Experimental Astronomy最新文献

The spatial-temporal evolution of coronal plasma parameters of the solar outer atmosphere at global scales, derived from solar full-disk imaging spectroscopic observation in the extreme-ultraviolet band, is critical for understanding and forecasting solar eruptions. We propose a multi-slits extreme ultraviolet imaging spectrograph for global coronal diagnostics with high cadence and present the preliminary instrument designs for the wavelength range from 18.3 to 19.8 nm. The instrument takes a comprehensive approach to obtain global coronal spatial and spectral information, improve the detected cadence and avoid overlapping. We first describe the relationship between optical properties and structural parameters, especially the relationship between the overlapping and the number of slits, and give a general multi-slits extreme-ultraviolet imaging spectrograph design process. The multilayer structure is optimized to enhance the effective areas in the observation band. Five distantly-separated slits are set to divide the entire solar field of view, which increase the cadence for raster scanning the solar disk by 5 times relative to a single slit. The spectral resolving power of the optical system with an aperture diameter of 150 mm are optimized to be greater than 1461. The spatial resolution along the slits direction and the scanning direction are about (4.4^{prime prime }) and (6.86^{prime prime }), respectively. The Al/Mo/B(_4)C multilayer structure is optimized and the peak effective area is about 1.60 cm(^2) at 19.3 nm with a full width at half maximum of about 1.3 nm. The cadence to finish full-disk raster scan is about 5 minutes. Finally, the instrument performance is evaluated by an end-to-end calculation of the system photon budget and a simulation of the observational image and spectra. Our investigation shows that this approach is promising for global coronal plasma diagnostics.

The High Energy Cosmic-Radiation Detection Facility (HERD) is dedicated to achieving several scientific objectives, including the search for dark matter, precise measurement of the cosmic ray spectrum, and gamma-ray sky survey observations. HERD’s innovative design incorporates a three-dimensional imaging calorimeter with five sensitive faces, significantly enhancing geometric acceptance. However, this design introduces a new challenge for reconstructing particles incident from all directions. This article aims to integrate rapidly advancing deep learning techniques into the reconstruction task. Utilizing simulation data, Deep Neural Networks (DNN), Convolutional Neural Networks (CNN), and other deep learning networks are employed to reconstruct the energy of isotropic electrons. Model performance sees a significant boost through the application of end-layer visible energy correction and a “multi-class multi-prediction” approach, involving different models trained for distinct energy ranges. Moreover, recognizing differences between simulation and physical samples, the model is validated using the beam test data. The model predicts an energy resolution of better than 1% for simulation isotropic electrons ranging from 10 to 1000 GeV. In the case of beam data, the model achieves an energy resolution of 1.3% at 200 GeV, comparable to traditional methods. The results demonstrate the significant potential of deep learning in the reconstruction of three-dimensional calorimeters.

With the increasing aperture as well as the observation frequency of radio telescopes in the current period, the deformation caused by time-varying loads such as temperature and wind has been emphasized. Existing methods for measuring deformations often fall short in meeting the demands of full attitude coverage, quasi-real-time response, and high accuracy. This study introduces a novel geometric-optical measurement approach based on light-tracing. Diverging from traditional methods, this approach doesn’t directly measure the surface deformation of the main reflector. Instead, it creates a more easily measurable variable and establishes a mapping relationship between this variable and the main reflector deformation. In this innovative scheme, multiple laser modules are strategically positioned on the main reflector, treating the sub reflector as a spot projection surface. When the panel is displaced, the spot on the projection surface will follow and be displaced. In practice, the main reflector deformation can be solved by recording the position change of the light spots on the projection surface and utilizing the inverse reconstruction model. Besides, effective strategies are proposed to improve the robustness of the scheme. Next, the accuracy and real-time performance of the proposed method are verified through simulations and experiments. Results indicate that the proposed approach presents a fresh perspective to enhance the efficiency and precision of deformation measurements for large-aperture antennas.

