GPS无线电掩星技术反演地球大气参数中若干问题的研究
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摘要
GPS无线电掩星反演地球大气参数方法是上世纪八十年代末提出的一种具有挑战性的理论。在目前的地球大气监测手段中，它具有诸多优势，如全天候观测、高垂直分辨率、全球覆盖性、高性能价格比等等，因而有着独特的地位。目前国际上已经有多个国家为实施该方法发射了多颗小卫星。目前该理论在其应用过程中不断地得到发展和完善。我们试图通过该项研究初步掌握该技术的特点及其实施技巧，以便为将来国内实施GPS无线电掩星技术反演地球大气参数项目时提供某种程度上的理论研究支持。
对GPS无线电掩星技术反演地球大气参数方法中的若干问题进行了较为全面的分析和研究。
1）给出GPS无线电掩星反演地球大气参数过程中计算大气折射角的解析表达式。以圆轨道假设下的大气折射角计算值为先验约束,采用迭代法对不引入圆轨道假设情况的大气折射角进行归算,在此基础,利用反演方法得到了引入和不引入圆轨道假定两种情况下大气参数(气压和温度)的差分序列。结果表明: 卫星圆轨道假设对GPS 无线电掩星反演大气参数的影响,在气压方面为1mbar左右,而在气温方面为10K左右。这一结果支持了目前无线电掩星定性误差估计研究中通常引入卫星圆轨道假设这个近似处理方法的合理性;同时也表明:若在高精度反演地球大气参数时,摒弃圆轨道假定是必要的.
2）探讨了空基无线电掩星技术应用于反演地球大气参数方法，并将该方 法编制成资料处理软件；对实测资料进行处理和分析后，给出了地球大气参数反演结果。发现：指数函数外推法引入数据处理后大大改进了大气温度的归算结果，而对气压归算的影响却很小。
3）对MSISE90模型进行了简要的介绍，并指出Hedin本人在该模型问世后
对它的一些修正、改进之处。基于修正后的MSISE90大气密度模型，生成了一个可供GPS无线电掩星反演地球大气参数时使用的先验温度序列。
4）GPS掩星监测大气方法中需要载有GPS接收机的卫星的精密定轨信息，而该卫星的轨道误差对GPS掩星监测大气的影响进行分析是十分必要的。基于地球大气模式CIRA86，我们采用了三维射线跟踪方法模拟了5次完整的GPS掩星事件，估计了LEO卫星的轨道误差对GPS掩星测量中关键参数的影响。
5）利用GPS/MET实验中5组GPS和LEO卫星的实际轨道，分别模拟了无LEO卫星轨道误差和有轨道误差情况下的GPS信号在电离层中的传播，并生成了对应的电离层延迟量。就掩星观测中电离层延迟对LEO卫星轨道误差的响应程度进行了估计和分析。初步结果显示：在掩星观测中，相对于同样大小的横向T和法向N的轨道误差而言，径向轨道误差对掩星监测大气的影响是最为显著的。
6）对无线电信号在电离层中的传播路径进行了数值模拟；针对掩星观测中的五组实际卫星轨道数据（包括GPS和LEO卫星），给出了在太阳射电辐射流量（FLUX）分别为0，70，160和240等几种情况下的电离层延迟量对10.7cm波长的太阳辐射流量的响应结果；这分别对应着无太阳辐射、太阳射电辐射处于活动低谷、平静期和高峰期等几种情形。从中可以发现，掩星观测中电离层延迟量对10.7cm波长的太阳射电辐射流量的响应表现为如下特性：电离层延迟同参数FLUX的大小有明显的对应关系，即FLUX越大，则掩星观测中的电离层延迟越大；对于上升掩星情况而言，掩星观测中电离层延迟量起先逐渐增加，然后达到某一峰值，其后逐渐下降；在掩星观测的初期和中期，太阳射电辐射处于活动低谷、平静期和高峰期等几种情形之间的电离层延迟量差异都较为显著，而在掩星观测的后期，几种情形相互间电离层延迟量的差异都比较小。
7) 对应用于局部地区大气监测的LEO卫星轨道设计中的力学模型进行了精化，并给出了重新设计结果。
Some problems are solved or thorough explored in sensing Earth's atmosphere via GPS radio occultation methodology. Firstly, an analytic expression for the angle of refraction in GPS radio occultation in the general case is presented. The angle of refraction without assuming a circular orbit is calculated iteratively starting with the value from the circular assumption. The atmospheric parameters are then calculated by inversion with and without the circular assumption. It is shown that the bias caused by the circular assumption is up to about 1 mbar in the pressure and up to about one degree Celsius in the temperature. On one hand, this result supports the practice of using the circular assumption in qualitative error analyses; on the other hand,
it shows the necessity of foregoing the circular assumption when the highest accuracy is required of the atmospheric parameters. Secondly, the way of remote sensing of terrestrial atmospheric parameters using spaceborne GPS radio occultation technique is discussed. Based on this method, data analysis software has been coded and is used to reduce real radio occultation data. It is confirmed that exponential-function extrapolation contributes much to the improvement of inverted temperature; however it does much less for pressure inversion. Compared with relevant published results from abroad, our results are, at large, agreeable with foreign investigators' relevant works. Thirdly, MSISE90 atmospheric density model is briefly introduced and the amendments in this model by Hedin are pointed out. Based on MSISE90, a priori temperature series are produced for input parameter in GPS radio occultation data reduction. Fourthly, orbit information of the Low Earth Orbiter carrying a GPS receiver is needed in the conception of atmosphere monitor by GPS occultation. It is unavoidable to analyze the effects of orbit uncertainty of the low Earth Orbiter on the observable in GPS occultation for atmosphere monitor. Based on the existent Earth atmosphere model, three dimensional ray-tracing techniques are employed to simulate five representative complete GPS occultation events. The effect of the orbit error is quantified on the key observable in occultation. Fifthly, based on Haselgrove's and Budden's Equations, the propagation process of GPS signal in the ionosphere is simulated. Five groups of orbit data for GPS and LEO satellites are employed to simulate and generate the ionospheric phase delay respectively in two cases, one is LEO orbit without forced perturbation
