Experimental Astronomy最新文献

The spectroscopy focusing array is one of the four main scientific instruments of the enhanced X-ray Timing and Polarimetry mission, tasked with spectral and timing observation in the energy range 0.5-10 keV. An engineering model of the spectroscopy focusing array with a 4 mirror shells assembly and a focal plane detector using commercial detectors has now been developed. To evaluate the performance, the spectral and timing calibration of the engineering model has been held in the 100-m X-ray Test Facility. A multi-target X-ray source with multiple emission lines is used to calibrate the spectral performance. A timing X-ray source based on a grid controlled X-ray tube has been utilized for the timing calibration. The timing X-ray source can generate X-ray pulses to measure the response time distribution, and can also simulate the pulsar lightcurves to examine the detection ability for pulsars. The energy-channel relation and energy resolution are determined through spectral calibration. The energy resolution at 5.95 keV is 142 eV, now. According to the timing calibration, the mean response time of the engineering model is 1.55 (upmu )s, the full width at half maximum of the response time distribution is 0.45 (upmu )s, and the engineering model has sufficient ability to detect the profile of millisecond pulsars.

The design and usability of a fully autonomous robotic control system (SunbYte - Sheffield University Balloon “lYfted” TElescope) for solar tracking and observational applications onboard high-altitude balloons are addressed here. The design is based on a six-step development plan balancing scientific objectives and practical engineering requirements. The high-altitude solar observational system includes low-cost components such as a Cassegrain-type telescope, stepper motors, harmonic drives, USB cameras and microprocessors. OpenCV installed from ROS (Robotic Operating System), python and C facilitated the collection, compression, and processing of housekeeping and scientific data. This processed data was then transmitted to the ground station through the launch vehicle’s telecommunication link. The SunbYte system allows the brightest spot in the sky, the sun, to be identified, and a telescope pointed towards it with high enough accuracy that a scientific camera can capture images. This paper gathers and presents the results from primarily two missions with the High-Altitude Student Platform (HASP, NASA Balloon Program office and LaSpace). Additionally, a discussion will be made comparing these with an earlier iteration flown with the German-Swedish “REXUS/BEXUS” programme coordinated by the European Space Agency. By capturing and analysing a series of tracking images with the location of the Sun at the calibrated centre, the system demonstrated the tracking capabilities on an unstable balloon during ascent. Housekeeping sensor data was collected to further analyse the thermal and mechanical performance. The low temperature increased friction in the drive train and reduced the responsiveness of the harmonic drive actuation system. This caused some issues which require further work in future missions, for example, with SunbYte 4 and its work when flying with the HEMERA ZPB (Zero Pressure Balloon) program.

As a new member of the high energy astronomical transient monitoring network, Gamma-ray Transient Monitor (GTM) is an all-sky monitor onboard the Distant Retrograde Orbit (DRO) mission which has been launched in March 2024. In this work, we investigate the space radiation environment of DRO, and study the in-flight background of GTM using GEANT4. The background count rate on each of the 5 GTP detectors of GTM is estimated to be about 800(sim )1000 counts/s in the energy range from 20 keV to 1 MeV after one-year operation on orbit. We find that there are two distinct spectral lines clearly visible in the background spectrum, i.e. the 59 keV emission line from the embedded calibration source (^{241})Am and the 511 keV emission line induced by space radiations, which are suitable for the in-flight energy gain calibration. These results provide important reference for the development of payload, design of observation strategies, in-flight calibration of instrument and research of scientific objectives.

The cosmic microwave background (CMB) radiation, the relic afterglow of the Big Bang, has become one of the most useful and precise tools in modern precision cosmology. In this article, we employ Tsallis non-extensive statistical framework to calculate the cosmic microwave background (CMB) temperature and its probability distribution by utilising a recently proposed blackbody radiation inversion (BRI) technique and the cosmic background explorer/ far infrared absolute spectrophotometer (COBE/FIRAS) dataset. Here, we have used the best-fit values of q = 0.99888 ± 0.00016 and q = 1.00012 ± 0.00001, obtained by fitting COBE/FIRAS data with two different versions of non-extensive models. We compare the results with the more conventional extensive statistical analysis i.e. for q = 1.

We present Daksha, a proposed high energy transients mission for the study of electromagnetic counterparts of gravitational wave sources, and gamma ray bursts. Daksha will comprise of two satellites in low earth equatorial orbits, on opposite sides of the Earth. Each satellite will carry three types of detectors to cover the entire sky in an energy range from 1 keV to (>1) MeV. Any transients detected on-board will be announced publicly within minutes of discovery. All photon data will be downloaded in ground station passes to obtain source positions, spectra, and light curves. In addition, Daksha will address a wide range of science cases including monitoring X-ray pulsars, studies of magnetars, solar flares, searches for fast radio burst counterparts, routine monitoring of bright persistent high energy sources, terrestrial gamma-ray flashes, and probing primordial black hole abundances through lensing. In this paper, we discuss the technical capabilities of Daksha, while the detailed science case is discussed in a separate paper.

We present the science case for the proposed Daksha high energy transients mission. Daksha will comprise of two satellites covering the entire sky from 1 keV to (>1) MeV. The primary objectives of the mission are to discover and characterize electromagnetic counterparts to gravitational wave source; and to study Gamma Ray Bursts (GRBs). Daksha is a versatile all-sky monitor that can address a wide variety of science cases. With its broadband spectral response, high sensitivity, and continuous all-sky coverage, it will discover fainter and rarer sources than any other existing or proposed mission. Daksha can make key strides in GRB research with polarization studies, prompt soft spectroscopy, and fine time-resolved spectral studies. Daksha will provide continuous monitoring of X-ray pulsars. It will detect magnetar outbursts and high energy counterparts to Fast Radio Bursts. Using Earth occultation to measure source fluxes, the two satellites together will obtain daily flux measurements of bright hard X-ray sources including active galactic nuclei, X-ray binaries, and slow transients like Novae. Correlation studies between the two satellites can be used to probe primordial black holes through lensing. Daksha will have a set of detectors continuously pointing towards the Sun, providing excellent hard X-ray monitoring data. Closer to home, the high sensitivity and time resolution of Daksha can be leveraged for the characterization of Terrestrial Gamma-ray Flashes.

