Experimental Astronomy最新文献

The primary scientific objective of the High Energy Burst Searcher (HEBS) is to serve as a crucial component of the global space monitoring network for high-energy celestial burst sources. HEBS aims to monitor the high-energy electromagnetic counterparts of gravitational wave events, as well as the high-energy radiation from rapid radio bursts, gamma-ray bursts, magnetar flares, and other high-energy celestial phenomena across the entire sky. This effort will provide essential data support for related physical research, including energy spectra, light curves, and positional information. The probe is deployed on the Satech-01 satellite and operates in a 500 km solar-synchronous orbit. HEBS is equipped with two types of detectors: the Gamma Ray Detector (GRD) and the Charged Particle Detector (CPD). The GRD employs lanthanum bromide crystals coupled with silicon photomultiplier (SiPM) technology, as well as sodium iodide crystals paired with SiPM technology, to detect X-rays and gamma rays in the energy range of 6 keV to 5.9 MeV. It enables the localization of gamma-ray bursts and other high-energy events through the coordinated detection of multiple probes oriented in different directions. The CPD utilizes plastic scintillator technology coupled with SiPM to detect charged particles within the energy range of 150 keV to 5 MeV. When combined with the GRD, it effectively identifies and distinguishes space particle events from actual celestial phenomena. The payload processor (Electronics Box, EBOX) features onboard triggering and positioning capabilities, transmitting trigger times and positional data via Beidou short messaging in quasi-real time. This information will guide other telescopes in conducting follow-up observations.

Over the decades, astronomical X-ray telescopes have utilized the Wolter type-1 optical design, which provides stigmatic imaging in axial direction but suffers from coma and higher-order aberrations for off-axis sources. The Wolter-Schwarzschild design, with stigmatic imaging in the axial direction, while suffering from higher-order aberrations, is corrected for coma, thus performing better than the Wolter type-1. The Wolter type-1 and Wolter-Schwarzschild designs are optimized for on-axis but have reduced angular resolution when averaged over a wide field of view, with the averaging weighted by the area covered in the field of view. An optical design that maximizes angular resolution at the edge of the field of view rather than at the center is more suitable for wide-field X-ray telescopes required for deep-sky astronomical surveys or solar observations. A Hyperboloid-Hyperboloid optical design can compromise axial resolution to enhance field angle resolution, hence providing improved area-weighted average angular resolution over the Wolter-Schwarzschild design, but only for fields of view exceeding a specific size. Here, we introduce a new optical design that is free from coma aberration and capable of maximizing angular resolution at any desired field angle. This design consistently outperforms Wolter-1, Wolter-Schwarzschild, and Hyperboloid-Hyperboloid designs when averaged over any field of view size. The improvement in performance remains consistent across variations in other telescope parameters such as diameter, focal length, and mirror lengths. By utilizing this new optical design, we also present a design for a full-disk imaging solar X-ray telescope.

The detection of Line-of-sight (LOS) velocity of coronal mass ejections (CMEs) is crucial for understanding and forecasting their propagation. The LOS velocity can be derived from the Sun-as-a-star extreme ultraviolet spectrograph based on the Doppler effect. However, the poor spectral resolution of existing instruments is not sufficient for detection. In the paper, we propose a dual-band Sun-as-a-star spectrograph with high spectral resolution for measuring the LOS velocity of CMEs. Based on a multilayer concave grating operating in a normal incident mode, we optimized the parameters of the spectrograph for the wavelength ranges of 18.3( sim )21.3 nm and 49.6( sim )52.9 nm. The spectral resolving power for these two ranges exceeds 1000 and 2000, respectively, which is about three times higher than that of the Extreme ultraviolet Variability Experiment onboard the Solar Dynamics Observatory. B(_4)C/Al and B(_4)C/Mo/Al multilayer structures were optimized to improve the diffraction efficiency across both bands simultaneously. We also evaluated the instrument performance by calculating the photon numbers. Additionally, we discussed the degradation of spectral resolution caused by the stability of satellite platform, determining that the stability should be better than ±7.2(^{prime prime })(( pm )0.002(^circ )) within the exposure time of 60 s. Our investigation provides a new way to observe Sun-as-a-star extreme ultraviolet spectrum.