and the other is LEO orbit with forced perturbation. The response of ionospheric phase delay to the LEO satellite orbit biases is assessed and analyzed. The preliminary results have shown that the response of ionospheric phase delay to the LEO orbit biases is much greater in the radial direction than those in the transverse or the normal directions. Sixthly, the propagation of radio signal in the ionosphere is simulated. Based on five data sets of real satellite state vectors from radio occultation measurements, the phase delays are respectively calculated with four different FLUX, i.e., FLUX=0, 70, 160 and 240. It corresponds to four representative conditions, that is to say, no solar activity, low solar activity, average solar activity and peak solar activity. The simulation has shown such features as follows: ionospheric phase delay is obviously correlated with solar radio flux, and the greater solar radio flux, the greater ionospheric phase delay; as for a rising occultation event, at the beginning, the phase delay increases, then it reaches a peak, finally it decreases till the end of occultation event. The phase delay differences among three different solar radio flux conditions tend to enlarge in the first most part of occultation event, however, they tend to narrow in the rest of the occultation event. Finally, some force models are adapted for LEO orbital design dedicated to the regional atmospheric monitor by radio occultation. The orbit design are renewed.
对GPS无线电掩星技术反演地球大气参数方法中的若干问题进行了较为全面的分析和研究。
1）给出GPS无线电掩星反演地球大气参数过程中计算大气折射角的解析表达式。以圆轨道假设下的大气折射角计算值为先验约束,采用迭代法对不引入圆轨道假设情况的大气折射角进行归算,在此基础,利用反演方法得到了引入和不引入圆轨道假定两种情况下大气参数(气压和温度)的差分序列。结果表明: 卫星圆轨道假设对GPS 无线电掩星反演大气参数的影响,在气压方面为1mbar左右,而在气温方面为10K左右。这一结果支持了目前无线电掩星定性误差估计研究中通常引入卫星圆轨道假设这个近似处理方法的合理性;同时也表明:若在高精度反演地球大气参数时,摒弃圆轨道假定是必要的.
2）探讨了空基无线电掩星技术应用于反演地球大气参数方法，并将该方 法编制成资料处理软件；对实测资料进行处理和分析后，给出了地球大气参数反演结果。发现：指数函数外推法引入数据处理后大大改进了大气温度的归算结果，而对气压归算的影响却很小。
3）对MSISE90模型进行了简要的介绍，并指出Hedin本人在该模型问世后
对它的一些修正、改进之处。基于修正后的MSISE90大气密度模型，生成了一个可供GPS无线电掩星反演地球大气参数时使用的先验温度序列。
4）GPS掩星监测大气方法中需要载有GPS接收机的卫星的精密定轨信息，而该卫星的轨道误差对GPS掩星监测大气的影响进行分析是十分必要的。基于地球大气模式CIRA86，我们采用了三维射线跟踪方法模拟了5次完整的GPS掩星事件，估计了LEO卫星的轨道误差对GPS掩星测量中关键参数的影响。
5）利用GPS/MET实验中5组GPS和LEO卫星的实际轨道，分别模拟了无LEO卫星轨道误差和有轨道误差情况下的GPS信号在电离层中的传播，并生成了对应的电离层延迟量。就掩星观测中电离层延迟对LEO卫星轨道误差的响应程度进行了估计和分析。初步结果显示：在掩星观测中，相对于同样大小的横向T和法向N的轨道误差而言，径向轨道误差对掩星监测大气的影响是最为显著的。
6）对无线电信号在电离层中的传播路径进行了数值模拟；针对掩星观测中的五组实际卫星轨道数据（包括GPS和LEO卫星），给出了在太阳射电辐射流量（FLUX）分别为0，70，160和240等几种情况下的电离层延迟量对10.7cm波长的太阳辐射流量的响应结果；这分别对应着无太阳辐射、太阳射电辐射处于活动低谷、平静期和高峰期等几种情形。从中可以发现，掩星观测中电离层延迟量对10.7cm波长的太阳射电辐射流量的响应表现为如下特性：电离层延迟同参数FLUX的大小有明显的对应关系，即FLUX越大，则掩星观测中的电离层延迟越大；对于上升掩星情况而言，掩星观测中电离层延迟量起先逐渐增加，然后达到某一峰值，其后逐渐下降；在掩星观测的初期和中期，太阳射电辐射处于活动低谷、平静期和高峰期等几种情形之间的电离层延迟量差异都较为显著，而在掩星观测的后期，几种情形相互间电离层延迟量的差异都比较小。
7) 对应用于局部地区大气监测的LEO卫星轨道设计中的力学模型进行了精化，并给出了重新设计结果。
Some problems are solved or thorough explored in sensing Earth's atmosphere via GPS radio occultation methodology. Firstly, an analytic expression for the angle of refraction in GPS radio occultation in the general case is presented. The angle of refraction without assuming a circular orbit is calculated iteratively starting with the value from the circular assumption. The atmospheric parameters are then calculated by inversion with and without the circular assumption. It is shown that the bias caused by the circular assumption is up to about 1 mbar in the pressure and up to about one degree Celsius in the temperature. On one hand, this result supports the practice of using the circular assumption in qualitative error analyses; on the other hand,
