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1.
Within the scope of the Global Geodetic Observing System, Doppler Orbit Determination and Radiopositioning Integrated by Satellite – as a geodetic technique – can provide precise and continuous monitoring of the geocenter motion related to mass redistribution in the Earth, ocean and atmosphere system. We have reanalyzed 1998 DORIS/SPOT-4 (Satellite pour l’ Observation de la Terre) data that were previously generating inconsistent geocenter positions (?65 cm offset). We show here that this error is due to an incorrect phase center correction provided with the DORIS preprocessed data resulting from a +12 cm offset in the cross-track direction that has been confirmed since. We also conclude that a 1 mm error in the cross-track offset of non-yawing sun-synchronous SPOT satellites will generate a ?6.5 mm error in the derived Z-geocenter. Other non-yawing satellites would also be affected by a similar effect whose amplitude could be easily estimated from the orbit inclination 相似文献
2.
Latitude-lumped coefficients (LLC) are defined, representing geopotential-orbit variations for dual-satellite crossovers (DSC). Formulae are derived for their standard errors from the covariances of geopotential field models. Numerical examples are
presented for pairs of the altimeter-bearing satellites TOPEX/Poseidon, ERS 1, and Geosat, using the error matrices of recent
gravity models. The DSC, connecting separate missions, will play an increasingly important role in oceanography spanning decades
only when its nonoceanographic signals are thoroughly understood. In general, the content of even the long-term averaged DSC
is more complex then their single satellite crossover (SSC) counterpart. The LLC, as the spatial spectra for the geopotential-caused
crossover effects, discriminate these source-differences sharply. Thus, the zero-order LLC in DSC data contains zonal gravity
information not present in SSC data. In addition, zero- and first-order LLC of DSC data can reveal a geocenter discrepancy
between the orbit tracking of the separate satellite missions. For example, DSC analysis from orbits computed with JGM 2 show
that the y-axis of the geocenter for Geosat in 1986–1988 is shifted with respect to T/P by 6–9 cm towards the eastern Pacific. Also,
where the time-gap is necessarily large (as between, say, Geosat and T/P missions) oceanographic (sea-level) differences in
DSC may corrupt the geopotential interpretation of the data. Most importantly, as we illustrate, media delays for the altimeter
(from the ionosphere, wet troposphere and sea-state bias) are more likely sources of contamination across two missions than
in SSC analyses. Again, the LLC of zero order best shows this contrast. Using the higher-order LLC of DSC for both Geosat-T/P
and ERS 1-T/P as likely representation of geopotential-only error, we show by comparison with the predicted standard errors
of JGM 2 that the latter's previously calibrated covariance matrix is generally valid.
Received: 14 February 1996 / Accepted: 27 March 1997 相似文献
3.
Impact of Earth radiation pressure on GPS position estimates 总被引：10，自引：8，他引：2
C. J. Rodriguez-Solano U. Hugentobler P. Steigenberger S. Lutz 《Journal of Geodesy》2012,86(5):309-317
GPS satellite orbits available from the International GNSS Service (IGS) show a consistent radial bias of up to several cm
and a particular pattern in the Satellite Laser Ranging (SLR) residuals, which are suggested to be related to radiation pressure
mismodeling. In addition, orbit-related frequencies were identified in geodetic time series such as apparent geocenter motion
and station displacements derived from GPS tracking data. A potential solution to these discrepancies is the inclusion of
Earth radiation pressure (visible and infrared) modeling in the orbit determination process. This is currently not yet considered
by all analysis centers contributing to the IGS final orbits. The acceleration, accounting for Earth radiation and satellite
models, is introduced in this paper in the computation of a global GPS network (around 200 IGS sites) adopting the analysis
strategies from the Center for Orbit Determination in Europe (CODE). Two solutions covering 9 years (2000–2008) with and without
Earth radiation pressure were computed and form the basis for this study. In previous studies, it has been shown that Earth
radiation pressure has a non-negligible effect on the GPS orbits, mainly in the radial component. In this paper, the effect
on the along-track and cross-track components is studied in more detail. Also in this paper, it is shown that Earth radiation
pressure leads to a change in the estimates of GPS ground station positions, which is systematic over large regions of the
Earth. This observed “deformation” of the Earth is towards North–South and with large scale patterns that repeat six times
per GPS draconitic year (350 days), reaching a magnitude of up to 1 mm. The impact of Earth radiation pressure on the geocenter
and length of day estimates was also investigated, but the effect is found to be less significant as compared to the orbits
and position estimates. 相似文献
4.