Project “Saptarshi” was initiated by the National Centre for Geodesy, Indian Institute of Technology Kanpur to set up the modern space geodetic infrastructure in the country. This project primarily focuses on the establishment of an Indian Geodetic VLBI network. The purpose of this paper is to anticipate the potential impact of the geodetic VLBI network in India to the national and international scientific products. Saptarshi proposes to establish three VLBI stations along with a correlator at one facility. In this work, we investigate how adding proposed Indian VLBI antennas will affect terrestrial and celestial reference frames as well as Earth Orientation Parameters (EOP). Additionally, we shortly demonstrate scenario of VLBI observations of one of the Indian regional navigation satellite system called Navigation with Indian Constellation (NavIC) to determine its orbit. Two VLBI networks were simulated to observe the NAVIC satellite along with quasars to check how well the orbit of this satellite can be recovered from VLBI observations. To investigate the impact on the terrestrial reference frame, three types of 24-h sessions, IVS-R1 (legacy), IVS-VGOS (next generation VLBI), and IVS-AOV (Asia Oceania VLBI), were studied to examine the gain in precision of geodetic parameters when adding the proposed Indian VLBI antennas. IVS-type Intensive sessions were also investigated with the proposed Indian antennas to assess the improvement in the estimation of dUT1 as one important VLBI product. Furthermore, the u-v coverage of some radio sources of the southern hemisphere was compared utilizing observing networks with and without the proposed Indian antennas. Apart from that, we briefly discuss other benefits of the establishment of Indian geodetic VLBI in the scientific fields of atmosphere, metrology, and space missions.

The 100-m X-ray Test Facility (100XF) was developed according to the calibration requirement of the first X-ray astronomical satellite Insight-HXMT in china. After that, the 100XF has provided calibration services for other X-ray astronomical satellites. In order to test the energy response matrices of space-borne detectors and to extend the capability of 100XF, a monochromator based on channel-cut crystals is developed. So far, 3.0-20.7 keV monochromatic X-rays have been realized successfully with Si(111) crystal. The monochromaticity ((Delta ) (mathrm E_textrm{FWHM})/E) is better than 0.6% @5.9 keV, the flux stability can reach 2.6% in about one hour. The energy stability is particularly good, the variation is 0.05% in about one hour. Further more, the beam spot spreads in the plane orthogonal to the rocking direction after a propagation of 100-meter, which is sufficient and useful for testing detectors with large sensitive area. In this paper, we present the research and establishment of the X-ray monochromator at the 100XF.

Automatic classification of stellar spectra contributes to the study of the structure and evolution of the Milky Way and star formation. Currently available methods exhibit unsatisfactory spectral classification accuracy. This study investigates a method called DSRL, which is primarily used for automated and accurate classification of LAMOST stellar spectra based on MK classification criteria. The method utilizes discrete wavelet transform to decompose the spectra into high-frequency and low-frequency information, and combines residual networks and long short-term memory networks to extract both high-frequency and low-frequency features. By introducing self-distillation (DSRL-1, DSRL-2, and DSRL-3), the classification accuracy is improved. DSRL-3 demonstrates superior performance across multiple metrics compared to existing methods. In both three-class(F ,G ,K) and ten-class(A0, A5, F0, F5, G0, G5, K0, K5, M0, M5) experiments, DSRL-3 achieves impressive accuracy, precision, recall, and F1-Score results. Specifically, the accuracy performance reaches 94.50% and 97.25%, precision performance reaches 94.52% and 97.29%, recall performance reaches 94.52% and 97.22%, and F1-Score performance reaches 94.52% and 97.23%. The results indicate the significant practical value of DSRL in the classification of LAMOST stellar spectra. To validate the model, we visualize it using randomly selected stellar spectral data. The results demonstrate its excellent application potential in stellar spectral classification.

The X-ray Integral Field Unit (X-IFU) is the high-resolution X-ray spectrometer to fly on board the Athena Space Observatory of the European Space Agency (ESA). It is being developed by an international Consortium led by France, involving twelve ESA member states, plus the United States. It is a cryogenic instrument, involving state of the art technology, such as micro-calorimeters, to be read out by low noise electronics. As the instrument was undergoing its system requirement review (in 2022), a life cycle assessment (LCA) was performed to estimate the environmental impacts associated with the development of the sub-systems that were under the responsibility of the X-IFU Consortium. The assessment included the supply, manufacturing and testing of sub systems, as well as involved logistics and manpower. We find that the most significant environmental impacts arise from testing activities, which is related to energy consumption in clean rooms, office work, which is related to energy consumption in office buildings, and instrument manufacturing, which is related to the use of mineral and metal resources. Furthermore, business travels is another area of concern, despite the policy to reduced flying adopted by the Consortium. As the instrument is now being redesigned to fit within the new boundaries set by ESA, the LCA will be updated, with a focus on the hot spots identified in the first iteration. The new configuration, consolidated in 2023, is significantly different from the previously studied version and is marked by an increase of the perimeter of responsibility for the Consortium. This will need to be folded in the updated LCA, keeping the ambition to reduce the environmental footprint of X-IFU, while complying with its stringent requirements in terms of performance and risk management.