Experimental Astronomy最新文献

{"title":"Experimental comparison of fabrication-driven performance in corrugated feed horns for the ngVLA","authors":"Sara Salem Hesari,&nbsp;Eric Lemay,&nbsp;Gregory Nuspel,&nbsp;Adam Densmore","doi":"10.1007/s10686-026-10083-7","DOIUrl":"10.1007/s10686-026-10083-7","url":null,"abstract":"<div><p>This letter presents the design, fabrication, and experimental validation of a corrugated feed horn for the Next Generation Very Large Array (ngVLA) Band-5 receiver operating over the 30–50 GHz frequency range. The proposed horn employs an axially corrugated circular waveguide with a flared throat, logarithmic spiral opening, and tapered groove geometry, optimized using full two-dimensional field integration to maximize aperture efficiency while accounting for phase, amplitude, taper, and cross-polarization effects. To evaluate the impact of fabrication method and material, three feed horns with identical electromagnetic designs were made: a CNC-machined tellurium copper, a CNC-machined aluminum, and a tellurium copper horn using metal additive manufacturing. All three feed horns were characterized for return loss and radiation patterns under identical conditions at the Communications Research Centre (CRC) in Ottawa Canada using their compact antenna test range (CATR) anechoic chamber. Measured results show excellent agreement with simulations for the CNC-machined feeds, achieving a return loss better than 23 dB across the operating band. The additively manufactured feed shows larger deviations primarily in cross-polarization response, highlighting the direct impact of fabrication-induced geometric deviations on cross-polarization performance at millimeter-wave frequencies.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10686-026-10083-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149338447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A quantitative image-processing framework for eclipse shadow band analysis","authors":"Joseph Conti","doi":"10.1007/s10686-026-10086-4","DOIUrl":"10.1007/s10686-026-10086-4","url":null,"abstract":"<div><p>Eclipse shadow bands are transient intensity patterns that can appear on the ground near solar eclipse totality. This study presents a reusable image-processing framework for quantitatively characterizing shadow bands using ground-based video recordings collected with consumer-grade cameras. The framework quantifies band prominence, orientation, separation, velocity, and power spectral density. Applied to two eclipse datasets, the method detected statistically significant shadow band activity during eclipse windows consistent with atmospheric scintillation theory. The analysis further identified statistically significant shadow bands persisting for more than 10 min after totality (C3), temporal rotation of shadow band orientation, and simultaneous shadow band modes with distinct orientations and velocities. The persistence of shadow bands well after C3, under high partial solar obscuration, provides observational evidence supporting the hypothesis that, under favorable atmospheric conditions, shadow bands may also occur outside the path of totality in regions experiencing only a partial eclipse. These results demonstrate that consumer-grade video recordings can support quantitative characterization of detailed and dynamic shadow band behavior and provide a framework for future observational and atmospheric studies.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149338817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analytical modelling of STIX instrumental background and its application in the spectral and imaging analysis","authors":"Karol Kułaga,&nbsp;Tomasz Mrozek,&nbsp;Janusz Sylwester,&nbsp;Arun Kumar Awasthi,&nbsp;Michalina Litwicka,&nbsp;Daniel Ścisłowski,&nbsp;Olivier Limousin","doi":"10.1007/s10686-026-10084-6","DOIUrl":"10.1007/s10686-026-10084-6","url":null,"abstract":"<div><p>STIX records X-rays from Solar activity from 4 to 150 keV with 32 detectors, each divided into 12 pixels. Background is obtained using the BKG detector and is known to essentially correspond to the background radioactive sources onboard STIX. This study aims to construct an analytical model of the STIX background based on available measures. The model will allow predicting the background at any time interval of the mission. We analysed 256 background files recorded by STIX from January 2022 to July 2023, and we assume that onboard calibration sources (<span>(^{133})</span>Ba) dominate the background. We fitted with an exponential function corresponding to the half-life of <span>(^{133})</span>Ba to the background in each of the 384 pixels and each of the science energy bins. Interpolated background values were validated against additional files for consistency. These values were then integrated into image reconstruction algorithms to assess variability in source parameters across background approaches. A determined background was also