Analysis of the bias between TOPEX and GPS vTEC determinations 总被引：4，自引：2，他引：2
The TOPEX/Poseidon satellite was jointly developed and deployed by the National Aeronautics and Space Administration (NASA),
USA, and the Centre National d’Etudes Spatiales (CNES), France (for details see Chelton et al. In: Fu L-L, Cazenave A (eds)
International geophysics series, vol 69, ISBN 0-12-269545-3, Academic Press, CA, pp 1–131, 2001), with the main scientific
goal of sea surface height monitoring. The process that ends with the TOPEX main observable (the range between the satellite
and the sea surface) involves the measurement of several parameters of the radar pulses reflected by the sea surface and the
computation of several other corrections. After several calibration campaigns performed by the Calibration/Validation team
of the mission, it was found that TOPEX range determinations were systematically shorter than expected and it was decided
to add an empirical correction of +15 mm to the TOPEX range-computation algorithm. As a by-product, TOPEX provides vertical
total electron content (vTEC) determinations which have turned out to be a very important data source for the ionospheric
research community. Since TOPEX vTEC measurements became available, several comparison studies have detected a constant bias,
from +2 to +5 TECu, when TOPEX is compared to other vTEC sources, e.g., Global Positioning System (GPS), Doppler Orbitography
and Radio-positioning Integrated by Satellite (DORIS), (TOPEX always greater than the others). In this work, we show that
miscalibration of the corrections used in the TOPEX processing algorithm can cause the shortening effect of TOPEX ranges and
at the same time the constant bias on the TOPEX vTEC values. It is also shown that changes on TOPEX System Biases of less
than 10 mm for the Ku-band and between 40 and 70 mm for the C-band, can make both effects disappear. The analyzed hypothesis
is supported by theoretical considerations and data analysis available in the specialized literature.
On behalf of the authors of the contribution ‘Analysis of the bias between TOPEX and GPS vTEC determinations’, I declare that
the paper has not been, nor is in the process of being published in any other publication. 相似文献
5.
Ephemeris errors of GPS satellites 总被引：2，自引：0，他引：2
Oscar L. Colombo 《Journal of Geodesy》1986,60(1):64-84
Ephemeris errors are supposed to be a major factor limiting the usefulness ofGPS in high precision geodesy. Considerations of orbital mechanics suggest that, regardless of their complexity, the uncertainties
in the solar radiation pressure model, the gravity field model, and the estimated initial state, may have simple effects on
the ephemeris. This possibility has been tested by fitting linear combinations of simple functions—chosen on theoretical grounds—to
simulated errors of three-day ephemerides. With a set of five functions for the across-track component, six for the radial,
and seven for the along-track, it has been possible to fit the position errors to better than 1% of theirr.m.s values, in all the caces studied. The simulations included —besides solar radiation pressure errors—gravity field model and
initial state uncertainties, as well as an unknown constant force along the axis of the solar panels. The solar radiation
force was calculated taking into account the shape, orientation, and physical properties (reflectivity and specularity) of
the main parts of the spacecraft, under various conditions of illumination (continuous sunlight, eclipses, etc.). 相似文献
6.
Dynamic orbit determination and gravity field model improvement from GPS, DORIS and Laser measurements on TOPEX/POSEIDON satellite 总被引：1，自引：1，他引：1
Summary. In the framework of the GRIM series of gravity field models, the CNES/GRGS GINS precise orbit determination software has
been adapted to dynamic GPS data processing. That is simultaneous processing of all available observables (i.e. GPS, DORIS,
Laser) and all available satellite orbits (i.e. GPS, TOPEX/POSEIDON) can now be performed.
The TOPEX/POSEIDON (T/P) mission satellite is equipped with a GPS receiver, a DORIS receiver and a laser reflector that represents
an unprecedented opportunity to compare and combine these three tracking systems to estimate orbital parameters and gravity
field coefficients.
Different combinations including : GPS + DORIS, DORIS + LASER, GPS + DORIS + LASER, have been tested and have shown small
but systematic improvement in T/P orbit accuracy when GPS and DORIS data were processed simultaneously.
