利用GPS计算TEC的方法及其对电离层扰动的观测

在总结用ＧＰＳ研究电离层电子总量ＴＥＣ的数据处理方法基础上,分析了利用伪距观测量和载波相位观测量计算电离层ＴＥＣ的特点及误差来源．在处理过程中考虑了卫星的硬件延迟偏差,分析了应用ＩＲＩ模型进行接收机硬件延迟偏差修正的可能性,发现利用少量ＧＰＳ数据和ＩＲＩ模型修正接收机硬件延迟偏差有一定的困难．最后,利用一些ＧＰＳ观测数据有针对性地研究了电离层对若干次扰动事件的响应．包括一次大的太阳耀斑期间的电离层ＴＥＣ变化、一次较典型的电离层行扰以及日食期间的电离层ＴＥＣ的相对变化等电离层物理问题．结果表明,利用该方法计算ＴＥＣ的精度可满足电离层扰动现象的研究．     

Irregular structures observed below 71 km in the night-time polar D-region

A new rocket range, SvalRak, was opened in November 1997 at Ny-Ålesund (79°N) in the Svalbard archipelago. The first instrumented rocket was launched on 20 November, 1997, at 1730 UT during geomagnetically quiet conditions. The payload was instrumented to measure plasma parameters in the mesosphere and lower thermosphere, but the payload only reached an altitude of 71 km. This resulted in a very flat trajectory through the lower D-region. The positive ion concentrations were larger than expected, and some unexpected plasma irregularities were observed below 71 km. The irregularities were typically 100 m in spatial extent, with plasma densities a factor of two to five above the ambient background. In the dark polar night the plasma below 71 km must consist mainly of positive and negative ions and the only conceivable ionising radiation is a flux of energetic particles. Furthermore only relativistic electrons have the large energies and the small gyro radii required in order to explain the observed spatial structure. The source of these electrons is uncertain.     

我国高精度GPS陆海垂直运动监测网的建立与精度分析

为了将验潮站得到的海平面变化信息与难潮站所在陆地垂直运动分离开来,获得海平面变化的绝对信息,在我国沿海５个难潮站建立了一个高精度的ＧＰＳ陆海垂直运动监测网,采用ＧＡＭＩＴ和Ｇｌｏｏｋ软件对数据进行处理,并顾及影响高程因素中由于方位不对称引起的大气延迟改进的Ｎｉｅｌｌ模型,我们最终得到ＧＰＳ监测网毫米级的高程精度。     

WAAS系统下单频GPS用户电离层延迟改正新方法

对于现有WAAS等差分GPS系统而言,在电离层活动激烈及系统不能正常发送或用户无法正常接收电离层延迟改正信息时,如何确保其所服务区域内单频GPS用户的电离层延迟的实时改正效果,是需要进一步解决的问题。本文提出一种能够同时克服这些不足的单频GPS电离层延迟实时改正方案,并用算例初步验证了其有效性。     

The traveltime perturbations for seismic body waves in factorized anisotropic inhomogeneous media

The traveltime perturbation equations for the quasi-compressional and the two quasi-shear waves propagating in a factorized anisotropic inhomogeneous (FAI) media are derived. The concept of FAI media simplifies considerably these equations. In the FAI medium, the density normalized elastic parameters a _ijkl ( X _i ) can be described by the relation a _ijkl ( X _i) = f ²( x _i ) A _ijkl, where A _ijkl are constants, independent of coordinates x _i and f ²( x _i) is a continuous smooth function of x _i . The types of anisotropy ( A _ijkl ) and inhomogeneity [ f ( x _i)] are not restricted. The traveltime perturbations of individual seismic body waves ( q ^P , qS 1 and qS 2) propagating in the FAI medium depend, of course, both on the structural pertubations [δ f ²( x _i)] and on the anisotropy perturbations (δ A _ijkl ), but both these effects are fully separated. The perturbation equations for the time delay between the two qS -waves propagating in the FAI medium are simplified even more. If the unperturbed (background) medium is isotropic, the perturbation of the time delay does not depend on the structural perturbations (δ f ²( x _i) at all. This striking result, valid of course only in the framework of first-order perturbation theory, will simplify considerably the interpretation of the time delay between the two split qS -waves in inhomogeneous anisotropic media. Numerical examples are presented.     