Ground-based observations of spacecraft signals have been used to study space weather. However, single spacecraft measurements observed from the Earth have limitations in studying the structure and evolution of solar plasma as they are unable to differentiate spatial and temporal variations. To overcome this limitation and improve our understanding of interplanetary scintillation, we simultaneously observed radio signals transmitted by two co-orbiting spacecraft: the ESA Mars Express (MEX) and the Chinese National Space Administration Tianwen-1 (TIW-1). We conducted the observations from April to November 2021 using the University of Tasmania’s VLBI radio telescopes at 8.4 GHz. We employed the Planetary Radio Interferometer and Doppler Experiment (PRIDE) technique to determine the topocentric Doppler measurements and residual phase of the carrier signal. These observables were used to quantify the phase fluctuations of the spacecraft signals caused by solar wind and hydrodynamic turbulence in the interplanetary medium. The measured phase fluctuations RMS from both spacecraft show small differences which are caused by factors such as the spacecraft’s motion, onboard electronics, and variations in the uplink signal path through Earth’s ionosphere. These fluctuations decrease with solar elongation and correlate with solar radio flux at 10.7 cm (2800 MHz), indicating solar activity. The estimated total electron contents along MEX and TIW-1’s radio lines of sight are similar, with higher values at lower solar elongations. Simultaneous multi-spacecraft observations also enable RFI characterization, frequent spacecraft performance comparisons, and investigation of solar activity effects on spacecraft performance and scientific outcomes.

The Athena mission entered a redefinition phase in July 2022, driven by the imperative to reduce the mission cost at completion for the European Space Agency below an acceptable target, while maintaining the flagship nature of its science return. This notably called for a complete redesign of the X-ray Integral Field Unit (X-IFU) cryogenic architecture towards a simpler active cooling chain. Passive cooling via successive radiative panels at spacecraft level is now used to provide a 50 K thermal environment to an X-IFU owned cryostat. 4.5 K cooling is achieved via a single remote active cryocooler unit, while a multi-stage Adiabatic Demagnetization Refrigerator ensures heat lift down to the 50 mK required by the detectors. Amidst these changes, the core concept of the readout chain remains robust, employing Transition Edge Sensor microcalorimeters and a SQUID-based Time-Division Multiplexing scheme. Noteworthy is the introduction of a slower pixel. This enables an increase in the multiplexing factor (from 34 to 48) without compromising the instrument energy resolution, hence keeping significant system margins to the new 4 eV resolution requirement. This allows reducing the number of channels by more than a factor two, and thus the resource demands on the system, while keeping a 4’ field of view (compared to 5’ before). In this article, we will give an overview of this new architecture, before detailing its anticipated performances. Finally, we will present the new X-IFU schedule, with its short term focus on demonstration activities towards a mission adoption in early 2027

X-ray Polarimeter Satellite (XPoSat) is India’s first landmark mission dedicated to X-ray polarimetry, with the aim of measuring and studying X-rays emitted by bright astronomical objects such as black hole X-ray binaries, pulsar wind nebulae, and accretion-powered pulsars. Polar Satellite Launch Vehicle-C58 (PSLV-C58) launched the XPoSat mission on 1st January 2024, equipped with two significant, scientific instruments: XSPECT (X-ray Spectroscopy and Timing) and POLIX (POLarimeter Instrument in X-rays). With the launch of XPoSat, a new and important fourth dimension of polarization has been added. POLIX became the first in the world to provide measurements of polarization in 8–30 kilo electron Volt (keV) energy band. XSPECT is a spectroscopy payload responsible for providing timing and spectral information in 0.8–15 keV energy band of X-ray emissions from about 54 potential identified cosmic X-ray sources. Astronomical sources emitting X-rays are sites of strong gravity, and strong magnetic fields and have a variety of geometries for scattering, which are expected to give rise to polarization signatures in these sources. This article provides a comprehensive overview from mission specifications to mission design, mission planning, mission analysis, and mission operations aspects of spacecraft configuration, operations, and on-orbit operations of XPoSat mission with the science brought by the first-time flown payload in high energy bands, which will allow astronomers to explore materials under intense magnetic and gravitational fields. The challenges involved in planning and executing the mission operations with critical scenarios have also been highlighted.

