Time-variable gravity field determination from GRACE-FO data using the Celestial Mechanics Approach

2020 ◽  
Author(s):  
Martin Lasser ◽  
Ulrich Meyer ◽  
Daniel Arnold ◽  
Adrian Jäggi
Keyword(s):  
Gravity Field ◽  
Celestial Mechanics ◽  
Noise Model ◽  
Stochastic Parameters ◽  
Gravity Field Determination ◽  
Phase Bias ◽  
Set Up ◽  
Noise Models ◽  
K Band

<p>We study gravity field determination from GRACE-FO satellite-to-satellite tracking using the inter-satellite K-band link and kinematic positions of the satellites as observations and pseudo-observations respectively. We employ 10-second kinematic positions from a precise point positioning where the undifferenced carrier phase ambiguities are fixed to integer values using observation-specific phase bias products from the CODE analysis centre.<br />We present an up-to-date GRACE-FO time series computed with the Celestial Mechanics Approach extended by empirical noise models derived from the post-fit residuals to better characterise the stochastic behaviour of both observation types. We investigate the interplay between the empirical noise model and the co-estimation of stochastic parameters set-up to absorb unmodelled signal (short term mass variations, accelerometer errors etc.).<br />We validate our results of GRACE-FO gravity field determination by analysing the residuals of combined orbits calculated using both kinematic positions and K-band data, and by analysing the quality of co-estimated gravity field solutions.</p>

scholarly journals Earth’s Time-Variable Gravity from GRACE Follow-On K-Band Range-Rates and Pseudo-Observed Orbits

2021 ◽  
Vol 13 (9) ◽  
pp. 1766
Author(s):  
Igor Koch ◽  
Mathias Duwe ◽  
Jakob Flury ◽  
Akbar Shabanloui
Keyword(s):  
Gravity Field ◽  
Time Variable ◽  
Time Variable Gravity ◽  
Gravity Field Recovery ◽  
Variable Gravity ◽  
Earth’S System ◽  
Grace Mission ◽  
Insight Into ◽  
K Band

During its science phase from 2002–2017, the low-low satellite-to-satellite tracking mission Gravity Field Recovery And Climate Experiment (GRACE) provided an insight into Earth’s time-variable gravity (TVG). The unprecedented quality of gravity field solutions from GRACE sensor data improved the understanding of mass changes in Earth’s system considerably. Monthly gravity field solutions as the main products of the GRACE mission, published by several analysis centers (ACs) from Europe, USA and China, became indispensable products for quantifying terrestrial water storage, ice sheet mass balance and sea level change. The successor mission GRACE Follow-On (GRACE-FO) was launched in May 2018 and proceeds observing Earth’s TVG. The Institute of Geodesy (IfE) at Leibniz University Hannover (LUH) is one of the most recent ACs. The purpose of this article is to give a detailed insight into the gravity field recovery processing strategy applied at LUH; to compare the obtained gravity field results to the gravity field solutions of other established ACs; and to compare the GRACE-FO performance to that of the preceding GRACE mission in terms of post-fit residuals. We use the in-house-developed MATLAB-based GRACE-SIGMA software to compute unconstrained solutions based on the generalized orbit determination of 3 h arcs. K-band range-rates (KBRR) and kinematic orbits are used as (pseudo)-observations. A comparison of the obtained solutions to the results of the GRACE-FO Science Data System (SDS) and Combination Service for Time-variable Gravity Fields (COST-G) ACs, reveals a competitive quality of our solutions. While the spectral and spatial noise levels slightly differ, the signal content of the solutions is similar among all ACs. The carried out comparison of GRACE and GRACE-FO KBRR post-fit residuals highlights an improvement of the GRACE-FO K-band ranging system performance. The overall amplitude of GRACE-FO post-fit residuals is about three times smaller, compared to GRACE. GRACE-FO post-fit residuals show less systematics, compared to GRACE. Nevertheless, the power spectral density of GRACE-FO and GRACE post-fit residuals is dominated by similar spikes located at multiples of the orbital and daily frequencies. To our knowledge, the detailed origin of these spikes and their influence on the gravity field recovery quality were not addressed in any study so far and therefore deserve further attention in the future. Presented results are based on 29 monthly gravity field solutions from June 2018 until December 2020. The regularly updated LUH-GRACE-FO-2020 time series of monthly gravity field solutions can be found on the website of the International Centre for Global Earth Models (ICGEM) and in LUH’s research data repository. These operationally published products complement the time series of the already established ACs and allow for a continuous and independent assessment of mass changes in Earth’s system.

