用于射电天文数字频谱仪的新进展

根据在射电天文频谱观测中出现的新需求,介绍了近年来数字技术的新进展.达到GHz采样速率的多位高速模数转换器(Analog-to-Digital Converter,ADC)、海量数字处理芯片现场可编程门阵列(Field Progxammable Gate Array,FPGA)以及运行在这些芯片上的并行快速傅里叶变换知识产权(Fast Fourier,Transform Intellectual Property,FFT IP)内核,结合高性能数据总线的系统集成,为射电天文构建新型FFT频谱仪提供了可能的技术选择.与现有其他类型频谱仪相比,集成了这些新技术的数字型FFT频谱仪有更大的带宽、更高的谱分辨率、更高的动态范围和整体稳定性,此类频谱仪的出现显示了射电频谱技术已经进入了新一代数字技术应用的阶段.     

云台射电频谱仪预研

简要介绍了用于研究分子夭文学的各种射电频谱仪及国内外发展状况,讨论了各种频谱仪的优缺点,最后提出了云台建立射电频谱仪的型式。     

太阳射电频谱仪数据采集与处理(自相关频谱仪原理与应用)

本文论述了 0 .7～ 1 .4GHz太阳射电频谱仪数据采集与处理系统是如何实现的。正在研制的此仪器采用了多通道频谱仪与自相关频谱仪结合使用的方案。首先 ,本文详细讨论了自相关频谱仪的原理 ,并介绍了北京大学研制的自相关频谱仪的结构。在此基础上着重讨论了多通道频谱仪与自相关频谱仪的同步控制的解决方案 ,以及大容量数据采集实时存盘的解决方案。最后 ,介绍了我们为数据预处理采用的一些方案。     

嫦娥四号低频射电频谱仪2C数据对宇宙黑暗时代的探测能力分析

嫦娥四号着陆器搭载的低频射电频谱仪(Low Frequency Radio Spectrometer, LFRS)已成功开展观测,每月把观测数据传回地面,并且把经过一定预处理后的2C级别的频谱数据释放给科学团队。旨在评估该级别数据是否满足探测宇宙黑暗时代21 cm整体谱的要求,对生成的2C级别数据进行了长时间积分,并模拟仿真银河系前景射电辐射。通过对两套数据进行对比分析发现,2C数据减弱40～50 dB,几乎不包含银河系前景的远场辐射信号,这种大幅度的减弱进而影响了该载荷对宇宙黑暗时代的探测能力。     

1998年4月15日微波爆发观测

北京天文台１ ．０２ ．０ＧＨｚ 太阳射电频谱仪从１９９４ 年开始观测至１９９８ 年９ 月记录到太阳射电爆发１７１ 个,２ ．６３ ．８ＧＨｚ 太阳射电频谱仪１９９６ 年９ 月投入观测至１９９８ 年９ 月,记录到１４６ 个太阳射电爆发。１９９８ 年４ 月１５ 日太阳射电爆发同时在这两台频谱仪上记录到。这个事件在时间和频率上显示了丰富的幅度和结构的变化。发现了微波Ⅲ型爆发对群,并存在着丰富的快速活动现象。取得了高时间分辨率、高质量的动态谱资料,为研究耀斑各种尺度的时间及空间演化过程提供了丰富的信息。     

紫金山天文台太阳射电频谱仪定标

定标是射电天文观测中基础而重要的工作.定标工作可以得到太阳观测中的一个重要物理量:太阳射电辐射流量,可以扣除射电频谱仪的通道不均匀性,清晰显示射电频谱特征.结合紫金山天文台射电频谱仪的观测数据,详细介绍了定标的基本方法,分析了定标常数的变化情况,最后给出了定标结果,并与野边山射电偏振计以及RHESSI(The Reuven Ramaty High Energy Solar Spectroscopic Imager)卫星硬X射线波段的几个太阳耀斑的观测结果进行了比较,结果符合耀斑的光变特征.其中对一个耀斑脉冲相硬X射线流量和微波光变的相关性的分析表明这些观测可以用来研究有关的辐射机制以及相应的能量释放和粒子加速过程.     

基于多相滤波器的宽带射电频谱仪设计

提出了一种基于多相滤波器的新型宽带射电频谱仪的设计方案。通过多相滤波器实现宽带射电信号的滤波,对滤波后的基带信号进行数字功率检波,再通过积分控制,最终得到射电信号的频谱强度。仿真分析表明,这一设计具有很好的效果,通过多相滤波器,使信号的速率大为降低,克服了传统频谱仪以及采用FFT实现频谱变换方法的缺点,可以实现对超宽带射电信号的实时频谱分析。     

23周峰年云台米波频谱观测系统

本文介绍云南天文台用于观测研究太阳射电２３０ ～３００ ＭＨｚ 米波爆发精细结构动态频谱仪研究的历史和现状,以及利用现代计算机网络技术,有效地解决了由于高时间人辨率和高频率分辩率观测采样带来的大数据量存储和处理。该系统经过不断改进和完善,目前已投入２３ 周峰年太阳射电爆发频谱观测     

一种新型射电天文频谱仪——声表面波频谱仪

本文简要介绍一种以傅里叶交换的线性调频Z变换(CZT)算法为工作原理,以声表面波(SAW)器件为支持性技术的新型射电频谱仪.给出它在紫金山天文台青海站13.7m射电天文望远镜13mm接收系统上对22GHz水分子脉泽源试观测的结果,实践表明它具有宽带、高频率分辨率、全固化、机械稳定性好、对工作环境要求不高、可靠性高等优点.在射电天文星际分子谱线观测技术中有一定实用价值.     