it shows the necessity of foregoing the circular assumption when the highest accuracy is required of the atmospheric parameters. Secondly, the way of remote sensing of terrestrial atmospheric parameters using spaceborne GPS radio occultation technique is discussed. Based on this method, data analysis software has been coded and is used to reduce real radio occultation data. It is confirmed that exponential-function extrapolation contributes much to the improvement of inverted temperature; however it does much less for pressure inversion. Compared with relevant published results from abroad, our results are, at large, agreeable with foreign investigators' relevant works. Thirdly, MSISE90 atmospheric density model is briefly introduced and the amendments in this model by Hedin are pointed out. Based on MSISE90, a priori temperature series are produced for input parameter in GPS radio occultation data reduction. Fourthly, orbit information of the Low Earth Orbiter carrying a GPS receiver is needed in the conception of atmosphere monitor by GPS occultation. It is unavoidable to analyze the effects of orbit uncertainty of the low Earth Orbiter on the observable in GPS occultation for atmosphere monitor. Based on the existent Earth atmosphere model, three dimensional ray-tracing techniques are employed to simulate five representative complete GPS occultation events. The effect of the orbit error is quantified on the key observable in occultation. Fifthly, based on Haselgrove's and Budden's Equations, the propagation process of GPS signal in the ionosphere is simulated. Five groups of orbit data for GPS and LEO satellites are employed to simulate and generate the ionospheric phase delay respectively in two cases, one is LEO orbit without forced perturbation
and the other is LEO orbit with forced perturbation. The response of ionospheric phase delay to the LEO satellite orbit biases is assessed and analyzed. The preliminary results have shown that the response of ionospheric phase delay to the LEO orbit biases is much greater in the radial direction than those in the transverse or the normal directions. Sixthly, the propagation of radio signal in the ionosphere is simulated. Based on five data sets of real satellite state vectors from radio occultation measurements, the phase delays are respectively calculated with four different FLUX, i.e., FLUX=0, 70, 160 and 240. It corresponds to four representative conditions, that is to say, no solar activity, low solar activity, average solar activity and peak solar activity. The simulation has shown such features as follows: ionospheric phase delay is obviously correlated with solar radio flux, and the greater solar radio flux, the greater ionospheric phase delay; as for a rising occultation event, at the beginning, the phase delay increases, then it reaches a peak, finally it decreases till the end of occultation event. The phase delay differences among three different solar radio flux conditions tend to enlarge in the first most part of occultation event, however, they tend to narrow in the rest of the occultation event. Finally, some force models are adapted for LEO orbital design dedicated to the regional atmospheric monitor by radio occultation. The orbit design are renewed.
引文
[1]Fishbach F F. A satellite method for temperature and pressure below 24km, Bull Amer Meteorol Soc, 1965,9:528-532.
[2]Fjeldbo G, Eshleman V R. The bistatic Radar-occultation method for the study of planetary atmospheres, J. Geophys. Res., 1965,70:3217-3225.
[3]Fjeldbo G, Eshleman V R. Garriott O K, et al. The two frequency bistatic Radar-occultation method for the study of planetary ionospheres,J. Geophys. Res., 1965, 70, 3701-3710.
[4]Eshleman V R. The radio occultation method for the study of planetary atmospheres, Planet. space sci.1973,21:1521-1531.
[5]Yunck T P, Lindal G F, Liu C H. The role of GPS in precise Earth observation, Proceedings of IEEE Position, Location and Navigation Symposium, Orlando,FL, Nov. 29th-Dec. 2nd,1988.
