Experimental Astronomy最新文献

The spiral structure is an important morphology within galaxies, providing information on the formation, evolution, and environment of spiral galaxies. The number of spiral arms is one of the important parameters to describe the morphology of spiral galaxies. In this project, we study the classification of spiral galaxies by the number of spiral arms based on deep learning algorithms. The data set for this project consists of eligible samples from Galaxy Zoo 2 and Galaxy Zoo DECaLS. To better identify the texture features of the spiral arms, we designed a convolutional neural network model incorporating Gabor filter (Gabor Residual Filtering Convolutional Net, GReFC-Net), and used other networks for 3 and 4-way classifications. In the 3-way case, the GReFC-Net algorithm achieves the highest precision, recall, F1-score, and AUC value, which are 96.25%, 96.23%, 96.21%, and 0.9937. In the 4-way case, the GReFC-Net algorithm has the highest recall, F1-score and AUC value, which are 95.57%, 95.42% and 0.9957. The interpretability of GReFC-Net is analyzed by the SHAP method, and the results show that the network can identify the spiral arm structure of spiral galaxies well. It can be seen that the GReFC-Net algorithm can be effectively applied to the automatic measurement task of spiral arm structure in a large number of spiral galaxies.

In this study, we have presented the results of the precipitable water vapor (PWV) for the Eastern Anatolia Observatory (in Turkish: Doğu Anadolu Gözlemevi, the acronym is DAG) site in Erzurum, Türkiye. The DAG has Türkiye’s largest and the first near infrared (NIR) telescope with a mirror diameter of 4 meters at the altitude of 3170 m. The DAG telescope is going to take the first light in the end of summer 2024. This study is focused on the examining of the precipitable water vapor data for the NIR observations at the DAG. In this context, the NWC SAF Total Precipitable Water (TPW) data obtained by both the satellite based and the radiosonde balloon validated with six radiosonde stations were examined by temporal, vertical and horizontal analyses for the DAG site between June 2019 to December 2020. The results obtained from these analyzes indicate that the mean and median TPW values at the DAG site were approximately 7 mm and the minimum and maximum values were 0.59 mm and 24.12 mm, respectively. The monthly median TPW values at the DAG site varied between approximately 3-10 mm, with a decreasing trend from June to January and an increase in the first seven months of 2020. These results also indicate that the TPW data obtained by its 15 minutes temporal resolution, aligns closely with the radiosonde measurements. Furthermore, the values of PWV at both lower and upper levels of the atmosphere are minimal while the values increase slightly in the middle layer of the atmosphere. As a result, the effective monitoring of the PWV in a site would result in the generation of higher quality astronomical IR observations and be important in terms of the optimum operating cost for an observatory.

ESA’s PLATO mission aims the detection and characterization of terrestrial planets around solar-type stars as well as the study of host star properties. The noise-to-signal ratio (NSR) is the main performance parameter of the PLATO instrument, which consists of 24 Normal Cameras and 2 Fast Cameras. In order to justify, verify and breakdown NSR-relevant requirements the software simulator PINE was developed. PINE models the signal pathway from a target star to the digital output of a camera based on physical models and considers the major noise contributors. In this paper, the simulator’s coarse mode is introduced which allows fast performance analyses on instrument level. The added value of PINE is illustrated by exemplary applications.

The enhanced X-ray Timing and Polarimetry mission (eXTP) is a next-generation flagship X-ray astronomy satellite currently in phase-B study. The large Area Detector (LAD) on board eXTP contains 40 modules, each consisting of a set of 4(times )4 large area SDDs and 4(times )4 collimators, and has a designed effective area of 3.0 m(^2) at 8 keV and a Field of View (FoV) of 1(^circ ). To achieve such a large effective area, the collimator’s Open Area Ratio (OAR) should be greater than 70%. In this paper, we introduce the measurement methods used to determine the OAR and the rocking curve (angular response) of the LAD collimator at the 100-m X-ray Test Facility (100XF) of the Institute of High Energy Physics (IHEP) in Beijing, and report the results of the collimators manufactured under different conditions. The measured OARs of the collimators are usually smaller than the theoretical values by a few percent, which is due to the non-uniformity and irregularity of the pores. The measured rocking curves are usually broader than the theoretical triangular curves, and the lower the energy of the incident X-ray the broader the rocking curve. This broadening of the rocking curve is the result of reflection on the inner wall of the pores. Our results also show that increasing the etching time in the manufacturing of the collimators can increase the OARs but does not change significantly the shape of the rocking curves.

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.