卫星激光测距的超近地靶校准技术的研究

介绍一种新的超近距离 (小于 1m)靶距测量技术。该技术已于 1999年 5月和 1999年 7月成功地用于武汉固定卫星激光测距站和“中国地壳运动观测网络”的流动卫星激光测距系统中 ,校准卫星激光测距系统内各种光路、电路的延时。经这两个系统长期观测 ,证明此技术运行可靠 ,效果很好 ,校准精度优于 1cm     

折射延迟改正模型

在分析了一些主要的天顸延迟改正模型，并对几种连分式形式的映射函数模型作了归纳后，认为：前者只能都基于大气球对称分布模型，采用差不多相同的各向同性的改正模型，各种映射函数模型的连分式之间，差别仅是形式上的，没有实质性差异。文章利用普尔科沃大气折射表的表列数据作模拟计算，求解折射率差和映射函数的参数证明，可以用天文大气折射定值作模拟处理，得到折射延迟改正模型中的所有参数，并得出结论：映射函数的形式是次要的，随着项数的增加，都能提高模拟精度。文章给出了模拟过程。     

Jason Microwave Radiometer Performance and On-Orbit Calibration

Results are presented from the on-orbit calibration of the Jason Microwave Radiometer (JMR). The JMR brightness temperatures (TBs) are calibrated at the hottest and coldest ends of the instrument's dynamic range, using Amazon rain forest and vicarious cold on-Earth theoretical brightness temperature references. The retrieved path delay values are validated using collocated TOPEX Microwave Radiometer and Radiosonde Observation path delay (PD) values. Offsets of 1–4 K in the JMR TBs and 8–12 mm in the JMR PDs, relative to TMR measurements, were initially observed. There were also initial TB offsets of 2 K between the satellite's yaw state. The calibration was adjusted by tuning coefficients in the antenna temperature calibration algorithm and the antenna pattern correction algorithm. The calibrated path delay values are demonstrated to have no significant bias or scale errors with consistent performance in all nonprecipitating weather conditions. The uncertainty of the individual path delay measurements is estimated to be 0.74 cm ± 0.15, which exceeds the mission goal of 1.2 cm RMS.     

Monitoring the TOPEX and Jason-1 Microwave Radiometers with GPS and VLBI Wet Zenith Path Delays

Monitoring of altimeter microwave radiometer measurements is necessary in order to identify radiometer drifts or offsets that if uncorrected will introduce systematic errors into ocean height measurements. To examine TOPEX Microwave Radiometer (TMR) and Jason-1 Microwave Radiometer (JMR) behavior, we have used coincident wet zenith delay estimates from Very Long Baseline Interferometry (VLBI) and Global Positioning System (GPS) geodetic sites near altimeter ground tracks. We derived a TMR path delay drift rate of ?1.1 ± 0.1 mm/yr using GPS data for the period from 1993.0–1999.0 and ?1.2 ± 0.5 mm/yr using VLBI data. Thereafter, the drift appears to have leveled off. Already after 2.3 years (82 cycles) of the Jason-1 mission, it is clear that there have been significant systematic errors in the JMR path delay measurements. From comparison with GPS wet delays, there is an offset of ?5.2 ± 0.6 mm at about cycle 30 and a more abrupt offset of ?11.5 ± 0.8 mm at cycle 69. If we look at the behavior of the JMR coldest brightness temperatures, we see that the offsets near cycle 30 and cycle 69 are mainly caused by corresponding offsets in the 23.8 GHz channel of ?0.49 ± 0.12 K and ?1.18 ± 0.13 K, although there is a small 34.0 GHz offset at cycle 69 of 0.75 ± 0.22 K. Drifts in the 18.0 and 34.0 GHz channels produce a small path delay drift of 0.3 ± 0.5 mm/yr.