Processing of sliding spotlight mode data with consideration of orbit geometry

2009 ◽  
Author(s):  
Alicja Ossowska ◽  
Rainer Speck
Keyword(s):  
Orbit Geometry

scholarly journals The normalised Sentinel-1 Global Backscatter Model, mapping Earth’s land surface with C-band microwaves

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Bernhard Bauer-Marschallinger ◽  
Senmao Cao ◽  
Claudio Navacchi ◽  
Vahid Freeman ◽  
Felix Reuß ◽  
...  
Keyword(s):  
Land Surface ◽  
Radar Sensors ◽  
Model Mapping ◽  
The Mean ◽  
Noise Correction ◽  
New Perspective ◽  
Orbit Geometry ◽  
Microwave Backscatter ◽  
Global Surface

AbstractWe present a new perspective on Earth’s land surface, providing a normalised microwave backscatter map from spaceborne Synthetic Aperture Radar (SAR) observations. The Sentinel-1 Global Backscatter Model (S1GBM) describes Earth for the period 2016–17 by the mean C-band radar cross section in VV- and VH-polarisation at a 10 m sampling. We processed 0.5 million Sentinel-1 scenes totalling 1.1 PB and performed semi-automatic quality curation and backscatter harmonisation related to orbit geometry effects. The overall mosaic quality excels (the few) existing datasets, with minimised imprinting from orbit discontinuities and successful angle normalisation in large parts of the world. Regions covered by only one or two Sentinel-1 orbits remain challenging, owing to insufficient angular variation and not yet perfect sub-swath thermal noise correction. Supporting the design and verification of upcoming radar sensors, the obtained S1GBM data potentially also serve land cover classification and determination of vegetation and soil states. Here, we demonstrate, as an example of its potential use, the mapping of permanent water bodies and evaluate against the Global Surface Water benchmark.

scholarly journals Solar Orbiter’s first Venus flyby: observations from the Radio andPlasma Wave instrument

2021 ◽  
Author(s):  
Lina Hadid ◽  
Keyword(s):  
Plasma Waves ◽  
Bow Shock ◽  
The Sun ◽  
Gravity Assist ◽  
Tail Region ◽  
Plasma Properties ◽  
In Situ Observations ◽  
Orbit Geometry ◽  
High Cadence

<p>On December 27, 2020, Solar Orbiter completed its first gravity assist manoeuvre of Venus. While this flyby was performed to provide the spacecraft with sufficient velocity to get closer to the Sun and observe its poles from progressively higher inclinations, the Radio and Plasma Wave (RPW) consortium, along with other operational in-situ instruments, had the opportunity to perform high cadence measurements and study the plasma properties in the induced magnetosphere of Venus. In this work we present an overview of the in situ observations performed by RPW, inside the induced magnetosphere of Venus, during this first encounter of Solar Orbiter.<br />These data allowed conclusive identification of various waves at low and higher frequencies than previously observed and detailed investigation regarding the structure of the induced magnetosphere of Venus. Furthermore, noting that prior studies were mainly focused on the magnetosheath region and could only reach 10-12 Venus radii (RV) down the tail, the particular orbit geometry of Solar Orbiter’s VGAM1, allowed the first investigation of the nature of the plasma waves continuously from the bow-shock to the magnetosheath, extending to ∼ 70 R V in the far distant tail region.</p>

Study on Relative Orbit Geometry of Spacecraft Formations in Elliptical Reference Orbits

2008 ◽  
Vol 31 (1) ◽  
pp. 123-134 ◽  
Author(s):  
Fanghua Jiang ◽  
Junfeng Li ◽  
Hexi Baoyin ◽  
Yunfeng Gao
Keyword(s):  
Relative Orbit ◽  
Spacecraft Formations ◽  
Orbit Geometry