X-ray mirror modules are the core components of X-ray astronomy research, which can focus X-rays from space and significantly improve detection sensitivity. This X-ray optical device are typically composed of nested multiple mirror shells and require maintaining a constant working temperature. Due to the thin-walled structure of the mirror shells and the fact that the inner surface reflects X-rays, direct contact temperature control is not feasible, making temperature control challenging. To evaluate the thermo-optical performance of the mirrors, based on the 100-m X-ray Test Facility (100XF) of the Institute of High Energy Physics (IHEP), a thermo-optical test device with high cleanliness was developed in this study. This system enables precise control of the mirror temperature and synchronous testing of X-ray performance, establishing the unique X-ray thermo-optical testing capability in China. The system consists of a high cleanliness level thermal sink, a liquid nitrogen circuit, multi-layer insulation, a temperature controller, and low-temperature probes. This system has demonstrated the capability to test the thermo-optical performance of X-ray mirror modules and has successfully conducted thermo-optical tests on the mirror module of the follow-up X-ray telescope (FXT) payload onboard the Einstein Probe (EP), achieving precise temperature control of the X-ray mirrors and testing its X-ray optical performance at different operating temperatures. The thermo-optical performance of the mirror module obtained from the thermal tests has been verified in-orbit. This paper provides a detailed description of the design, development, and validation of this system, as well as an overview of the results of the thermo-optical tests conducted on the FXT.

Soft protons populating the space environment have affected the performance of the X-ray detectors on board Chandra and XMM-Newton, and they pose a threat for future high energy astrophysics missions with larger aperture, such as ATHENA. In this paper, we aim to predict the soft proton induced ATHENA backgrounds from the modelling of the orbital flux obtained using eROSITA on board SRG. To this end, we analysed the background measured by eROSITA and with the help of simulations we defined a range of values for the potential count-rate of quiet-time soft protons focused through the mirror shells. We used it to derive an estimate of the orbital soft proton flux, from which the induced background for the WFI and X-IFU detectors can be predicted, assuming ATHENA in the same L2-orbit as SRG. The scaling, based on the computed proton transmission yields of the optics and optical/thermal filters, indicates that the soft proton induced WFI and X-IFU backgrounds could be expected within the requirement. Regardless of where ATHENA will be placed (L1 or L2), our analysis also suggests that increasing somewhat the thickness of the WFI optical blocking filter, e.g. by (sim )30%, would help to further reduce the soft proton flux onto the detector, which might be worth in case the planned magnetic diverters perform worse than expected due to soft proton neutralisation at the mirror level.

Eastern Anatolia Observatory (DAG), located at 39.78 degrees North latitude (N) and 41.23 degrees East longitude (E) with 3170 m altitude above the sea level in the east part of Türkiye, having the first 4m class infrared (IR) telescope. DAG telescope is not only the largest telescope in Türkiye but also the most important telescope in the northern hemisphere because it also covers a large observational gap thanks to its location over the World. The atmospheric conditions of the DAG site have a major impact on the quality of observations in ground-based astronomy. The atmospheric conditions of an observatory site being effective and important for both optical and infrared observations is a key parameter in assessing the performance of astronomic observations and observatory sites. In this study, as an observatory site, a detailed long-term atmospheric and astronomical analysis of DAG site were presented for near-infrared observations, especially. Within the scope of basic atmospheric and astronomical parameters, it has been revealed that the DAG site is an observatory site with a great astronomical observation potential, due to its location, robust infrastructure, astronomical and atmospheric properties originating from geography.

The grazing-incidence optics with Wolter-I type geometry is commonly used in X-ray astronomy. The manufacturing technologies are still under development for future space missions to fulfill the stringent performance requirements with reduced weight and cost, e.g. the planned enhanced X-ray Timing and Polarimetry Mission. To improve the manufacturing process, it is necessary to study the relationship between metrological characterization and angular resolution via ray-optics or wave-optics models. The model calculations produce inconsistent results depending on the characteristics of wide-band surface errors, which require validation before their application in the Wolter-I type optics. In this work, two samples of the single-reflection mirrors with an elliptical shape are produced to validate the models. The first sample uses the Aluminum alloy substrate and the second sample uses the Aluminum alloy coated with Nickel-Phosphorous as the substrate. Tungsten is coated on both substrates to increase the X-ray reflectivity. The metrological characterization is inspected using the Fizeau interferometer and 3D optical profiler. The X-ray calibration of the mirror is performed in the 100-m X-ray Test Facility of Institute of High Energy Physics using the Color X-ray Camera. Both ray-optics and wave-optics models are validated in a wide scope of applications from smooth to relatively rough surfaces. The proper treatments of the metrological data are required as input to the model calculations: the post-fit distribution of figure errors, the micro-roughness defined in a specific frequency band, and the smoothed power spectral density of the surface errors. The validated models can be further applied in Wolter-I optics to predict mirror performances or to provide precision processing requirements.

