Experimental Astronomy最新文献

This study presents a multi-physics co-design framework addressing electromagnetic-thermal coupling challenges in radio frequency system-on-chip (RFSoC) modules for the 110 m QiTai radio Telescope (QTT). A hierarchical electromagnetic assessment methodology combining near-field scanning (2.4 ~ 40 GHz) and signature separation algorithms enables precise identification of nine dominant radiation sources at the component level, while board-level power loading analysis establishes a 70dB shielding effectiveness (SE) requirement for stable operation. The proposed electromagnetic-topology-optimized detachable shielding enclosure integrates nonlinear strain-compensated conductive elastomers (σ = 1.8 × 10³ S/m, ε_max = 150%) and waveguide-embedded multi-mode optical interfaces (λ = 850/1310nm), achieving > 70dB SE with maintained optical communication integrity (BER < 10⁻¹²). Concurrent DELPHI-derived thermal network optimization results in a unified shielding-cooling architecture, reducing the maximum junction temperature from 84.1 °C to 40.0 ± 0.5 °C under 35 W/cm² power density through enhanced heat flux paths. Anechoic chamber measurements validate the frequency-dependent SE degradation mechanism of optical-fiber-embedded waveguides, confirming compliance with IEC 61000-4-21 Class A standards. The framework systematically resolves shielding-communication trade-offs and thermal accumulation constraints in high-density RFSoCs, providing a scalable paradigm for next-generation radio telescope electronics operating in extreme observational environments.

Radio interferometry relies on distributed telescopes having precise time and frequency sources that allow them to operate coherently over timescales up to several hours. As radio telescopes are being connected to fiber-based high-speed communication networks, it is of interest to make use of these for time and frequency distribution. The White Rabbit protocol enables the accurate and precise distribution of time and frequency signals over telecommunication optical fibers. We set out to evaluate the quantitative limits for interferometers over a range of observing frequencies when synchronized through White Rabbit. We develop a method to quantify the possible loss of sensitivity due to the phase noise contribution of a White Rabbit link. Our findings include a new expression for the coherence loss due to flicker phase noise. As this type of noise is common in frequency transfer links, its use extends beyond the case of White Rabbit. Furthermore, we designed a calibration procedure to measure the dispersion on already deployed fiber networks. We demonstrate adding a White Rabbit signal to an existing high-speed production network, together with data traffic on other wavelengths on the same fiber. Finally we built a VLBI setup with fiber links of 35 and 169 km, connecting two radio telescopes together. The agreement between our predicted and measured coherence loss indicates the usefulness of our approach, and that White Rabbit is suitable for clock distribution in radio interferometry instruments. We find that regular White Rabbit v3 switches support observing frequencies up to 3.5 GHz, and their low-jitter version up to 15 GHz.

With the advancement of astronomy, the demand for high-resolution astronomical images has become increasingly urgent. However, the imaging of ground-based telescopes is often affected by factors such as hardware limitations, atmospheric turbulence, and noise, thereby limiting the execution of high-precision scientific tasks. Moreover, due to the scarcity of paired high- and low-resolution observations, directly training super-resolution models on real data remains a significant challenge. Therefore, we construct a synthetic dataset, GalaxySR-DS, by simulating the degradation process using DownSampleGAN (DSGAN). In addition, we propose a lightweight super-resolution (SR) model, Frequency and Spatial-Channel Cross Transformer (FSCFormer). It combines the Frequency Transformation Module (FTB) and the Spatial-Channel Cross Transformation Module (SCCTB), and has complementary advantages in modeling high-frequency details and maintaining the global structure, thereby improving the reconstruction quality. We select ten representative lightweight SR models as baselines for comparison. Experimental results show that the FSCFormer model achieves an average PSNR improvement of 0.02-0.85 dB while maintaining lower computational cost. This study offers an effective approach for the high-precision analysis of astronomical observation data. In particular, under constrained observational resources, it maximizes the scientific value of existing data and promotes a paradigm shift in observational astronomy research. The code will be available at https://github.com/jiaweimmiao/FSCFormer.