[6]Melbourne W E, Davis C, Duncan, et al. The application of space borne GPS to atmospheric limb sounding and global change monitoring, JPL Publ., 94-18, 1994:147.
[7]Ware R, Exner M, Feng D, et al. GPS sounding of the atmosphere from low Earth orbit:Preliminary results, Bull. Amer. Met. Soc., 1996,77: 19-40.
[8]Haines B J, Bar-Sever Y E. Monitoring the TOPEX microwave radiometer with GPS: stability of columnar water vapor measurements, Geophys. Res. Lett., 1998,25: 3563-3566.
[9]Hajj G A, Romans L J. Ionospheric electron density profiles obtained with the GPS: results from the GPS/MET experiment, Radio Sci. 1998, 33(1): 175-190.
[10]Lemoine F G, Pavis N K, Kenyon S C, et al. New high-resolution model developed for Earth's gravitational field, EOS, Trans. Amer. Geophys.
Union, 1998, 79: 113-118.
[11]Rocken C, Anthes R, Exner M, et al. Analysis and validation of GPS/MET data in the neutral atmosphere, J. Geophys. Res.,1997, 102: 29849-29866.
[12]Rocken C, Kuo Y H, Schreiner W S, et al. COSMIC system description,
Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1):21-52.
[13]Kuo Y H, Chao B F, Lee L C. A Constellation of microsatellites promises to help in a range of geoscience research, EOS, 1999.80(40): 467-471.
[14]Wu C C, Kuo H C, Hsu H H et al. Weather and climate research in Taiwan:
Potential application of GPS/MET data, Special issue of Terrestrial,
Atmospheric and Oceanic Science, 2000,11(1): 211-234.
[15]Chao J K, Lee L C. The causes and effects of adverse space weather,
Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1): 313-336.
[16]Kuo Y H, Zou X, Huang W. The impact of GPS data on the prediction of an extratropical cyclone: An observing system simulation experiment. J.Dyn.Atmos.Ocean, 1997,27: 439-470.
[17]Leroy S. The measurement of geopotential heights by GPS radio occultation, J. Geophys. Res., 1997.102: 6971-6986.
[18]Leroy S, North G R. The application of COSMIC data to global change research, Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1): 187-210.
[19]Tsai W H, Huang L F, Chen M F, et al. A tomographic study of
seasonal variations of the equatorial anomaly in the Asian sector, Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1): 337-348.
[20]Hwang C. Gravity recovery using COSMIC GPS data: application of
orbital perturbation theory, Journal of Geodesy,2001,(75):117-136.
[21]Hajj G A, Lee L C, Pi X, et al. COSMIC GPS ionospheric sensing and
space weather, Special issue of Terrestrial, Atmospheric and Oceanic
Science, 2000,11(1): 235-272.
[22]Dymond K F, Nee J B, Thomas R J. The tiny ionospheric photometer: An instrument for measuring ionospheric gradients for the COSMIC constellation,Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1):273-290.
[23]Liu J Y, Chu Y H, Chen M Q, et al. Modeling and ground observations of the ionosphere related to the COSMIC project, Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1): 349-364.
[24]Leitinger R, Kirchengast G. Inversion of the plasma signal in GNSS
occultations---simulation studies and sample results, Acta Geod. Geophy.
Hung.,1997,32:379-394.
[25]Leitinger R, Ladreiter H P, Kirchengast G. Ionosphere tomography with
data from satellite reception of Global Navigation Satellite System signals and ground reception of Navy Navigation Satellite System signals, Radio Sci.,1997,32(4): 1657-1669.
[26]ESA,http://www.esa.int/export/esaLP
/VFEVCKSC_futuremissions_0.html，2002
[27]Reigber Ch, http://op.gfz-potsdam.de/champ/,2000
[28]CSR, http://www.csr.utexas.edu/grace/,2002
[29]Haojian Yan, Dong Huang, and Cheng Huang. Sequential Atmospheric Profiles near a Fixed Location Derived from GPS-LEO Occultation Measurements, Geophys. Res. Lett., 1999, 26:451-453.
[30]黄栋，严豪健，黄珹. GPS无线电掩星监测地球大气技术中的一种长时间序列地面测点方法,天文学报,2000,41(1):51-57.
[31]张训械，Hoeg P, Larsen G B,等. 奥斯特/GPS掩星与地面雷达联合观测电
离层电子密度的初步结果.全球定位系统，2000,25(3):1-5.
[32]曾桢,胡雄,张训械.无线电掩星和激光雷达观测结果比较.空间科学学报，
2001,21(2):165-171.
[33]胡国荣.星载GPS低轨卫星定轨理论研究 [博士论文D]，武汉：中国科学院测量与地球物理研究所，1999.
[34]季善标. GPS动态定位研究与应用 [博士论文D]，上海：中国科学院上海天文台，1999.
[35]王小亚. GPS在地球物理方面的应用 [博士论文D]，上海：中国科学院上海天文台，2001.
