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Florian Zus Ludwig GrunwaldtStefan Heise Grzegorz MichalakTorsten Schmidt Jens Wickert 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
On 21 June 2010 the TerraSAR-X satellite was joined by the TanDEM-X satellite. A Global Positioning System (GPS) radio occultation (RO) experiment using the twin satellites has been carried out to estimate the precision of GPS atmospheric soundings. For the Day Of Year (DOY) 330–336, 2011, we analyze phase and amplitude data recorded by GPS receivers separated by a few hundred meters in a low earth orbit and derive collocated atmospheric refractivity profiles. In the altitude range 10–20 km the standard deviation between TerraSAR-X and TanDEM-X refractivity does not exceed 0.15%. The standard deviation is rapidly increasing for lower and higher altitudes; close to the surface and at an altitude of 30 km the standard deviation reaches 0.8% and 0.5%, respectively. Systematic deviations between TerraSAR-X and TanDEM-X refractivity in the considered altitude range (0–30 km) are negligible. The results confirm the anticipated high precision of the GPS RO technique. However, the difference in the retrieved refractivity in the lower troposphere for different Open Loop (OL) signal tracking parameters, altered onboard TanDEM-X for DOY 49–55, 2012, calls for an in depth analysis. At the moment we can not exclude that a potential bias in the OL Doppler model introduces a bias in our retrieved refractivity at altitudes <8 km. 相似文献
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A. Jäggi O. Montenbruck Y. Moon M. Wermuth R. König G. Michalak H. Bock D. Bodenmann 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is the first Synthetic Aperture Radar (SAR) mission using close formation flying for bistatic SAR interferometry. The primary goal of the mission is to generate a global digital elevation model (DEM) with 2 m height precision and 10 m ground resolution from the configurable SAR interferometer with space baselines of a few hundred meters. As a key mission requirement for the interferometric SAR processing, the relative position, or baseline vector, of the two satellites must be determined with an accuracy of 1 mm (1D RMS) from GPS measurements collected by the onboard receivers. The operational baseline products for the TanDEM-X mission are routinely generated by the German Research Center for Geosciences (GFZ) and the German Space Operations Center (DLR/GSOC) using different software packages (EPOS/BSW, GHOST) and analysis strategies. For a further independent performance assessment, TanDEM-X baseline solutions are generated at the Astronomical Institute of the University of Bern (AIUB) on a best effort basis using the Bernese Software (BSW). 相似文献
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