流动VLBI站氢原子钟的研制与性能测试

氢脉泽是射电天文所必需的频率标准.文中对为流动vLBI站研制的新一代氢脉泽的物理结构特点进行了讨论，包括对腔泡结构、磁屏蔽、原子束光学系统等.同时性能测试表明在80秒到1天之间频率稳定度优于1×10     

Fast neutral particles as probes of the extent of Io's exosphere

The spatial extent of ion cyclotron waves at Io has been interpreted as requiring a multistep acceleration and transport process: exospheric ions are accelerated outward (relative to Jupiter) due to the corotation electric field, neutralized due to charge exchange in the surrounding exosphere, and then reionized after traveling far across magnetic field lines, at which point they generate the waves. The trajectories of the particles away from Io are sensitive to the location of their initial ionization. This paper examines the spatial distributions of fast neutrals produced under varying conditions in order to provide constraints on the possible structure and nature of the Io exosphere. While a rapid onset of cyclotron waves at a specific location around Io can be modeled with a single, point-source region of ions, such as might occur over a volcano, the regional extent of the waves suggests multiple or distributed sources.     

SOHM-4与MHM-2010氢原子频标的特点比较

基于对已投入国家授时中心守时运转的SOHM-4型与MHM-2010型氢原子频标的长期关注,对这两种氢原子频标的性能作了较详细的比较和分析。讨论了它们共同的优点、各自的特长和不足之处,还给出了稳定度的测试结果。     

拱星OH脉泽辐射频谱的双峰结构和多重分离的膨胀拱星壳

对一些OH／IR星的拱星OH脉泽的观测结果表明,在双峰结构谱线轮廓上常常可以发现一些小峰叠加在双峰上,即在谱线轮廓的双峰结构中的每个峰是由几个小峰叠加而成的．从脉泽的辐射转移方程和拱星包层的速度结构出发,研究拱星OH脉泽辐射频谱的轮廓特征,提出多重分离的膨胀拱星亮模型,很好地解释了双峰结构的奇特观测现象．     

X-ray emission of OH megamaser galaxies

The properties of OH megamaser galaxies in the x-ray region are discussed. Observational data from the XMM-Newton x-ray satellite are presented for three megamasers, IRAS 01418+1651, IRAS 11010+4107, and IRAS 13218+0552. Based on a sample of OH megamaser galaxies it is shown that the x-ray and OH emission are closely coupled. Megamaser emission also correlates with the column density of the medium and the OH emissivity increases as the square of the column density. The results of this study indicate that in OH megamaser galaxies an active nucleus, x-ray heating of molecules, and saturation of the maser emission can play an important role. In some megamasers, active star formation may be the dominant source. __________ Translated from Astrofizika, Vol. 50, No. 2, pp. 171–182 (May 2007).     

应用于被动氢钟的简单滤波器实现

在被动型氢原子钟数字伺服电路中,使用FPGA对误差信号进行数字信号处理。设计了一种简单的低通滤波器,与传统的FIR滤波器相比,节省了FPGA的使用资源,并且性能优于传统滤波器,能够很好地应用于被动型氢钟。     

恒星脉泽源的IRAS观测结果和分析

本文利用红外天文卫星(IRAS)点源表(PSC)及低分辨率光谱表(LRS)的资料,较为系统地讨论了各种恒星脉泽源在中远红外颜色及光谱的特征,并结合其空间分布,物理性质和演化状态探讨了产生这些特征的原因。     

Spectral variations and long-period intensity variations of auroral kilometric radiation from INTERBALL-2 satellite measurements

A statistical analysis of the auroral kilometric radiation (AKR) measurements in the POLRAD experiment on the INTERBALL-2 satellite has revealed a dependences of the size and location of the AKR generation region on geomagnetic activity: the generation region rises upward and expands with increasing magnetic disturbances. Based on our two-year measurements, we found seasonal AKR intensity variations: the AKR maximum and minimum are observed in winter and summer, respectively. The seasonal variations and the dependence of the spectrum on geomagnetic activity are assumed to have a common physical nature—the background-plasma density variations in the region of the AKR source attributable to plasma flows from the ionosphere into the magnetosphere.     

Local Oscillator Distribution Using A Geostationary Satellite

A satellite communication system suitable for distribution of local oscillator reference signals for a widely spaced microwave array has been developed and tested experimentally. The system uses a round-trip correction method to remove effects of atmospheric fluctuations and radial motion of the satellite. This experiment was carried out using Telstar-5, a commercial Ku-band geostationary satellite. A typical Ku-band satellite has uplink and downlink capacity at 14–14.5 GHz and 11.7–12.2 GHz, respectively. For this initial experiment, both earth stations were located at the same site to facilitate direct comparison of the received signals. The local oscillator reference frequency was chosen to be 300 MHz and was sent as the difference between two Ku-band tones. The residual error after applying the round trip correction has been measured to be better than 3 ps for integration times ranging from 1 to 2000 s. For integration times greater than 500 s, the system outperforms a pair of hydrogen masers with the limitation believed to be ground-based equipment phase stability. The idea of distributing local oscillators using a geostationary satellite is not new; several researchers experimented with this technique in the eighties, but the achieved accuracy was 3 to 100 times worse than the present results. Since then, the cost of both leased satellite bandwidth and the Ku-band ground equipment has dropped substantially and the performance of various components has improved. An important factor is the availability of narrow bands which can be leased on a communications satellite. We lease three 100 kHz bands at approximately one hundredth the cost of a full 36 MHz-wide transponder. Further tests of the system using terminals separated by large distances and comparison tests with two hydrogen masers and radio interferometry of astronomical objects are needed.     

被动型氢钟波谱信号观测装置的设计

简单介绍了被动型氢钟的量子系统,阐述了波谱信号观测装置的设计。该装置采用标准10MHz晶振产生被动型氢钟的微波激射信号(1.420406GHz),然后将该信号输入氢钟的脉泽振荡器中。脉泽振荡器输出的信号经过低噪声放大、两次混频及滤波后所得的谱线包含了量子系统的信息,通过分析最终的谱线即可得知量子系统的优劣。该装置已用于对两台被动型氢钟的测试,并根据测试结果对量子系统进行了改进。