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Reduced-dynamic and kinematic baseline determination for the Swarm mission


The Swarm mission of the European Space Agency was launched in November 2013 with the objective of performing measurements of the earth’s magnetic field with unprecedented accuracy. At the beginning of data collection, two satellites started to fly in orbits with a separation in ascending nodes of 1°–1.5° at an altitude of about 480 km, and a third satellite has been placed in a higher orbit with an altitude of 530 km. The three spacecraft are equipped with dual-frequency eight-channel GPS receivers for the generation of precise orbits. Although such orbits support the fulfillment of the primary objectives of the mission, precise space baselines may be helpful for studying the earth’s gravity field, a spin-off application of the Swarm mission. Hitherto, a particular challenge for the computation of precise baselines from Swarm has been the presence of half-cycle ambiguities in GPS carrier phase observations, which complicate the implementation of integer ambiguity resolution methods. The present study shows the feasibility of generating carrier phase observations with full-cycle ambiguities, which in turn has been used to improve the performance of reduced-dynamic and kinematic precise baseline determination schemes. The implemented strategies have been tested in a period of 90 days in 2016. The obtained reduced-dynamic and kinematic baseline products were evaluated by inter-product and inter-agency comparisons using two independent software tools.

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The present study uses data made available by the European Space Agency (ESA/ESTEC), Noordwijk, the Center for Orbit Determination in Europe (CODE) and the International Laser Ranging Service (ILRS). The support of these institutions is gratefully acknowledged. The authors acknowledge the reviewers for their valuable remarks that helped to improve the original manuscript. GAA wishes to thank the support provided by the Consejo Nacional de Ciencia y Tecnología de México, the Deutscher Akademischer Austauschdienst (Grant No. 213633 - A/10/72692) and the TU München Graduate School.

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Correspondence to Gerardo Allende-Alba.

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Allende-Alba, G., Montenbruck, O., Jäggi, A. et al. Reduced-dynamic and kinematic baseline determination for the Swarm mission. GPS Solut 21, 1275–1284 (2017).

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  • Swarm
  • Space baseline determination
  • Half-cycle ambiguity resolution
  • GPS