scholarly journals PPP-based Swarm kinematic orbit determination

2018 ◽  
Author(s):  
Le Ren ◽  
Steffen Schön
Keyword(s):  
Gravity Field ◽  
Orbit Determination ◽  
External Validation ◽  
Ionospheric Scintillation ◽  
Kinematic Orbit ◽  
Cycle Slips ◽  
Gravity Field Recovery ◽  
Swarm Satellites ◽  
Least Squares Adjustment ◽  
Reduced Dynamic

Abstract. ESA's Swarm mission offers excellent opportunities to study the ionosphere and to bridge the gap in gravity field recovery between GRACE and GRACE-FO. In order to contribute to these studies, at IfE Hannover, a software based on Precise Point Positioning (PPP) batch least-squares adjustment is developed for kinematic orbit determination. In this paper, the main achievements are presented. The approach for the detection and repair of cycle slips caused by ionospheric scintillation is introduced, which is based on the Melbourne-Wübbena and ionosphere-free linear combination. The results show that around 95 % cycle slips can be repaired and the majority of the cycle slips occur on L2. After the analysis and careful preprocessing of the observations, one year kinematic orbits of Swarm satellites from Sept., 2015 to Aug., 2016 are computed with the PPP approach. The kinematic orbits are validated with the reduced-dynamic orbits published by ESA in Swarm Level 2 products and the SLR measurements. The differences between our kinematic orbits and ESA reduced-dynamic orbits are at the 1.5 cm, 1.5 cm and 2.5 cm level in the along, cross and radial track, respectively. Remaining systematics are characterised by spectral analyses. The external validation with SLR measurements shows rms errors at the 4 cm level. Finally, fully populated covariance matrices of the kinematic orbits obtained from 30 s, 10 s and 1 s data rate are discussed. It is shown that for data rates larger than 10 s, the correlation should be taken into account when using POD coordinates as input for the gravity field recovery.

scholarly journals PPP-based Swarm kinematic orbit determination

2018 ◽  
Vol 36 (5) ◽  
pp. 1227-1241
Author(s):  
Le Ren ◽  
Steffen Schön
Keyword(s):  
Least Squares ◽  
Gravity Field ◽  
Orbit Determination ◽  
External Validation ◽  
European Space Agency ◽  
Kinematic Orbit ◽  
Cycle Slips ◽  
Swarm Satellites ◽  
Least Squares Adjustment ◽  
Reduced Dynamic

Abstract. The Swarm mission of the European Space Agency (ESA) offers excellent opportunities to study the ionosphere and to provide temporal gravity field information for the gap between the Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission (GRACE-FO). In order to contribute to these studies, at the Institut für Erdmessung (IfE) Hannover, a software based on precise point positioning (PPP) batch least-squares adjustment is developed for kinematic orbit determination. In this paper, the main achievements are presented. The approach for the detection and repair of cycle slips caused by ionospheric scintillation is introduced, which is based on the Melbourne–Wübbena and ionosphere-free linear combination. The results show that around 95 % of cycle slips can be repaired and the majority of the cycle slips occur on L2. After the analysis and careful preprocessing of the observations, 1-year kinematic orbits of Swarm satellites from September 2015 to August 2016 are computed with the PPP approach. The kinematic orbits are validated with the reduced-dynamic orbits published by the ESA in the Swarm Level 2 products and SLR measurements. The differences between IfE kinematic orbits and ESA reduced-dynamic orbits are at the 1.5, 1.5 and 2.5 cm level in the along-track, cross-track and radial directions, respectively. Remaining systematics are characterized by spectral analyses, showing once-per-revolution period. The external validation with SLR measurements shows RMSEs at the 4 cm level. Finally, fully populated covariance matrices of the kinematic orbits obtained from the least-squares adjustment with 30, 10 and 1 s data rate are discussed. It is shown that for data rates larger than 10 s, the correlation between satellite positions should be taken into account, for example, for the recovery of gravity field from kinematic orbits.

GRACE Follow-On Gravity Field Recovery from Combined Laser Ranging Interferometer and Microwave Ranging System Measurements

2021 ◽  
Author(s):  
Saniya Behzadpour ◽  
Andreas Kvas ◽  
Torsten Mayer-Gürr
Keyword(s):  
Gravity Field ◽  
Laser Ranging ◽  
Measurement Technology ◽  
Additional Measurement ◽  
Covariance Functions ◽  
Gravity Field Recovery ◽  
Global Gravity ◽  
Least Squares Adjustment ◽  
Noise Covariance ◽  
Component Estimation

<p>Besides a K-Band Ranging System (KBR), GRACE-FO carries a Laser Ranging Interferometer (LRI) as a technology demonstration to provide measurements of inter-satellite range changes. This additional measurement technology provides supplementary observations, which allow for cross-instrument diagnostics with the KBR system and, to some extent, the separation of ranging noise from other sources such as noise in the on-board accelerometer (ACC) measurements.</p><p>The aim of this study is to incorporate the two ranging systems (LRI and KBR) observations in ITSG-Grace2018 gravity field recovery. The two observation groups are combined in an iterative least-squares adjustment with variance component estimation used to determine the unknown noise covariance functions for KBR, LRI, and ACC measurements. We further compare the gravity field solutions obtained from the combined solutions to KBR-only results and discuss the differences with a focus on the global gravity field and LRI calibration parameters.</p>

scholarly journals Assessing reduced-dynamic parametrizations for GRAIL orbit determination and the recovery of independent lunar gravity field solutions

