GNSS scale determination using calibrated receiver and Galileo satellite antenna patterns

Villiger, Arturo; Dach, Rolf; Schaer, Stefan; Prange, Lars; Zimmermann, Florian; Kuhlmann, Heiner; Wübbena, Gerhard; Schmitz, Martin; Beutler, Gerhard; Jäggi, Adrian

doi:10.1007/s00190-020-01417-0

Cited by 32 publications

(27 citation statements)

References 19 publications

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“…The solutions derived by the two independent methods with different observations and metadata agree well with each other. The Galileo-based solution agrees very well with the latest study by Villiger et al (2020). Moreover, these two solutions also agree with the VLBI-based scale (+ 0.77 ppb) better than the SLR-based scale (-0.77) does.…”

Section: Discussionsupporting

confidence: 84%

“…When taking this terrestrial scale into account, GPS and Galileobased coordinates agree on the level of a few millimeters in the height component. By fixing the antenna offsets of Galileo to the calibrated values, z-ΔPCO GPS have been computed by Villiger et al (2020). He reported a system-wise change of −150 mm and −221 mm for the z-PCO GPS by using robot calibrations and chamber calibrations for ground stations, respectively.…”

Section: Methods I: Galileo With Calibrated Antenna Offsetsmentioning

confidence: 99%

“…Zero values are due to the fixing to the a priori values. between the robot-calibration-based solution and the chamber-calibration-based solution in Villiger et al (2020). We compared the estimated GNSS-based scale with the scale determined by the VLBI and SLR.…”

Section: Estimated Z-1pco Gps and Terrestrial Scalementioning

confidence: 99%

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Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check

et al. 2020

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The GPS satellite transmitter antenna phase center offsets (PCOs) can be estimated in a global adjustment by constraining the ground station coordinates to the current International Terrestrial Reference Frame (ITRF). Therefore, the derived PCO values rest on the terrestrial scale parameter of the frame. Consequently, the PCO values transfer this scale to any subsequent GNSS solution. A method to derive scale-independent PCOs without introducing the terrestrial scale of the frame is the prerequisite to derive an independent GNSS scale factor that can contribute to the datum definition of the next ITRF realization. By fixing the Galileo satellite transmitter antenna PCOs to the ground calibrated values from the released metadata, the GPS satellite PCOs in the z-direction (z-PCO) and a GNSS-based terrestrial scale parameter can be determined in GPS + Galileo processing. An alternative method is based on the gravitational constraint on low earth orbiters (LEOs) in the integrated processing of GPS and LEOs. We determine the GPS z-PCO and the GNSS-based scale using both methods by including the current constellation of Galileo and the three LEOs of the Swarm mission. For the first time, direct comparison and cross-check of the two methods are performed. They provide mean GPS z-PCO corrections of $$- 186 \pm 25$$ - 186 ± 25 mm and $$- 221 \pm 37$$ - 221 ± 37 mm with respect to the IGS values and $$+ 1.55 \pm 0.22$$ + 1.55 ± 0.22 ppb (parts per billion) and $$+ 1.72 \pm 0.31$$ + 1.72 ± 0.31 in the terrestrial scale with respect to the IGS14 reference frame. The results of both methods agree with each other with only small differences. Due to the larger number of Galileo observations, the Galileo-PCO-fixed method leads to more precise and stable results. In the joint processing of GPS + Galileo + Swarm in which both methods are applied, the constraint on Galileo dominates the results. We discuss and analyze how fixing either the Galileo transmitter antenna z-PCO or the Swarm receiver antenna z-PCO in the combined GPS + Galileo + Swarm processing propagates to the respective freely estimated z-PCO of Swarm and Galileo.

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Section: Discussionsupporting

confidence: 84%

Section: Methods I: Galileo With Calibrated Antenna Offsetsmentioning

confidence: 99%

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Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check

et al. 2020

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“…The phases of the annual signal in the GAL BX + E0 are shifted by approximately 45° with respect to the remaining series. However, one should note that the most up-to-date information about the phase center calibrations of the Galileo satellites and ground antennas is not taken into account within this processing (Villiger et al 2020). Whether the change of this processing feature would improve or not the GCC estimates should be further investigated.…”

Section: Geocenter Coordinates From the Multi-gnss Solutionsmentioning

confidence: 99%

Geocenter coordinates derived from multi-GNSS: a look into the role of solar radiation pressure modeling