Five tuned gravity field models have been generated by accumulating different combinations of T/P normal equations associated
to the GPS, DORIS and Laser data. GPS data have a greater dynamic impact on gravity field spherical harmonics coefficient
determination than DORIS and Laser data. Furthermore, the results obtained with the solutions including and T/P normal equations suggest that indeed these different tracking systems are somehow complementary in a dynamic sense.
Received 30 March 1995; Accepted 19 September 1996 相似文献
7.
Daniel Gambis 《Journal of Geodesy》2006,80(8-11):649-656
DORIS (Détermination d’Orbite et Radiopositionnement Intégrés par Satellite) is a system used for precise orbit determination (POD) and ground-station positioning. It has been implemented on-board various satellites: the SPOT (Système pour l’Observation de la Terre) remote sensing satellites SPOT-2, SPOT-3, SPOT-4, SPOT-5, TOPEX/Poseidon and more recently on its successors Jason-1 and ENVISAT. DORIS is also a terrestrial positioning system that has found many applications in geophysics and geodesy; in particular, it contributes to the realization of the International Terrestrial Reference Frame, ITRF2000 and the forthcoming ITRF2005. Although not its primary objective, DORIS can bring information on Earth orientation monitoring, mainly polar motion and length of day (LOD) variations that complement other astrogeodetic techniques. In this paper, we have analyzed various recent polar motion solutions derived from independent analysis centers using different software packages and applying various analysis strategies. Comparisons of these solutions to the International Earth Rotation and Reference Systems Service (IERS) C04 solution are performed. Depending on the solutions, the accuracy of DORIS polar components are in the range of 0.5–1 mas corresponding to a few centimeters on the Earth’s surface. This is approximately ten times larger than results derived from GPS, which are typically 0.06 mas in both components. This does not allow DORIS results to be taken into account in the IERS–EOP combinations. A gain in the precision could come from technical improvements to the DORIS system, in addition to improvement of the orbit, tropospheric, ionospheric and Earth gravity field modeling. 相似文献
8.
We can presently construct two independent time series of sea level, each at a precision of a few centimeters, from Geosat
(1985–1988) and TOPEX/Poseidon (1992–1995) collinear altimetry. Both are based on precise satellite orbits computed using
a common geopotential model, JGM-2 (Nerem et al. 1994). We have attempted to connect these series using Geosat-T/P crossover
differences in order to assess long-term ocean changes between these missions. Unfortunately, the observed result are large-scale
sea level differences which appear to be due to a combination of geodetic and geopotential error sources. The most significant
geodetic component seems to be a coordinate system bias for Geosat sea level (relative to T/P) of −7 to −9 cm in the y-axis (towards the Eastern Pacific). The Geosat-T/P sea height differences at crossovers (with JGM-2 orbits) probably also
contain stationary geopotential-orbit error of about the same magnitude which also distort any oceanographic interpretation
of the observed changes. We also found JGM-3 Geosat orbits have not resolved the datum errors evident from the JGM-2 Geosat
-T/P results. We conclude that the direct altimetric approach to accurate determination of sea level change using Geosat and
T/P data still depends on further improvement in the Geosat orbits, including definition of the geocenter.
Received: 11 March 1996; Accepted: 19 September 1996 相似文献
9.
