Comparison between Laser Ranging Interferometer and K/Ka band Ranging instruments.

2020 ◽  
Author(s):  
Sebastien Allgeyer ◽  
Herbert McQueen ◽  
Paul Tregoning
Keyword(s):  
Spectral Analysis ◽  
Spectral Band ◽  
Harmonic Spectrum ◽  
Laser Ranging ◽  
Range Data ◽  
Satellite Mission ◽  
Ka Band ◽  
Gravity Signal ◽  
Improved Accuracy

<div> <p><span>The GRACE Follow-On mission is the first twin-satellite mission</span><span> equipped with a laser ranging interferometer (LRI) to measure the inter-satellite distance between the pair of satellites. The LRI operates independently of the K/Ka-band interferometer (KBR</span><span>) and uses</span><span> wavelengths</span><span> </span><span>10</span><sup><span>4</span></sup><span> times</span><span> shorter than the K-band</span><span> system.  </span><span>Released at the end of July 2019, the LRI range data is </span><span>therefore </span><span>expected to be of higher accuracy than the KBR and offers the possibility of a better spatial resolution. We compare the LRI and KBR observations of the GRACE-FO mission, from launch to December 2019, to assess the quality of the new LRI system.</span><span> </span><span>Spectral analysis of the level1B data shows that the noise level of the LRI is 3 </span><span>orders</span><span> of magnitude smaller than the KBR</span><span> and that </span><span>the gravity signal can be detected in the spectral band up to </span><span>30mHz in the LRI data </span><span>compared</span><span> to </span><span>20mHz</span><span> </span><span>i</span><span>n</span><span> the </span><span>KBR</span><span> data</span><span>.</span><span> </span><span> We compare</span><span> gravity </span><span>fields</span><span> estimated using LRI </span><span>and KBR and show which parts of the spherical harmonic spectrum are affected by the improved accuracy of the LRI observations.</span></p> </div>

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

2020 ◽  
Author(s):  
Igor Koch ◽  
Mathias Duwe ◽  
Jakob Flury ◽  
Akbar Shabanloui
Keyword(s):  
Laser Ranging ◽  
Satellite Measurements ◽  
Satellite Mission ◽  
The Earth ◽  
Gravity Fields ◽  
Data Products ◽  
Level 1 ◽  
Orbit Types ◽  
Gravity Recovery

<p>The dual-satellite mission GRACE Follow-On (GRACE-FO) was launched in May 2018 as the successor of the Gravity Recovery And Climate Experiment (GRACE). In May 2019 first level 1 data products were made available to the community and are now published regularly. These products, among others, include orbits, accelerometer measurements, star camera data and micron and sub-micron precise inter-satellite range measurements. The data products are used by different groups to compute estimates of monthly gravity fields of the Earth. The in-house developed GRACE-SIGMA software is used at the Institut of Geodesy/Leibniz University Hannover for the estimation of monthly gravity fields. Several parts of the software’s processing chain, such as background modeling, were updated recently and different parametrization scenarios were tested. First solutions were estimated based on laser ranging interferometer measurements. Moreover, different orbit types, such as reduced-dynamic and kinematic, were tested. In this contribution, we present the influence of these updates and tests on the quality of the gravity fields. The obtained solutions are assessed in terms of error degree standard deviations and post-fit residuals of the inter-satellite measurements.</p>

scholarly journals Spatiotemporal Fusion of Formosat-2 and Landsat-8 Satellite Images: A Comparison of “Super Resolution-Then-Blend” and “Blend-Then-Super Resolution” Approaches

2021 ◽  
Vol 13 (4) ◽  
pp. 606
Author(s):  
Tee-Ann Teo ◽  
Yu-Ju Fu
Keyword(s):  
Satellite Images ◽  
Traditional Approach ◽  
Spectral Band ◽  
Super Resolution ◽  
High Temporal Resolution ◽  
Landsat 8 ◽  
Fusion Model ◽  
Image Blending ◽  
Fine Resolution

The spatiotemporal fusion technique has the advantages of generating time-series images with high-spatial and high-temporal resolution from coarse-resolution to fine-resolution images. A hybrid fusion method that integrates image blending (i.e., spatial and temporal adaptive reflectance fusion model, STARFM) and super-resolution (i.e., very deep super resolution, VDSR) techniques for the spatiotemporal fusion of 8 m Formosat-2 and 30 m Landsat-8 satellite images is proposed. Two different fusion approaches, namely Blend-then-Super-Resolution and Super-Resolution (SR)-then-Blend, were developed to improve the results of spatiotemporal fusion. The SR-then-Blend approach performs SR before image blending. The SR refines the image resampling stage on generating the same pixel-size of coarse- and fine-resolution images. The Blend-then-SR approach is aimed at refining the spatial details after image blending. Several quality indices were used to analyze the quality of the different fusion approaches. Experimental results showed that the performance of the hybrid method is slightly better than the traditional approach. Images obtained using SR-then-Blend are more similar to the real observed images compared with images acquired using Blend-then-SR. The overall mean bias of SR-then-Blend was 4% lower than Blend-then-SR, and nearly 3% improvement for overall standard deviation in SR-B. The VDSR technique reduces the systematic deviation in spectral band between Formosat-2 and Landsat-8 satellite images. The integration of STARFM and the VDSR model is useful for improving the quality of spatiotemporal fusion.