[36]黄栋，黄珹，李金岭等.GPS 无线电掩星技术监测地球大气，地球科学进展，1997，12(3):217-223.
[37]李洪涛，许国昌，薛鸿印等. GPS应用程序设计，北京：科学出版社，1999
[38]沈镜祥，施品浩，刘基余等. 空间大地测量，[M] 武汉：中国地质大学出版社，1990
[39]叶叔华，黄珹等. 天文地球动力学，济南：山东科学技术出版社，2000
[40]张守信. 外弹道测量与卫星轨道测量基础，北京：国法工业出版社，1992
[41]刘林. 人造地球卫星轨道力学，北京：高等教育出版社，1992
[42]李济生. 人造卫星精密轨道确定，北京：解放军出版社，1995
[43]Smith E K, Weintraub S. The constants in the equation for atmospheric refractive index at radio frequencies. J.Res.Natl.Bur.Stand.,1953, 50(1): 39-41.
[44]Thayer D. An improved equation for the radio refractive index of air, Radio Sci.,1974,9(10):803-807.
[45]Mortensen M D, Hoeg P. Inversion of GPS occultation measurements using Fresnel diffraction theory, Geophys. Res. Lett., 1998,25(13):2441-2444
[46]Kursinski E R, Hajj G A, Schofield J T, et al. Observing Earth's atmosphere with radio occultation measurements using the Global
Positioning System, J. Geophys. Res., 1997,102: 23429-23465.
[47 ]Weber R, Springer T. Analysis activities, IGS 2000 annual report (JPL 400-994), IGS Central Bureau, JPL, California Institute of Technology, Pasadena, California,2000
[48]Bertiger W I, Bar-Sever Y E, Christensen E J, et al. GPS precise tracking of Topex/Poseidon: Results and implications, J. Geophys. Res., 1994,99: 24449-24464.
[49]Bertiger W I, Wu S. Single frequency GPS orbit determination for low Earth orbiters, paper presented at the National Tech. Meeting, Inst. of Nav.,Santa Monica, Calif.,1996.
[50]董晓军. TOPEX卫星精密定轨及测高资料分析研究，[博士论文D]，上海：中国科学院上海天文台，1999.
[51]Kursinski E R. The GPS radio occultation concept: theoretical performance and initial results, Ph.D Thesis, California Institute of Technology, California,1997.
[52]Hocke K, Kirchengast G, Steiner A. Ionospheric correction and inversion of GNSS occultation data: problems and solutions, IMG/UoG Technical Report for ESA/ESTEC-No. 2/1997, Graz, Austria,1997.
[53] Vorob'ev V V, Gurvich A S, Kan V, et al. Structure of the ionosphere based on radio occultation data from GPS 'Microlab-1' satellites: preliminary results. Earth Obs. Rem. Sens. 1999,15: 609-622.
[54]Ladreiter H P, Kirchengast G. GPS/GLONASS sensing of the neutral
atmosphere: Model independent correction of ionospheric influences, Radio Sci,1996,31:877-891.
[55]Bassiri S, Hajj G A. Higher-order ionospheric effects on the GPS observables and means of modeling them, Manuscripta Geodetica, 1993, 18: 280-289.
[56]Vorob'ev V V, Krasil'nikova T G. Estimation of the accuracy of the
atmospheric refractive index recovery from Doppler shift measurements at frequencies used in the NAVSTAR system, Phys. Atmos. Ocean, 1994,29: 602-609.
[57]Rich F J,Basu S. Ionospheric physics, Geophysics and the Space Environment, edited by A. S. Jursa, Air Force Geophys. Lab., Bedford, Mass.,1985.
[58]Kelly M C. The Earth's ionosphere: plasma physics and electrodynamics, 487,Academic,San Diego, Calif.,1989.
[59]季善标，朱文耀，熊永清. 精密GPS卫星钟差的改正和应用，空间科学学报，2001,21(1):42-48.
[60]蒋虎，黄珹，严豪健. 无线电掩星反演大气参数误差分析及应用进展，地球物理学进展，2001,16(1):82-88.
[61]Kursinski E R, Hajj G A, Bertiger W I, et al. Initial results of radio occultation observations of Earth's atmosphere using the global positioning system, Science, 1996a, 271:1107-1110.
[62]蒋虎,卫星圆轨道假设对GPS 无线电掩星反演地球大气参数的影响,天文学报，2001，42(3）:243-247
[63]Hedin A E. Extension of the MSIS thermospheric model into the middle and lower atmosphere. J. Geophys. Res.1991,96:1159
[64]Labitzke K, Barnett J J. Edwards, B (eds.), Handbook MAP 16, SCOSTEP, University of Illinois, Urbana, 1985.
[65]Ware R. GPS Sounding of Earth's Atmosphere, GPS World, 1992,3: 56-57
[66]Yuan L, Anthes R A, Ware R H, et al. Sensing climate change using the Global Positioning System, J. Geophys. Res.,1993,98 :14 ,925- 14,937.