K. Le Bail 《Journal of Geodesy》2006,80(8-11):541-565
The noise spectrum in DORIS ground- station motion is investigated by means of the Allan variance method applied to the decomposition of the 3D signal into its principal components in the time domain. Sets of weekly position time-series from 1994 to 2005 derived by three IDS Analysis Centres (IGN-JPL, INASAN, and LEGOS-CLS) for 119 stations at 69 sites are considered. The observing satellites are SPOT-2, SPOT-3, SPOT-4, and SPOT-5, TOPEX/Poseidon, and ENVISAT. Annual and semi-annual perturbations, as well as the 117.3-day term associated with the TOPEX/Poseidon orbit, are found at most stations. Their amplitudes reach up to 19.3, 23.7, and 13.3 mm, respectively, for the three analysis centres (ACs). When corrected for these components and a linear drift, the time-series dominantly show white noise (WN) at the 10–45mm level the noise level is the highest in the East direction, probably in connection with the high orbit inclinations. The noise level is minimum for the high latitude stations, mostly and intensively observed by the SPOT satellites, and the determination of the noise type is unclear; longer observation spans would be needed to decide between interannual variations and flicker noise. The improvement in positioning due to the DORIS constellation extension from three to five satellites in 2002, and the network rejuvenation program initiated in 2000, results in a decrease of the noise level by a factor of 1.7 in a WN context, both before and after the changes. One example of the benefit of studying the signal in the time eigenspace domain is the detection of anomalously large WN in the East direction for station HBKB (Hartebeesthoek, Africa) that masks the above-mentioned improvement. Studying the projection on the local frame of the second and third time-eigenspace components, a noise excess is detected in the North direction for some of the ACs. Station stability derived from our time-series analysis confirms, in general, the expected performance based on the careful technical review of the station components (antenna, pillar, etc.). The respective merits of our noise qualification method, based on direct time-series analysis in the time-eigenspace domain without any a priori statistical model, in comparison with other methods, such as the selection of a mixed-noise model by maximum likelihood estimation, are discussed. 相似文献
10.
11.
针对DORIS测站和卫星USO频率偏差引起的测量数据不准确的问题,提出了一种频偏估计方法,消除了测量数据中的最大误差项。在摄动加速度模型仅考虑40×40阶重力场、固体潮和日月三体引力的条件下,利用该方法处理了SPOT-5卫星10d的测量数据。结果表明,实时轨道的径向精度优于30cm,与SPOT-5卫星的实时轨道精度相当;3D精度优于80cm,达到了SPOT-5卫星的设计精度。 相似文献
12.
13.
The New Hebrides experiment consisted of setting up a pair of DORIS beacons in remote tropical islands in the southwestern
Pacific, between 1993 and 1997. Because of orbitography requirements on TOPEX/Poséidon, the beacons were only transmitting
to SPOT satellites. Root-mean-square (RMS) scatters at the centimeter level on the latitude and vertical components were achieved,
but 2-cm RMS scatters affected the longitude component. Nevertheless, results of relative velocity (123 mm/year N250°) are
very consistent with those obtained using the global positioning system (GPS) (126 mm/yr N246°). The co-seismic step (12 mm
N60°) related to the Walpole event (M
W = 7.7) is consistent with that derived from GPS (10 mm N30°) or from the centroid moment tensor (CMT) of the quake (12 mm
N000°).
Received: 19 November 1999 / Accepted: 17 May 2000 相似文献
14.
Daniela Thaller Rolf Dach Manuela Seitz Gerhard Beutler Maria Mareyen Bernd Richter 《Journal of Geodesy》2011,85(5):257-272
Satellite Laser Ranging (SLR) observations to Global Navigation Satellite System (GNSS) satellites may be used for several
purposes. On one hand, the range measurement may be used as an independent validation for satellite orbits derived solely
from GNSS microwave observations. On the other hand, both observation types may be analyzed together to generate a combined
orbit. The latter procedure implies that one common set of orbit parameters is estimated from GNSS and SLR data. We performed
such a combined processing of GNSS and SLR using the data of the year 2008. During this period, two GPS and four GLONASS satellites
could be used as satellite co-locations. We focus on the general procedure for this type of combined processing and the impact
on the terrestrial reference frame (including scale and geocenter), the GNSS satellite antenna offsets (SAO) and the SLR range
biases. We show that the combination using only satellite co-locations as connection between GNSS and SLR is possible and
allows the estimation of SLR station coordinates at the level of 1–2 cm. The SLR observations to GNSS satellites provide the
scale allowing the estimation of GNSS SAO without relying on the scale of any a priori terrestrial reference frame. We show
that the necessity to estimate SLR range biases does not prohibit the estimation of GNSS SAO. A good distribution of SLR observations
allows a common estimation of the two parameter types. The estimated corrections for the GNSS SAO are 119 mm and −13 mm on
average for the GPS and GLONASS satellites, respectively. The resulting SLR range biases suggest that it might be sufficient
to estimate one parameter per station representing a range bias common to all GNSS satellites. The estimated biases are in
the range of a few centimeters up to 5 cm. Scale differences of 0.9 ppb are seen between GNSS and SLR. 相似文献
15.
