共查询到20条相似文献，搜索用时 231 毫秒
1.
Lunar gravity field determination using SELENE same-beam differential VLBI tracking data 总被引：2，自引：0，他引：2
S. Goossens K. Matsumoto Q. Liu F. Kikuchi K. Sato H. Hanada Y. Ishihara H. Noda N. Kawano N. Namiki T. Iwata F. G. Lemoine D. D. Rowlands Y. Harada M. Chen 《Journal of Geodesy》2011,85(4):205-228
A lunar gravity field model up to degree and order 100 in spherical harmonics, named SGM100i, has been determined from SELENE and historical tracking data, with an emphasis on using same-beam S-band differential VLBI data obtained in the SELENE mission between January 2008 and February 2009. Orbit consistency throughout the entire mission period of SELENE as determined from orbit overlaps for the two sub-satellites of SELENE involved in the VLBI tracking improved consistently from several hundreds of metres to several tens of metres by including differential VLBI data. Through orbits that are better determined, the gravity field model is also improved by including these data. Orbit determination performance for the new model shows improvements over earlier 100th degree and order models, especially for edge-on orbits over the deep far side. Lunar Prospector orbit determination shows an improvement of orbit consistency from 1-day predictions for 2-day arcs of 6 m in a total sense, with most improvement in the along and cross-track directions. Data fit for the types and satellites involved is also improved. Formal errors for the lower degrees are smaller, and the new model also shows increased correlations with topography over the far side. The estimated value for the lunar GM for this model equals 4902.80080±0.0009 km3/s2 (10 sigma). The lunar degree 2 potential Love number k 2 was also estimated, and has a value of 0.0255 ± 0.0016 (10 sigma as well). 相似文献
2.
Yehuda Bock Richard I. Abbot Charles C. Counselman III Robert W. King 《Journal of Geodesy》1986,60(3):241-254
By interferometric analysis ofGPS phase observations made at Owens Valley, Mojave, and Mammoth Lakes, California, we determined the coordinate components of the71–245–313 km triangle of baselines connecting these sites. A separate determination was made on each of four days, April 1–4, 1985. The satellite ephemerides used in these determinations had been derived from observations on other baselines. Therms scatters of the four daily determinations of baseline vector components about their respective means ranged from a minimum of6 mm for the north component of the71-km baseline to a maximum of34 mm for the vertical component of the245-km baseline. To test accuracy, we compared the mean of ourGPS determinations of the245-km baseline between Owens Valley and Mojave with independent determinations by others using very-long-baseline interferometry(VLBI) and satellite laser ranging(SLR). TheGPS-VLBI difference was within 2 parts in10 7 for every vector component. TheGPS-SLR difference was within6 parts in10 8 in the horizontal coordinates, but83 mm in height. 相似文献
3.
A unified scheme for processing GPS dual-band phase observations 总被引：3，自引：4，他引：3
A unified computational scheme is presented for sequential least-squares processing ofGPS dual-band carrier-beat-phase observations in network-mode positioning with orbit relaxation, and in orbit determination applications.
This scheme is applicable to any spatial and temporal distribution of stations and satellites during a particularGPS experiment. Full covariance matrices can be specified for carrier-beat-phases and for weighted constraints on the ionosphere
in order to improve phase ambiguity resolution. Physically meaningful choices for these covariance matrices are developed. 相似文献
4.
Stochastic estimation of tropospheric path delays in global positioning system geodetic measurements 总被引：5，自引：2，他引：5
Water vapor radiometric (WVR) and surface meteorological (SM) measurements taken during three Global Positioning System (GPS) geodetic experiments are used to calculate process noise levels for random walk and first-order Gauss-Markov temporal models
of tropospheric path delays. Entire wet and combined wet and dry zenith delays at each network site then are estimated simultaneously
with the geodetic parameters without prior calibration. The path delays and corresponding baseline estimates are compared
to those obtained with calibrated data and stochastic residual delays. In this manner, the marginal utility of a priori tropospheric
calibration is assessed given the ability to estimate the path delays directly using only theGPS data. Estimation of total zenith path delays with appropriate random walk or Gauss-Markov models yields baseline repeatabilities
of a few parts in 108. This level of geodetic precision, and accuracy as suggested by analyses on collocated baselines estimated independently
by very long baseline interferometry, is comparable to or better than that obtained after path delay calibration usingWVR and/orSM measurements. Results suggest thatGPS data alone have sufficient strength to resolve centimeter-level zenith path delay fluctuations over periods of a few minutes. 相似文献
5.
