2003年上海天文台激光测距观测报告

介绍了2003年度上海天台卫星激光测距观测慨况，同时介绍了我国第一颗带激光反射器的航天器——神舟四号轨道舱的激光观测和双波长卫星激光测距实验。     

Geosat卫星定轨中的大气阻力摄动

在利用卫星测高资料定轨的过程中，大气阻力摄动的影响较大。本文在比较几种常用大气密度模型误差对定轨影响的基础上，将密度改正公式引入到Geosat卫星的精密定轨中。结果显示，该公式可以有效地提高卫星的径向定轨精度。     

2003年上海天文台激光测距观测报告

介绍了 2 0 0 3年度上海天文台卫星激光测距观测概况 ,同时介绍了我国第一颗带激光反射器的航天器—神舟四号轨道舱的激光观测和双波长卫星激光测距实验。     

光学波段上的频率相关映射函数

基于大气折射母函数方法，本给出频率相关的对流层大气延迟改下 射函数，这个结果可以应用到工作在光学波段上的空间技术上，如卫星激光测距等。新公式可以在10°或更低高度角保持很高的精度。     

月球激光测距的现状及可能的改进方法

月球激光测距（LLR）代表了单光子探测技术的高峰，是国际激光测距界奋斗的目标。本文回顾了月球激光测距的现状以及它所持有的技术难度，同时介绍了我们为增加月球激光测距回波光子数所提出的一些可能的改进方法。特别介绍了在月球激光测距中利用月面反射器近旁的月面扩展源探测与计算大气倾斜量，进而对测月的激光束实施大气倾斜量实时改正这样一个全新的概念，最后介绍了云南天文台的激光测距系统以及它的近期工作目标。     

利用卫星激光观测对大气折射模型的综合比较

利用3天22个测站的Lageos-1激光测距资料,解算出卫星的一条轨道,再利用此轨道和地面测站检验原有的大气折射模型.得到定轨常用的Marini(1973)模型以及Yan (1999)模型、UNSW932模型、Cfa2.2(1985)模型等的改正特点.     

有限距离目标的大气折射改正

大气折射映射函数研究中的母函数方法大大地提高了对流层大气折射改正的计算精度，进而提供了在近地平时低高度观测的足够高精度大气折射改正计算方法。作为高精度大气折射模型的进一步考虑，有限距离目标，例如小于几百千米高度，可能对大气延迟和天大气折射都能引入额外的改正。本应用了天大气折射一些新定义，以及详细地讨论了一种有限距离目标的大气折射改正的计算模型，其中包含在映射函数中的角自变量从传统的真天顶距到本征天顶距的改变，对大气延迟和天大气折射的模拟计算表明：本结果对小于向百千米的目标在低于10°的观测具有一定的影响。     

大气对532nm激光影响在漫反射激光测距中的应用

激光光束在大气中的传输是与大气特征有关的,如大气湍流、大气散射与吸收,而且激光测距的回波除了与距离有关外,其回波数及精度也与大气特征相关。漫反射激光测距的目标是低轨空间碎片,在一定反射截面的条件下,应用一定功率的激光进行地面靶板漫反射测距试验,以确定多少功率的激光器可实现空间碎片的漫反射测距,这时地面靶的距离选取应该具有代表性,它代表了在一定斜程下穿过整个大气层的效应。通过对大气湍流和大气衰减对激光传输的影响进行分析,理论上计算出在低轨目标为400km时,漫反射激光测距试验地面靶的水平距离该取多远时才能代表在一定斜程下穿过400km大气层的效应,从而为漫反射激光测距试验地面靶距离的选取提供参考依据。     

关于大气分布模型

简述了大气垂直分布情况和高空探测方法,分析了目前只能采用球对称大气分布模型的原因;论证了随观测站、随方位而异的天文大气折射实测模型和折射延迟改正模型,已经包含了观测站上空大气实际分布的非球对称特性,不必再去寻找或建立随地势而异和随季节而变的大气分布模型,避免了大气分布模型选择不当的影响,从一个方面为提高天文大气折射改正精度和电磁波大气折射延迟改正精度提供了保证。     

提高中性大气折射延迟改正精度的可能途径

针对空间大地测量技术对中性大气折射延迟改正精度的要求,阐述了折射延迟改正值应随测站和随方位而异的必要性．指出,在尚不能直接测定天文大气折射值的情况下,现有的各种改正模型对大气分布模型的依赖性,不能达到预期的精度和降低观测的截止角．根据云南天文台低纬子午环的特殊结构,和测定大气折射的实践,提出了提高折射延迟改正精度的新方法,即：利用各观测站不同方位从天顶附近直到低地平高度角的天文大气折射实测数据,求解得到折射率差和映射函数的参数,从而建立随测站和随方位而异的大气折射延迟改正模型．这一新方法的实施,将能在不需采用大气分布模型的情况下,把天顶延迟的改正精度提高到1 mm以内,低地平高度角的折射延迟改正精度提高到厘米级,并且把截止高度角压缩到5°以内．     

Test of a differential photometer for extinction gradient correction in full-disk helioseismology

The ground based full disk velocity Doppler measurements used in helioseismology suffer from an atmospheric noise component when the sky transparency is not perfect. It is due to the non uniform integration of the line of sight component of the solar rotation produced by the differential atmospheric extinction across the direction of the solar equator. A simple two-channel differential photometer is proposed for measuring this differential extinction. The first laboratory tests of this instrument show that it has the capability of performing the required correction without adding a significant level of new instrumental noise contribution.