2020 ◽  
Author(s):  
Stefano Bertone ◽  
Daniel Arnold ◽  
Valère Girardin ◽  
Martin Lasser ◽  
Ulrich Meyer ◽  
...  
Keyword(s):  
Gravity Field ◽  
Orbit Determination ◽  
Lunar Gravity ◽  
Lunar Gravity Field ◽  
Reduced Dynamic

scholarly journals Assessment of two methods for gravity field recovery from GOCE GPS-SST orbit solutions

2003 ◽  
Vol 1 ◽  
pp. 121-126 ◽  
Author(s):  
K. Arsov ◽  
R. Pail
Keyword(s):  
Gravity Field ◽  
Numerical Integration ◽  
Precise Orbit Determination ◽  
Integral Approach ◽  
Satellite Mission ◽  
Long Wavelength ◽  
Alternative Processing ◽  
Gravity Field Recovery ◽  
Least Squares Adjustment

Abstract. In the course of the GOCE satellite mission, the high-low Satellite to Satellite Tracking (SST) observations have to be processed for the determination of the long wavelength part of the Earth’s gravity field. This paper deals with the formulation of the high-low SST observation equations, as well as the methods for gravity field recovery from orbit information. For this purpose, two approaches, i.e. the numerical integration of orbit perturbations, and the evaluation of the energy equation based on the Jacobi integral, are presented and discussed. Special concern is given to the numerical properties of the corresponding normal equations. In a closed-loop simulation, which is based on a realistic orbit GOCE configuration, these methods are compared and assessed. However, here we process a simplified case assuming that non-conservative forces can be perfectly modelled. Assuming presently achievable accuracies of the Precise Orbit Determination (POD), it turns out that the numerical integration approach is still superior, but the energy integral approach may be an interesting alternative processing strategy in the near future.Key words. High-low SST – gravity field – GOCE – variational equations – least squares adjustment

scholarly journals Time-variable gravity field recovery from kinematic positions of Low Earth Orbiting satellites

2021 ◽  
Author(s):  
Thomas Grombein ◽  
Martin Lasser ◽  
Daniel Arnold ◽  
Ulrich Meyer ◽  
Adrian Jäggi
Keyword(s):  
Time Series ◽  
Gravity Field ◽  
Time Variable ◽  
Kinematic Orbit ◽  
Time Variable Gravity ◽  
Gravity Field Recovery ◽  
The Earth ◽  
Leo Satellites ◽  
Variable Gravity ◽  
Gnss Data

<p>For the monitoring of mass transport and mass distribution in the Earth’s system, the gravity field and its temporal variations provide an important source of information. Dedicated satellite missions like GRACE and GRACE-FO allow to resolve the Earth’s time-variable gravity field based on ultra-precise inter-satellite ranging. In addition, any (non-dedicated) Low Earth Orbiting (LEO) satellite equipped with an on-board GNSS receiver may also serve as a gravity field sensor. For this purpose, the collected GNSS data is used to derive kinematic LEO orbit positions that can subsequently be utilized as pseudo-observations for gravity field recovery. Although this technique is less sensitive and restricted to the long wavelength part of the gravity field, it provides valuable information, particularly for those months where no inter-satellite ranging measurements are available from GRACE or GRACE-FO. Furthermore, the increasing number of operational LEO satellites makes it attractive to produce combined Multi-LEO gravity field solutions that will take advantage of the variety of complementary orbital configurations and can offer additional sensitivities to selected coefficients of solutions based on inter-satellite ranging.</p><p>At the Astronomical Institute of the University of Bern (AIUB) GPS-based kinematic orbits are routinely processed for various LEO satellites like missions dedicated to gravity (GOCE, GRACE/-FO), altimetry (Jason, Sentinel), or further constellations of Earth-observing satellites like SWARM. Beside conventional ambiguity-float orbits, also ambiguity-fixed orbits are recently being computed based on new phase bias and clock products of the Center for Orbit Determination in Europe (CODE). The kinematic orbit positions offer the opportunity to derive time series of monthly gravity field solutions for the different LEO satellites that are eventually combined on the level of normal equations.</p><p>In this contribution, we will present first results of our effort to generate a combined time series of monthly gravity field solutions based on the kinematic orbits of multiple LEO satellites. In a first step, the focus is laid on the GRACE/-FO missions that provide the longest time series in terms of collected GNSS data and that will therefore serve as a backbone for future combinations. We analyze the impact of accelerometer data on the recovery of time-variable mass variations. This will be particularly important for the handling of non-dedicated gravity missions, for which accelerometer measurements are usually not available. Furthermore, we study and compare the performance of gravity field recoveries based on ambiguity-float and ambiguity-fixed kinematic orbit solutions. We assess our results with respect to superior gravity field models based on inter-satellite ranging for selected areas with strong mass change signals like in Greenland, West-Antarctica or the Amazon river basin.</p>

Sign in / Sign up

Export Citation Format

Share Document