tested in OSPEX to evaluate its impact on spectral fitting. The analysis shows that the STIX background is non-uniform, with pixel-to-pixel variations affecting moiré patterns in weak flares. Our approximation matches background files collected during quiet Sun periods, but it can also differ from them during high activity or perihelion, where onboard files include additional signals. In such cases, our radioactive-source-based background offers a more reliable basis for imaging and spectral analysis than file-based background and enables a higher degree of automation in the analysis. Background analysis from Jan 2022 to Jul 2023 shows that STIX background is usually dominated by <span>(^{133})</span>Ba over the full energy spectrum. Interpolated background methods improve accuracy during high solar activity or close Sun approaches, where standard methods falter. This enhances X-ray image quality and enables reconstruction from fewer counts, supporting more precise analyses, especially of microflares.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10686-026-10084-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149235077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A chemically etched D-band waveguide orthomode transducer for CMB measurements","authors":"E. Manzan,&nbsp;A. Mennella,&nbsp;F. Cavaliere,&nbsp;C. Franceschet,&nbsp;S. Mandelli,&nbsp;F. Montonati,&nbsp;M. Zannoni,&nbsp;P. de Bernardis,&nbsp;M. Bersanelli,&nbsp;E. Boria,&nbsp;N. Brancadori,&nbsp;A. Coppolecchia,&nbsp;M. Gervasi,&nbsp;L. Lamagna,&nbsp;A. Limonta,&nbsp;S. Masi,&nbsp;A. Paiella,&nbsp;A. Passerini,&nbsp;F. Pezzotta,&nbsp;G. Pettinari,&nbsp;F. Piacentini,&nbsp;E. Tommasi,&nbsp;D. Viganò,&nbsp;A. Volpe","doi":"10.1007/s10686-026-10082-8","DOIUrl":"10.1007/s10686-026-10082-8","url":null,"abstract":"<div><p>This study presents a prototype D-band waveguide orthomode transducer (OMT) fabricated using chemically etched brass platelets. This method offers a fast, cost-effective, and scalable approach for producing such devices above 100 GHz, making it well-suited for current and future Cosmic Microwave Background polarization experiments, where large focal planes with thousands of receivers are required to detect the faint primordial <i>B</i>-modes. Chemical etching has already demonstrated its effectiveness in manufacturing corrugated feedhorn arrays with state-of-the-art performance up to 150 GHz. Here, we evaluate its applicability to more complex structures, such as OMTs. We designed a single OMT prototype operating in the 130–170 GHz range, fabricated by chemically etching 0.15 mm-thick brass plates, which were then stacked, aligned, and mechanically clamped. Simulations based on metrological measurements of the OMT profile predict reflected power below −10 dB, cross-polarization better than −30 dB, and transmission around −0.5 dB in the 140−170 GHz band. Measurements yield transmisison around −1.5/−2 dB and cross-polarization <span>(&lt;-)</span>20 dB. Further simulations show that the degradation in the transmission is related to defects and roughness along the etched profile (<span>(textrm{RMS}simeq )</span>3 <span>(mu )</span>m), which is a typical and unavoidable effect of chemical etching. The discrepancy in cross-polarization, instead, could arise from a <span>(sim )</span>1.5<span>(^{circ })</span> rotation of the polarization angle within the measurement chain. Our results show that chemical etching is a fast, low-cost, and scalable technique for producing waveguide OMTs with state-of-the-art performance in terms of reflected power and cross-polarization. However, at frequencies above 100 GHz our results show that the mechanical precision limitations of the chemical etching process degrade the transmission coefficient.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10686-026-10082-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149234710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correction to: Kosmiko: from CMOS imaging sensors to pixel-calibrated particle instruments","authors":"Frédéric Wrobel,&nbsp;Juliette Wrobel,&nbsp;Tadec Maraine,&nbsp;Jérôme Boch,&nbsp;Clément Risso,&nbsp;Luigi Dilillo,&nbsp;Frédéric Saigné","doi":"10.1007/s10686-026-10085-5","DOIUrl":"10.1007/s10686-026-10085-5","url":null,"abstract":"","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149189743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kosmiko: from CMOS imaging sensors to pixel-calibrated particle instruments","authors":"Frédéric Wrobel,&nbsp;Juliette Wrobel,&nbsp;Tadec Maraine,&nbsp;Jérôme Boch,&nbsp;Clément Risso,&nbsp;Luigi Dilillo,&nbsp;Frédéric Saigné","doi":"10.1007/s10686-026-10081-9","DOIUrl":"10.1007/s10686-026-10081-9","url":null,"abstract":"<div><p>We present a low-cost, reproducible methodology for detecting ionizing-event candidates in the natural radiation environment by using CMOS active-pixel sensors operated in darkness. The detector platform, called Kosmiko, is based on a