SWARM GPS Precise Orbit Determination Receiver Initial In-Orbit Performance Evaluation

F. Zangerl, F. Griesauer, M. Sust, O. Montenbruck, B. Buchert, A. Garcia

Abstract:	SWARM is a European space mission with the objective to study the earth's geomagnetic field and its variation over time by means of a constellation of three identical satellites in polar low-earth orbits [1]. In addition to instruments for magnetic- and electric-field measurements each satellite carries a dual-frequency GPS-Receiver for Precise Orbit Determination (POD). An in-orbit receiver validation campaign successfully performed at the beginning of 2014 during a period of increased solar activity initiated closer investigations of ionosphere induced phase fluctuations. After reviewing mission, receiver and specified performance, in-orbit measurement data are presented and compared with ground-test results. Effects not predicted by previous analyses and ground tests are traced back to their atmospheric origins and carefully separated from potential receiver faults. Of particular interest is the receiver performance evaluation with the support of POD and in-situ electron density measurement results. INTRODUCTION SWARM is an Earth Explorer Mission run by the European Space Agency (ESA) with the objective to study the earth's geomagnetic field and its variation over time by means of a constellation of three identical satellites in polar low-earth orbits. Each satellite carries two highly sensitive magnetometers for scalar as well as vector measurements of the magnetic field as well as an Electrical Field Instrument (EFI) formed by a Thermal Ion Imager and a Langmuir Probe. Magnetic- and electric field measurements are supported by an accelerometer, a star tracker as well as a dual-frequency GPS-Receiver providing observables suitable for the determination of spacecraft position with centimeter-level accuracy by means of ground based Precise Orbit Determination (POD). In the present paper we provide results of the evaluation of initial in-orbit measurements provided by the three spaceborne GPS receivers during the commissioning phase which widely overlapped with a period of increased solar activity, resembling a stress case for a high precision dual-frequency POD receiver.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	1459 - 1468
Cite this article:	Zangerl, F., Griesauer, F., Sust, M., Montenbruck, O., Buchert, B., Garcia, A., "SWARM GPS Precise Orbit Determination Receiver Initial In-Orbit Performance Evaluation," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 1459-1468.
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