The Jiao Tong University Spectroscopic Telescope Project

The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.

New design of large fully-steerable radio telescope reflector based on homogenized mesh structure

The self-weight of a large fully-steerable radio telescope is one of the important factors affecting its performance.In the existing reflector system scheme,the problem of surface accuracy caused by its large and heavy structure has seriously restricted the application and implementation of large radio telescopes.Therefore,a new mesh structure scheme for a large fully-steerable radio telescope reflector is proposed in this paper.This scheme is based on a homogenized mesh back-up structure in the form of a quasi-geodesic grid and regular quasi-tri-prism or tetrahedron,which can significantly reduce the structural complexity and self-weight of the reflector under the condition that the reflector can meet the desired performance requirements.Finally,the feasibility and rationality of the scheme are evaluated by numerical simulation analysis,which has significant advantages and provides a new design for the reflector of a large fullysteerable radio telescope.

Upgrade Procedure for the Delingha 13.7-m Telescope

The 13.7-m millimeter-wave radio telescope of Purple Mountain Observatory operates at 3200-m above the sea level near Delingha,Qinghai Province,China.Equipped with a superconducting SIS receiver,the telescope is used in the millimeter-wave band ranging from 85 to 115 GHz.An upgrade procedure is reported here which includes a superconducting SIS receiver,a new phase-locked local oscillator,a dedicated multi-line backend system,and a new control system based on industrial computer with PCI bus.With the dedicated multi-line backend system,the CO and isotopic lines around 110 GHz are obtained simultaneously.In recent years,scientific activities with this telescope have been focused on studies of Galactic molecular clouds and star formation regions,including surveys of molecular lines from IRAS sources and large-scale map of molecular clouds.Other programs include studies of the circumstellar envelope of late-type stars and interaction of Galactic supernova remnants with dense molecular gas.

A High-Temperature Superconducting Wideband Bandpass Filter at the L Band for Radio Astronomy

In order to ensure the normal operation of radio astronomy observations,an extremely sensitive receiver system needs to be equipped in front of the large radio telescope.An 8-pole wideband high-temperature superconducting(HTS)filter using a Coplanar Spiral Resonator Structure with a passband of 1160~1670 MHz is developed to suppress strong radio interference.The filter is fabricated on a 36 mm×14 mm YBCO HTS film,which is deposited on a 0.5 mm thick MgO substrate.The minimum insertion loss measured in the liquid nitrogen temperature region is 0.03 dB,and the first parasitic passband appears at 2600 MHz.The measured results are in good agreement with the simulations.The filter can be used in radio telescope receivers for the observation of neutral hydrogen and pulsars,as well as in high-sensitivity satellite navigation instruments.

中国科学技术大学-中国科学院紫金山天文台2.5米大视场巡天望远镜(墨子巡天望远镜)

中国科学技术大学-中国科学院紫金山天文台2.5米大视场巡天望远镜(即墨子巡天望远镜,WFST)是中国科学技术大学“双一流”学科平台建设项目,双方于2018年3月1日召开望远镜项目预研启动会,2019年7月正式开展望远镜建设,2023年8月望远镜建成并开展调试观测,2023年9月17日望远镜首光仪式暨科学战略研讨会召开,并成功发布仙女座星系图片,标志着望远镜设备基本达到设计标准,已经可以开展天文观测研究。墨子巡天望远镜口径2.5米,采用国际先进的主焦光学系统设计和主镜主动光学矫正技术,可实现3度视场范围内均匀高像质和极低像场畸变成像,配备7.65亿像素大靶面主焦相机,具备大视场、高像质、宽波段的特点。墨子巡天望远镜安置于青海省海西州茫崖市冷湖镇赛什腾山海拔4200米的天文台址,是冷湖天文观测基地首个投入运行并开展天文观测研究的大型设备。墨子巡天望远镜通过获取天体高精度位置和多波段亮度观测数据,监测移动天体和光变天体,高效搜寻和监测天文动态事件,可以在高能时域天文、太阳系天体普查、银河系结构和近场宇宙学等研究领域取得突破性原始创新成果。同时,墨子巡天望远镜将面向国家航天强国战略,开展太阳系近地天体等搜寻与监测研究,服务航天安全和深空探测战略需求。

面向新疆奇台110 m射电望远镜宽带双极化Vivaldi馈源设计

射电望远镜一般要在宽频段内进行连续观测,但传统相控阵天线设计方法难以兼顾宽频带和大角度扫描特性.紧耦合天线的设计方法为宽带大角度扫描天线提供了新的设计思路,基于此设计了一款宽带双极化Vivaldi相控阵馈源.首先结合Wheeler提出的连续电流片概念及等效电路对紧耦合原理进行理论分析,然后针对Vivaldi天线分析了阵元间的强耦合能够有效拓展天线的工作带宽.在此基础上设计了一款宽带Vivaldi相控阵馈源.馈源阵列由8×9 Vivaldi天线阵元组成,该阵列的工作带宽为2-8GHz,并且能够在E面和H面均实现±45∘的扫描特性.最后对该馈源阵列进行了样机加工和测试,测试结果与仿真结果具有较好的一致性.

