astrophysics

WEEVIL: design and commissioning of an ice-sublimation chamber and a cryogenic submillimeter radiometer for studying rarefied gas plumes

D. Belousov, J. Fritschi, O. Mokhtari et al. (+4 more)

We present WEEVIL (WatEr Emission of Vapor from Ice in the Laboratory), an experimental facility developed to study ice sublimation under laboratory conditions to support observations of comets and icy moons. The setup combines a submillimeter heterodyne radiometer and a high-vacuum cryogenic chamber, enabling spatially and temporally resolved monitoring of gas plumes formed during ice sublimation under controlled laboratory conditions. This paper describes the facility's design and implementation. Furthermore, we present the commissioning of the experimental setup, including the first water-vapor spectra acquired during an ice sublimation experiment.
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All authors D. Belousov, J. Fritschi, O. Mokhtari, L. L. Stöckli, D. Piazza, A. Murk, N. Thomas

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

AI Agents as a Research Team: A Human-Supervised Case Study in Stellar Spectroscopy

Marwan Gebran and Ian Bentley

We present a qualitative case study of a human-supervised team of specialized AI agents supporting an astronomy research project. The Bot Spectroscopist team, described in the project record as operating through Grok Bot powered by xAI Grok, divided work among orchestration, numerical implementation, data curation, spectroscopy critique, literature search, figure preparation, manuscript editing, and review. Human decisions determined scientific scope, model changes, and manuscript inclusion. The scientific application is CondGen, a deterministic label-to-spectrum network extending our previous work to five individual elemental abundances. The reported baseline assessment achieved a mean absolute error (MAE) of 0.003681 in continuum-normalized flux on 21,657 synthetic test spectra. Existing binned diagnostics show that reconstruction error varies with effective temperature and abundance. The bots also flagged a non-monotonic cool-star magnesium response for further investigation; a matched SYNSPEC abundance sweep is needed to assess its physical fidelity. Building on a pre-existing spectral database, notebooks, and research program, the authors estimate that the reported analysis, diagnostics, figure preparation, and initial manuscript drafting were assembled in less than a week through human prompting and exchanges among agents. No comparison with a human team starting from the same resources was performed, so this elapsed-time account does not establish a productivity or labor saving. The study illustrates task delegation, artifact exchange, critique, and correction under human supervision.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.space-ph

What Caused the Orbital Decay of the Twin Van Allen Probes to Diverge?

Ayisha M Ashruf, Ankush Bhaskar, C Vineeth et al. (+1 more)

The Van Allen Probes were launched into nearly identical orbits and experienced the same solar and geomagnetic environment, yet their post-mission lifetimes diverged dramatically. Probe A underwent rapidly accelerating orbital decay and reentered the atmosphere in March 2026, while Probe B remains in orbit. We investigate the cause of this divergence using reconstructed orbital trajectories, modeled thermospheric densities, and measures of low-altitude residence and atmospheric drag. We find that small differences in orbital evolution progressively increased Probe A residence time in the lower thermosphere, where the steep density gradient made additional low-altitude exposure increasingly important. Enhanced thermospheric density during periods of geomagnetic activity further amplified this difference, leading to greater drag and accelerating orbital decay of Probe A. Our results show how small differences in orbital evolution can be amplified through the coupled effects of thermospheric drag and space weather, producing substantially different orbital lifetimes even for twin spacecraft sharing nearly identical initial orbits.
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All authors Ayisha M Ashruf, Ankush Bhaskar, C Vineeth, Tarun Kumar Pant

Instrumentation and Methods for Astrophysics · Cross-listed from hep-ex

Precision measurement of ocean tides using cosmic-ray muons

Jiwon Seo, Jongseok Chung, Chang Hyon Ha et al. (+8 more)

Cosmic-ray muons provide a natural probe of the integrated mass along their trajectories. Here we show that cosmic-ray muons can monitor ocean-tide-induced variations in seawater overburden within an underwater tunnel. The observed modulation closely tracks independent tide-gauge measurements, yielding an attenuation response coefficient of $k=43.2\pm1.0$~counts$\rm /h/m$ and resolving meter-scale variations in seawater overburden. A spatial muography scan validates the overburden model, confirming that the seawater contribution is essential to reproduce the observed attenuation. Unlike conventional tide gauges that measure sea level locally, muography measures the integrated overburden above the detector. These results demonstrate that muography can quantitatively resolve small, time-dependent variations in environmental overburden, providing a new approach to monitoring dynamic natural systems.
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All authors Jiwon Seo, Jongseok Chung, Chang Hyon Ha, TongZhou Huang, Jinyoung Kim, Sooa Kim, Hani Kimku, Byoung-cheol Koh, Minsu Kwak, Sihyun Lee, Yujin Lee

Instrumentation and Methods for Astrophysics

Opportunity Lost in Searching for Technosignatures

Steve Prabu, David DeBoer, Andrew Siemion et al. (+6 more)

The sensitivity of radio technosignature searches has improved dramatically over the last five decades; however, as the RFI environment from which these searches are conducted has become increasingly polluted, our advancements in telescope sensitivity have not necessarily been complemented by less ambiguous technosignature searches. In this work, we investigate the resulting loss of opportunity to conduct unambiguous technosignature searches from Earth. We introduce three new concepts, opportunity lost, volume lost, and self-censorship, to quantify the impact of orbiting RFI sources on Earth-based technosignature searches. Using publicly available orbital data between 2008 and 2025, we find an approximately two-fold increase in the spatial occupancy of satellites within representative telescope beams, with the exact magnitude of the loss strongly dependent on telescope pointing. We further demonstrate that the cumulative effect of faint emission from multiple satellites increase the effective system temperature and consequently reduce the volume over which a technosignature of a given intrinsic power can be detected. Using approximately 10,000 archival observations from the Murchison Widefield Array spanning 2014–2024, we find suggestive evidence for increasing RFI occupancy across most of the frequencies observed by the MWA. While other opportunities for terrestrial technosignature searches exist, we argue for the protection and utilisation of uniquely radio-quiet environments such as the lunar farside, which offers an opportunity to regain the ability to perform unambiguous technosignature searches that is being progressively lost on Earth.
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All authors Steve Prabu, David DeBoer, Andrew Siemion, Andre R. Offringa, Natasha Hurley-Walker, Charlie K. Ashe, Sofia. Z. Sheikh, Steve Croft, Greg Sleap