High-rate GPS clock corrections from CODE: support of 1 Hz applications

Bock, Heike; Dach, Rolf; Jäggi, Adrian; Beutler, Gerhard

doi:10.1007/s00190-009-0326-1

Cited by 166 publications

(87 citation statements)

References 22 publications

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“…The reduced-dynamic and kinematic Swarm PSOs are computed using the GPS High-precision Orbit determination Software Tools (GHOST), which are developed at the Deutsches Zentrum für Luft-und Raumfahrt in close cooperation with TU Delft (Wermuth et al 2010). The POD strategy for both orbit types is based on an undifferenced approach and uses the ionosphere-free combination of GPS observations along with precise GPS orbits and high-rate 5-s clocks computed by the Center for Orbit Determination in Europe (CODE) (Bock et al 2009). To determine the Swarm orbits with highest accuracy, it is necessary to take the GPS antenna phase center variations (PCVs) into account in the POD Jäggi et al 2015).…”

Section: Impact On Pod Performancementioning

confidence: 99%

Impact of Swarm GPS receiver updates on POD performance

2016

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The Swarm satellites are equipped with state-of-the-art Global Positioning System (GPS) receivers, which are used for the precise geolocation of the magnetic and electric field instruments, as well as for the determination of the Earth's gravity field, the total electron content and low-frequency thermospheric neutral densities. The onboard GPS receivers deliver high-quality data with an almost continuous data rate. However, the receivers show a slightly degraded performance when flying over the geomagnetic poles and the geomagnetic equator, due to ionospheric scintillation. Furthermore, with only eight channels available for dual-frequency tracking, the amount of collected GPS tracking data is relatively low compared with various other missions. Therefore, several modifications have been implemented to the Swarm GPS receivers. To optimise the amount of collected GPS data, the GPS antenna elevation mask has slowly been reduced from 10° to 2°. To improve the robustness against ionospheric scintillation, the bandwidths of the GPS receiver tracking loops have been widened. Because these modifications were first implemented on Swarm-C, their impact can be assessed by a comparison with the close flying Swarm-A satellite. This shows that both modifications have a positive impact on the GPS receiver performance. The reduced elevation mask increases the amount of GPS tracking data by more than 3 %, while the updated tracking loops lead to around 1.3 % more observations and a significant reduction in tracking losses due to severe equatorial scintillation. The additional observations at low elevation angles increase the average noise of the carrier phase observations, but nonetheless slightly improve the resulting reduced-dynamic and kinematic orbit accuracy as shown by independent satellite laser ranging (SLR) validation. The more robust tracking loops significantly reduce the large carrier phase observation errors at the geomagnetic poles and along the geomagnetic equator and do not degrade the observations at midlatitudes. SLR validation indicates that the updated tracking loops also improve the reduced-dynamic and kinematic orbit accuracy. It is expected that the Swarm gravity field recovery will benefit from the improved kinematic orbit quality and potentially also from the expected improvement of the kinematic baseline determination and the anticipated reduction in the systematic gravity field errors along the geomagnetic equator. Finally, other satellites that carry GPS receivers that encounter similar disturbances might also benefit from this analysis.

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Section: Impact On Pod Performancementioning

confidence: 99%

Impact of Swarm GPS receiver updates on POD performance

2016

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“…mismodelling of the antenna phase centre variations (PCV) and the highorder ionosphere-induced errors. In recent years, dedicated algorithms were developed to mitigate the impact of those errors on the kinematic orbits and corresponding gravity field solutions (Jäggi et al 2009(Jäggi et al , 2015Bock et al 2011). However, the kinematic orbits may still suffer from some unknown or mismodelled systematic errors, as well as artefacts that are difficult to be modelled for Low Earth Orbiters (LEO), e.g.…”

Section: Introductionmentioning

confidence: 99%

Earth’s gravity field modelling based on satellite accelerations derived from onboard GPS phase measurements

Guo

Ditmar

Zhao

et al. 2017

J Geod

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GPS data collected by satellite gravity missions can be used for extracting the long-wavelength part of the Earth's gravity field. We propose a new data processing method which makes use of the 'average acceleration' approach to gravity field modelling. In this method, satellite accelerations are directly derived from GPS carrier phase measurements with an epoch-differenced scheme. As a result, no ambiguity solutions are needed and the systematic errors that do not change much from epoch to epoch are largely eliminated. The GPS data collected by the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite mission are used to demonstrate the added value of the proposed method. An analysis of the residual accelerations shows that accelerations derived in this way are more precise, with noise being reduced by about 20 and 5% at the cross-track component and the other two components, respectively, as compared to those based on kinematic orbits. The accelerations obtained in this way allow the recovery of the gravity field to a slightly higher maximum degree compared to the solution based on kinematic orbits. Furthermore, the gravity field solution has an overall better performance. Errors in spherical harmonic coefficients are smaller, especially at low degrees. The cumulative geoid height error is reduced by about 15 and 5% up to degree 50 and 150, respectively. An analysis in the spatial domain shows that large errors along the geomagnetic equator, which are caused by a high electron density coupled with large short-term variations, are substantially reduced. Finally, the new method allows for a better observation of mass transport signals. In particular, sufficiently realistic signatures of regional mass anomalies in North America and south-west Africa are obtained.

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“…This is assured as a result of the processing outlined above, since both are derived by a doubledifference solution which eliminates all clock parameters. Finally, the reference clock for the solution is always chosen among ground station H-maser clocks (Bock 2009), so that it is unaffected by a possible LPI violation. Below we study the attainable sensitivity of the test using simulated data.…”

Section: A) Description Of the Experimentsmentioning

confidence: 99%

Clocks in Space for Tests of Fundamental Physics

2017

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International audienceIn this paper we describe some of the past, present and near future experiments that take advantage of clocks in space for tests of fundamental physics, together with some of the theoretical background. It is impossible to describe all missions and projects in the field, and we will only mention some of the most important ones. Nonetheless, we hope that the reader will learn from the past, appreciate the present and look forward to the future of space clocks in fundamental physics

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High-rate GPS clock corrections from CODE: support of 1 Hz applications

Cited by 166 publications

References 22 publications

Impact of Swarm GPS receiver updates on POD performance

Impact of Swarm GPS receiver updates on POD performance

Earth’s gravity field modelling based on satellite accelerations derived from onboard GPS phase measurements

Clocks in Space for Tests of Fundamental Physics

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