[67]蒋虎. 空基 GPS 遥感地球大气参数方法研究. 测绘学报,2001,
30(3):238-241.
[68]朱文耀，黄珹. 我国低轨道卫星定轨精度分析. 中国科学院上海天文台年刊，1998，19：58-67.
[69]Haselgrove J. The Hamilton ray path equations. J.Atmos. Terr. Phys.,1963,25:397-399.
[70]Budden K G. The propagation of radio waves. 1985,Cambridge University Press, Cambridge
[71]Hoeg P, Hauchcorne A, Kirchengast G, et al., Derivation of atmospheric properties using a radio occultation technique, DMI Scientific Report 95-4, Danish Meteorological Institute, Copenhagen, Denmark,1996
[72]Jiang Hu, Effect of the assumption circular satellite orbit on the derivation of Earth's atmospheric parameters from GPS radio occultation data, Chinese Astronomy and astrophysics, 2002, 26(1):64-68.
[73]蒋虎, 黄珹. 低轨卫星轨道误差对中性层延迟量影响的模拟研究,
地球物理学报，2002，接受
[74]Kursinski E R, Hajj G A, Hardy K R. Atmospheric profiles from radio occultation measurements of GPS satellites, SPIE International symposium on aerospace science and sensing, microwave instrumentation for remote sensing of the Earth,Orlando, Florida,1993.
[75] Hardy K R, Hajj G A, Kursinski E R. Accuracies of atmospheric profiles obtained from GPS occultations, International Journal of satellite communications,1994,12: 463-473.
[76]Syndegaard S. Retrieval analysis and methodologies in atmospheric limb sounding using the GNSS radio occultation technique. Scientific Report 99-6, Danish Meteorological Institute, Copenhagen, 1999.
[77]Rius A, Ruffini G, Cucurull L. Improving the vertical resolution of ionospheric tomography with GPS occultations, Geophys. Res. Lett., 1997, 24: 2291-2294.
[78]黄栋. GPS无线电掩星技术监测地球大气，[博士论文D]，上海：中国科学院上海天文台，1999.
[2]Fjeldbo G, Eshleman V R. The bistatic Radar-occultation method for the study of planetary atmospheres, J. Geophys. Res., 1965,70:3217-3225.
[3]Fjeldbo G, Eshleman V R. Garriott O K, et al. The two frequency bistatic Radar-occultation method for the study of planetary ionospheres,J. Geophys. Res., 1965, 70, 3701-3710.
[4]Eshleman V R. The radio occultation method for the study of planetary atmospheres, Planet. space sci.1973,21:1521-1531.
[5]Yunck T P, Lindal G F, Liu C H. The role of GPS in precise Earth observation, Proceedings of IEEE Position, Location and Navigation Symposium, Orlando,FL, Nov. 29th-Dec. 2nd,1988.
[6]Melbourne W E, Davis C, Duncan, et al. The application of space borne GPS to atmospheric limb sounding and global change monitoring, JPL Publ., 94-18, 1994:147.
[7]Ware R, Exner M, Feng D, et al. GPS sounding of the atmosphere from low Earth orbit:Preliminary results, Bull. Amer. Met. Soc., 1996,77: 19-40.
[8]Haines B J, Bar-Sever Y E. Monitoring the TOPEX microwave radiometer with GPS: stability of columnar water vapor measurements, Geophys. Res. Lett., 1998,25: 3563-3566.
[9]Hajj G A, Romans L J. Ionospheric electron density profiles obtained with the GPS: results from the GPS/MET experiment, Radio Sci. 1998, 33(1): 175-190.
[10]Lemoine F G, Pavis N K, Kenyon S C, et al. New high-resolution model developed for Earth's gravitational field, EOS, Trans. Amer. Geophys.
Union, 1998, 79: 113-118.
[11]Rocken C, Anthes R, Exner M, et al. Analysis and validation of GPS/MET data in the neutral atmosphere, J. Geophys. Res.,1997, 102: 29849-29866.
[12]Rocken C, Kuo Y H, Schreiner W S, et al. COSMIC system description,
Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1):21-52.
[13]Kuo Y H, Chao B F, Lee L C. A Constellation of microsatellites promises to help in a range of geoscience research, EOS, 1999.80(40): 467-471.
[14]Wu C C, Kuo H C, Hsu H H et al. Weather and climate research in Taiwan:
Potential application of GPS/MET data, Special issue of Terrestrial,
Atmospheric and Oceanic Science, 2000,11(1): 211-234.
[15]Chao J K, Lee L C. The causes and effects of adverse space weather,
Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1): 313-336.
[16]Kuo Y H, Zou X, Huang W. The impact of GPS data on the prediction of an extratropical cyclone: An observing system simulation experiment. J.Dyn.Atmos.Ocean, 1997,27: 439-470.
[17]Leroy S. The measurement of geopotential heights by GPS radio occultation, J. Geophys. Res., 1997.102: 6971-6986.
