The impact of GPS receiver modifications and ionospheric activity on Swarm baseline determination. (May 2018)

• Record Type: Journal Article
• Authors: Mao, X.; Visser, P.N.A.M.; van den IJssel, J.
• Is Part Of: Acta astronautica. Volume 146(2018)
• Page Start: 399
• Page End: 408
• Publication Date: 2018-05
• Subjects: Precise baseline determination -- Swarm satellite -- Ionospheric scintillation -- GPS receiver modifications -- Antenna patterns; Astronautics -- Periodicals; Outer space -- Exploration -- Periodicals; Astronautics; Periodicals; 629.405
• DOI: 10.1016/j.actaastro.2018.03.009
• Languages: English
• ISSNs: 0094-5765

Abstract

Abstract: The European Space Agency (ESA) Swarm mission is a satellite constellation launched on 22 November 2013 aiming at observing the Earth geomagnetic field and its temporal variations. The three identical satellites are equipped with high-precision dual-frequency Global Positioning System (GPS) receivers, which make the constellation an ideal test bed for baseline determination. From October 2014 to August 2016, a number of GPS receiver modifications and a new GPS Receiver Independent Exchange Format (RINEX) converter were implemented. Moreover, the on-board GPS receiver performance has been influenced by the ionospheric scintillations. The impact of these factors is assessed for baseline determination of the pendulum formation flying Swarm-A and -C satellites. In total 30 months of data - from 15 July 2014 to the end of 2016 - is analyzed. The assessment includes analysis of observation residuals, success rate of GPS carrier phase ambiguity fixing, a consistency check between the so-called kinematic and reduced-dynamic baseline solution, and validations of orbits by comparing with Satellite Laser Ranging (SLR) observations. External baseline solutions from The German Space Operations Center (GSOC) and Astronomisches Institut - Universität Bern (AIUB) are also included in the comparison. Results indicate that the GPS receiver modifications and RINEX converter changes are effective to improve the baseline determination. This research eventually shows a consistency level of 9.3/4.9/3.0 mm between kinematic and reduced-dynamic baselines in the radial/along-track/cross-track directions. On average 98.3 % of the epochs have kinematic solutions. Consistency between TU Delft and external reduced-dynamic baseline solutions is at a level of 1 mm level in all directions. Highlights: The analysis of 30 months data for the Swarm constellation. The influence of changing ionospheric activity is analyzed. GPS receiver modifications improve baseline determination. The corrected GPS data obtains better baseline precision. Inter-agency comparison shows good agreement.