Raspberry Pi 5 that controls simultaneously two Sony IMX477 camera modules in raw acquisition mode. Each run consists of a calibration step followed by continuous image acquisition. Candidate events are identified online by comparing each pixel intensity to its intrinsic threshold derived from calibration stage. Pixels that have intensities above their threshold are stored, whereas the others are discarded, which strongly reduces the data volume and enables long-duration acquisitions. The method includes the identification and filtering of hot, noisy and recurrent pixels, together with camera-health indicators based on dark-level statistics, noise distributions and percentiles. Offline analysis then provides event-rate observables, including frame-of-interest rate, cluster rate, intensity distributions, track-like topology indicators and saturated-pixel occurrence. The goal is not to identify individual particle species, but to provide a documented and deployable methodology for comparing ionizing-event rates under different conditions in the natural radiation environment. The complete hardware, software workflow and data products are described to ease reproducibility and future network deployment. Observations about components of the camera and about the local environment are also discussed.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149034789","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient deep learning for single imaging cherenkov telescope event classification: improving over standard ML with minimal compute cost","authors":"Chinmay Borwankar,&nbsp;Praduman Pandey,&nbsp;Mradul Sharma,&nbsp;Kuldeep Yadav","doi":"10.1007/s10686-026-10080-w","DOIUrl":"10.1007/s10686-026-10080-w","url":null,"abstract":"<div><p>Gamma–hadron separation is a critical task in the analysis of data from imaging atmospheric Cherenkov telescopes (IACTs). The current standard approach in the field typically employs ensemble learning methods, such as random forests, trained on Hillas parameters of events derived from image moments. In this work, we present a lightweight deep learning model based on a simple two-layer convolutional neural network (CNN) followed by attention pooling, designed specifically for single-telescope IACT image classification. The attention pooling mechanism uses query vectors generated from Hillas parameters, providing global event-level context to guide feature aggregation from the convolution feature maps. Unlike several recent deep learning approaches that apply extensive image preprocessing—such as Gaussian kernel smoothing, oversampling to square grids, or custom hexagonal convolution kernels—our method directly uses a <span>(varvec{textrm{25} times textrm{25}})</span> pixel matrix extracted around the cleaned image, fed to the network without further spatial transformations. Comparison of the classification performance of proposed model with that of a standard random forest model on simulated IACT data, shows enhanced background suppression for the CNN model at all levels of signal acceptance. Application of the novel method to the real MACE data collected during observations of Crab nebula shows up to 25 % increase in detection significance relative to standard method. The deep learning model can be trained on a 16-core CPU machine in <span>(sim )</span> 90 minutes, and achieves an inference rate of about 2.96 kHz on CPU, enabling rapid deployment without the need for GPUs. While the scope of the present work is restricted to the single-telescope case, the results demonstrate that lightweight architectures with minimal pre-processing can provide a practical and effective alternative to standard machine learning methods by offering higher classification performance, together with the computational efficiency and simplicity needed for large-scale analyses.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Solar X-ray Polarization Detector (SXPD): a solar flare detector based on GMPD","authors":"Haoran Liu,&nbsp;Hongbang Liu,&nbsp;Difan Yi,&nbsp;Tianyi Xiong,&nbsp;Huanbo Feng,&nbsp;Junhua Feng,&nbsp;Zuke Feng,&nbsp;Fei Xie,&nbsp;Huijun Hu,&nbsp;Enwei Liang","doi":"10.1007/s10686-026-10079-3","DOIUrl":"10.1007/s10686-026-10079-3","url":null,"abstract":"<div><p>We present the design of a solar flare detector, the Solar X-ray Polarization Detector (SXPD), based on the Gas Microchannel Plate Pixel Detector (GMPD). The primary scientific objectives are to measure the polarization state and spectrum of individual solar flares in the soft X-ray band, where polarized bremsstrahlung radiation is expected to be produced by high-energy electron beams accelerated within the solar magnetic field and plasma. The SXPD comprises two key modules: a Pinhole Imaging Tube and a GMPD module. This paper provides a detailed description of the structural design and performance of the SXPD. With its imaging capability, the SXPD can resolve individual solar flares in the soft X-ray energy range with an angular resolution of 1.5 arcsec. Based on conservative estimates, over typical durations, the detector can achieve an MDP of 15.0% - 23.0% for B-class flares, 8.0% - 12.0% for C-class flares, 2.0% - 2.3% for M-class flares, and 0.6% - 1.0% for X-class flares.