[18]Leroy S, North G R. The application of COSMIC data to global change research, Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1): 187-210.
[19]Tsai W H, Huang L F, Chen M F, et al. A tomographic study of
seasonal variations of the equatorial anomaly in the Asian sector, Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1): 337-348.
[20]Hwang C. Gravity recovery using COSMIC GPS data: application of
orbital perturbation theory, Journal of Geodesy,2001,(75):117-136.
[21]Hajj G A, Lee L C, Pi X, et al. COSMIC GPS ionospheric sensing and
space weather, Special issue of Terrestrial, Atmospheric and Oceanic
Science, 2000,11(1): 235-272.
[22]Dymond K F, Nee J B, Thomas R J. The tiny ionospheric photometer: An instrument for measuring ionospheric gradients for the COSMIC constellation,Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1):273-290.
[23]Liu J Y, Chu Y H, Chen M Q, et al. Modeling and ground observations of the ionosphere related to the COSMIC project, Special issue of Terrestrial, Atmospheric and Oceanic Science, 2000,11(1): 349-364.
[24]Leitinger R, Kirchengast G. Inversion of the plasma signal in GNSS
occultations---simulation studies and sample results, Acta Geod. Geophy.
Hung.,1997,32:379-394.
[25]Leitinger R, Ladreiter H P, Kirchengast G. Ionosphere tomography with
data from satellite reception of Global Navigation Satellite System signals and ground reception of Navy Navigation Satellite System signals, Radio Sci.,1997,32(4): 1657-1669.
[26]ESA,http://www.esa.int/export/esaLP
/VFEVCKSC_futuremissions_0.html，2002
[27]Reigber Ch, http://op.gfz-potsdam.de/champ/,2000
[28]CSR, http://www.csr.utexas.edu/grace/,2002
[29]Haojian Yan, Dong Huang, and Cheng Huang. Sequential Atmospheric Profiles near a Fixed Location Derived from GPS-LEO Occultation Measurements, Geophys. Res. Lett., 1999, 26:451-453.
[30]黄栋，严豪健，黄珹. GPS无线电掩星监测地球大气技术中的一种长时间序列地面测点方法,天文学报,2000,41(1):51-57.
[31]张训械，Hoeg P, Larsen G B,等. 奥斯特/GPS掩星与地面雷达联合观测电
离层电子密度的初步结果.全球定位系统，2000,25(3):1-5.
[32]曾桢,胡雄,张训械.无线电掩星和激光雷达观测结果比较.空间科学学报，
2001,21(2):165-171.
[33]胡国荣.星载GPS低轨卫星定轨理论研究 [博士论文D]，武汉：中国科学院测量与地球物理研究所，1999.
[34]季善标. GPS动态定位研究与应用 [博士论文D]，上海：中国科学院上海天文台，1999.
[35]王小亚. GPS在地球物理方面的应用 [博士论文D]，上海：中国科学院上海天文台，2001.
[36]黄栋，黄珹，李金岭等.GPS 无线电掩星技术监测地球大气，地球科学进展，1997，12(3):217-223.
[37]李洪涛，许国昌，薛鸿印等. GPS应用程序设计，北京：科学出版社，1999
[38]沈镜祥，施品浩，刘基余等. 空间大地测量，[M] 武汉：中国地质大学出版社，1990
[39]叶叔华，黄珹等. 天文地球动力学，济南：山东科学技术出版社，2000
[40]张守信. 外弹道测量与卫星轨道测量基础，北京：国法工业出版社，1992
[41]刘林. 人造地球卫星轨道力学，北京：高等教育出版社，1992
[42]李济生. 人造卫星精密轨道确定，北京：解放军出版社，1995
[43]Smith E K, Weintraub S. The constants in the equation for atmospheric refractive index at radio frequencies. J.Res.Natl.Bur.Stand.,1953, 50(1): 39-41.
[44]Thayer D. An improved equation for the radio refractive index of air, Radio Sci.,1974,9(10):803-807.
[45]Mortensen M D, Hoeg P. Inversion of GPS occultation measurements using Fresnel diffraction theory, Geophys. Res. Lett., 1998,25(13):2441-2444
[46]Kursinski E R, Hajj G A, Schofield J T, et al. Observing Earth's atmosphere with radio occultation measurements using the Global
Positioning System, J. Geophys. Res., 1997,102: 23429-23465.
[47 ]Weber R, Springer T. Analysis activities, IGS 2000 annual report (JPL 400-994), IGS Central Bureau, JPL, California Institute of Technology, Pasadena, California,2000
[48]Bertiger W I, Bar-Sever Y E, Christensen E J, et al. GPS precise tracking of Topex/Poseidon: Results and implications, J. Geophys. Res., 1994,99: 24449-24464.
[49]Bertiger W I, Wu S. Single frequency GPS orbit determination for low Earth orbiters, paper presented at the National Tech. Meeting, Inst. of Nav.,Santa Monica, Calif.,1996.