The magnetic field strength and its topology play an important role in understanding the formation, evolution, and dynamics of the solar corona. Also, it plays a significant role in addressing long-standing mysteries such as coronal heating problem, origin and propagation of coronal mass ejections, drivers of space weather, origin and acceleration of solar wind, and so on. Despite having photospheric magnetograms for decades, we do not have reliable observations of coronal magnetic field strengths today. To measure the coronal magnetic field precisely, the spectropolarimetry channel of the Visible Emission Line Coronagraph (VELC) on board the Aditya-L1 mission is designed. Using the observations of coronal emission line Fe XIII [10747Å ], it is possible to generate full Stokes maps (I, Q, U, and V) that help in estimating the Line-of-Sight (LOS) magnetic field strength and to derive the magnetic field topology maps of solar corona in the Field of View (FOV) (1.05 – 1.5 R(_{odot })). In this article, we summarize the instrumental details of the spectropolarimetry channel and detailed calibration procedures adopted to derive the modulation and demodulation matrices. Furthermore, we have applied the derived demodulation matrices to the observed data in the laboratory and studied their performance.

In the universe, there are up to 2 trillion galaxies with different features ranging from the number of stars, light spectrum, age, or visual appearance. Consequently, automatic classifiers are required to perform this task; furthermore, as shown by some related works, while greater the number of classes considered, the performance of the classifiers tends to decrease. This work is focused on the morphological classification of galaxies. They can be associated with a subset of 10 classes arranged in a hierarchy derived from the Hubble sequence. The proposed method, Bayesian and Convolutional Neural Networks (BCNN), is composed of two main modules. The first module is a convolutional neural network trained with the images of galaxies, and its predictions feed the second module. The second module is a Bayesian network that evaluates the hierarchy and helps to improve the prediction accuracy by combining the predictions of the first module through probabilistic inference over the Bayesian network. A collection of galaxies sourced from the Principal Galaxies Catalog and the APM Equatorial Catalogue of Galaxies are used to perform the experiments. The results show that BCNN performed better than five CNNs in multiple evaluation measures, reaching the scores 83% in hierarchical F-measure, 78% in accuracy, and 67% in exact match evaluation.

The primary objective of this study is to employ Multi-Criteria Decision Analysis (MCDA) and Geographical Information System (GIS) techniques to identify and assess potential sites for astronomical observations in Antarctica. Our study focuses on the development of the Suitability Index for Astronomical Sites in Antarctica (SIASA). This index is formulated by merging data from satellites and models, providing extensive temporal and spatial coverage over two decades. To assess its suitability, we employed a combination of MCDA and GIS techniques, allowing us to evaluate various data, including cloud cover (CC), precipitable water vapor (PWV) levels, elevation, atmospheric temperature and wind speed. Our analysis confirmed the exceptional characteristics of Antarctica: An average of 361 cloud-free days per year, exceptionally low PWV values (0 mm), and an average elevation of 2.300 meters. The stable atmospheric wind profile further enhances its suitability for astronomical observations. Long-term trends and correlations of the data were also studied. SIASA values identified the eastern and inner parts of the Transatlantic Mountains as highly favorable for astronomical observations, while the coastal areas were considered less suitable. The best sites cover 10% of Antarctica in all SIASA scenarios, with Dome A, Ridge A and Dome F having the highest values of all stations. These findings hold considerable importance in planning future astronomical sites on the continent.