scholarly journals GRAIL gravity field determination using the Celestial Mechanics Approach

Icarus ◽  
2015 ◽  
Vol 261 ◽  
pp. 182-192 ◽  
Author(s):  
Daniel Arnold ◽  
Stefano Bertone ◽  
Adrian Jäggi ◽  
Gerhard Beutler ◽  
Leos Mervart
Keyword(s):  
Gravity Field ◽  
Celestial Mechanics ◽  
Gravity Field Determination

Comparison of empirical noise models for GRACE Follow-On derived with the Celestial Mechanics Approach

2021 ◽  
Author(s):  
Martin Lasser ◽  
Ulrich Meyer ◽  
Daniel Arnold ◽  
Adrian Jäggi
Keyword(s):  
Gravity Field ◽  
Celestial Mechanics ◽  
Low Noise ◽  
Empirical Modelling ◽  
The Earth ◽  
Gravity Fields ◽  
Range Rate ◽  
University Of Bern ◽  
The Cost ◽  
Noise Models

<p>A key component of any model is the accurate specification of its quality. In gravity field modelling from satellite data, as it is done with the observation collected by GRACE Follow-On, usually least-squares adjustments are performed to obtain a monthly solution of the Earth’s gravity field. However,<br>the jointly estimated formal errors usually do not reflect the error level that could be expected but provides much lower error estimates. We take the Celestial Mechanics Approach (CMA), developed at the Astronomical Institute, University of Bern (AIUB), and extend it by an empirical modelling of the noise based on the post-fit residuals between the final GRACE Follow-On orbits, that are co-estimated together with the gravity field, and the   observations, expressed in position residuals to the kinematic positions and in K-band range-rate residuals. We compare and validate the solutions that employ empirical modelling with solutions that do not contain sophisticated noise modelling by examining the stochastic behaviour of the respective post-fit residuals, by investigating areas where a low noise is expected and by inspecting the mass trend estimates in certain areas of global interest. Finally, we investigate the influence of the empirically weighted solutions in a combination of monthly gravity fields based on other approaches as it is done in the COST-G framework.</p>

STUDY OF INACCURACY IN THE OPERATION OF THE MAIN CONTROLLER OF STB MACHINE

2019 ◽  
Keyword(s):  
Normal Distribution ◽  
Stable Process ◽  
Random Errors ◽  
Actual Length ◽  
Experimental Data Processing ◽  
Set Up ◽  
Main Regulator ◽  
Transmission Gear ◽  
Selection Of

At production of fabrics, including fabrics for agricultural purpose, an important role is played by the cor-rect adjustment of operation of machine main regulator. The quality of setup of machine main controller is determined by the proper selection of rotation angle of warp beam weaving per one filling thread. In the pro-cess of using the regulator as a result of mistakes in adjustment, wear of transmission gear and backlashes in connections of details there are random changes in threads length. The purpose of the article is the research of property of random errors of basis giving by STB machine regulator. Mistakes can be both negative, and positive. In case of emergence only negative or only positive mistakes operation of the machine becomes im-possible as there will be a consecutive accumulation of mistakes. As a result of experimental data processing for stable process of weaving and the invariable diameter of basis threads winding of threads it is revealed that the random error of giving is set up as linear function of the accidental length having normal distribution. Measurements of accidental deviations in giving of a basis by the main regulator allowed to construct a curve of normal distribution of its actual length for one pass of weft thread. The presented curve of distribution of random errors in giving of a basis is the displaced curve of normal distribution of the accidental sizes. Also we define the density of probability of normal distribution of basis giving errors connected with a margin er-ror operation of the main regulator knowing of which allows to plan ways of their decrease that is important for improvement of quality of the produced fabrics.

