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

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. 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.