Combination of precise orbit solutions for Sentinel-3A using Variance Component Estimation

Kobel, Cyril; Arnold, Daniel; Jäggi, Adrian

doi:10.5194/adgeo-50-27-2019

Cited by 6 publications

(2 citation statements)

References 9 publications

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“…Models and standards used in the present analysis are summarized in Table 4. Even though the modeling of nongravitational forces introduces some uncertainties in the dynamical leveling of the CoM trajectory, experience from past LEO missions and cross comparison with other POD centers shows that associated uncertainties in mean height are typically less than 5 mm (Kobel et al 2019;Fernández et al 2019). As such, force model deficiencies are unlikely to explain the observed ≈ 25 mm PCO difference between manufacturer and in-flight calibration.…”

Section: Antenna Calibrationmentioning

confidence: 99%

Sentinel-6A precise orbit determination using a combined GPS/Galileo receiver

Montenbruck

Hackel

Wermuth

et al. 2021

J Geod

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The Sentinel-6 (or Jason-CS) altimetry mission provides a long-term extension of the Topex and Jason-1/2/3 missions for ocean surface topography monitoring. Analysis of altimeter data relies on highly-accurate knowledge of the orbital position and requires radial RMS orbit errors of less than 1.5 cm. For precise orbit determination (POD), the Sentinel-6A spacecraft is equipped with a dual-constellation GNSS receiver. We present the results of Sentinel-6A POD solutions for the first 6 months since launch and demonstrate a 1-cm consistency of ambiguity-fixed GPS-only and Galileo-only solutions with the dual-constellation product. A similar performance (1.3 cm 3D RMS) is achieved in the comparison of kinematic and reduced-dynamic orbits. While Galileo measurements exhibit 30–50% smaller RMS errors than those of GPS, the POD benefits most from the availability of an increased number of satellites in the combined dual-frequency solution. Considering obvious uncertainties in the pre-mission calibration of the GNSS receiver antenna, an independent inflight calibration of the phase centers for GPS and Galileo signal frequencies is required. As such, Galileo observations cannot provide independent scale information and the estimated orbital height is ultimately driven by the employed forces models and knowledge of the center-of-mass location within the spacecraft. Using satellite laser ranging (SLR) from selected high-performance stations, a better than 1 cm RMS consistency of SLR normal points with the GNSS-based orbits is obtained, which further improves to 6 mm RMS when adjusting site-specific corrections to station positions and ranging biases. For the radial orbit component, a bias of less than 1 mm is found from the SLR analysis relative to the mean height of 13 high-performance SLR stations. Overall, the reduced-dynamic orbit determination based on GPS and Galileo tracking is considered to readily meet the altimetry-related Sentinel-6 mission needs for RMS height errors of less than 1.5 cm.

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Section: Antenna Calibrationmentioning

confidence: 99%

Sentinel-6A precise orbit determination using a combined GPS/Galileo receiver

Montenbruck

Hackel

Wermuth

et al. 2021

J Geod

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“…Some noticeable examples can be found in Koch and Kusche (2002), where VCE is used for geopotential regularization, and in Kusche (2003) within the weight determination for GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) gravity recovery solutions. In the context of combining Terrestrial Reference Frames (TRF), Bähr et al (2007) presents a comparison between three VCE methods, and more recently Kobel et al (2019) implemented a VCE approach to combine the orbits of the Low Earth Orbit (LEO) satellite Sentinel-3. In this contribution, we make use of least-squares variance component estimation (LSVCE), originally developed by Teunissen (1988).…”

Section: Introductionmentioning

confidence: 99%

Combination of GNSS orbits using least-squares variance component estimation

Mansur

Sakic

Brack

et al. 2022

J Geod

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Over the past years, the International GNSS Service (IGS) has been putting efforts into extending its service by setting up and running the Multi-GNSS experiment and pilot project (MGEX). Several MGEX analysis centers (ACs) contribute by providing solutions containing not only GPS and GLONASS but also Galileo, BeiDou, and QZSS. As the current IGS combination software can only handle the orbits of one constellation at a time, it requires substantial modifications to obtain a consistent MGEX orbit product. In this contribution, we present a least-squares framework for a Multi-GNSS orbit combination, where the weights used to combine the ACs’ orbits are determined by least-squares variance component estimation. We introduce and compare two weighting strategies, where either AC-specific weights or AC and constellation-specific weights are used. An automated Z-score test is implemented yielding a common set of core satellites that are used to determine the weights. Both strategies are tested using MGEX orbit solutions for a period of two and a half years. They yield similar results with an agreement with the ACs’ orbits at the one centimeter level for GPS and up to a few centimeters for the other constellations. The 3D-RMS is generally slightly better with the AC and constellation weighting. A comparison of our combination approach with the official IGS combination using three years of GPS and GLONASS orbits shows an agreement of better than 5 mm and 12 mm for GPS and GLONASS, respectively, while the agreement of the official IGS combination with the ACs’ GPS solutions is only around $$15\,\textrm{mm}$$ 15 mm . An external validation using satellite laser ranging shows that the mean residuals of our combined products are around $$-3\,\textrm{mm}$$ - 3 mm for Galileo, $$6\,\textrm{mm}$$ 6 mm for GLONASS, $$-8\,\textrm{mm}$$ - 8 mm for BeiDou, and $$-31\,\textrm{mm}$$ - 31 mm for QZSS.

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GNSS-based precise orbit determination for maneuvering LEO satellites

et al. 2023

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Maneuverability is essential for low Earth orbit (LEO) satellites to fulfill various operational objectives. However, the precise orbit determination (POD) process might deteriorate due to imperfect satellite orbital dynamics modeling. This article develops a generic POD strategy with maneuver handling for LEO satellites equipped with high-performance spaceborne Global Navigation Satellite System (GNSS) receivers. Given the time span of an executed maneuver, a set of constant thrust accelerations in the satellite body-fixed reference frame is estimated without using a-priori maneuver accelerations. In addition, different numbers of velocity pulses are estimated at predefined epochs determined by the duration of a maneuver. POD experiments are done for the GRACE-FO and Sentinel-3 satellites, for which the orbit maneuvers vary significantly. The orbits are assessed via internal consistency checks and external orbit validations. Internally, in each direction, the agreement between the reduced-dynamic and kinematic orbits reaches a level of 1 cm, which is comparable with the reference day without maneuvers. Externally, comparisons with the official GRACE-FO products and orbits from the Sentinel-3 Copernicus POD Quality Working Group confirm the reliability of the new orbits with maneuver handling. Finally, satellite laser ranging and K-band ranging measurements indicate a 1-cm accuracy of the absolute orbits and a 2-mm accuracy of the GRACE-FO relative orbits. The maneuver handling strategy is tested in the Bernese GNSS Software, consistently developed at the Astronomical Institute of the University of Bern.

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Combination of precise orbit solutions for Sentinel-3A using Variance Component Estimation

Cited by 6 publications

References 9 publications

Sentinel-6A precise orbit determination using a combined GPS/Galileo receiver

Sentinel-6A precise orbit determination using a combined GPS/Galileo receiver

Combination of GNSS orbits using least-squares variance component estimation

GNSS-based precise orbit determination for maneuvering LEO satellites

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