2020

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The Global Navigational Satellite System (GNSS) technique is naturally sensitive to the geocenter motion, similar to all satellite techniques. However, the GNSS-based estimates of the geocenter used to contain more orbital artifacts than the geophysical signals, especially for the Z component of the geocenter coordinates. This contribution conveys a discussion on the impact of solar radiation pressure (SRP) modeling on the geocenter motion estimates. To that end, we process 3 years of GPS, GLONASS, and Galileo observations (2017–2019), collected by a globally distributed network of the ground stations. All possible individual system-specific solutions, as well as combinations of the available constellations, are tested in search of characteristic patterns in geocenter coordinates. We show that the addition of a priori information about the SRP-based forces acting on the satellites using a box-wing model mitigates a great majority of the spurious signals in the spectra of the geocenter coordinates. The amplitude of the 3 cpy (about 121 days) signal for GLONASS has been reduced by a factor of 8.5. Moreover, the amplitude of the spurious 7 cpy (about 52 days) signal has been reduced by a factor of 5.8 and 3.1 for Galileo and GPS, respectively. Conversely, the box-wing solutions indicate increased amplitudes of the annual variations in the geocenter signal. The latter reaches the level of 10–11 mm compared to 4.4 and 6.0 mm from the satellite laser ranging observations of LAGEOS satellites and the corresponding GNSS series applying extended empirical CODE orbit model (ECOM2), respectively. Despite the possible improvement in the GLONASS-based Z component of the geocenter coordinates, we show that some significant power can still be found at periods other than annual. The GPS- and Galileo-based estimates are less affected; thus, a combination of GPS and Galileo leads to the best geocenter estimates.

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“…Previous studies, e.g., Zhu et al (2003) and Cardellach et al (2007), provided a relation to express the dependency of the scale and the PCO of the GPS satellites. Moreover, it is possible to realize an independent scale by estimating antenna pattern of the GNSS satellites, for instance by transferring this information via LEO satellites such as GRACE and TOPEX/Poseidon (Haines et al 2015;Männel 2016) or via calibrated antenna pattern for Galileo from the GSA (European GNSS Agency) (Rebischung 2019;Villiger et al 2020). The realization of the network scale by Fig.…”

mentioning

confidence: 99%

Reference system origin and scale realization within the future GNSS constellation “Kepler”

Glaser

Michalak

Männel

et al. 2020

J Geod

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Currently, Global Navigation Satellite Systems (GNSS) do not contribute to the realization of origin and scale of combined global terrestrial reference frame (TRF) solutions due to present system design limitations. The future Galileo-like medium Earth orbit (MEO) constellation, called “Kepler”, proposed by the German Aerospace Center DLR, is characterized by a low Earth orbit (LEO) segment and the innovative key features of optical inter-satellite links (ISL) delivering highly precise range measurements and of optical frequency references enabling a perfect time synchronization within the complete constellation. In this study, the potential improvements of the Kepler constellation on the TRF origin and scale are assessed by simulations. The fully developed Kepler system allows significant improvements of the geocenter estimates (realized TRF origin in long-term). In particular, we find improvements by factors of 43 for the Z and of 8 for the X and Y component w. r. t. a contemporary MEO-only constellation. Furthermore, the Kepler constellation increases the reliability due to a complete de-correlation of the geocenter coordinates and the orbit parameters related to the solar radiation pressure modeling (SRP). However, biases in SRP modeling cause biased geocenter estimates and the ISL of Kepler can only partly compensate this effect. The realized scale enabling all Kepler features improves by 34% w. r. t. MEO-only. The dependency of the estimated satellite antenna phase center offsets (PCOs) upon the underlying TRF impedes a scale realization by GNSS. In order to realize the network scale with 1 mm accuracy, the PCOs have to be known within 2 cm for the MEO and 4 mm for the LEO satellites. Independently, the scale can be realized by estimating the MEO PCOs and by simultaneously fixing the LEO PCOs. This requires very accurate LEO PCOs; the simulations suggest them to be smaller than 1 mm in order to keep scale changes below 1 mm.

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GNSS scale determination using calibrated receiver and Galileo satellite antenna patterns

Cited by 32 publications

References 19 publications

Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check

Two methods to determine scale-independent GPS PCOs and GNSS-based terrestrial scale: comparison and cross-check

Geocenter coordinates derived from multi-GNSS: a look into the role of solar radiation pressure modeling

Reference system origin and scale realization within the future GNSS constellation “Kepler”

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