     

2010年上海天文台卫星激光测距观测报告

介绍了2010年上海天文台卫星激光测距的常规观测和白天千赫兹激光测距情况。在国际上首次对同步轨道卫星开展了千赫兹激光测距,作用距离达38800多千米,测距系统性能达到国际先进水平。利用2套独立的激光测距系统,开展了激光收发分离测距实验,为行星际异步应答式激光测距模拟试验提供了实测数据。最后概述了空间碎片目标激光测距进展情况。     

On Choosing a Rational Flight Trajectory to the Moon

The algorithm for choosing a trajectory of spacecraft flight to the Moon is discussed. The characteristic velocity values needed for correcting the flight trajectory and a braking maneuver are estimated using the Monte Carlo method. The profile of insertion and flight to a near-circular polar orbit with an altitude of ~100 km of an artificial lunar satellite (ALS) is given. The case of two corrections applied during the flight and braking phases is considered. The flight to an ALS orbit is modeled in the geocentric geoequatorial nonrotating coordinate system with the influence of perturbations from the Earth, the Sun, and the Moon factored in. The characteristic correction costs corresponding to corrections performed at different time points are examined. Insertion phase errors, the errors of performing the needed corrections, and the errors of determining the flight trajectory parameters are taken into account.     

Long-periodic and secular perturbations to the orbits of Explorer 19 and Lageos due to direct solar radiation pressure

A theory for the long-term variations in the orbit of a spherically symmetric satellite due to direct solar radiation pressure is tested using two satellite orbit analyses. The first of these analyses is in terms of mean elements for the balloon satellite Explorer 19. The results are compared with the expected theoretical variations with short-period terms omitted. The second analysis utilises satellite laser ranging observations of the geodetic satellite, Lageos. A novel long-term analysis technique is developed primarily for laser ranging studies. The technique is tested along with the solar radiation pressure perturbation theory by comparing the results from the theory and the analysis.     

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.     

月球激光测距的新技术方法研究

月球激光测距是国内外所瞩目的宏伟目标 ,代表着单光子探测技术的高峰。本论文的目的是探索提高激光测月回波光子数的新方法 ,进而增加激光测月成功的几率。其思路是源于一个新的想法 :在激光测月过程中引入大气波前倾斜量实时补偿的技术。首先介绍激光测月的现状和其难度所在 :回波光子数太少 ,基本上属于亚光子探测范畴。在现有技术条件下 ,本文对影响激光测月回波光子数的因素逐一进行分析讨论 ,提出应该把激光束截面能量分布和大气湍流效应包括进去。为此分析讨论了大气湍流和大气中光场的基本统计性质、激光束在大气中传输时所受大气湍流的影响以及大气湍流对激光测距的影响 ,得出大气湍流特别对激光测月有着明显影响的结论。在此基础上对传统的激光测距方程进行了修正 ,使其应用到激光测月时更符合真实的情况 ,从而指导补偿的进行。涉及到在激光测月中对受大气湍流而畸变的激光束进行补偿 ,本文抓住重点 ,通过分析看出对大气倾斜量的实时补偿是提高激光测月回波光子数的重要因素。结合激光测月以及云南天文台现有测距系统的实际情况 ,本文独创性地提出利用激光测月目标近旁一定大小区域的扩展面源探测与计算大气倾斜量 ,然后对激光测月中的激光束进行大气倾斜量实时补偿的新技术方法。在分析比较     

基于PCl-Express高速图像采集卡对扩展源大气倾斜量的实时补偿

为能够实时补偿大气湍流对月球激光测距带来的渡前倾斜量误差,采用相关跟踪自适应光学系统,并根据其大计算量、高实时性的要求,创新地设计了基于PCI-Express高速图像采集卡及其硬实时操作系统驱动程序,完成对扩展源目标大气倾斜量的实时补偿.详细介绍了整体系统的软硬件设计,给出了一种PCI-Express高速图像采集卡设计结果及其RTAI实时驱动程序的软件设计结果,完成了进一步提高图像传输速度,减小相关跟踪系统系统延迟,提高系统响应带宽的目标,最终实现了图像数据的实时传输(≤28 μS)及波前倾斜量的实时补偿(≤348 μS).     

射电天文及卫星测地中大气折射的改正及其精度

本文综述了电离层、对流层中电波折射引起的射电天文观测及卫星测地中的各种误差及各种改正方法和它们的精度。 对流层影响的主要改正方法是实测大气温度、压力等参数,用数学模型计算。电离层影响的改正目前有三种方法:一是实时测量电离层主要参数——电子总含量的变化,然后用数学模型方法改正。二是采用双频同时观测的手段来消除电离层折射的影响。三是采用自校准方法。文中还比较了两种不同的自校准方法——常规自校准方法和多余量自校准方法。     

Relativistic effects for near-earth satellite orbit determination

The relativistic formulations for the equations which describe the motion of a near-Earth satellite are compared for two commonly used coordinate reference systems (RS). The discussion describes the transformation between the solar system barycentric RS and both the non-inertial and inertial geocentric RSs. A relativistic correction for the Earth's geopotential expressed in the solar system barycentric RS and the effect of geodesic precession on the satellite orbit in the geocentric RS are derived in detail. The effect of the definition of coordinate time on scale is also examined. A long-arc solution using 3 years of laser range measurements of the motion of the Lageos satellite is used to demonstrate that the effects of relativity formulated in the geocentric RS and in the solar system barycentric RS are equivalent to a high degree of accuracy.     

云南天文台人造卫星观测与相关应用研究

回顾了过去２０年，特别是近１０年来云南天文台人造卫星的观测与应用情况。介绍在观测仪器的研制、改进和观测方法研究以及有关激光测月资料的归算与应用方面所作过的工作。根据既有的条件，就今后若干年内可能进行的几项工作提出了粗浅的看法。