Experimental Astronomy最新文献

PRATUSH – Probing ReionizATion of the Universe using Signal from Hydrogen – is a proposed cosmology experiment to detect the global red-shifted 21-cm signal from the Cosmic Dawn and Epoch of Reionization (CD/EoR). PRATUSH orbiting the Moon will seek to precisely measure the low-frequency radio sky-spectrum over 40 to 200 MHz. The scientific observations would be made in the radio-quiet region when in the farside of the Moon, and the data would be transmitted back to Earth when in the near-side. PRATUSH was proposed to the Indian Space Research Organization (ISRO) during a call for proposals in the announcement of opportunity for science payloads in 2018. PRATUSH is in the pre-project studies phase. Here we present a mission concept and baseline design of the proposed payload optimized to operate over the Cosmic Dawn signal band of 55 - 110 MHz. Starting with a description of the fundamental design principles followed, we discuss the PRATUSH baseline design and sensitivity. We further enumerate the challenges that are common to most PRATUSH like experiments, which have been proposed to seek a detection of the CD/EoR signal in orbit in the lunar farside. Due to the highly sensitive nature of the measurement, PRATUSH is designed to operate as a solo experiment with a dedicated spacecraft. Our simulations, assuming a mission lifetime of two years, estimate that PRATUSH would have the sensitivity required to detect the CD signal predicted by the standard models with varying degrees of confidence.A concept model of PRATUSH is under development, which is expected to lead to the engineering model followed by flight model subject to mission approval.

This article presents the design and implementation of a soft X-ray polarized calibration platform based on Bragg’s Law and Fresnel’s Law, which is used to calibrate low-energy polarization detector(LPD/POLAR-2) that has potential deployment onboard the China Space Station. The platform is equipped with versatile equipment that can generate both completely and partially polarized X-ray beams, and provides precise control over the diffraction angle, achieving the desired polarization degree. It covers the 3–8 keV energy band, with a high fraction of monochromatic light (>93%)(The proportion of monochromatic light is defined as the ratio of the number of photons falling within three times the sigma of the target peak centre value to the total photons.) and good monochromaticity(In this article, we evaluate the monochromaticity of the polarized source using the Full Width at Half Maximum (FWHM) of its all-in-one peak.), and is suitable for calibrating LPD’s large-field-of-view soft X-ray polarization detector using its vertically incident and obliquely incident polarized X-rays. The completely and partially polarized X-ray beams generated at 8.0 keV by the calibration platform are used to test the polarization measurement capabilities of the soft X-ray polarized detector and verify the linearity between the calibration source’s polarization and the measurable modulation of the polarimeter.

An observation simulator is established for the Spectroscopy Focusing Array (SFA) and Polarimetry Focusing Array (PFA) onboard the planned enhanced X-ray Timing and Polarimetry observatory (eXTP). It consists of photon generation, imaging, detection, and event readout to generate data products, which can be analyzed by the standard astronomical analysis software. It is used to simulate a few astronomical sources to estimate and understand the impact of the payload and platform design configurations on the scientific goals of eXTP, including the background estimation of the central pixel in SFA, position dependence of silicon drift detector signals and its impacts, and pointing jitter requirements. The joint data analysis of the SFA and PFA payloads shows that the PFA image can help estimate the impact of nearby sources on the target source and select the proper pixels for the background estimation of the central pixel in SFA. The spectral and timing study of the millisecond pulsar depicts that the position dependence of silicon drift detector signals itself has an insignificant impact on the results. The type-C low-frequency quasi-periodic oscillations of black holes ranging from 0.01 Hz to 30 Hz are considered to raise the pointing jitter requirements of the telescope. In this case, the stability of the telescope should be less than 12(^{prime prime }) to avoid any spurious modulation signal. These examples demonstrate the necessity of an end-to-end observation simulator in the space mission, which will be further tested and improved by the ground segment in a wider range of applications.

In an effort to map our meteor showers, a total of 76,765 meteoroids were triangulated by the United Arab Emirates Astronomical Camera Network between 01 January 2017 and 31 December 2021 as part of the global Cameras for Allsky Meteor Surveillance network. The calculated meteoroid orbits were analyzed by a newly developed user-friendly software to identify potential new meteor showers. The software is designed to run in three different modes that assign orbits to either a known shower, to any of the previously reported meteor showers listed in the IAU Working List of Meteor Showers, while the remainder of orbits are linked to find newly defined meteor showers using one of three Discriminant-criterion methods. 12 new meteors showers were identified and added to the IAU Working List, most of which identify the hitherto unknown debris streams of Jupiter-family comets.

POLAR-2, a plastic scintillator based Compton polarimeter, is currently under development and planned for a launch to the China Space Station in 2025. It is intended to shed a new light on our understanding of Gamma-Ray Bursts by performing high precision polarization measurements of their prompt emission. The instrument will be orbiting at an average altitude of 383 km with an inclination of 42° and will be subject to background radiation from cosmic rays and solar events. In this work, we tested the performance of plastic scintillation bars, EJ-200 and EJ-248M from Eljen Technology, under space-like conditions, that were chosen as possible candidates for POLAR-2. Both scintillator types were irradiated with 58 MeV protons at several doses from 1.89 Gy(corresponding to about 13 years in space for POLAR-2) up to 18.7 Gy, that goes far beyond the expected POLAR-2 life time. Their respective properties, expressed in terms of light yield, emission and absorption spectra, and activation analysis due to proton irradiation are discussed. Scintillators activation analyses showed a dominant contribution of β + decay with a typical for this process gamma-ray energy line of 511 keV.

