Radial variations of a satellite orbit due to gravitational errors: Implications for satellite altimetry

Wagner, C. A.

doi:10.1029/jb090ib04p03027

Cited by 57 publications

(26 citation statements)

References 26 publications

(30 reference statements)

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“…The classes of orbit perturbation frequencies arising from gravity field error are summarized in Table 1. The orbit error arising from the gravity model can be segregated into time-invariant and time varying components [e.g., Tapley and Rosborough, 1985;Engelis, 1985;Wagner, 1985;Melvin, 1988]. All such error is a function of geographic position.…”

Section: • = (N-2p+q) (3•+(o) -Q(o+rn(•-o)mentioning

confidence: 99%

The temporal and spatial characteristics of TOPEX/POSEIDON radial orbit error

Marshall¹,

Zelensky²,

Klosko³

et al. 1995

J. Geophys. Res.

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Satellite orbit error has long been the bane of oceanographers who analyze altimetry data. However, radial orbit error on TOPEX/POSEIDON (T/P) has been reduced to the 3 to 4‐cm root‐mean‐square (rms) level over a 10‐day repeat cycle, which represents an order of magnitude improvement over earlier altimetry missions such as Geosat. Consequently, oceanographers are now able to directly evaluate the absolute ocean topography to unprecedented accuracy levels. While significantly reduced, the T/P orbit error still requires quantification. This study examines the spatial and temporal characteristics of the T/P radial orbit error, as assessed through the analysis of laser tracking residuals and orbit comparisons with independently generated trajectories. Spectral analyses of the orbit differences between the orbits determined from satellite laser ranging and Doppler Orbitography and Radiopositioning Integrated by Satellite data and the independently determined reduced dynamic Global Positioning System (GPS) ephemerides indicate that the predominant power is at the once‐per‐orbital revolution frequency with 2‐ to 3‐cm peaks. When the orbit differences are colinearly aligned to a fixed geographic grid and spectral analysis is performed at each geographic grid point, a nearly 60‐day period is found with maximum amplitudes in the 2‐ to 4‐cm range. The contribution of both conservative and nonconservative force and measurement mismodeling to this error signal are assessed. We demonstrate that the ∼60‐day error period seen at fixed geographic locations arises from weaknesses in the dynamic ocean tidal models used in the orbit calculations. New tidal models have been developed which significantly reduce this error. Second‐generation orbits incorporating many model improvements have been computed and demonstrate a significant reduction in the radial orbit error signals. Some orbit error still exists, and methods for further model improvements and the possibility of achieving 1‐cm radial rms orbit accuracy in T/P are discussed.

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Section: • = (N-2p+q) (3•+(o) -Q(o+rn(•-o)mentioning

confidence: 99%

The temporal and spatial characteristics of TOPEX/POSEIDON radial orbit error

Marshall¹,

Zelensky²,

Klosko³

et al. 1995

J. Geophys. Res.

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“…To first order, the Earth's gravity field can be considered spherically symmetric, which results in elliptical satellite orbits [Kaula, 1966]. Numerous theoretical studies have shown that uncertainties in the orbital eccentricity, semimajor axis and period all lead to errors in estimates of the radial distance between the centers of mass of the Earth and satellite that are dominated by sinusoidal variability at the orbital period [e.g., Colombo, 1984;Wagner, 1985Wagner, , 1989Tapley and Rosborough, 1985;Engelis, 1988;Schrama, 1989]. The amplitude and phase of the 1-cycle per revolution (cpr) sinusoidal time-dependent orbit errors vary slowly with time.…”

Section: Characteristics Of Orbit Errorsmentioning

confidence: 99%

Spectral characteristics of time‐dependent orbit errors in altimeter height measurements

Chelton¹,

Schlax²

1993

J. Geophys. Res.

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A mean reference surface and time‐dependent orbit errors are estimated simultaneously for each exact‐repeat ground track from the first two years of Geosat sea level estimates based on the Goddard Earth model (GEM)‐T2 orbits. Motivated by orbit theory and empirical analysis of Geosat data, the time‐dependent orbit errors are modeled as 1 cycle per revolution (cpr) sinusoids with slowly varying amplitude and phase. The method recovers the known “bow tie effect” introduced by the existence of force model errors within the precision orbit determination (POD) procedure used to generate the GEM‐T2 orbits. The bow tie pattern of 1‐cpr orbit errors is characterized by small amplitudes near the middle and larger amplitudes (up to 160 cm in the 2 years of data considered here) near the ends of each 5‐ to 6‐day orbit arc over which the POD force model is integrated. A detailed examination of these bow tie patterns reveals the existence of daily modulations of the amplitudes of the 1‐cpr sinusoid orbit errors with typical and maximum peak‐to‐peak ranges of about 14 cm and 30 cm, respectively. The method also identifies a daily variation in the mean orbit error with typical and maximum peak‐to‐peak ranges of about 6 cm and 30 cm, respectively, that is unrelated to the predominant 1‐cpr orbit error. It is suggested that the two daily signals arise from daily adjustments of the drag coefficient in the GEM‐T2 POD procedure. Application of the simultaneous solution method to the much less accurate Geosat height estimates based on the Naval Astronautics Group orbits concludes that the accuracy of POD is not important for collinear altimetric studies of time‐dependent mesoscale variability (wavelengths shorter than 1000 km), as long as the time‐dependent orbit errors are dominated by 1‐cpr variability and a long‐arc (several orbital periods) orbit error estimation scheme such as that presented here is used. The accuracy of POD becomes more important for studies of larger‐scale variability.

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“…Using analytical theory it may be shown that many different terms in the gravity field lead to the same orbit perturbations, and it is therefore possible to select a relatively small subset of gravity model coefficients which may be adjusted relative to an existing gravity model, in order to achieve an improvement in the accuracy of this model for only one satellite. The analytical theory of orbit perturbations due to the gravity field has been presented in many forms [9,10,11]. A somewhat alternative appoach has been taken by DUT/SOM, which will be summarized in the following.…”

Section: Gravity Field Model Errorsmentioning

confidence: 99%

Application of satellite altimeter data to orbit error correction and gravity model adjustment

Zandbergen

Wakker

Ambrosius

1990

Advances in Space Research

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The full exploitation of the oceanographical information contained in altimeter height observations made during altimetry missions of the past (SEASAT), present (GEOSAT) and future (ERS-1, TOPEX/Poseidon), requires very accurate satellite orbits. Although the dynamic models involved in the orbit computation are of steadily increasing accuracy, the strived-for accuracy of 10 cm of the radial position component may not be achieved for all these missions in the near future.Several techniques have been devised to apply altimeter or cross-over data to satellite orbit correction and gravity model adjustment. This paper will address two methods which are currently being developed at Deift University of Technology (DUT). Using analytical theory, a gravity model may be adjusted with a limited number of laser range and cross-over difference observations by applying constraint matrices. This technique was successfully applied to tune the GEM-Ti model. With the same theory a new method of orbit error correction used by the so-called cross-over minimization technique for restricted areas has been devised, which allows the recovery of the eliminated orbit error, and the combination of these errors from several areas into a global error model.

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Radial variations of a satellite orbit due to gravitational errors: Implications for satellite altimetry

Cited by 57 publications

References 26 publications

The temporal and spatial characteristics of TOPEX/POSEIDON radial orbit error

The temporal and spatial characteristics of TOPEX/POSEIDON radial orbit error

Spectral characteristics of time‐dependent orbit errors in altimeter height measurements

Application of satellite altimeter data to orbit error correction and gravity model adjustment

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