Analog simulation of satellite times-in-view

SIMULATION ◽  
1967 ◽  
Vol 8 (2) ◽  
pp. 105-110
Author(s):  
Roger N. Bryan
Keyword(s):  
Real Time ◽  
Digital Computer ◽  
Satellite Orbit ◽  
Analog Computer ◽  
Paper Strip ◽  
Analysis Tool ◽  
Analog Simulation ◽  
Satellite Geometry ◽  
The One ◽  
Orbit Geometry

During the planning stages of any communication or com mand/control system utilizing satellites, it is necessary to examine the ground-terminal/satellite geometry for many proposed configurations in order to find the one most suitable. By "most suitable," I mean the configuration exhibiting the greatest ground-terminal-to-satellite acces sibility as demonstrated by a maximum time-in-view. The procedures I describe in this paper provide a means for rapidly generating ground terminal/satellite visibility records via an analog computer simulation of the Earth's surface/satellite orbit geometry. The analog simulation has several significant advantages relative to similar digital computer approaches-(1) it is significantly faster (easily 15,000 times real-time) and less expensive to operate; (2) the output, ink-on-paper strip-chart recordings, is directly interpretable without further data reduction; (3) system parameter changes are readily introduced while a simula tion is in progress; (4) the Systems Analyst can maintain a decidedly greater rapport with his configuration analysis. The disadvantages are: (1) diminished accuracy, and (2) exclusion of Earth/orbit non-linearities and anomalies—in a real-time tracking or scheduling simulation, these dis advantages are serious; in a systems analysis tool such as this time-in-view simulation, they are not of great con sequence. I have devoted the first five sections of this paper to a description of the development of the vector-matrix model underlying the simulation. The sixth section describes the mechanization of the model using an electronic analog computer. The equations from which the computer potentiometer settings are derived are quite tedious to manipulate man ually—even aided by a desk calculator. In an appendix, I describe the simple digital computer (in my case, a RE- COMP II) program used to obtain the desired potentiom eter settings. It strikes me that, while lack of simultaneity in the usage of the analog and digital machines precludes the use of the word hybrid, we may validly coin the expression "syner getic computing" to describe this simulation.

scholarly journals Earth Ice Age Dynamics: A Bimodal Forcing Hypothesis

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhongping Lai ◽  
Yantian Xu ◽  
Peisong Zheng
Keyword(s):  
Southern Hemisphere ◽  
Ice Age ◽  
High Latitudes ◽  
Ice Ages ◽  
Age Dynamics ◽  
Leading Role ◽  
The Earth ◽  
Northern High Latitude ◽  
Orbit Geometry ◽  
The Tropics

The Earth has gone through multiple ice ages in the past million years. Understanding the ice age dynamics is crucial to paleoclimatic study, and is helpful for addressing future climate challenges. Though ice ages are paced by variations in Earth’s orbit geometry, how various climatic system components on the Earth respond to insolation forcing and interact with each other remains unclear. A prevailing view argues that the initial responses occur in the northern high latitudes (i.e. the northern high-latitude hypothesis, NHH). This opinion is challenged by recent reports, such as the lead of climate change in the Southern Hemisphere (SH) relative to that in the Northern Hemisphere (NH), the southern control on Atlantic meridional overturning circulations (AMOC), and the potential significance of Southern Hemisphere (SH). Alternatively, the tropical hypothesis (TH) argues for a leading role of the tropics. Both the NHH and the TH belong to a single-forcing mechanism, and have difficulty in interpreting phenomena, such as the saw-tooth pattern of the ice ages. Here we present a new proposal concerning the Earth’s ice age dynamics: the bimodal forcing hypothesis (BFH). The essential assumption of this hypothesis is that for glacial-interglacial cycles, the cooling (glaciation) starts from the northern high latitudes, whereas the warming (deglaciations) starts from the SH. Particularly, the BFH emphasizes the significance of SH oceans in accumulating and transferring heat for deglaciations. Thus, it is capable to reasonably explain the saw-tooth pattern. We compiled 100 paleotemperature records globally for validation. The BFH is consistent with most of these records, and provides a straightforward and comprehensible way to interpret ice age on Earth.