The Rotterdam Initiative in Reducing Waste Discharges at Source

1991 ◽  
Vol 24 (10) ◽  
pp. 171-177
Author(s):  
T. Vellinga ◽  
J. P. J. Nijssen
Keyword(s):  
Public Relations ◽  
Action Plan ◽  
Detailed Balance ◽  
River Rhine ◽  
The North ◽  
Complementary Role ◽  
Action Programme ◽  
The North Sea ◽  
Set Up

Much of the material dredged from the port of Rotterdam is contaminated to such a degree that it must be placed in specially constructed sites. The aim of Rotterdam is to ensure that the dredged material will once again be clean. This will entail the thorough cleansing of the sources of the contamination of the sediment in the harbours and in the River Rhine. The Rotterdam Rhine Research Project (RRP) is one of the means to achieve this based on: technical research, legal research, public relations and dialogues with dischargers. The programme for five selected heavy metals is almost complete. For many heavy metal discharge points between Rotterdam and Rheinfelden, a specially devised independent load assessment has been carried out four times. Balance studies were used to determine the relative contributions of the point discharges to the total. Currently the results are being used in an attempt to negotiate agreements with a selected number of the major dischargers. At present, more detailed balance studies are being set up and exploratory measurements carried out for organic micropollutants. It may be concluded that the research is progressing successfully and methods and techniques developed seem satisfactory and broadly applicable. The Rhine Action Programme encompasses an international effort to improve the quality of the Rhine water. Although the RRP plays a modest complementary role to the Rhine Action Plan, there is no doubt of the value of this Rotterdam initiative. The mode of work followed in the RRP contains elements that can be of use in combatting the contamination of the North Sea by rivers other than the Rhine.

What Advantages Can Be Expected from the Acceptance of Variable Quality Standards for Sewage Treatment Effluents?

1988 ◽  
Vol 20 (4-5) ◽  
pp. 249-251
Author(s):  
Jacques Bernard
Keyword(s):  
Water Quality ◽  
Sewage Treatment ◽  
Quality Standards ◽  
Quality Level ◽  
Environment Protection ◽  
Economical Benefit ◽  
Quality Objective ◽  
Set Up ◽  
Variable Quality

The flow and the water quality of the rivers vary throughout the year. Very frequently the environment protection authorities set up a quality objective for the river water and this mini mum quality level is constant. So, it wou1d seem possible to accept variable quality standards for plant effluents. A first approach of the problem,by a small French task group,based on three actual cases leads to the provisory conclusion that such a regulation is suitable and presents economical benefit only in some very limit ed cases.

DRUG REGULATORY PROCEDURES IN TANZANIA: A GLIMPSE

2015 ◽  
Vol 3 (2) ◽  
pp. 1-7 ◽  
Author(s):  
Achin Jain ◽  
M P Venkatesh M P ◽  
Pramod T.M. Kumar
Keyword(s):  
Quality Control ◽  
Medical Devices ◽  
Emerging Market ◽  
Well Being ◽  
New Drugs ◽  
Regulatory Body ◽  
Herbal Drugs ◽  
Drug Products ◽  
Set Up

In Tanzania, Tanzania Food and Drugs Authority (TFDA), is a regulatory body responsible for controlling the quality,safety and effectiveness of food, drugs, herbal drugs, cosmetics and medical devices. The Authority has been ensuringsafety, efficacy and quality of medicines by quality control tests; in addition to other quality assessment mechanisms.The guidelines laid by TFDA have also emanated from commitment to democracy and gives strong emphasis to thefulfilment of the needs of the less privileged rural population.Tanzania is an emerging market; the pharmaceutical market is valued at over US$250 million, and is growing at anannual rate of around 16.5% and is expected to reach approximately US$550 billion in 2020. Currently, the market ishighly dependent on imports, which account for around 75% of the total pharmaceutical market.The procedures and approval requirements of new drugs, variations, import, export and disposal have been set up bythe TFDA, which help in maintaining quality of the drug products that are imported as well being produced locally 

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