With the TOPEX/POSEIDON mission having reached the end of its nominal three-year lifetime, a larg... more With the TOPEX/POSEIDON mission having reached the end of its nominal three-year lifetime, a large number of ocean tides models incorporating TOPEX/POSEIDON altimetry data have been released. Because the major part of these models is based on the two classical analysis methods, i.e. harmonic and response analysis, it is interesting to compare and interpret the results of these two methods. Clearly, this requires that the same data are used and moreover that the data are processed with the same scheme. Therefore, both analysis methods have been implemented and three years of TOPEX/POSEIDON altimeter data have been processed to solve the major diurnal and semi-diurnal constituents of the global ocean tides by harmonic and response analysis. The results of both methods are evaluated from the diierences with the most recent Grenoble hydrodynamic model and from the t with the harmonic constants of a globally-distributed set of tide gauges. It was found that the solutions from the harmoni...
How the spatial, temporal and geographical distribution of laser range measurements, and the sele... more How the spatial, temporal and geographical distribution of laser range measurements, and the selection of satellite and perturbation force model, affect orbital and parameter solutions was investigated. Satellite perturbation due to the Earth gravity field, atmospheric drag, solar and lunar attraction, direct solar radiation pressure and solid Earth tides were considered. Dynamic model errors (not laser range measurement precision) limit
The accuracy of a computer program (SORKA) which uses the laser range observations acquired at on... more The accuracy of a computer program (SORKA) which uses the laser range observations acquired at one tracking station in order to provide real time position prediction updates during a pass is assessed. The program is compared with a GEODYN GEOS 1 orbit solution. State vector differences are interpreted as SORKA estimate errors and are transformed into errors in the classical orbital elements as well as into radial, cross track and along track errors. The program was also applied to simulated GEOS 3 data. Results are presented for three GEOS 1 passes. Total position errors before the processing of the first observation of the second and third pass, (primarily errors in cross track and along track direction) are so small that at the first laser firings during the second and third pass the satellite is within the laser beam.
Altimeter data (RA) of the ERS-1 and TOPEX/-POSEIDON (T/P) missions and radiometer data (AVHRR) o... more Altimeter data (RA) of the ERS-1 and TOPEX/-POSEIDON (T/P) missions and radiometer data (AVHRR) of the NOAA mission are analysed to study the evolution of sea surface height and sea surface temperature on a variety of time and space scales. For this purpose the data are translated into monthly grids with a 1° spatial resolution. The total time span is about 3.5 years (April '92 - August '95). Fourier, EOF, and time-longitude analyses show a perfect agreement between the T/P and ERS-1 results. A significant difference, however, is encountered when estimating the tilt over the time span at issue: 0.7 mm/yr (T/P) versus 3.7 mm/yr (ERS-1). It is shown that this is not due to a systematic difference in the altimeter bias but must be caused by local differences in the media corrections. The temperature grids show a temperature rise of 0.045 K/yr. The peak of the annual cycle in the sea level lags the peak in the sea surface temperature by about 0.5 months in the northem hemisphere and by about 1.5 months in the southem hemisphere. Dominant patterns, among which a biannual cycle (ENSO), an annual cycle (mainly steric), and a 100-days cycle (eddy activity) are extracted by estimating EOFs, of which 6 are needed to recover 50% of the observed variability.
On the proposed satellite-based navigation system NAVSAT, a study has been performed concerning t... more On the proposed satellite-based navigation system NAVSAT, a study has been performed concerning the characteristics of the control segment. Starting from the outcome of earlier preliminary studies of ESA, this study shows that the concept is feasible.
International Association of Geodesy Symposia, 1990
The WEGENER/MEDLAS project is aimed at the determination of crustal deformations in the Mediterra... more The WEGENER/MEDLAS project is aimed at the determination of crustal deformations in the Mediterranean area, the region where the Eurasian, the African and the Arabic tectonic plates meet (Reinhart, 1985). The deformations are to be derived from the very precise distance measurements to the geodetic satellite LAGEOS (Cohen, 1985), that are obtained by mobile satellite laser ranging (SLR) systems. Participating mobile laser systems are MTLRS-1 from Germany, MTLRS-2 from the Netherlands and the US TLRS-1 system. From 1985, they are being deployed at about 15 carefully selected locations in this region, occupying each site at intervals of about one or two years. From the SLR tracking data acquired at these sites, successive and very precise solutions for the positions of the mobile laser systems are computed. The small differences between these solutions are assumed to be related to the tectonic deformations in the region. This paper will mainly discuss the analysis results that have been computed from full-rate laser range observations. These results are based on the measurements taken during the first two observation campaigns, that were organized in 1986 and 1987. In addition, a preliminary result from the analysis of quick-look data of the 1989 campaign will also be presented.