The Radio Frequency Interference (RFI) generated by the surrounding environment will significantly reduce the observation efficiency of the large radio telescope. The Tian-Ma Radio Telescope (TMRT) has established a RFI monitoring system to keep watch on its surrounding RFI environment chronically in the L, S, C and X bands. The system consists of antennas, receivers, back-ends and control system. To achieve automatic system operation, we design and implement an automation software based on Tango Controls open source framework. This paper will briefly introduce the TMRT RFI Monitoring System (TRMS), and describe the functional design, architecture design and implementation of the automation software. Finally, with the help of this system, we carry out automatic remote monitoring of the RFI environment around the TMRT in the 1.12—12.4 GHz frequency band, and then analyze and verify the observation results.

Cosmic Ray Laboratory – TIFR, Ooty, India is operating the largest tracking muon telescope as a component of the GRAPES-3 (Gamma Ray Astronomy PeV EnergieS at phase – 3) experiment. The basic building blocks of the telescope are proportional counters (PRCs), a large number of which are fabricated in-house for the planned expansion of the existing muon telescope to double its area and enhance the solid angle coverage from 2.3 sr to 3.7 sr as well as achieving higher sensitivity for studying space weather and atmospheric phenomena, cosmic ray composition, etc. The existing muon telescope consists of 3712 PRCs, and after the planned expansion which requires an additional 3776 PRCs, the area of the telescope will increase from the present 560 m(^{2}) to 1130 m(^{2}). Each of the PRCs will need to be individually equipped with front-end electronics for processing the output signals. The output pulses from PRCs are extremely feeble, and their charges are in the order of (sim )100 pC. The tiny signal has to be isolated from potential sources of noise before its processing. High-performance, ultra-low noise, and cost-effective electronics are designed, developed, and mass-produced in-house for about 8000 channels of PRCs. The quality of data is improved significantly by interfacing the new electronics with PRCs of the existing muon telescope due to improved signal-to-noise (S/N) ratio, and the data acquisition is made effective as a result of multifold improvement achieved by avoiding undesired interruptions in the data.

The Chasing All Transients Constellation Hunters (CATCH) space mission plans to launch three types of micro-satellites (A, B, and C). The type-B CATCH satellites are dedicated to locating transients and detecting their time-dependent energy spectra. A type-B satellite is equipped with lightweight Wolter-I X-ray optics and an array of position-sensitive multi-pixel Silicon Drift Detectors. To optimize the scientific payloads for operating properly in orbit and performing the observations with high sensitivities, this work performs an in-orbit background simulation of a type-B CATCH satellite using the Geant4 toolkit. It shows that the persistent background is dominated by the cosmic X-ray diffuse background and the cosmic-ray protons. The dynamic background is also estimated considering trapped charged particles in the radiation belts and low-energy charged particles near the geomagnetic equator, which is dominated by the incident electrons outside the aperture. The simulated persistent background within the focal spot is used to estimate the observation sensitivity, i.e. 4.22 (times ) 10(^{-13}) erg cm(^{-2}) s(^{-1}) with an exposure of 10(^{4}) s and a Crab-like source spectrum, which can be utilized further to optimize the shielding design. The simulated in-orbit background also suggests that the magnetic diverter just underneath the optics may be unnecessary in this kind of micro-satellites, because the dynamic background induced by charged particles outside the aperture is around 3 orders of magnitude larger than that inside the aperture.

The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) consists of two small satellites operating in the same Earth orbit with opposite phases. Its scientific goal is to monitor the electromagnetic counterparts associated with Gravitational Wave events (GWE) and other cosmic high energy transient sources. As the main detector, the Gamma-Ray Detector (GRD) adopts LaBr(_{3}):Ce scintillator coupled with SiPM array. Each GRD has two output channels, i.e. high gain channel (8 (sim ) 250 keV) and low gain channel (50 (sim ) 6000 keV). In this paper, we present the low gain calibration results of GRDs with radioactive sources on ground, including the E-C relation, energy resolution, absolute detection efficiency and spatial response. Meanwhile, the consistency between the measurements and Geant4 simulation demonstrates the accuracy of the simulation code.

The LOw Frequency ARray (LOFAR) is a European radio telescope operating since 2010 in the frequency bands 10 - 80 MHz and 110 - 250 MHz. This article provides an analysis of the energy consumption and the carbon footprint of LOFAR. The approach used is a Life Cycle Analysis (LCA). We find that one year of LOFAR operations requires 3,627 MWh of electricity, 48,714 m³ gas and 135,497 liters of fuel. The associated carbon emission is 1,867 tCO2e/year. Results include the footprint stemming from operations of all LOFAR stations and central processing, but exclude scientific post-processing and activities. The electrical energy required for scientific processing is assessed separately. It ranges from 1% (standard imaging and time-domain), to 40% (wide field long baseline imaging) of the energy consumption for the observation. The outcome provides a transparent baseline in making LOFAR more sustainable and can serve as a blueprint for the analysis of other research infrastructures.