[50]董晓军. TOPEX卫星精密定轨及测高资料分析研究，[博士论文D]，上海：中国科学院上海天文台，1999.
[51]Kursinski E R. The GPS radio occultation concept: theoretical performance and initial results, Ph.D Thesis, California Institute of Technology, California,1997.
[52]Hocke K, Kirchengast G, Steiner A. Ionospheric correction and inversion of GNSS occultation data: problems and solutions, IMG/UoG Technical Report for ESA/ESTEC-No. 2/1997, Graz, Austria,1997.
[53] Vorob'ev V V, Gurvich A S, Kan V, et al. Structure of the ionosphere based on radio occultation data from GPS 'Microlab-1' satellites: preliminary results. Earth Obs. Rem. Sens. 1999,15: 609-622.
[54]Ladreiter H P, Kirchengast G. GPS/GLONASS sensing of the neutral
atmosphere: Model independent correction of ionospheric influences, Radio Sci,1996,31:877-891.
[55]Bassiri S, Hajj G A. Higher-order ionospheric effects on the GPS observables and means of modeling them, Manuscripta Geodetica, 1993, 18: 280-289.
[56]Vorob'ev V V, Krasil'nikova T G. Estimation of the accuracy of the
atmospheric refractive index recovery from Doppler shift measurements at frequencies used in the NAVSTAR system, Phys. Atmos. Ocean, 1994,29: 602-609.
[57]Rich F J,Basu S. Ionospheric physics, Geophysics and the Space Environment, edited by A. S. Jursa, Air Force Geophys. Lab., Bedford, Mass.,1985.
[58]Kelly M C. The Earth's ionosphere: plasma physics and electrodynamics, 487,Academic,San Diego, Calif.,1989.
[59]季善标，朱文耀，熊永清. 精密GPS卫星钟差的改正和应用，空间科学学报，2001,21(1):42-48.
[60]蒋虎，黄珹，严豪健. 无线电掩星反演大气参数误差分析及应用进展，地球物理学进展，2001,16(1):82-88.
[61]Kursinski E R, Hajj G A, Bertiger W I, et al. Initial results of radio occultation observations of Earth's atmosphere using the global positioning system, Science, 1996a, 271:1107-1110.
[62]蒋虎,卫星圆轨道假设对GPS 无线电掩星反演地球大气参数的影响,天文学报，2001，42(3）:243-247
[63]Hedin A E. Extension of the MSIS thermospheric model into the middle and lower atmosphere. J. Geophys. Res.1991,96:1159
[64]Labitzke K, Barnett J J. Edwards, B (eds.), Handbook MAP 16, SCOSTEP, University of Illinois, Urbana, 1985.
[65]Ware R. GPS Sounding of Earth's Atmosphere, GPS World, 1992,3: 56-57
[66]Yuan L, Anthes R A, Ware R H, et al. Sensing climate change using the Global Positioning System, J. Geophys. Res.,1993,98 :14 ,925- 14,937.
[67]蒋虎. 空基 GPS 遥感地球大气参数方法研究. 测绘学报,2001,
30(3):238-241.
[68]朱文耀，黄珹. 我国低轨道卫星定轨精度分析. 中国科学院上海天文台年刊，1998，19：58-67.
[69]Haselgrove J. The Hamilton ray path equations. J.Atmos. Terr. Phys.,1963,25:397-399.
[70]Budden K G. The propagation of radio waves. 1985,Cambridge University Press, Cambridge
[71]Hoeg P, Hauchcorne A, Kirchengast G, et al., Derivation of atmospheric properties using a radio occultation technique, DMI Scientific Report 95-4, Danish Meteorological Institute, Copenhagen, Denmark,1996
[72]Jiang Hu, Effect of the assumption circular satellite orbit on the derivation of Earth's atmospheric parameters from GPS radio occultation data, Chinese Astronomy and astrophysics, 2002, 26(1):64-68.
[73]蒋虎, 黄珹. 低轨卫星轨道误差对中性层延迟量影响的模拟研究,
地球物理学报，2002，接受
[74]Kursinski E R, Hajj G A, Hardy K R. Atmospheric profiles from radio occultation measurements of GPS satellites, SPIE International symposium on aerospace science and sensing, microwave instrumentation for remote sensing of the Earth,Orlando, Florida,1993.
[75] Hardy K R, Hajj G A, Kursinski E R. Accuracies of atmospheric profiles obtained from GPS occultations, International Journal of satellite communications,1994,12: 463-473.
[76]Syndegaard S. Retrieval analysis and methodologies in atmospheric limb sounding using the GNSS radio occultation technique. Scientific Report 99-6, Danish Meteorological Institute, Copenhagen, 1999.
[77]Rius A, Ruffini G, Cucurull L. Improving the vertical resolution of ionospheric tomography with GPS occultations, Geophys. Res. Lett., 1997, 24: 2291-2294.
[78]黄栋. GPS无线电掩星技术监测地球大气，[博士论文D]，上海：中国科学院上海天文台，1999.