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Bandwidth correction of Swarm GPS carrier phase observations for improved orbit and gravity field determination

Schreiter, Lucas and Montenbruck, Oliver and Zangerl, Franz and Siemes, Christian and Arnold, Daniel and Jäggi, Adrian (2021) Bandwidth correction of Swarm GPS carrier phase observations for improved orbit and gravity field determination. GPS Solutions, 25 (2), p. 70. Springer. doi: 10.1007/s10291-021-01107-0. ISSN 1080-5370.

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Abstract

Gravity fields derived from GPS tracking of the three Swarm satellites have shown artifacts near the geomagnetic equator, where the carrier phase tracking on the L2 frequency is unable to follow rapid ionospheric path delay changes due to a limited tracking loop bandwidth of only 0.25 Hz in the early years of the mission. Based on the knowledge of the loop filter design, an analytical approach is developed to recover the original L2 signal from the observed carrier phase through inversion of the loop transfer function. Precise orbit determination and gravity field solutions are used to assess the quality of the correction. We show that the a posteriori RMS of the ionosphere-free GPS phase observations for a reduced-dynamic orbit determination can be reduced from 3 to 2 mm while keeping up to 7% more data in the outlier screening compared to uncorrected observations. We also show that artifacts in the kinematic orbit and gravity field solution near the geomagnetic equator can be substantially reduced. The analytical correction is able to mitigate the equatorial artifacts. However, the analytical correction is not as successful compared to the down-weighting of problematic GPS data used in earlier studies. In contrast to the weighting approaches, up to 9-10% more kinematic positions can be retained for the heavily disturbed month March 2015 and also stronger signals for gravity field estimation in the equatorial regions are obtained, as can be seen in the reduced error degree variances of the gravity field estimation. The presented approach may also be applied to other low earth orbit missions, provided that the GPS receivers offer a sufficiently high data rate compared to the tracking loop bandwidth, and provided that the basic loop-filter parameters are known.

Item URL in elib:https://elib.dlr.de/141324/
Document Type:Article
Title:Bandwidth correction of Swarm GPS carrier phase observations for improved orbit and gravity field determination
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Schreiter, LucasAIUBhttps://orcid.org/0000-0003-4634-7360
Montenbruck, OliverDLR/GSOChttps://orcid.org/0000-0003-4783-745X
Zangerl, FranzRUAGUNSPECIFIED
Siemes, ChristianTU Delfthttps://orcid.org/0000-0001-8316-1130
Arnold, DanielAIUBhttps://orcid.org/0000-0003-3574-0837
Jäggi, AdrianAIUBUNSPECIFIED
Date:9 March 2021
Journal or Publication Title:GPS Solutions
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:25
DOI :10.1007/s10291-021-01107-0
Page Range:p. 70
Publisher:Springer
ISSN:1080-5370
Status:Published
Keywords:Orbit determination, Tracking loop, Loop filter, Ionospheric artifacts, Gravity field determination
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space System Technology
DLR - Research area:Raumfahrt
DLR - Program:R SY - Space System Technology
DLR - Research theme (Project):R - Vorhaben Infrastruktur und Unterstützung für Raumflugbetrieb (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Space Operations and Astronaut Training
Deposited By: Montenbruck, Dr.rer.nat.hab. Oliver
Deposited On:17 Mar 2021 17:34
Last Modified:17 Mar 2021 17:34

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