scholarly journals IW Sentinel-1 satellite scenes for the investigation of mine slope stability: experiences from the Riacho dos Machados gold mine (Brazil)

2021 ◽  
Vol 25 (1) ◽  
pp. 93-99
Author(s):  
Marcos Eduardo Hartwig ◽  
Leandro Ribes De Lima ◽  
Daniele Perissin
Keyword(s):  
Open Pit ◽  
Southeastern Brazil ◽  
Gold Mine ◽  
Persistent Scatterer Interferometry ◽  
Surface Displacements ◽  
Persistent Scatterer ◽  
Minas Gerais State ◽  
Mine Slope ◽  
Radar Satellite ◽  
Orbit Geometry

In the last decade, the Persistent Scatterer Interferometry – PSI have been largely employed to predict instabilities and failure in open pit mines. The PSI is a powerful technique, which combines radar satellite data in order to detect and monitor tiny surface displacements over vast areas. In the last years, the Sentinel-1 radar mission have produced images of the globe acquired with different spatial and temporal resolutions that are now freely available. In recent years, the footwall slopes of the Riacho dos Machados Gold Mine – MRDM (Minas Gerais state, southeastern Brazil) have recorded large planar failures controlled by foliation planes. Therefore, the focus of this paper is to evaluate a stack of 39 Interferometric Wide Sentinel-1 scenes, spanning from January 2018 to April 2019, acquired in descending orbit geometry, for the detection and monitoring of surface displacements in the MRDM. The results have shown that descending IW Sentinel-1 scenes can be used to provide a broad picture of the Line-Of-Sight - LOS deformation phenomena. In order to monitor the evolution of the deformation phenomena induced by mining activities, LOS deformation maps with millimeter accuracy could be only delivered at least each 12 days.

scholarly journals GPS, GLONASS, and Galileo orbit geometry variations caused by general relativity focusing on Galileo in eccentric orbits

GPS Solutions ◽  
2021 ◽  
Vol 26 (1) ◽  
Author(s):  
Krzysztof Sośnica ◽  
Grzegorz Bury ◽  
Radosław Zajdel ◽  
Javier Ventura-Traveset ◽  
Luis Mendes
Keyword(s):  
General Relativity ◽  
Semimajor Axis ◽  
Satellite Orbit ◽  
Earth Satellite ◽  
Satellite Orbits ◽  
De Sitter ◽  
Size And Shape ◽  
Eccentric Orbits ◽  
Spacetime Curvature ◽  
Orbit Geometry

AbstractThree main effects from general relativity (GR) may change the geometry and orientation of artificial earth satellite orbits, i.e., the Schwarzschild, Lense–Thirring, and De Sitter effects. So far, the verification of GR effects was mainly based on the observations of changes in the orientation of satellite orbital planes. We directly observe changes of the satellite orbit geometry caused by GR represented by the semimajor axis and eccentricity. We measure the variations of orbit size and shape of GPS, GLONASS, and Galileo satellites in circular and eccentric orbits and compare the results to the theoretical effects using three years of real GNSS data. We derive a solution that assumes the GR to be true, and a second solution, in which the post-Newtonian parameters are estimated, thus, allowing satellites to find their best spacetime curvature. For eccentric Galileo, GR changes the orbital shape and size in perigee in such a way that the orbit becomes smaller but more circular. In the apogee, the semimajor axis decreases but eccentricity increases, and thus, the orbit becomes more eccentric. Hence, the orbital size variabilities for eccentric orbits are greatly compensated by the orbital shape changes, and thus the total effect of satellite height change is much smaller than the effects for the size and shape of the orbit, individually. The mean semimajor axis offset based on all GPS, GLONASS, and Galileo satellites is − 17.41 ± 2.90 mm, which gives a relative error of 0.36% with respect to the theoretical value.

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