Finding Approximate Shape Regularities for Reverse Engineering

2001 ◽  
Vol 1 (4) ◽  
pp. 282-290 ◽  
Author(s):  
F. C. Langbein ◽  
B. I. Mills ◽  
A. D. Marshall ◽  
R. R. Martin
Keyword(s):  
Reverse Engineering ◽  
Small Groups ◽  
Input Data ◽  
Boundary Representation ◽  
Range Data ◽  
Engineering Systems ◽  
Post Processing ◽  
Processing Step ◽  
3D Range Data

Current reverse engineering systems can generate boundary representation (B-rep) models from 3D range data. Such models suffer from inaccuracies caused by noise in the input data and algorithms. The quality of reverse engineered geometric models can be improved by finding candidate shape regularities in such a model, and constraining the model to meet a suitable subset of them, in a post-processing step called beautification. This paper discusses algorithms to detect such approximate regularities in terms of similarities between feature objects describing properties of faces, edges and vertices, and small groups of these elements in a B-rep model with only planar, spherical, cylindrical, conical and toroidal faces. For each group of similar feature objects they also seek special feature objects which may represent the group, e.g. an integer value which approximates the radius of similar cylinders. Experiments show that the regularities found by the algorithms include the desired regularities as well as spurious regularities, which can be limited by an appropriate choice of tolerances.

scholarly journals Impact of Honeycomb Polylactide Infill% in FDM Printed PLA/Nylon for Improved Mechanical Properties

2020 ◽  
Vol 8 (5) ◽  
pp. 3662-3668
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Conventional Process ◽  
Improved Accuracy ◽  
Made In

In conventional manufacturing procedures liable upon the forces acting on the materials may lead to breakage during motion of the part undergoing construct which is inevitable to no change its shape and position. In pretty much every case, materials have anisotropic by its nature and virtue. As additive manufacturing (AM) techniques embedded undergoing processes with improved accuracy of the parts being developed. Since there is far disadvantage of the quality of the AM product, constantly improvements made the process of AM is being escalating than conventional process. The assessment of the product and the complexity of the parts can’t be resolved or found before it developing a methodology which impact mechanical properties of the printed parts. An effort has been made in the present work to improve the products mechanical properties by increasing the infill percentage. Study has been carried out as in view of increased infill with elaborated percentages of 15%, 30%, 40% and 50% to enhance the mechanical properties of the parts.

Business and Technology Issues in Wireless Networking

2007 ◽  
pp. 90-95
Author(s):  
D. Wright
Keyword(s):  
Quality Of Service ◽  
Mobile Computing ◽  
Comparative Evaluation ◽  
Range Data ◽  
Metropolitan Area Networks ◽  
Ground Speed ◽  
Market Growth ◽  
Major Development ◽  
Communications Standards

A major development in the enabling technologies for mobile computing and commerce is the evolution of wireless communications standards from the IEEE 802 series on local and metropolitan area networks. The rapid market growth and successful applications of 802.11, WiFi, is likely to be followed by similar commercial profitability of the emerging standards, 802.16e, WiMAX, and 802.20, WiMobile, both for network operators and users. This article describes the capabilities of these three standards and provides a comparative evaluation of features that impact their applicability to mobile computing and commerce. In particular, comparisons include the range, data rate in Mbps and ground speed in Km/h plus the availability of quality of service for voice and multimedia applications.

Mechatronical System of Testing of Hydrodinamical Bearings

2006 ◽  
Vol 113 ◽  
pp. 375-378
Author(s):  
Mindaugas Jurevichius ◽  
Vladas Vekteris
Keyword(s):  
Spectral Analysis ◽  
Testing System ◽  
Data Input ◽  
Input Output ◽  
Hydrodynamic Bearings ◽  
Structure Control

This article presents a Mechatronic Hydrodynamic Bearings Testing System and describes its main functions. The System’s structure, control and principles of data input/output are given here. The System enables one to evaluate the quality of bearings by spectral analysis of oscillations and orbits of the rotor pivot. Potentials of the System and realization of diagnostic measurements by means of this System are described.

scholarly journals The Application of the Bispectrum Analysis to Detect the Rotor Unbalance of the Induction Motor Supplied by the Mains and Frequency Converter

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 3009
Author(s):  
Pawel Ewert
Keyword(s):  
Spectral Analysis ◽  
Fourier Transform ◽  
Induction Motor ◽  
Induction Motors ◽  
Frequency Converter ◽  
Experimental Tests ◽  
Test Mass ◽  
Mechanical Vibrations ◽  
Stator Current

This article presents the effectiveness of bispectrum analysis for the detection of the rotor unbalance of an induction motor supplied by the mains and a frequency converter. Two diagnostic signals were analyzed, as well as the stator current and mechanical vibrations of the tested motors. The experimental tests were realized for two low-power induction motors, with one and two pole pairs, respectively. The unbalance was modeled using a test mass mounted on a specially prepared disc and directly on the rotor and the influence of this unbalance location was tested and discussed. The results of the bispectrum analysis are compared with results of Fourier transform and the effectiveness of unbalance detection are discussed and compared. The influence of the registration time of the analyzed signal on the quality of fault symptom analyses using both transforms was also tested. It is shown that the bispectrum analysis provides an increased number of fault symptoms in comparison with the classical spectral analysis as well as it is not sensitive to a shorter registration time of the diagnostic signals.

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