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Article

Precise Orbit Determination for Climate Applications of GNSS Radio Occultation including Uncertainty Estimation

1
Wegener Center for Climate and Global Change (WEGC), University of Graz, Brandhofgasse 5, 8010 Graz, Austria
2
Institute for Geophysics, Astrophysics and Meteorology/Institute of Physics, University of Graz, Universitätsplatz 5, 8010 Graz, Austria
3
FWF-DK Climate Change, University of Graz, Liebiggasse 9, 8010 Graz, Austria
4
Astronomical Institute University of Bern (AIUB), University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
5
European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), Eumetsat Allee 1, 64295 Darmstadt, Germany
*
Author to whom correspondence should be addressed.
Current address: KNAPP AG - Logistics, Günter Knapp-Straße 5-7, 8075 Hart bei Graz, Austria.
Remote Sens. 2020, 12(7), 1180; https://doi.org/10.3390/rs12071180
Received: 29 February 2020 / Revised: 28 March 2020 / Accepted: 31 March 2020 / Published: 7 April 2020
(This article belongs to the Special Issue GPS/GNSS for Earth Science and Applications)
Global Navigation Satellite System (GNSS) Radio Occultation (RO) is a highly valuable remote sensing technique for probing the Earth’s atmosphere, due to its global coverage, high accuracy, long-term stability, and essentially all-weather capability. In order to ensure the highest quality of essential climate variables (ECVs), derived from GNSS signal tracking by RO satellites in low Earth orbit (LEO), the orbit positions and velocities of the GNSS transmitter and LEO receiver satellites need to be determined with high and proven accuracy and reliability. Wegener Center’s new Reference Occultation Processing System (rOPS) hence aims to integrate uncertainty estimation at all stages of the processing. Here we present a novel setup for precise orbit determination (POD) within the rOPS, which routinely and in parallel performs the LEO POD with the two independent software packages Bernese GNSS software (v5.2) and NAPEOS (v3.3.1), employing two different GNSS orbit data products. This POD setup enables mutual consistency checks of the calculated orbit solutions and is used for position and velocity uncertainty estimation, including estimated systematic and random uncertainties. For LEOs enabling laser tracking we involve position uncertainty estimates from satellite laser ranging. Furthermore, we intercompare the LEO orbit solutions with solutions from other leading orbit processing centers for cross-validation. We carefully analyze multi-month, multi-satellite POD result statistics and find a strong overall consistency of estimates within LEO orbit uncertainty target specifications of 5 cm in position and 0.05 mm/s in velocity for the CHAMP, GRACE-A, and Metop-A/B missions. In 92% of the days investigated over two representative 3-month periods (July to September in 2008 and 2013) these POD uncertainty targets, which enable highly accurate climate-quality RO processing, are satisfied. The moderately higher uncertainty estimates found for the remaining 8% of days (∼5–15 cm) result in increased uncertainties of RO-retrieved ECVs. This allows identification of RO profiles of somewhat reduced quality, a potential benefit for adequate further use in climate monitoring and research. View Full-Text
Keywords: LEO satellites; precise orbit determination; radio occultation; satellite laser ranging; CHAMP; GRACE; Metop; uncertainty estimation; validation; climate applications LEO satellites; precise orbit determination; radio occultation; satellite laser ranging; CHAMP; GRACE; Metop; uncertainty estimation; validation; climate applications
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MDPI and ACS Style

Innerkofler, J.; Kirchengast, G.; Schwärz, M.; Pock, C.; Jäggi, A.; Andres, Y.; Marquardt, C. Precise Orbit Determination for Climate Applications of GNSS Radio Occultation including Uncertainty Estimation. Remote Sens. 2020, 12, 1180. https://doi.org/10.3390/rs12071180

AMA Style

Innerkofler J, Kirchengast G, Schwärz M, Pock C, Jäggi A, Andres Y, Marquardt C. Precise Orbit Determination for Climate Applications of GNSS Radio Occultation including Uncertainty Estimation. Remote Sensing. 2020; 12(7):1180. https://doi.org/10.3390/rs12071180

Chicago/Turabian Style

Innerkofler, Josef, Gottfried Kirchengast, Marc Schwärz, Christian Pock, Adrian Jäggi, Yago Andres, and Christian Marquardt. 2020. "Precise Orbit Determination for Climate Applications of GNSS Radio Occultation including Uncertainty Estimation" Remote Sensing 12, no. 7: 1180. https://doi.org/10.3390/rs12071180

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