Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: The reconstruction of muon energies is crucial for the data analysis of neutrino experiments using large water Cherenkov detectors, but the resolution for muon energy reconstruction using traditional methods is poor. Here, we propose a revised approach to remove noisy optical modules along the track produced by the propagation of muons through water. The number of photons on the optical modules is first corrected by the attenuation properties of light in water. Then the difference in time between the observed optical modules and the expected ones is determined based on the geometry of the triggered optical modules. Finally, the standard of correction is measured by the ratio of photon number before and after correction. Optical modules selection conditions were optimized according to these parameters, with most noisy optical modules successfully removed, improving the resolution of muon energy reconstruction.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: The primary mirrors of current and future large telescopes always employ a segmented mirror configuration. The small but non-negligible gaps between neighboring segments cause additional diffraction, which restricts the performance of high-contrast coronagraph. To solve this problem, we propose a coronagraph system based on a single liquid crystal spatial light modulator (SLM). This spatial light modulator is used for amplitude apodization, and its feasibility and potential performance are demonstrated using a laboratory setup using the stochastic parallel gradient descent (SPGD) algorithm to control the spatial light modulator, which is based on point spread function (PSF) sensing and evaluation and optimized for maximum contrast in the discovery working area as a merit function. The system delivers a contrast in the order of 10−6, and shows excellent potential to be used in current and future large aperture telescopes, both on the ground and in space.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-06-06 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: Research on adaptive deformable mirror technology for voice coil actuators (VCAs) is an important trend in the development of large ground-based telescopes. A voice coil adaptive deformable mirror contains a large number of actuators, and there are problems with structural coupling and large temperature increases in their internal coils. Additionally, parameters of the traditional proportional integral derivative (PID) control cannot be adjusted in real-time to adapt to system changes. These problems can be addressed by introducing fuzzy control methods. A table lookup method is adopted to replace real-time calculations of the regular fuzzy controller during the control process, and a prototype platform has been established to verify the effectiveness and robustness of this process. Experimental tests compare the control performance of traditional and fuzzy proportional integral derivative (Fuzzy-PID) controllers, showing that, in system step response tests, the fuzzy control system reduces rise time by 20.25%, decreases overshoot by 78.24%, and shortens settling time by 67.59%. In disturbance rejection experiments, fuzzy control achieves a 46.09% reduction in the maximum deviation, indicating stronger robustness. The Fuzzy-PID controller, based on table lookup, outperforms the standard controller significantly, showing excellent potential for enhancing the dynamic performance and disturbance rejection capability of the voice coil motor actuator system.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-04-18 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: Adaptive optics (AO) is essential for high-quality ground-based observations with large telescopes because it counters the impact of wavefront aberrations caused by atmospheric turbulence. The new vacuum solar telescope(NVST) is one of the most important high-resolution solar observation instruments in the world. Three sets of solar adaptive optics systems have been developed and installed on this telescope: conventional adaptive optics, ground layer adaptive optics, and multi- conjugate adaptive optics. These have been in operation from 2018 to 2023. This paper details the development and application of solar adaptive optics on the NVST and discusses the newest instrumentation.
Subjects: Astronomy >> Astronomical Instruments and Techniques submitted time 2024-02-07 Cooperative journals: 《天文技术与仪器(英文)》
Abstract: Before charge-coupled device detectors became widely employed in observational astronomy, for more than a hundred years, the main detection method was photography on astronomical glass plates. Recently, in order to preserve these historical data and maintain their usability, the International Astronomical Union has appealed to all countries for global digitization of astronomical plates by developing or adopting advanced digitization technology. Specialized digitizers with high precision and high measuring speed represent key equipment for this task. The Shanghai Astronomical Observatory and the Nishimura Co., Ltd in Japan cooperated between 2013 and 2016 to develop the first Chinese high-precision astronomical plate digitizer, which was then used for complete digitization of all nighttime-observation astronomical plates in China. Then, in 2019–2021, the Shanghai Astronomical Observatory independently developed new models of plate digitizers that enabled countries such as Uzbekistan and Italy to digitize their astronomical plates. Additionally, a new high-precision and multifunction digitizer was also used to digitize valuable microscope slides from the Shanghai Natural History Museum, providing a successful example of crossdomain application of high-precision digitization technology.