With the TOPEX/POSEIDON mission having reached the end of its nominal three-year lifetime, a larg... more With the TOPEX/POSEIDON mission having reached the end of its nominal three-year lifetime, a large number of ocean tides models incorporating TOPEX/POSEIDON altimetry data have been released. Because the major part of these models is based on the two classical analysis methods, i.e. harmonic and response analysis, it is interesting to compare and interpret the results of these two methods. Clearly, this requires that the same data are used and moreover that the data are processed with the same scheme. Therefore, both analysis methods have been implemented and three years of TOPEX/POSEIDON altimeter data have been processed to solve the major diurnal and semi-diurnal constituents of the global ocean tides by harmonic and response analysis. The results of both methods are evaluated from the diierences with the most recent Grenoble hydrodynamic model and from the t with the harmonic constants of a globally-distributed set of tide gauges. It was found that the solutions from the harmoni...
How the spatial, temporal and geographical distribution of laser range measurements, and the sele... more How the spatial, temporal and geographical distribution of laser range measurements, and the selection of satellite and perturbation force model, affect orbital and parameter solutions was investigated. Satellite perturbation due to the Earth gravity field, atmospheric drag, solar and lunar attraction, direct solar radiation pressure and solid Earth tides were considered. Dynamic model errors (not laser range measurement precision) limit
The accuracy of a computer program (SORKA) which uses the laser range observations acquired at on... more The accuracy of a computer program (SORKA) which uses the laser range observations acquired at one tracking station in order to provide real time position prediction updates during a pass is assessed. The program is compared with a GEODYN GEOS 1 orbit solution. State vector differences are interpreted as SORKA estimate errors and are transformed into errors in the classical orbital elements as well as into radial, cross track and along track errors. The program was also applied to simulated GEOS 3 data. Results are presented for three GEOS 1 passes. Total position errors before the processing of the first observation of the second and third pass, (primarily errors in cross track and along track direction) are so small that at the first laser firings during the second and third pass the satellite is within the laser beam.
Altimeter data (RA) of the ERS-1 and TOPEX/-POSEIDON (T/P) missions and radiometer data (AVHRR) o... more Altimeter data (RA) of the ERS-1 and TOPEX/-POSEIDON (T/P) missions and radiometer data (AVHRR) of the NOAA mission are analysed to study the evolution of sea surface height and sea surface temperature on a variety of time and space scales. For this purpose the data are translated into monthly grids with a 1° spatial resolution. The total time span is about 3.5 years (April '92 - August '95). Fourier, EOF, and time-longitude analyses show a perfect agreement between the T/P and ERS-1 results. A significant difference, however, is encountered when estimating the tilt over the time span at issue: 0.7 mm/yr (T/P) versus 3.7 mm/yr (ERS-1). It is shown that this is not due to a systematic difference in the altimeter bias but must be caused by local differences in the media corrections. The temperature grids show a temperature rise of 0.045 K/yr. The peak of the annual cycle in the sea level lags the peak in the sea surface temperature by about 0.5 months in the northem hemisphere and by about 1.5 months in the southem hemisphere. Dominant patterns, among which a biannual cycle (ENSO), an annual cycle (mainly steric), and a 100-days cycle (eddy activity) are extracted by estimating EOFs, of which 6 are needed to recover 50% of the observed variability.
On the proposed satellite-based navigation system NAVSAT, a study has been performed concerning t... more On the proposed satellite-based navigation system NAVSAT, a study has been performed concerning the characteristics of the control segment. Starting from the outcome of earlier preliminary studies of ESA, this study shows that the concept is feasible.
International Association of Geodesy Symposia, 1990
The WEGENER/MEDLAS project is aimed at the determination of crustal deformations in the Mediterra... more The WEGENER/MEDLAS project is aimed at the determination of crustal deformations in the Mediterranean area, the region where the Eurasian, the African and the Arabic tectonic plates meet (Reinhart, 1985). The deformations are to be derived from the very precise distance measurements to the geodetic satellite LAGEOS (Cohen, 1985), that are obtained by mobile satellite laser ranging (SLR) systems. Participating mobile laser systems are MTLRS-1 from Germany, MTLRS-2 from the Netherlands and the US TLRS-1 system. From 1985, they are being deployed at about 15 carefully selected locations in this region, occupying each site at intervals of about one or two years. From the SLR tracking data acquired at these sites, successive and very precise solutions for the positions of the mobile laser systems are computed. The small differences between these solutions are assumed to be related to the tectonic deformations in the region. This paper will mainly discuss the analysis results that have been computed from full-rate laser range observations. These results are based on the measurements taken during the first two observation campaigns, that were organized in 1986 and 1987. In addition, a preliminary result from the analysis of quick-look data of the 1989 campaign will also be presented.
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