G. Beutler W. Gurtner M. Rothacher T. Schildknecht I. Bauersima 《Journal of Geodesy》1986,60(3):205-220
Summary Carrier phase measurements are potentially the most precise observations available from theGPS satellite system, the formal precision being of the order of one centimeter per observation. If the so called double differences
are used as the basic observable, the analysis is relatively simple, since satellite- and receiver-clocks may be represented
by basic models. We investigate the feasibility of double difference phase observations for orbit determination using the
material of the 1985 High Precision Baseline Test, where the coordinates of the so called fiducial points (Haystack, Ft. Davis
Richmond and Mojave) are held fixed.TI-4100 andAFGL-receiver observations were used in the same orbit determination process.
Although no surface weather data had been available to us, the orbit quality seems to be of the order of0.1 ppm. When we use these orbits to estimate the coordinates of the five “non-fiducial points” Owens Valley, Hat Creek Mammoth Lake,
Austin and Dahlgren we get a repeatability of the order of5 cm for latitude and longitude and10 cm for height, if the observations of the first four days of the campaign are compared to those of the second four days.
If we use our orbits estimated withTI andAFGL observations to process the Mojave—Owens Valley baseline (length245 km) measured by the twoSERIES-X receivers, we obtain day to day repeatabilities of1.6 cm (0.06 ppm) in length,2 cm (0.08 ppm) in latitude,4 cm (0.16 ppm) in longitude and7 cm (0.29 ppm) in height.
Since there are indications that regional networks will be realized in the near future, the results presented here should
encourage the realization of regional high precision orbit determination services. 相似文献
6.
Considering present attempts to develop a gradiometer with an accuracy between 10−3
E and 10−4
E, two applications for such a device have been studied: (a) mapping the gravitational field of the Earth, and (b) estimating
the geocentric distance of a satellite carrying the instrument. Given a certain power spectrum for the signal and 10−4
E (rms) of white measurement noise, the results of an error analysis indicate that a six-month mission in polar orbit at a height
of 200 km, with samples taken every three seconds, should provide data for estimating the spherical harmonic potential coefficients
up to degree and order 300 with less than 50% error, and improve the coefficients through degree 30 by up to four orders of
magnitude compared to existing models. A simulation study based on numerical orbit integrations suggests that a simple adjustment
of the initial conditions based on gradiometer data could produce orbits where the geocentric distance is accurate to 10 cm
or better, provided the orbits are 2000 km high and some improvement in the gravity field up to degree 30 is first achieved.
In this sense, the gravity-mapping capability of the gradiometer complements its use in orbit refinement. This idea can be
of use in determining orbits for satellite altimetry. Furthermore, by tracking the gradiometer-carrying spacecraft when it
passes nearly above a terrestrial station, the geocentric distance of this station can also be estimated to about one decimeter
accuracy. This principle could be used in combination with VLBI and other modern methods to set up a world-wide 3-D network
of high accuracy. 相似文献
7.
The Center for Orbit Determination in Europe (CODE) has been involved in the processing of combined GPS/GLONASS data during the International GLONASS Experiment (IGEX). The resulting precise orbits were analyzed using the program SORBDT. Introducing one satellites positions as pseudo-observations, the program is capable of fitting orbital arcs through these positions using an orbit improvement procedure based on the numerical integration of the satellites orbit and its partial derivative with respect to the orbit parameters. For this study, the program was enhanced to estimate selected parameters of the Earths gravity field. The orbital periods of the GPS satellites are —in contrast to those of the GLONASS satellites – 2:1 commensurable (P
Sid:P
GPS) with the rotation period of the Earth. Therefore, resonance effects of the satellite motion with terms of the geopotential occur and they influence the estimation of these parameters. A sensitivity study of the GPS and GLONASS orbits with respect to the geopotential coefficients reveals that the correlations between different geopotential coefficients and the correlations of geopotential coefficients with other orbit parameters, in particular with solar radiation pressure parameters, are the crucial issues in this context. The estimation of the resonant geopotential terms is, in the case of GPS, hindered by correlations with the simultaneously estimated radiation pressure parameters. In the GLONASS case, arc lengths of several days allow the decorrelation of the two parameter types. The formal errors of the estimates based on the GLONASS orbits are a factor of 5 to 10 smaller for all resonant terms.