南极大视场望远镜光学系统研究进展

南极特殊环境可为天文台址提供绝佳的天文观测条件且具有极高的空间碎片过境频率等特性,因此,南极大视场望远镜在天文观测、空间碎片管理和深空探测等领域具有重要研究意义。本文基于南极天文观测科学目标的需求,综合考虑南极天文台址视宁度数据要求,针对满足南极使用的大视场望远镜光学系统关键科学问题,首先总结与分析了南极天文台址的特征。其次,我国先后在南极地区部署的几批大视场光学望远镜,囊括了几类典型的大视场光学系统,本文详细探讨了南极大视场望远镜目前采用的多类典型大视场光学系统的设计理论,并对南极地区现有和规划中的大视场望远镜项目进行了全面的阐述,介绍了这些系统的关键技术特点。最后,深入探讨了南极大视场望远镜在天文探测科学研究领域所取得的重要进展,重点介绍该领域的前沿动态与一些关键性的突破。

Simulation of RFI Cancellation Using Subspace Projection Algorithm for PAF Receiver

The simulation of radio frequency interference(RFI) cancellation by applying a spatial filtering technique for phased array feed(PAF) is presented. In order to better reflect the characteristics of PAF, a new signal model is to add the coupling coefficient among elements of PAF to the conventional array signal model. Then the subspace projection(SP) algorithm is used to cancel RFI from the correlation matrix of the signal, and finally, the 2D power image is drawn. The power variation of signal-of-interest direction and RFI direction before and after using the SP algorithm is analyzed. The new signal model and simulation strategy can be used to test and verify the beamformer.

Solar image reconstruction method under atmospheric turbulence at Fuxian Lake Solar Observatory

Strong atmospheric turbulence reduces astronomical seeing,causing speckle images acquired by ground-based solar telescopes to become blurred and distorted.Severe distortion in speckle images impedes image phase deviation in the speckle masking reconstruction method,leading to the appearance of spurious imaging artifacts.Relying only on linear image degradation principles to reconstruct solar images is insufficient.To solve this problem,we propose the multiframe blind deconvolution combined with non-rigid alignment(MFBD-CNRA)method for solar image reconstruction.We consider image distortion caused by atmospheric turbulence and use non-rigid alignment to correct pixel-level distortion,thereby achieving nonlinear constraints to complement image intensity changes.After creating the corrected speckle image,we use the linear method to solve the wavefront phase,obtaining the target image.We verify the effectiveness of our method results,compared with others,using solar observation data from the 1 m new vacuum solar telescope(NVST).This new method successfully reconstructs high-resolution images of solar observations with a Fried parameter r0 of approximately 10 cm,and enhances images at high frequency.When r0 is approximately 5 cm,the new method is even more effective.It reconstructs the edges of solar graining and sunspots,and is greatly enhanced at mid and high frequency compared with other methods.Comparisons confirm the effectiveness of this method,with respect to both nonlinear and linear constraints in solar image reconstruction.This provides a suitable solution for image reconstruction in ground-based solar observations under strong atmospheric turbulence.

基于分布式控制的天文多终端设备观测系统

大视场双筒巡天望远镜(R2Pub)采用双镜筒双终端设备同时巡天,极大提高实测天文观测效率。常规实测天文控制系统不能主观控制协调多终端系统。采用分布式控制与通讯方法,可高效协调观测终端,实现列表观测和自定义观测计划。连续观测的实验表明,不同终端同时观测时,24小时内本底中值和均值浮动均在1σ范围内,观测稳定可靠。

A study of the strong pulses detected from PSR B0656+14 using the Urumqi 25-m radio telescope at 1540 MHz

We report on the properties of strong pulses from PSR B0656+14 by analyzing the data obtained using the Urumqi 25-m radio telescope at 1540 MHz from August 2007 to September 2010.In 44 h of observational data,a total of 67 pulses with signal-to-noise ratios above a 5σthreshold were detected.The peak flux densities of these pulses are 58 to 194 times that of the average profile,and their pulse energies are 3 to 68 times that of the average pulse.These pulses are clustered around phases about 5-ahead of the peak of the average profile.Compared with the width of the average profile,they are relatively narrow,with the full widths at half-maximum ranging from 0.28 ° to 1.78 °.The distribution of pulse-energies follows a lognormal distribution.These sporadic strong pulses detected from PSR B0656+14 have different characteristics from both typical giant pulses and its regular pulses.