In the frame of the International DORIS Service (IDS), the Laboratoire d’Etudes en Géophysique et Océanographie Spatiales (LEGOS)/Collecte Localisation Satellites (CLS) Analysis Center (LCA) processes DORIS measurements from the SPOT, TOPEX/Poseidon and Envisat satellites and provides weekly station coordinates of the whole network to the IDS. Based on DORIS measurements, the horizontal and vertical velocities of 57 DORIS sites are computed. The 3D positions and velocities of the stations with linear motion are estimated simultaneously from the 12-year (1993–2004) combined normal equation matrix. We include 35 DORIS sites assumed to be located in the stable zones of 9 tectonic plates. For the motion of these plates, we propose a model (LCAVEL-1) of angular velocities in the ITRF2000 reference frame. Based on external comparison with the most recent global plate models (PB2002, REVEL, GSRM-1 and APKIM2000) and on internal analysis, we estimate an average velocity error of the DORIS solution of less than 3 mm/year. The LCAVEL-1 model presents new insights of the Somalia/Nubia pair of plates, as the DORIS technique has the advantage of having a few stations located on those two plates. We also computed (and provide in this article) the horizontal motion of the sites located close to plate boundaries or in the deformation zones defined in contemporary models. These computations could be used in further analysis for these particular regions of the Earth not moving as rigid plates. 相似文献
16.
S. Hackel O. Montenbruck P. Steigenberger U. Balss C. Gisinger M. Eineder 《Journal of Geodesy》2017,91(5):547-562
The radar imaging satellite mission TerraSAR-X requires precisely determined satellite orbits for validating geodetic remote sensing techniques. Since the achieved quality of the operationally derived, reduced-dynamic (RD) orbit solutions limits the capabilities of the synthetic aperture radar (SAR) validation, an effort is made to improve the estimated orbit solutions. This paper discusses the benefits of refined dynamical models on orbit accuracy as well as estimated empirical accelerations and compares different dynamic models in a RD orbit determination. Modeling aspects discussed in the paper include the use of a macro-model for drag and radiation pressure computation, the use of high-quality atmospheric density and wind models as well as the benefit of high-fidelity gravity and ocean tide models. The Sun-synchronous dusk–dawn orbit geometry of TerraSAR-X results in a particular high correlation of solar radiation pressure modeling and estimated normal-direction positions. Furthermore, this mission offers a unique suite of independent sensors for orbit validation. Several parameters serve as quality indicators for the estimated satellite orbit solutions. These include the magnitude of the estimated empirical accelerations, satellite laser ranging (SLR) residuals, and SLR-based orbit corrections. Moreover, the radargrammetric distance measurements of the SAR instrument are selected for assessing the quality of the orbit solutions and compared to the SLR analysis. The use of high-fidelity satellite dynamics models in the RD approach is shown to clearly improve the orbit quality compared to simplified models and loosely constrained empirical accelerations. The estimated empirical accelerations are substantially reduced by 30% in tangential direction when working with the refined dynamical models. Likewise the SLR residuals are reduced from \(-3\,\pm \,17\) to \(2\,\pm \,13\) mm, and the SLR-derived normal-direction position corrections are reduced from 15 to 6 mm, obtained from the 2012–2014 period. The radar range bias is reduced from \(-10.3\) to \(-6.1\) mm with the updated orbit solutions, which coincides with the reduced standard deviation of the SLR residuals. The improvements are mainly driven by the satellite macro-model for the purpose of solar radiation pressure modeling, improved atmospheric density models, and the use of state-of-the-art gravity field models. 相似文献
17.