23周上云台米波频谱观测系统

本文介绍云南天文台用于观测研究太阳射电２３０￣３００ＭＨｚ米波爆发精细结构动态频谱仪研究的历史和现状,以及利用现代计算机网络技术,有效地解决了由于高时间人辨率和高频率分辨率观测采样带来的大数据量存储和处理。该系统经过不断改进和完善,目前已投入２３周峰年太阳射电爆发频谱观测。     

哈雷彗星1986年光谱的谱线证认

1986年3—4月间,哈雷彗星的日心距为1和1.5 A.U.附近。我们使用云南天文台1米RCC望远镜和卡焦摄谱仪,取得了7张长狭缝光谱。这是我国唯一的一组哈雷彗星长狭缝光谱。光谱色散度为165(?)/mm,分辨率不小于7(?)。本文主要给出6张Kodak 103_a-O底片上3000—5100(?)波段的谱线证认结果。光谱片上主要出现了CN、C_2、C_3、CH、NH、OH等分子发射线,还可能存在NH_2、CH~+、N、H_2CO等发射线。光谱中连续辐射、吸收线较强,离子谱线少而弱,表明哈雷彗星是富尘的。OH(3090)发射线的出现既证实了卫星观测结果,又说明云南天文台的紫外观测条件是优越的。     

A Model of The 2–4 μm Spectrum of Comet Halley

Recent observations of Halley's Comet show a broad absorption band centred at 3.4 μm and which can be explained on the basis of a bacterial grain model. This revised version was published online in July 2006 with corrections to the Cover Date.     

A model of the 2–4Μm spectrum of Comet Halley

Recent observations of Halley's Comet show a broad absorption band centred at 3.4 m and which can be explained on the basis of a bacterial grain model.     

Evidence for the nucleus rotation in streamer patterns of Comet Halley's dust tail

A generalized Finson-Probstein formalism was used to analyse the streamer patterns in the dust tail of Comet Halley as observed between 22 February and 11 March, 1986. A periodic appearance of a pattern of double streamers was found in the dust tail, indicating a time interval in the emission of this structures of about 6.5 days, if interpreted as synchrones. The time interval between the emission of the two components of each double streamer is about 2.5 days. The results are discussed with respect to the rotation of Halley's nucleus.This work is based on observations made at the European Southern Observatory by ESO staff personal and by observers of the Astronomical Institute of the Ruhr-University, Bochum. We, furthermore, used an exposure made at the U.K. Schmidt telescope at Siding Spring, Australia, operated by the Royal Observatory Edinburgh, and published by Sekanina and Larson (1986).     

我国对苏梅克-列维9号慧星撞击木星事件的观测(英)

1994年7月16日─22日，苏梅克－列维9号周期慧星的21颗碎片连续撞击木星事件是一次极为罕见的天文现象．文中概括介绍了我国天文学家对慧木相撞事件的光学和射电观测网点、课题设置以及所取得的主要观测结果．     

Models of dense cores in translucent regions of low mass star formation

We have constructed models for a region of low mass star formation where stellar winds ablate material from dark dense cores and return it to a translucent intercore medium from which subsequent generations of cores condense. Depletion of gas phase species onto grains plays a major role in the chemistry. For reasonable agreement between model core chemical fractional abundances and measured TMC-1 fractional abundances to obtain, the core collapse, once started, must be relatively uninhibited by turbulence or magnetic fields and the core lifetime must fall in a limited range determined by the assumed depletion rates. In a core with the TMC-1 fractional abundances, CH, OH, C₂H, H₂CO, HCN, HNC, and CN are the only simple species that have been detected in TMC-1 at radio and millimeter wavelengths to have fractional abundances that are roughly constant or increasing with time; this result bears considerably on previous work concerned with searches for spectroscopic evidence for and the diagnosis of collapse during protostellar formation, but depends on the fractions of the OH and CH emissions that are associated with the core centre rather than more extended gas or a core-stellar wind boundary layer. Model results for the abundance ratios of H₂O, CH₄, and NH₃ ices are in good agreement with those inferred for Halley's Comet.     

IPRT/AMATERAS: A New Metric Spectrum Observation System for Solar Radio Bursts

A new radio spectropolarimeter for solar radio observation has been developed at Tohoku University and installed on the Iitate Planetary Radio Telescope (IPRT) at the Iitate observatory in Fukushima prefecture, Japan. This system, named AMATERAS (the Assembly of Metric-band Aperture TElescope and Real-time Analysis System), enables us to observe solar radio bursts in the frequency range between 150 and 500 MHz. The minimum detectable flux in the observation frequency range is less than 0.7 SFU with an integration time of 10 ms and a bandwidth of 61 kHz. Both left and right polarization components are simultaneously observed in this system. These specifications are accomplished by combining the large aperture of IPRT with a high-speed digital receiver. Observational data are calibrated and archived soon after the daily observation. The database is available online. The high-sensitivity observational data with the high time and frequency resolutions from AMATERAS will be used to analyze spectral fine structures of solar radio bursts.     

On properties of microwave sources located above the neutral line of radial magnetic field

In this study we continue our investigation of the radio sources located above the neutral line of the radial magnetic field in solar active regions, i.e., the so-called neutral line associated sources (NLS). The nature of NLS is still far from being understood. To study it, we use the spectroscopic capabilities of the new broadband polarimetric facility of the RATAN-600 radio telescope. We study the radio spectra of NLS sources in several solar active regions over a wide range of variations of their sizes. We find the NLS radio emission fluxes to be related to the gradient of the quasi-longitudinal magnetic field in the photosphere. We estimate the vertical positions of NLS relative to the cyclotron radio sources. We find fine spectral features in the NLS emission, which confirm the presence of a current sheet in their sources. We associate the appreciable lack of polarization in such sources with their location near the tops of the coronal arches.