Microwave SQUID Multiplexing ((mu )MUX) is a widely used technique in the low-temperature detectors community as it offers a high capacity for reading large-scale Transition-Edge Sensor (TES) arrays. This paper proposes a Sliding Flux Ramp Demodulation (SFRD) algorithm for (mu )MUX readout system. It can achieve a sampling rate in the order of MHz while maintaining a multiplexing ratio of about one thousand. Advancing of this large array readout technique makes it possible to observe scientific objects with improved time resolution and event count rate. This will be highly helpful for TES calorimeters in X-ray applications, such as X-ray astrophysics missions.

The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a collaborative satellite developed by China and France, specifically designed for observing and studying Gamma-Ray Bursts (GRBs) as well as other variable sources. Among its four on-board payloads, the Gamma-Ray Monitor (GRM) is responsible for detecting high-energy photons ranging from 15 keV to 5 MeV, equipped with real-time triggering and localization capabilities. In this paper, we primarily focus on investigating the triggering performance of GRM. Firstly, the energy response matrix of each detector is obtained by using the Geant4 simulation toolkit. Based on the results of background simulations and given samples of GRB, the instrument’s sensitivity and the detection efficiency to GRBs from different directions are estimated. The results demonstrate that GRM exhibits superior sensitivity to GRBs with harder energy spectrum, enabling more than (80%) of the GRBs to be triggered within its field of view. By considering satellite orbit and attitude, we conduct a 3-year simulation of GRB observations which reveals that approximately 106 GRBs can be detected annually in the energy range of 50-300 keV by GRM. Moreover, it is observed that optimal triggering energy range correlates with the hardness index values of the GRBs. Finally, we discuss the on-orbit triggering algorithm that has been implemented by GRM along with developing a ground-based multi-timescale search algorithm for identifying potential GRB events. Our work contributes to understanding the on-orbit triggering performance characteristics demonstrated by GRM, while also providing a benchmark for refining ground-based strategies focused on detecting new instances of GRBs, thus amplifying the scientific output obtained from utilizing GRM’s capabilities.

As the observation frequency of large-aperture antennas increases, the requirements for measuring main reflector deformation have become more stringent. Recently, the rapid development of deep learning has led to its application in antenna deformation prediction. However, achieving high accuracy requires a large number of high-fidelity deformation samples, which is often challenging to obtain. To address these problems, this paper establishes a high-accuracy antenna surface deformation measurement model based on a multi-fidelity transfer learning neural network (MF-TLNN). Firstly, a low-fidelity surrogate model is constructed using a large number of simulation deformation samples to ensure its robustness. Secondly, the MF-TLNN structure is designed and trained using a small number of high-fidelity samples obtained from actual measurements of the main reflector deformation via out-of-focus (OOF) holography method. Thirdly, a Zernike correction module is utilized to provide additional constraints and ensure the stability of the results. Experimental results show that the proposed method can closely approximate radio holography measurements in terms of accuracy and is almost real-time in terms of speed.

A new method using the muon lateral distribution and an underground muon detector to achieve high discrimination power against hadrons is presented. The method is designed to be applied in the Andes Large-area PArticle detector for Cosmic-ray physics and Astronomy (ALPACA) experiment in Bolivia. This new observatory in the Southern hemisphere has the goal of detecting >100 TeV (gamma ) rays in search for the origins of Galactic cosmic rays. The method uses the weighted sum of the lateral distribution of the muons detected by underground detectors to separate between air showers initiated by cosmic rays and (gamma ) rays. We evaluate the performance of the method through Monte Carlo simulations with CORSIKA and Geant4 and apply the analysis to the prototype of ALPACA, ALPAQUITA. With the application of this method in ALPAQUITA, we achieve an improvement of about 18 % in the energy range from 60 to 100 TeV over the estimated sensitivity using only the total number of muons.