Microwave remote sensing of Jupiter's atmosphere from an orbiting spacecraft

Microwave remote sounding from a spacecraft flying by or in orbit around Jupiter offers new possibilities for retrieving important and presently poorly understood properties of its atmosphere. In particular, we show that precise measurements of relative brightness temperature as a function of off-nadir emission angles, combined with absolute brightness temperature measurements, can allow us to determine the global abundances of water and ammonia and study the dynamics and deep circulations of the atmosphere in the altitude range from the ammonia cloud region to depths greater than 30 bars in a manner which would not be achievable with ground-based telescopes.     

荆州地区自动气象站网超短波超视距数据通信

本文介绍了荆州地区自动气象站网的组成及其设计思想。通过对无线电波传播损耗的理论分析和研究,论述了超短波超规距数据通信的可行性,提出了通信系统的改进方法,为平原地区组建无线电通信网络提供了新思路。     

关于RSC(IERS)88 C01实现中的几个问题的讨论

本文讨论了IERS的RSC 88C01实现过程中在有关基本源选取和参考架定向确定等方面存在的问题,分析了它们对IERS天球参考架的影响,提出了建立和维持高精度天球参考架的几点建议。     

云南天文台太阳射电望远镜跟踪精度和定标精度

本文采用天线方向图半功率宽度和曲线偏离度两种方法,测得自动跟踪精度为8小时偏差不超过0.°01。同时改进了定标精度的计算公式,并从理论上寻找误差原理后,再计算自动定标系统的检验值,从而大大地提高了观测精度。     

IRAS 19227+1700:富碳星还是富氧星?

IRASl9227 1700作为富碳星列于新版碳星星表中．然而该星在IRAS红外双色图上处于典型的有较厚富氧拱星包层区域中，而不处于硅酸盐碳星通常所处的区域．而且有证据表明该星不但有主线和伴线羟基脉泽发射，还有靠近中心星的水脉泽发射．其IRASLRS谱在9—12μm范围有尘埃发射特征，近红外的观测又证实它确实存在热的拱星包层．因此IRAS19227 1700的拱星包层应该全是富氧性质的，它的中心星是富氧的可能性也极大．     

上海天文台25m天线驱动系统的探讨

对中国科学院上海天文台 2 5m天线的驱动结构进行了分析。并对该天线的方位速度及使用更多电机同时驱动天线方面的问题进行了探讨     

用大气层结模型和反演法研究大气对毫米波吸收的改正

作者结合射电天文和气象实测资料,使用大气层结模型和反演法,数值计算了大气中云的含水量和云天大气对射电源毫米波辐射总衰减的改正。其结果优于均匀气温模型和两层大气模型的结果以及跟踪太阳法的结果。     

Laboratory measurements of the Ka-band (7.5 mm to 9.2 mm) opacity of phosphine (PH3) and ammonia (NH3) under simulated conditions for the Cassini-Saturn encounter

Recently, a model for the centimeter-wavelength opacity of PH₃ under conditions characteristic of the outer planets was developed by Hoffman et al. (2001, PhD thesis), based on centimeter wavelength laboratory measurements. New laboratory measurements have been conducted which show that this model is also accurate at low pressures and temperatures, and at millimeter wavelengths such as will be employed in Cassini Ka-band (9.3 mm) radio occultation studies. The opacity of PH₃ in a hydrogen/helium (H₂/He) atmosphere has been measured at frequencies in the Ka-band region at 32.7 GHz (9.2 mm), 35.6 GHz (8.4 mm), 37.7 GHz (8.0 mm), and 39.9 GHz (7.5 mm) at pressures of 0.5, 1, and 2 bar and at temperatures of 295, 209, and 188 K. Additionally, new high-precision laboratory measurements of the opacity of NH₃ in an H₂/He atmosphere have been conducted under the same temperature and pressure conditions described for PH₃. These new measurements better constrain the NH₃ opacity model supporting use of a Ben-Reuven lineshape model. These measurements will also elucidate the interpretation of millimeter wavelength observations conducted with the NRAO/VLA at 43 GHz (7 mm).     

VLA observations of Jupiter’s synchrotron radiation at 15 and 22 GHz

We observed Jupiter’s synchrotron radiation at frequencies of 15 and 22 GHz using the VLA (Very Large Array) in its most compact configuration (D-array) in March 1991. The spatial brightness distribution of the emission at these high frequencies appears to be very similar to that seen at lower frequencies (5 GHz down to 330 MHz). We measured a total nonthermal flux density at 15 and 22 GHz of 1.5 ± 0.15 Jy and 1.5 ± 0.4 Jy, respectively (both normalized to a geocentric distance of 4.04 AU). These numbers agree well with model spectra of Jupiter’s synchrotron radiation that were obtained by fitting the planet’s nonthermal radio emission between 74 MHz and 8 GHz and suggest a maximum cutoff in electron energies at ∼100 MeV. The degree of linear polarization observed with the VLA is 21.5 ± 1.9% at 15 GHz.     

Quasars Associated with NGC 613, NGC 936 and NGC 941

The association of low redshift, active galaxies with high redshift quasars is here tested in two regions uniformly surveyed for quasars to faint limits. Three active galaxies in these regions all show significant association with nearby quasars. Radio, optical and X-ray data available for these galaxies give new information on the processes which accompany the proposed ejection of the quasars. It is concluded that the quasars are originally relatively compact compared to the galactic medium through which they exit but can be slowed. It is argued that effects of ejection can be seen on the galaxies and may be connected with spiral structure. Evidence for periodicity of the redshifts is discussed.