Two-step LRI1B data calibration approach

2020 ◽  
Author(s):  
Saniya Behzadpour ◽  
Andreas Kvas ◽  
Torsten Mayer-Gürr
Keyword(s):  
Gravity Field ◽  
Scale Factor ◽  
Laser Ranging ◽  
Measurement Technology ◽  
Additional Measurement ◽  
Time Offset ◽  
Range Rate ◽  
Calibration Parameters ◽  
Calibration Approach ◽  
Data Calibration

<p class="western" align="justify">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 improve the reliability of the range rate measurements and allow for a cross-instrument diagnostics and calibration with the K-band ranging (KBR) system.</p> <p class="western" align="justify">We present a two-step approach used for LRI1B data calibration within the ITSG-Grace2018 scheme, which is compatible with the entire v04 release timespan. The aim of this study is to mitigate the remaining systematics due to the LRI datation time offset and LRI scale factor. We discuss the implementation of calibration parameters and the contribution of the calibration approach to the overall accuracy of gravity field solutions.</p>

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>

Processing of GRACE FO satellite to satellite tracking data using the GRACE SIGMA software

2020 ◽  
Author(s):  
Mathias Duwe ◽  
Igor Koch ◽  
Jakob Flury ◽  
Akbar Shabanloui
Keyword(s):  
Gravity Field ◽  
Satellite Tracking ◽  
Background Modeling ◽  
Gravity Potential ◽  
Laser Ranging ◽  
Tracking Data ◽  
Variational Equations ◽  
Range Rate ◽  
Orbit Types ◽  
Computing Approach

<p>At our Institute we compute monthly gravity potential solutions from GRACE/GRACE-FO level 1B data by using the variational equations approach. The gravity field is recovered with our own MATLAB software "GRACE-SIGMA" that was recently updated in order to reduce the calculation time with parallel computing approach by approx. 80%. Also the processing chain has changed to update the background modeling and we made tests with different orbit types and different parametrizations. We discuss progress to include laser ranging interferometer data in gravity field solutions. We present validation results and analyze the properties of postfit range-rate residuals.</p>

The impact of accelerometer calibration approach on estimation of thermospheric density variations 

2021 ◽  
Author(s):  
Akbar Shabanloui ◽  
Jakob Flury ◽  
Sergiy Svitlov
Keyword(s):  
Gravity Field ◽  
Scale Factor ◽  
Satellite Orbits ◽  
Gravitational Forces ◽  
Main Challenge ◽  
The Impact ◽  
Calibration Approach

<p>The environmental non-gravitational accelerations observed by ultra-precise electro-static accelerometers onboard Low Earth Orbiters (LEOs) such as GRACE (FO) and Swarm missions provide a unique opportunity to estimate and monitor the neutral thermospheric density variations. One of main challenge in using such ultra-precise accelerometer observations for thermospheric density application is the calibration approach which delivers the realistic non-gravitational forces acting on satellite surface. The realistic scale factor and bias of accelerometers are estimated during retrieval of Earth’s monthly gravity field solutions.</p><p>In this contribution, a realistic accelerometer calibration approach based on Earth’s gravity solutions and precise satellite orbits is introduced and its impacts on neutral thermoshperic density variations for some special periods are investigated. This approach demonstrates the potential of using realistic calibrated ultra-prcise accelerometers for neutral thermospheric density studies.</p>

scholarly journals GRACETOOLS—GRACE Gravity Field Recovery Tools

Geosciences ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 350 ◽  
Author(s):  
Neda Darbeheshti ◽  
Florian Wöske ◽  
Matthias Weigelt ◽  
Christopher Mccullough ◽  
Hu Wu
Keyword(s):  
Open Source ◽  
Gravity Field ◽  
Transition Matrix ◽  
State Transition ◽  
Satellite Observations ◽  
Gravity Field Recovery ◽  
Grace Data ◽  
Range Rate ◽  
Analysis Platform ◽  
Recovery Tools

This paper introduces GRACETOOLS, the first open source gravity field recovery tool using GRACE type satellite observations. Our aim is to initiate an open source GRACE data analysis platform, where the existing algorithms and codes for working with GRACE data are shared and improved. We describe the first release of GRACETOOLS that includes solving variational equations for gravity field recovery using GRACE range rate observations. All mathematical models are presented in a matrix format, with emphasis on state transition matrix, followed by details of the batch least squares algorithm. At the end, we demonstrate how GRACETOOLS works with simulated GRACE type observations. The first release of GRACETOOLS consist of all MATLAB M-files and is publicly available at Supplementary Materials.