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148986206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation on mean temperature fluctuation of the cosmic microwave background using blackbody radiation inversion","authors":"Amal Pushp,&nbsp;Somita Dhal,&nbsp;Koustav Konar,&nbsp;R. K. Paul","doi":"10.1007/s10686-026-10078-4","DOIUrl":"10.1007/s10686-026-10078-4","url":null,"abstract":"<div><p>This work analyzes the COBE/FIRAS dataset to estimate the Cosmic Microwave Background (CMB) temperature and its associated uncertainty using the Blackbody Radiation Inversion (BRI) method. In particular, we investigate fluctuations in the mean CMB temperature and evaluate key statistical quantities, including the uncertainty and the second-order moment of the temperature distribution. We find the ensemble-averaged mean monopole temperature at <span>(varvec{2.729 pm 0.0195})</span> K. While the temperature distribution largely resembles a Gaussian profile, the wings show minor deviations resulting in an excess kurtosis of -0.03. Furthermore, analysis in frequency subsets reveals the signatures of non-Gaussianity to be frequency-dependent. It demonstrates that the BRI method is a reliable tool for precision thermometry and presents a broader application in probing the thermal characteristics of the early universe.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polarimetric decomposition-based analysis of Chandrayaan-2 L-band DFSAR data for potential water ice detection in lunar polar regions","authors":"Mulkala Saritha,&nbsp;Anjaneyulu Lokam,&nbsp;Kiran Dasari","doi":"10.1007/s10686-026-10077-5","DOIUrl":"10.1007/s10686-026-10077-5","url":null,"abstract":"<div><p>The DFSAR (Dual-Frequency Synthetic Aperture Radar) onboard the Chandrayaan-2 spacecraft, launched on July 22, 2019, represents a significant advance in radar-based exploration of solid celestial bodies. Chandrayaan-2 is equipped with an array of sophisticated sensors, including the DFSAR, which operates in both the L-band and the S-band in Fully Polarimetric (FP) and compact polarimetric (CP) modes. In this study, we utilize L-band Synthetic Aperture Radar (SAR) data to analyze the lunar regolith. The L-band has superior penetration capabilities, allowing for more effective retrieval of subsurface parameters compared to previous S-band SAR missions. By using L-band in Fully Polarimetric (FP) mode, we can effectively characterize the lunar surface. This technology enables detailed polarimetric analysis of the lunar surface, particularly in the challenging Permanently Shadowed Regions (PSRs) at the lunar poles. These PSRs serve as cold traps for water molecules and are ideal locations for exploring water ice. DFSAR, SLI data is imported, and pre-processing is carried out after generating the scattering matrix. Multilooking is performed with a factor of 38. Refined Lee filter [5x5] window size is applied after coherency matrix generation to remove the speckle in the data, and also multiple decomposition techniques are employed, including the <span>(H/A/bar{alpha })</span> decomposition (based on eigenvalue-eigenvector analysis) and the Yamaguchi four-component decomposition model (based on double-bounce, surface, and volume scattering), which effectively characterize the variations in surface roughness, material composition, and topography of the crater’s inner and outer walls. This study focuses on the polar and non-polar regions (Hermite-A, Peary, Gardner, and Korolev X crater regions), utilizing DFSAR data to conduct a comprehensive polarimetric analysis aimed at identifying the potential presence of water ice deposits. The results reveal the dominance of volume scattering within the walls of the crater, which is verified across all decomposition methods. Circular Polarization Ratio (CPR) analysis further demonstrates a pronounced difference between the interior and exterior regions, with the interior values suggesting rough textures and a higher probability of water ice presence. This aligns with prior studies that associate elevated CPR values and volume scattering with ice deposits in the lunar Polar Regions. To validate the SAR-based analysis, high-resolution lunar surface images captured by the Navigation camera onboard Pragyan Rover at the Chandrayaan-3 landing site were examined. The change in surface roughness before and after landing was reflected in scattering powers, confirming changes in the lunar terrain.</p></div>","PeriodicalId":551,"journal":{"name":"Experimental Astronomy","volume":"62 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10686-026-10077-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148927314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}