High-energy charged particles in cosmic ray (CR) generate anomalous signals or noise artifacts when colliding with astronomical detectors, introducing distortions in both imaging and spectral data. This phenomenon poses a significant challenge in differentiating celestial signatures from cosmic ray-induced artifacts, particularly during observation scenarios involving resolved galaxies. In this study, we propose a deep learning framework that integrates the multi-scale attention mechanism and dynamic adaptive loss function for CR detection. The multi-scale linear attention mechanism is adopted to achieve a synergistic perception of global context modelling and local texture features in resolved galaxies. The large kernel selection block is used to effectively extend the capture range of global dependence of CR structures. The efficient multi-scale attention block is introduced to further enhance the texture differentiation between CR and celestial fringes of resolved galaxies. Furthermore, a dynamic weighted loss function based on a Gaussian residual response is introduced, with the aim of adjusting the negative sample gradient weights through statistical analysis of background noise patterns adaptively. This approach significantly improves model performance in class-imbalanced CR detection tasks. Experimental results demonstrate that the proposed model achieves consistent performance improvements on enhancements in CR detection for resolved galaxies.

Solar coronagraphs often include narrowband filters located at an image of the telescope pupil. These filters are commonly illuminated with collimated light coming from an intermediate telecentric image of the corona. In this configuration, the intermediate image is located at the front focal plane of a collimator, while the telescope pupil is formed at its back focal plane. Collimators employed to illuminate the filter have long focal lengths and usually need to be designed as telephoto lenses for the purpose of minimizing the distance from the intermediate image to the pupil. This is particularly important for spaceborne instruments, whose dimensions are strictly constrained. However, conventional telephoto lenses cannot be employed in this case as they unavoidably increase the front-to-back focal length of the system. Reducing the number of optical elements in coronagraphs is also essential to minimize stray light and ghost images. In this work, we derive the equations for two-component telephoto lenses needed to minimize the front-to-back focal distance. We apply these equations to design a collimator for CMAG coronagraph. We study the image quality as a function of the telephoto ratio, we athermalize our design and we carry out a tolerance analysis. We demonstrate that the front-to-back focal length can be reduced by (textbf{45},mathbf {%}) for a field of view as large as 1.28° while keeping the root mean square wavefront error below (varvec{lambda /20}).

Recent work by Oberti et al, (Astron. Astrophys., 667, 48, 2022) argued and made a compelling case that classical astronomical adaptive optics (AO) tomography performance can be further enhanced by carefully designing and optically configuring the system to leverage inherent super-resolution (SR) capabilities. Our goal here is to further materialise the concept by providing the means to compute SR-enabling tomographic reconstructors for AO and showcase its broad uptake on soon every 10 m-class VIS/NIR telescopes and Giant Segmented Mirror Telescopes of up to 40 m in diameter. To that end we indicate the necessary tomography generalisations where we: (i) clarify how model-and-deploy is a generic methodological umbrella for linear minimum-mean-squared-error (LMMSE) tomographic reconstructors arising naturally from the solution of the tomographic inverse problem, thus unifying various solutions presented as distinct in the literature within a single framework, (ii) recall how such solutions are found as limiting cases of a model-based optimal control problem, thus elucidating how pseudo-open-loop control is a feature of the latter that allows LMMSE reconstructors to be adapted to closed-loop systems, (iii) review the two forms of the LMMSE tomographic reconstructors, highlighting the necessary adaptations to accommodate super-resolution, (iv) review the implementation in either dense-format vector-matrix-multiplication or sparse iterative forms and (v) discuss the implications for runtime and off-line real-time implementations, anticipating widespread adoption. We illustrate our examples with physical-optics numerical simulations for 10 m and 40 m-scale systems showing the performance benefits of super-resolution in the order of several tens of nm rms and the computational burden associated.