AcknowledgmentsThe authors would like to thank all the organizations involved in the IGS and the IGEX campaign, in particular those operating an IGS or IGEX observation site and providing the indispensable data for precise orbit determination. 相似文献
8.
Since the beginning of the International Global Navigation Satellite System (GLONASS) Experiment, IGEX, in October 1998,
the Center for Orbit Determination in Europe (CODE) has acted as an analysis center providing precise GLONASS orbits on a
regular basis. In CODE's IGEX routine analysis the Global Positioning System (GPS) orbits and Earth rotation parameters are
introduced as known quantities into the GLONASS processing. A new approach is studied, where data from the IGEX network are
combined with GPS observations from the International GPS Service (IGS) network and all parameters (GPS and GLONASS orbits,
Earth rotation parameters, and site coordinates) are estimated in one processing step. The influence of different solar radiation
pressure parameterizations on the GLONASS orbits is studied using different parameter subsets of the extended CODE orbit model.
Parameterization with three constant terms in the three orthogonal directions, D, Y, and X (D = direction satellite–Sun, Y = direction of the satellite's solar panel axis), and two periodic terms in the X-direction, proves to be adequate for GLONASS satellites. As a result of the processing it is found that the solar radiation
pressure effect for the GLONASS satellites is significantly different in the Y-direction from that for the GPS satellites, and an extensive analysis is carried out to investigate the effect in detail.
SLR observations from the ILRS network are used as an independent check on the quality of the GLONASS orbital solutions. Both
processing aspects, combining the two networks and changing the orbit parameterization, significantly improve the quality
of the determined GLONASS orbits compared to the orbits stemming from CODE's IGEX routine processing.
Received: 10 May 2000 / Accepted: 9 October 2000 相似文献
9.
The Global Positioning System,GPS, is widely used for time comparisons between distant laboratories. Over distances of the order of 1000km or less, the system has the capability of 1 to 2ns accuracy. However this requires a relative positioning with errors lower than 30cm. We show that this positioning can be derived from theGPS time comparisons themselves. An example for European laboratories is given. 相似文献
10.
Ellipsoidal heights have been determined for a test network in Lower Saxony withGPS. TheGPS results, with a relative precision of a few centimeters, have been used to compute quasigeoid heights by substracting leveling
heights. This data set is compared to mainly gravimetrically determined quasigeoid heights using least squares collocation
techniques. The discrepancies between the two data sets amount to about ±2cm, the maximum interstation distance is about50 km. This agreement shows, thatGPS can be used in combination with gravity information to obtain normal heights withcm-precision. 相似文献
11.
A technique for the analysis of low–low intersatellite range-rate data in a gravity mapping mission is explored. The technique
is based on standard tracking data analysis for orbit determination but uses a spherical coordinate representation of the
12 epoch state parameters describing the baseline between the two satellites. This representation of the state parameters
is exploited to allow the intersatellite range-rate analysis to benefit from information provided by other tracking data types
without large simultaneous multiple-data-type solutions. The technique appears especially valuable for estimating gravity
from short arcs (e.g. less than 15 minutes) of data. Gravity recovery simulations which use short arcs are compared with those
using arcs a day in length. For a high-inclination orbit, the short-arc analysis recovers low-order gravity coefficients remarkably
well, although higher-order terms, especially sectorial terms, are less accurate. Simulations suggest that either long or
short arcs of the Gravity Recovery and Climate Experiment (GRACE) data are likely to improve parts of the geopotential spectrum
by orders of magnitude.
Received: 26 June 2001 / Accepted: 21 January 2002 相似文献
12.
DifferentialGPS land kinematic positioning tests conducted at velocities of20 to100 km/h over a baseline of1,000 km using a combination of pseudo-range and phase measurements are described. An algorithm designed for high reliability and
accuracy of1 to2 m in real time field operational mode was utilized. The relatively long baseline used for the tests provided valuable information
on the effects of broadcast ephemeris errors on the differential results. The tests were conducted with two Texas InstrumentsTI4100 receivers using both theP andC/A codes to assess the effect of both code measurement noise, and ionospheric irregularities on differential positioning over
such a baseline. The use of cesium clocks to constrain time was also tested. Accuracies (in terms of repeatabilities) of the
order of1 to3 ppm, i.e.,1 to3 m, were obtained. 相似文献
13.
