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Evaluation and validation of mascon recovery using GRACE KBRR data with independent mass flux estimates in the Mississippi Basin 总被引：1，自引：1，他引：0
S. Klosko D. Rowlands S. Luthcke F. Lemoine D. Chinn M. Rodell 《Journal of Geodesy》2009,83(9):817-827
The direct recovery of surface mass anomalies using GRACE KBRR data processed in regional solutions provides mass variation
estimates with 10-day temporal resolution. The approach undertaken herein uses a tailored orbit estimation strategy based
solely on the KBRR data and directly estimates mass anomalies from the GRACE data. We introduce a set of temporal and spatial
correlation constraints to enable high resolution mass flux estimates. The Mississippi Basin, with its well understood surface
hydrological modelling available from the Global Land Data Assimilation System (GLDAS), which uses advanced land surface modeling
and data assimilation techniques, and a wealth of groundwater data, provides an opportunity to quantitatively compare GRACE
estimates of the mass flux in the entire hydrological column with those available from independent and reliable sources. Evaluating
GRACE’s performance is dependent on the accuracy ascribed to the hydrological information, which in and of itself is a complex
challenge (Rodell in Hydrogeol J, doi:, 2007). Nevertheless, the Mississippi Basin is one of the few regions having a large hydrological signal that can support
a meaningful GRACE comparison on the spatial scale resolved by GRACE. The isolation of the hydrological signal is dependent
on the adequacy of the forward mass flux modeling for tides and atmospheric pressure variations. While these models have non-uniform
global performance they are excellent in the Mississippi Basin. Through comparisons with the independent hydrology, we evaluate
the effect on the solution of changing correlation times and distances in the constraints, altering the parameter recovery
for areas external to the Mississippi Basin, and changing the relative strength of the constraints with respect to the KBRR
data. The accuracy and stability of the mascon solutions are thereby assessed, especially with regard to the constraints used
to stabilize the solution. We show that the mass anomalies, as represented by surface layer of water within regional cells
have accuracy estimates of ±2–3 cm on par with the best hydrological estimates and consistent with our accuracy estimates
for GRACE mass anomaly estimates. These solutions are shown to be very stable, especially for the recovery of semi-annual
and longer period trends, where for example, the phase agreement for the dominant annual signal agrees at the 10-day level
of resolution provided by GRACE. This validation confirms that mascons provide critical environmental data records for a wide
range of applications including monitoring ground water mass changes. 相似文献
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Dynamical orbital techniques were employed to estimate the center-of-mass station coordinates of six C-Band radars located
in the designated primary GEOS-C radar altimeter calibration area. This work was performed in support of the planned GEOS-C
mission (December, 1974 launch). The sites included Bermuda, Grand Turk, Antigua, Wallops Island (Virginia), and Merritt Island
(Florida). Two sites were estimated independently at Wallops Island yielding better than 40 cm relative height recovery, with
better than 10 cm and 1 m (relative) recovery for ϕ and λ respectively.
The tracking data used in this analysis were taken during 1969 when the radars tracked the GEOS-II transponder. The data used
were exclusively that from the estimated sites and included 18 orbital arcs which were less than two orbital revolutions in
length, having successive tracks over the area. In all, over 120 passes of data were used. Range biases were estimated. Error
analysis and comparisons with other investigators indicate that better than 2 m (1 σ) relative recovery has been achieved
at all sites.