Subjects: Astronomy >> Astrophysics submitted time 2023-12-29
Abstract: We studied the unique kinematic properties in massive filament G352.63-1.07 at 1000-AU spatial scale with the dense molecular tracers observed with the Atacama Large Millimeter/submillimeter Array (ALMA). We find the central massive core M1 (12 Msun) being separated from the surrounding filament with a velocity difference of v-v_sys=-2 km/s and a transverse separation within 3 arcsec. Meanwhile, as shown in multiple dense-gas tracers, M1 has a spatial extension closely aligned with the main filament and is connected to the filament towards its both ends. M1 thus represents a very beginning state for a massive young star-forming core escaping from the parental filament, within a time scale of ~4000 years. Based on its kinetic energy (3.5x10^44 erg), the core escape is unlikely solely due to the original filament motion or magnetic field, but requires more energetic events such as a rapid intense anisotropic collapse. The released energy also seems to noticeably increase the environmental turbulence. This may help the filament to become stabilized again.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-12-29
Abstract: Magnetars are neutron stars with extremely strong magnetic fields, frequently powering high-energy activity in X-rays. Pulsed radio emission following some X-ray outbursts have been detected, albeit its physical origin is unclear. It has long been speculated that the origin of magnetars' radio signals is different from those from canonical pulsars, although convincing evidence is still lacking. Five months after magnetar SGR 1935+2154's X-ray outburst and its associated Fast Radio Burst (FRB) 20200428, a radio pulsar phase was discovered. Here we report the discovery of X-ray spectral hardening associated with the emergence of periodic radio pulsations from SGR 1935+2154 and a detailed analysis of the properties of the radio pulses. The complex radio pulse morphology, which contains both narrow-band emission and frequency drifts, has not been seen before in other magnetars, but is similar to those of repeating FRBs - even though the luminosities are many orders of magnitude different. The observations suggest that radio emission originates from the outer magnetosphere of the magnetar, and the surface heating due to the bombardment of inward-going particles from the radio emission region is responsible for the observed X-ray spectral hardening.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astronomical Instruments and Techniques Subjects: Optics >> Instrumentation, measurement, and metrology Subjects: Optics >> Coherence and statistical optics submitted time 2023-06-28
Abstract: Co-phase and co-focus detection is one of the key technologies for large-aperture segmented mirror telescopes. In this paper, a new edge sensor based on fringes of equal thickness is developed, which can detect each segment's relative piston, tilt, and tip errors from the interferograms. Based on the co-focus demand for many ground-based seeing limited segmented mirror telescopes, an edge sensor prototype based on such a principle is built and applied in the indoor segmented mirror experiment system in the lab. According to the co-focus requirement of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, many simulations and experiments are carried out for co-focus error detection of the segmented mirror system. Experiment results show that the co-focus accuracy is better than 0."02 rms, which can meet the co-focus requirements of most large or extremely large segmented mirror astronomical telescopes.
Subjects: Astronomy >> Astrophysical processes submitted time 2018-05-28 Cooperative journals: 《天文研究与技术》
Abstract: This paper is aimed at separation treatment of low- and high-frequency components in polar motion forecasting and thenimproving time-series predictions. For the purpose, the empirical mode decomposition (EMD) is employed as a filter to extract low- and high-frequency signals from original pole coordinate data. The decomposition of the pole motion observations between 1986 and 2015 from the International Earth Rotation and Reference Systems Service (IERS) C04 seriesillustrates that the low-frequency fluctuations including inter-decadal, inter-annual, Chandler and annual wobbles and shorter-period high-frequency oscillationscan be separated from the observed time-series by the EMD. On the basis of separation, the least-squares (LS) extrapolation of models for annual and Chandler wobbles and for the linear trend are used for deterministic prediction of the low-frequency fluctuations, while the autoregressive (AR) technology is applied to forecasting the high-frequency oscillations plus LS fitting residuals. Pole coordinateforecasts are calculated as the sum of LS extrapolation and AR predictions (LS+AR).We have evaluated the accuracy of our long-term predictions (up to 1 year in the future) in comparison with the IERS official predictions in terms of year-by-year statistics of 5 years. It is shown that the accuracy of the LS+AR methodcan be significantly improved using a combination of the EMD and LS+AR (EMD+LS+AR). Also, the proposed prediction strategyoverall outperforms the IERS solutions. In addition, the predictions are compared with those from the Earth Orientation Parameters Prediction Comparison Campaign (EOP PCC). The comparison demonstrates that the developed schemeis a very accurate approach to predict polar motion. According to this study, it is concluded that polar motion predictions may be enhanced through separation treatment of different time-scale fluctuations and thus such processing seems to be necessary in pole coordinate prediction.