Terahertz atmospheric windows for high angular resolution terahertz astronomy from Dome A

Atmospheric transmission from Dome A, Antarctica, presents new possibilities in the field of terahertz astronomy, where space telescopes have been the only observational tools until now. Using atmospheric transmission measurements from Dome A with a Fourier transform spectrometer, transmission spectra and long-term stabilities have been analyzed at 1.461 THz, 3.393 THz, 5.786 THz and 7.1 THz, which show that important atmospheric windows for terahertz astronomy open for a reasonable length of time in the winter season. With large aperture terahertz telescopes and interferometers at Dome A, high angular resolution terahertz observations are foreseen of atomic fine-structure lines from ionized gas and a water ice feature from protoplanetary disks.

The Qitai radio telescope

This study presents a general outline of the Qitai radio telescope(QTT)project.Qitai,the site of the telescope,is a county of Xinjiang Uygur Autonomous Region of China,located in the east Tianshan Mountains at an elevation of about 1800 m.The QTT is a fully steerable,Gregorian-type telescope with a standard parabolic main reflector of 110 m diameter.The QTT has adopted an umbrella support,homology-symmetric lightweight design.The main reflector is active so that the deformation caused by gravity can be corrected.The structural design aims to ultimately allow high-sensitivity observations from 150 MHz up to115 GHz.To satisfy the requirements for early scientific goals,the QTTwill be equipped with ultra-wideband receivers and large field-of-view multi-beam receivers.A multi-function signal-processing system based on RFSo C and GPU processor chips will be developed.These will enable the QTT to operate in pulsar,spectral line,continuum and Very Long Baseline Interferometer(VLBI)observing modes.Electromagnetic compatibility(EMC)and radio frequency interference(RFI)control techniques are adopted throughout the system design.The QTT will form a world-class observational platform for the detection of lowfrequency(nano Hertz)gravitational waves through pulsar timing array(PTA)techniques,pulsar surveys,the discovery of binary black-hole systems,and exploring dark matter and the origin of life in the universe.The QTT will also play an important role in improving the Chinese and international VLBI networks,allowing high-sensitivity and high-resolution observations of the nuclei of distant galaxies and gravitational lensing systems.Deep astrometric observations will also contribute to improving the accuracy of the celestial reference frame.Potentially,the QTT will be able to support future space activities such as planetary exploration in the solar system and to contribute to the search for extraterrestrial intelligence.

Science with the 2.5-meter Wide Field Survey Telescope(WFST)

The Wide Field Survey Telescope(WFST) is a dedicated photometric surveying facility being built jointly by University of Science and Technology of China(USTC) and the Purple Mountain Observatory(PMO). It is equipped with a 2.5-meter diameter primary mirror, an active optics system, and a mosaic CCD camera with 0.73 gigapixels on the primary focal plane for highquality image capture over a 6.5-square-degree field of view. The installation of WFST near the summit of Saishiteng mountain in the Lenghu region is scheduled in summer of 2023, and the operation is planned to start three months later. WFST will scan the northern sky in four optical bands(u, g, r and i) at cadences from hourly/daily in the deep high-cadence survey(DHS) program, to semi-weekly in the wide field survey(WFS) program. During a photometric night, a nominal 30 s exposure in the WFS program will reach a depth of 22.27, 23.32, 22.84, and 22.31(AB magnitudes) in these four bands, respectively, allowing for the detection of a tremendous amount of transients in the low-z universe and a systematic investigation of the variability of Galactic and extragalactic objects. In the DHS program, intranight 90 s exposures as deep as 23(u) and 24 mag(g), in combination with target of opportunity follow-ups, will provide a unique opportunity to explore energetic transients in demand for high sensitivities, including the electromagnetic counterparts of gravitational wave events, supernovae within a few hours of their explosions,tidal disruption events and fast, luminous optical transients even beyond redshift of unity. In addition, the final 6-year co-added images, anticipated to reach g■25.8 mag in WFS or 1.5 mags deeper in DHS, will be of fundamental importance to general Galactic and extragalactic science. The highly uniform legacy surveys of WFST will serve as an indispensable complement to those of the Vera C. Rubin Observatory's Legacy Survey of Space and Time(LSST) that monitors the southern sky.