Recoverability of Callisto gravity field influenced by orbiter mission characteristics

2021 ◽  
Author(s):  
William Desprats ◽  
Daniel Arnold ◽  
Michel Blanc ◽  
Adrian Jäggi ◽  
Mingtao Li ◽  
...  
Keyword(s):  
Gravity Field ◽  
Noise Model ◽  
Force Model ◽  
Tracking Data ◽  
Science Center ◽  
National Space ◽  
Beta Angle ◽  
Dynamical Parameters ◽  
Range Rate ◽  
Orbiter Mission

<p>The exploration of Callisto is part of the extensive interest in the icy moons characterization. Indeed, Callisto is the Galilean moon with the best-preserved records of the Jovian system formation. Led by the National Space Science Center (NSSC), Chinese Academy of Science (CAS), the planned Gan De mission aims to send an orbiter around Callisto in order to characterize its surface and interior. Potential orbit configurations are currently under study for the Gan De mission proposal.</p><p>As part of a global characterization of Callisto, its gravity field can be inferred using radio tracking data from an orbiter. Mission characteristics such as orbit type, Earth beta angle and solar elongation will have a direct influence on the recoverability of its gravity field parameters. In this study, we will analyse this influence from closed-loop simulations using the planetary extension of the Bernese GNSS Softwareai.</p><p>A number of reference orbits with different orbital characteristics will be selected for the Gan De mission and, using an extended force model, will be propagated from different starting dates and different initial Earth beta angles. Realistic Doppler tracking data (2-way X-band Doppler range rate) will be simulated as measurements from ground stations, with a dedicated noise model. These observations will then be used to reconstruct the orbit along with dynamical parameters. The focus of this presentation will be on the quality of the retrieved gravity field parameters and tidal Love number k2.</p>

Gravity Field Recovery and Observation Noise Separation from Simultaneous Laser Ranging Interferometer and K-Band Ranging System Measurements

2020 ◽  
Author(s):  
Andreas Kvas ◽  
Saniya Behzadpour ◽  
Torsten Mayer-Guerr
Keyword(s):  
Gravity Field ◽  
Spherical Harmonic ◽  
Uncertainty Propagation ◽  
Stochastic Modelling ◽  
Laser Ranging ◽  
Polar Regions ◽  
Data Types ◽  
Covariance Functions ◽  
Gravity Field Recovery ◽  
K Band

<p>The unique instrumentation of GRACE Follow-On (GRACE-FO) offers two independent inter-satellite ranging systems with concurrent observations. Next to a K-Band Ranging System (KBR), which has already been proved during the highly-successfully GRACE mission, the GRACE-FO satellites are equipped with an experimental Laser Ranging Interferometer (LRI), which features a drastically increased measurement precision compared to the KBR. Having two simultaneous ranging observations available allows for cross-calibration between the instruments and, to some degree, the separation of ranging noise from other sources such as noise in the on-board accelerometer (ACC) measurements.  </p> <p>In this contribution we present a stochastic description of the two ranging observation types provided by GRACE-FO, which also takes cross-correlations between the two observables into account. We determine the unknown noise covariance functions through variance component estimation and show that this method is, to some extent, capable of separating between KBR, LRI, and ACC noise. A side effect of this stochastic modelling is that the formal errors of the spherical harmonic coefficients fit very well to empirical estimates, which is key for combination with other data types and uncertainty propagation. We further compare the gravity field solutions obtained from a combined least-squares adjustment to KBR-only and LRI-only results and discuss the differences between the time series with a focus on gravity field and calibration parameters. Even though, at the moment, global statistics only show a minor improvement when using LRI ranging measurements instead of KBR observations, some parts of the spectrum and geographic regions benefit significantly from the increased measurement accuracy of the LRI. Specifically, we see a higher signal-to-noise ratio in low spherical harmonic orders and the polar regions.</p>

scholarly journals Monthly spherical harmonic gravity field solutions determined from GRACE inter-satellite range-rate data alone

2006 ◽  
Vol 33 (2) ◽  
Author(s):  
S. B. Luthcke ◽  
D. D. Rowlands ◽  
F. G. Lemoine ◽  
S. M. Klosko ◽  
D. Chinn ◽  
...  
Keyword(s):  
Gravity Field ◽  
Spherical Harmonic ◽  
Rate Data ◽  
Range Rate

scholarly journals Multiresolution wavelet analysis applied to GRACE range rate residuals

2019 ◽  
Author(s):  
Saniya Behzadpour ◽  
Torsten Mayer-Gürr ◽  
Jakob Flury ◽  
Beate Klinger ◽  
Sujata Goswami
Keyword(s):  
Wavelet Analysis ◽  
Gravity Field ◽  
Recovery Process ◽  
Ocean Tide ◽  
Discrete Wavelet ◽  
Error Sources ◽  
Gravity Field Recovery ◽  
Multi Resolution Analysis ◽  
Range Rate ◽  
Process Observation

Abstract. For further improvements of gravity field models based on Gravity Recovery and Climate Experiment (GRACE) observations, it is necessary to identify the error sources within the recovery process. Observation residuals obtained during the gravity field recovery contain most of the measurement and modeling errors and thus can be considered as a realization of actual errors. In this work, we investigate the ability of wavelets to help in identifying specific error sources in GRACE range rate residuals. The Multi-Resolution Analysis (MRA) using Discrete Wavelet Transform (DWT) is applied to decompose the residual signal into different scales with corresponding frequency bands. Temporal, spatial, and orbit-related features of each scale are then extracted for further investigations. The wavelet analysis has proved to be a practical tool to find the main error contributors. Beside the previously known sources such as K-Band Ranging (KBR) system noise and systematic attitude variations, this method clearly shows effects which the classic spectral analysis is hardly able or unable to represent. These effects include long-term signatures due to satellite eclipse crossings and dominant ocean tide errors.

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