M. Feissel-Vernier K. Le Bail P. Berio D. Coulot G. Ramillien J. -J. Valette 《Journal of Geodesy》2006,80(8-11):637-648
Geocentre motion signals measured by satellite geodesy and those predicted from the observed mass redistribution in the ocean, atmosphere and terrestrial waters over 1993.1–2003.0 are analysed and compared under two viewpoints: the amplitudes and phases of the seasonal components, and the spectral signature of the non-seasonal components. The geodetic signals partly match the geophysical variations in the seasonal band, with possible remaining annual and semi-annual errors in both techniques, at the millimetre level in the equatorial plane for Satellite laser ranging (SLR) and Doppler Orbitography and radiopositioning integrated on Satellite (DORIS), and at the centimetre level in T z (Z-axis translation) for DORIS. Unlike SLR, the DORIS annual signatures in all three geocentre components have strongly varying amplitudes after 1996. The amplitude of the annual geophysical signal in T y is slowly growing with time. All three geophysical fluids contribute to this effect. The magnitude of the geophysically derived long-term geocentre motion is of the same magnitude in the T x , T y and T z directions, with a 0.5–1.0 mm Allan standard deviation for the 1-year sampling time, while the geodetic values are 2 mm in the equatorial plane for both SLR and DORIS, 4 mm for SLR and 9 mm for DORIS in the T z direction. The mismatch of the geodetic signal with the geophysical one in the inter-annual band is suggested to be due partly to excessive geodetic noise and partly to underestimated geophysical signal. 相似文献
18.
TOPEX/Poseidon orbit error assessment 总被引：1，自引：0，他引：1
A. J. E. Smith E. T. Hesper D. C. Kuijper G. J. Mets P. N. A. M. Visser B. A. C. Ambrosius K. F. Wakker 《Journal of Geodesy》1996,70(9):546-553
This paper discusses the accuracy of TOPEX/Poseidon orbits computed at Delft University, Section Space Research & Technology (DUT/SSR&T), from several types of tracking data,i.e. SLR, DORIS, and GPS. To quantify the orbit error, three schemes are presented. The first scheme relies on the direct altimeter observations and the covariance of the JGM-2 gravity field. The second scheme is based on crossover difference residuals while the third scheme uses the differences of dynamic orbit solutions with the GPS reduced-dynamic orbit. All three schemes give comparable results and indicate that the radial orbit error of TOPEX/Poseidon is 3–4 cm. From the orbit comparisons with GPS reduced dynamic, both the along-track and cross-track errors of the dynamic orbit solutions were found to be within 10–15 cm. 相似文献
19.
HJ-1卫星数据估算地表能量平衡 总被引：3，自引：0，他引：3
利用遥感数据估算和监测地表能量平衡的研究和应用一直以来都是学术探索的前沿和焦点,目前针对国际主流卫星数据(如MODIS,Landsat TM等)的算法研究有很多,且在不同的尺度上发展了一系列遥感技术和应用方法。本文以环境一号卫星(HJ-1)数据为主要数据源,研究和分析了地表能量平衡遥感估算方法。在下行短波和长波辐射,以及地表净辐射估算的基础上,重点研究了地表显热和潜热通量(蒸散)的估算方法,针对辐射温度代替空气动力学温度所引起的误差校正,对比分析了基于KB-1系数的热力学粗糙度长度,以及附加阻抗两种方法。使用2010年HJ-1B数据反演得到海河流域地表能量平衡各分量瞬时值,利用3个地面站点的测量数据对反演结果进行验证和误差分析。结果表明下行短波辐射的反演误差是地表净辐射反演误差的主要来源,地表温度的反演精度以及地表粗糙度的模拟精度是影响显热通量反演精度的主要因素。利用两种方法估算的显热通量趋势基本一致,但KB-1系数法的反演结果一般低于附加阻抗法。在下垫面较为复杂的区域,模型结果误差较大,需要更加精细的模型以刻画地表非均匀性的影响。 相似文献
20.
A collinearity diagnosis of the GNSS geocenter determination 总被引：4，自引：4，他引：0
The problem of observing geocenter motion from global navigation satellite system (GNSS) solutions through the network shift approach is addressed from the perspective of collinearity (or multicollinearity) among the parameters of a least-squares regression. A collinearity diagnosis, based on the notion of variance inflation factor, is therefore developed and allows handling several peculiarities of the GNSS geocenter determination problem. Its application reveals that the determination of all three components of geocenter motion with GNSS suffers from serious collinearity issues, with a comparable level as in the problem of determining the terrestrial scale simultaneously with the GNSS satellite phase center offsets. The inability of current GNSS, as opposed to satellite laser ranging, to properly sense geocenter motion is mostly explained by the estimation, in the GNSS case, of epoch-wise station and satellite clock offsets simultaneously with tropospheric parameters. The empirical satellite accelerations, as estimated by most Analysis Centers of the International GNSS Service, slightly amplify the collinearity of the $Z$ geocenter coordinate, but their role remains secondary. 相似文献