As an X-ray and gamma-ray all-sky monitor designed to observe high-energy astrophysical transients, Gravitational-wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) has also made a series of observational on burst events of gamma-rays and particles in the low Earth orbit. Pitch angle is one of the key parameters of charged particles traveling around the geomagnetic field. However, the usage of the all-sky monitor (GECAM-style) instruments to measure the pitch angle of charged particles is still lacking. In this work, we propose a novel method for GECAM and similar instruments to measure the pitch angle of charged particles based on detector counts distribution. The basic concept of this method, along with supporting simulation studies, is presented. With this method, the pitch angle of a peculiar electron precipitation event detected by GECAM-C is derived to be about 90(^circ), demonstrating the feasibility of our method. We note that the application of this method on GECAM-style instruments may open a new window for studying space particle events, such as Terrestrial Electron Beams (TEBs) and Lightning-induced Electron Precipitations (LEPs).

This paper presents a novel approach to estimate the (mu) and y-distortions in the Cosmic Microwave Background (CMB) using the COBE/FIRAS data. The analysis draws from the concept of blackbody radiation inversion (BRI), a mathematical technique typically used to determine the temperature distribution from a radiated power spectrum. We study the deviations from the ideal blackbody spectrum or the spectral distortions by incorporating first a non-zero chemical potential (mu) via the Bose-Einstein distribution and then also adding the Compton parameter y while keeping the monopole temperature constant. We infer the results as probability distribution functions on these distortions. Finally, we derive (mu = {(-,0.656 ;pm ; 2.048) times 10^{-5}}) and (y = {5.498 times 10^{-10} pm 2.775 times 10^{-6}}) at a (68%) confidence interval. Here we show how the BRI method performs in a test-case scenario, illustrating its potential for extracting spectral distortion parameters in CMB.

Space-Based Very Long Baseline Interferometry (SVLBI) significantly enhances the resolution and sensitivity of radio astronomical observations by placing radio telescopes in orbit. However, designing an effective satellite constellation for SVLBI is complex, as it involves multiple factors such as imaging performance, (u, v) coverage, resolution, and image fidelity. This paper is the first in a series focused on evaluating the (u, v) coverage capabilities of different satellite configurations. We investigated several constellation designs, including hybrid configurations that combine satellites in various orbital regimes. These hybrid setups demonstrated superior performance compared to those using satellites in a single orbit. Notably, a configuration with five satellites—three in Medium Earth Orbit (MEO) and two in Low Earth Orbit (LEO)—achieved the most uniform and dense (u, v) coverage with the fewest satellites. Finally, the most effective configurations were further tested using simplified simulations involving both point sources and extended sources to assess their practical imaging capabilities.

Radio Frequency Interference (RFI) presents a significant challenge for carrying out precision measurements in radio astronomy. In particular, RFI can be a showstopper when looking for faint cosmological signals such as the red-shifted 21-cm line from cosmic dawn (CD) and epoch of reionization (EoR). As wireless communications, satellite transmissions, and other RF technologies proliferate globally, understanding the RFI landscape has become essential for site selection and data integrity. We present findings from RFI surveys conducted at four distinct locations: three locations in India, the Gauribidanur Radio Observatory in Karnataka, Twin Lakes in Ladakh, Kalpong Dam in the Andaman Islands, and the Gruvebadet Atmosphere Laboratory in Ny-Ålesund, Svalbard, Norway. These sites, selected based on their geographical diversity and varying levels of human activity, were studied to assess RFI presence in 30-300 MHz bands, critical for low-frequency observations and experiments targeting the 21-cm CD/EoR signal. Using an automated RFI detection approach via the Hampel filter and singular value decomposition, the surveys identified both persistent and transient interference, which varies with location and time. The results provide a comprehensive view of the RFI environment at each site, informing the feasibility of long-term cosmological observations and aiding in the mitigation of RFI in radio astronomical data. The methods developed to characterize RFI can be easily generalized to any location and experiment.