Roger L. Merrell P.E. 《Journal of Geodesy》1986,60(3):265-277
Summary The Texas State Department of Highways and Public Transportation(SDHPT) has been usingGPS for over two years to establish primary geodetic reference points for engineering projects and mapping control. In accordance
with a Five YearGPS Implementation Plant developed in 1982, fourGPS, unmanned, automatic Regional Reference Point(RRP) stations will be installed by September 1, 1986. Five additional stations are planned as justified. EachRRP will consist of a dual frequencyGPS receiver that will ultimately track the satellites continuously. Operation of the receiver, telecommunications and other
station keeping chores will be handled by a microcomputer. TheRRP station network will be controlled through another centrally located microcomputer which is also interfaced with a larger
mainframe system. EachRRP is designed to service an area bounded by a200 KM radius and will act as the “other” receiver for roving field units operating in aGPS differential measurement mode. In order to meet the installation schedule, early decisions are being made concerning satellite
tracking rates, operational scenarios, and telecommunications to facilitate development of the basic hardware and software
systems. A period of continual enhancement to hardware, software andRRP operational procedures is expected asGPS technology expands. 相似文献
14.
Krzysztof Sośnica Lars Prange Kamil Kaźmierski Grzegorz Bury Mateusz Drożdżewski Radosław Zajdel Tomasz Hadas 《Journal of Geodesy》2018,92(2):131-148
The space segment of the European Global Navigation Satellite System (GNSS) Galileo consists of In-Orbit Validation (IOV) and Full Operational Capability (FOC) spacecraft. The first pair of FOC satellites was launched into an incorrect, highly eccentric orbital plane with a lower than nominal inclination angle. All Galileo satellites are equipped with satellite laser ranging (SLR) retroreflectors which allow, for example, for the assessment of the orbit quality or for the SLR–GNSS co-location in space. The number of SLR observations to Galileo satellites has been continuously increasing thanks to a series of intensive campaigns devoted to SLR tracking of GNSS satellites initiated by the International Laser Ranging Service. This paper assesses systematic effects and quality of Galileo orbits using SLR data with a main focus on Galileo satellites launched into incorrect orbits. We compare the SLR observations with respect to microwave-based Galileo orbits generated by the Center for Orbit Determination in Europe (CODE) in the framework of the International GNSS Service Multi-GNSS Experiment for the period 2014.0–2016.5. We analyze the SLR signature effect, which is characterized by the dependency of SLR residuals with respect to various incidence angles of laser beams for stations equipped with single-photon and multi-photon detectors. Surprisingly, the CODE orbit quality of satellites in the incorrect orbital planes is not worse than that of nominal FOC and IOV orbits. The RMS of SLR residuals is even lower by 5.0 and 1.5 mm for satellites in the incorrect orbital planes than for FOC and IOV satellites, respectively. The mean SLR offsets equal \(-44.9, -35.0\), and \(-22.4\) mm for IOV, FOC, and satellites in the incorrect orbital plane. Finally, we found that the empirical orbit models, which were originally designed for precise orbit determination of GNSS satellites in circular orbits, provide fully appropriate results also for highly eccentric orbits with variable linear and angular velocities. 相似文献
15.
SLR资料精密测定GLONASS卫星轨道 总被引：3，自引：0，他引：3
将SLR资料计算的轨道与CODE轨道进行了比较，并将比较结果转换到RTN坐标系中。通过比较分析发现，两种轨道差值在轨道径向、法向和沿轨方向的精度分别优于10cm、50cm和45cm；SLR和微波资料确定的GLONASS卫星轨道在径向存在系统误差，该系统误差随卫星轨道面的不同而不同。 相似文献
16.
The impact of accelerometry on CHAMP orbit determination 总被引：6，自引：0，他引：6
The contribution of the STAR accelerometer to the CHAMP orbit precision is evaluated and quantified by means of the following
results: orbital fit to the satellite laser ranging (SLR) observations, GPS reduced-dynamic vs SLR dynamic orbit comparisons,
and comparison of the measured to the modeled non-gravitational accelerations (atmospheric drag in particular). In each of
the four test periods in 2001, five CHAMP arcs of 2 days' length were analyzed. The mean RMS-of-fit of the SLR observations
of the orbits computed with STAR data or the non-gravitational force model were 11 and 24 cm, respectively. If the accelerometer
calibration parameters are not known at least at the few percent level, the SLR orbit fit deteriorates. This was tested by
applying a 10% error to the along-track scale factor of the accelerometer, which increased the SLR RMS-of-fit on average to
17 cm. Reference orbits were computed employing the reduced-dynamic technique with GPS tracking data. This technique yields
the most accurate orbit positions thanks to the estimation of a large number of empirical accelerations, which compensate
for dynamic modeling errors. Comparison of the SLR orbits, computed with STAR data or the non-gravitational force model, to
the GPS-based orbits showed that the SLR orbits employing accelerometer observations are twice as accurate. Finally, comparison
of measured to modeled accelerations showed that the level of geomagnetic activity is highly correlated with the atmospheric
drag model error, and that the largest errors occur around the geomagnetic poles.