中国天眼的超低丢包率天文数据流传输优化

当前UDP已经成为以中国天眼为代表的射电天文领域进行数据分发所采用的事实标准,在流量控制、拥塞控制、丢包重传等传统手段无法应用的情况下,为解决单处理器应用现有射电大数据流接入方法损耗过高的问题,形式化地论证丢包重传机制无法应用于射电天文场景,提出一套面向以FAST为代表的射电天文场景的定制化通信优化方法,包括基于缓存行对齐的巨型帧设计、CPU亲和性绑定、网卡直访缓存、三级缓存适配的内核缓冲区调整和旁路内核等手段。在25 Gbps的实际终端网络实验和8 Gbps模拟中,该套方法分别将网络传输丢包率从60%和e-4降为e-4和e-8,性能显著提高,验证了优化策略的有效性。

基于100 nm砷化镓pHEMT工艺的C波段宽带低噪声放大器芯片

作为射电天文接收机系统的关键器件,低噪声放大器的噪声和增益性能对接收机系统的灵敏度有重要影响.采用100 nm砷化镓赝配高电子迁移率晶体管(pseudomorphic High Electron Mobility Transistor, pHEMT)工艺,研制了一款可覆盖C波段(4–8 GHz)的低噪声放大器(Low Noise Amplifier, LNA).所设计的LNA采用3级共源级联放大拓扑结构,栅极、漏极双电源供电.常温下测试表明,该LNA在4–8 GHz频段内平均噪声温度为60 K,在5 GHz处获得最低噪声温度50 K,通带内增益(31±1.5) dB,输入输出回波损耗均优于10 dB,芯片面积为2.1×1.1 mm^(2),可以应用于C波段射电天文接收机以及卫星通信系统等.

《弗洛斯河上的磨坊》中的望远镜观测式叙事

乔治•爱略特深受天文学研究的影响,在创作早期小说《弗洛斯河上的磨坊》时将19世纪天文望远镜观测的原理、应用及影响渗透到人物关系的描摹中。她分别以望远镜观测捕捉光线及望远镜反射入射光线的原理、望远镜观测者的精神迷失和天文学研究扩展人的思维与认知来架构麦琪的情感经历。望远镜观测式叙事为我们更好地理解爱略特创作中的科学思想提供了独特的视角。

射电天文毫米波接收机强度校准

射电天文强度校准的目的是将接收设备对天文观测源的响应转换为天文意义上的流量.在常用的射电天文强度校准方法中,厘米波校准主要使用噪声注入模式,就是将1个标准噪声信号在馈源和极化器之后注入到接收机内部进行校准.由于毫米波微波器件的小型化导致噪声注入模式不易实现,加之注入模式可能引入噪声,因此BTL (Bell Telephone Laboratory)最早提出使用斩波轮技术进行毫米波校准,就是在馈源口面交替放置或者移除常温黑体进行校准;之后BIMA (Berkeley Illinois Maryland Association Array)又提出使用常温、热负载进行校准; ALMA (Atacama Large Millimeter Array)对单、双负载校准方式的精度进行计算后,认为双温度负载校准方式有潜力实现1%的校准精度,并最终设计出机械臂式双温度负载校准机构;此后, GBT (Green Bank Telescope) 4 mm波段制冷接收机设计出旋转盘式双温度校准机构; OSO (Onsala Space Observatory)最新研制的3 mm波段制冷接收机设计出波束切换式双温度校准机构.中国科学院新疆天文台QTT(Qi Tai Telescope)项目的启动推动了毫米波接收机研制进程,为提高毫米波强度校准精度,相关的技术预研已经开始.

FAST工程建设进展

"十一五"国家重大科技基础设施建设项目—500 m口径球面射电望远镜(FAST)工程,是利用贵州天然喀斯特洼地作为望远镜台址,建造世界第一大单口径射电望远镜—500 m口径主动反射球面射电望远镜,以实现大天区面积、高精度的天文观测.FAST工程由中国科学院和贵州省人民政府联合共建,于2016年9月25日竣工.

FAST望远镜主动反射面促动机构运动学研究

针对现有的FAST(Five-hundred-meter Aperture Spherical Telescope)主动反射面调整运动机构和促动器试验方案的不足,提出一种新型机构,能够有效地解决反射面边缘单元侧滑问题,并提高整个系统机械效率、可靠性,降低制造成本和运行维护费用.改进的核心是利用Sarrus机构产生理想的直线运动而没有任何侧滑.通过运动学分析证实了模型样机的可行性,静力分析表明这个系统具有足够的强度和刚度.模型的运行试验和仿真证明,即使在基座倾斜45°的条件下这种新型促动器机构能够可靠地防止反射面单元侧滑.这种改进为实际系统的设计和研制提供了至关重要的理论依据和试验数据.