The techniques employed here, given their independence of global tracking support, can be effectively employed to improve
various geodetic datums by providing very long and accurate baselines. C-Band data taken on GEOS-C should be employed to improve
such geodetic datums as the European—1950 using similar techniques. 相似文献
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Until very recently, there has been no identification of the significant gravitational constraints on the many common artificial earth satellite orbits in shallow resonance. Without them it is difficult to compare results derived for different sets of harmonics from different orbits. With them it is possible to extend these results to any degree without reintegration of the orbits. All such constraints are shown to be harmonic in the argument of perigee with constants determinable from tracking data: $$(C*,S*) = (C_0 ,S_0 ) + \sum\limits_{i = 1}^\infty {(C_{Ci} ,S_{Ci} )\cos i\omega + (C_{Si} ,S_{Si} )\sin i\omega .} $$ The constants are simple linear combinations of geopotential harmonics. Five such constants (lumped harmonics) have been derived for the GEOS-2 orbit (order 13, to 30th degree) whose principal resonant period is 6 days. These five lumped harmonics are shown to account for almost all (>98%) of the resonant information in the tracking. They agree well with recent gravitational models which include substantial amounts of GEOS-2 data. 相似文献
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The orbit of TETR-3 (1971-83B), inclination: 33°, passed through resonance with 15th order geopotential terms in February 1972. The resonance caused the orbit inclination to increase by 0.015°. Analysis of 48 sets of mean Kepler elements for this satellite in 1971–1972 (across the resonance) has established the following strong constraint for high degree, 15th order gravitational terms (normalized): This result combined with previous results on high inclination 15th order and other resonant orbits suggests that the coefficients of the gravity field beyond the 15th degree are smaller than Kaula's rule (). 相似文献
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Over 31,000 precision reduced optical observations of GEOS-I and II in 70 two-day orbital arcs have been used at Goddard Space
Flight Center (GSFC) in a dynamical solution to determine center-of-mass coordinates for 15 tracking stations on the European
Datum. Comparisons with the results obtained at Centre National d’Etudes Spatiales (CNES) give agreement of about 1.5 ppm
for chord lengths. After considering a scale correction to the European Datum (ED) of 1950 to account for the absence of geoid
heights at the time of its reduction, agreement to a few ppm between the CNES/GSFC and the ED chords is obtained. However,
a small systematic difference between survey and satellite results remains for stations in south-eastern France and Switzerland.
Presented at the International Union of Geodesy and Geophysics Meeting in Moscow, U.S.S.R., August 1971. 相似文献
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Spherical harmonics are the natural parameters for the Earth's gravity field as sensed by orbiting satellites, but problems of resolution arise because the spectrum of effects is narrow and unique to each orbit. Comprehensive gravity models now contain many hundreds of thousands of observations from more than thirty different near-Earth artificial satellites. With refinements in tracking systems, newer data is capable of sensing the spherical harmonics of the field experienced by these satellites to very high degree and order. For example, altimeter, laser and satellite-tracking-satellite systems contain gravitational information well above present levels of satellite gravity field recovery (l = 20), but significant aliasing results because the orbital parameters are too restricted compared to the large number of spherical harmonics.It is shown however that the unique spectrum of information for each satellite contained within a comprehensive spherical harmonic model can be represented by simple gravitational constraint equations (lumped harmonics). All such constraints are harmonic in the argument of perigee (ω) with constants determinable directly from tracking data or reconstituted from the comprehensive solution: . The constants are simple linear combinations of the geopotential harmonics. Through these lumped harmonics any satellite gravity field can be decomposed and then uniformly extended to any degree or tailored to a given orbit without reintegration of the trajectory and variational equations. They also make possible the inclusion of information into the field from special deep resonance passages, long arc zonal analyses, and satellites unique to other models. Numerous examples of the derivation, combination, extension and tailoring of the harmonics are presented. The importance of using data spanning an apsidal period is emphasized. 相似文献
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B. C. Douglas S. M. Klosko J. G. Marsh R. G. Williamson 《Celestial Mechanics and Dynamical Astronomy》1974,10(2):165-178
Analysis of the luni-solar tidal perturbations of the inclination of GEOS-1 (1965-89A,i=59°) and GEOS-2 (1968-002A,i=106°.) has yielded the valuesk
2=0.22 (=0.02) and 0.31 (=0.01) respectively for the apparent second degree Love number. For GEOS-1 a new purely numerical method involvingosculating elements was employed. For GEOS-2 it was necessary to analyze the variations of themean elements because of the very long period (450 days) of the dominant solar tidal perturbation. An additional analysis of the variation of the mean elements of GEOS-1 confirmed the value ofk
2 obtained from the osculating elements. The disparate values indicate that the simple 2nd degree zonal harmonic model of the tidal potential employed by ourselves and all other investigators is accommodating other effects in addition to those caused by the solid Earth tides. A recent paper by Lambecket al. (1973) indicates that ocean tide effects have significant perturbations on satellite orbits and cannot be neglected. 相似文献
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