Received: 7 May 2002 / Accepted: 18 November 2002
Correspondence to: S. Bruinsma
Acknowledgments. The TIGCM results were obtained from the CEDAR database. This study was supported by the Centre National d'Etudes Spatiales
(CNES). The referees are thanked for their helpful remarks and suggestions. 相似文献
17.
Cheinway Hwang Tzu-Pang Tseng Tingjung Lin Dražen Švehla Bill Schreiner 《Journal of Geodesy》2009,83(5):477-489
The joint Taiwan–US mission FORMOSAT-3/ COSMIC (COSMIC) was launched on April 17, 2006. Each of the six satellites is equipped
with two POD antennas. The orbits of the six satellites are determined from GPS data using zero-difference carrier-phase measurements
by the reduced dynamic and kinematic methods. The effects of satellite center of mass (COM) variation, satellite attitude,
GPS antenna phase center variation (PCV), and cable delay difference on the COSMIC orbit determination are studied. Nominal
attitudes estimated from satellite state vectors deliver a better orbit accuracy when compared to observed attitude. Numerical
tests show that the COSMIC COM must be precisely calibrated in order not to corrupt orbit determination. Based on the analyses
of the 5 and 6-h orbit overlaps of two 30-h arcs, orbit accuracies from the reduced dynamic and kinematic solutions are nearly
identical and are at the 2–3 cm level. The mean RMS difference between the orbits from this paper and those from UCAR (near
real-time) and WHU (post-processed) is about 10 cm, which is largely due to different uses of GPS ephemerides, high-rate GPS
clocks and force models. The kinematic orbits of COSMIC are expected to be used for recovery of temporal variations in the
gravity field. 相似文献
18.
Accurate geocentric three dimensional positioning is of great importance for various geodetic and oceanographic applications.
While relative positioning accuracy of a few centimeters has become a reality using Very Long Baseline Interferometry (VLBI), the uncertainty in the offset of the adopted coordinate system origin from the geocenter is still believed to be of the
order of one meter. Satellite Laser Ranging (SLR) is capable of determining this offset to better than10 cm, though, because of the limited number of satellites, this requires a long arc of data. The Global Positioning System (GPS) measurements provide a powerful alternative for an accurate determination of this origin offset in relatively short period
of time. Two strategies are discussed, the first utilizes the precise relative positions predetermined byVLBI, where as the second establishes a reference frame by holding only one of the tracking sites longitude fixed. Covariance
analysis studies indicate that geocentric positioning to an accuracy of a few centimeters can be achieved with just one day
of preciseGPS pseudorange and carrier phase data. 相似文献
19.
首次搭载GPS/BDS双模接收机全球导航卫星掩星探测仪(GNOS)的风云三号C星于2013年9月23日的成功发射,为研究低轨卫星对BDS定轨增强提供了便利。本文首先对低轨卫星GNOS搭载的GPS/BDS双模接收机的观测数据进行统计,并分析了伪距测量精度。然后在全球测站、区域测站两种布局情况下,对无GNOS的BDS单系统定轨、无GNOS的GPS/BDS双系统定轨、有GNOS的BDS单系统定轨增强、有GNOS的GPS/BDS双系统定轨增强4种方案进行北斗轨道及钟差比较分析。结果表明,GNOS对北斗卫星轨道增强在全球测站下,GEO卫星切向精度提升最为显著,提升程度达60%,其次是法向和其他类型卫星切向,部分弧段个别GEO卫星径向精度稍有下降。双系统定轨增强中可视弧段钟差重叠精度RMS值有0.1ns量级改善。7个国内测站区域监测网的定轨试验中对轨道进行了预报,结果表明GNOS对北斗GEO卫星轨道预报精度切向提升达85%,其余方向及卫星有较大改善,平均21.7%。可视弧段钟差重叠精度RMS值有0.5ns量级改善。 相似文献