scholarly journals I. On a simple mode of eliminating errors of adjustment in delicate observations of compared spectra

1881 ◽  
Vol 31 (206-211) ◽  
pp. 470-473
Keyword(s):  
Radial Component ◽  
Simple Mode ◽  
The Earth ◽  
Different Sources

When the identity or difference of position of two lines, bright or dark, in the spectra of two lights from different sources has to be compared with the utmost degree of accuracy, they are admitted simultaneously into different but adjacent parts of the slit of a spectroscope and viewed together. It was thus, for instance, that Dr. Huggins proceeded in determining the radial component of the velocity of the heavenly bodies relatively to the earth. It is requisite that the two lights that are to be compared should fall in a perfectly similar manner on the s lit: and it will be seen, from a perusal of his paper, how careful Dr. Huggins was in this respect.

scholarly journals Sequential modelling of the Earth’s core magnetic field

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Guillaume Ropp ◽  
Vincent Lesur ◽  
Julien Baerenzung ◽  
Matthias Holschneider
Keyword(s):  
Magnetic Field ◽  
Prior Information ◽  
Spatial Scales ◽  
Model Parameters ◽  
International Geomagnetic Reference Field ◽  
The Earth ◽  
Temporal And Spatial ◽  
Different Sources ◽  
Original Approach ◽  
Modelling Approach

Abstract We describe a new, original approach to the modelling of the Earth’s magnetic field. The overall objective of this study is to reliably render fast variations of the core field and its secular variation. This method combines a sequential modelling approach, a Kalman filter, and a correlation-based modelling step. Sources that most significantly contribute to the field measured at the surface of the Earth are modelled. Their separation is based on strong prior information on their spatial and temporal behaviours. We obtain a time series of model distributions which display behaviours similar to those of recent models based on more classic approaches, particularly at large temporal and spatial scales. Interesting new features and periodicities are visible in our models at smaller time and spatial scales. An important aspect of our method is to yield reliable error bars for all model parameters. These errors, however, are only as reliable as the description of the different sources and the prior information used are realistic. Finally, we used a slightly different version of our method to produce candidate models for the thirteenth edition of the International Geomagnetic Reference Field.

Future Gravity Mission Concepts for Sustained Observation of Mass Transport in the Earth System

2021 ◽  
Author(s):  
Roland Pail
Keyword(s):  
Mass Transport ◽  
Closed Loop ◽  
Cold Atom ◽  
Radial Component ◽  
Transport Processes ◽  
Single Pair ◽  
Earth System ◽  
Next Generation ◽  
The Earth ◽  
Gravity Mission

<p>Next Generation Gravity Missions are expected to enhance our knowledge of mass transport processes in the Earth system, establishing their products applicable to new scientific fields and serving societal needs. Compared to the current situation (GRACE Follow-On), a significant step forward to increase spatial and temporal resolution can only be achieved by new mission concepts, complemented by improved instrumentation and tailored processing strategies.</p><p>In extensive numerical closed-loop mission simulations studies, different mission concepts have been studied in detail, with emphasis on orbit design and resulting spatial-temporal ground track pattern, enhances processing and parameterization strategies, and improved post-processing/filtering strategies. Promising candidates for a next-generation gravity mission are double-pair and multi-pair constellations of GRACE/GRACE-FO-type satellites, as they are currently jointly studied by ESA and NASA. An alternative concept is high-precision ranging between high- and low-flying satellites. Since such a constellation observes mainly the radial component of gravity-induced orbit perturbations, the error structure is close to isotropic, which significantly reduces artefacts of along-track ranging formations. This high-low concept was proposed as ESA Earth Explorer 10 mission MOBILE and is currently further studies under the name MARVEL by the French space agency. Additionally, we evaluate the potential of a hybridization of electro-static and cold-atom accelerometers in order to improve the accelerometer performance in the low-frequency range.</p><p>In this contribution, based on full-fledged numerical closed-loop simulations with realistic error assumptions regarding their key payload, different mission constellations (in-line single-pair, Bender double-pair, multi-pairs, precise high-low tracking) are assessed and compared. Their overall performance, dealiasing potential, and recovery performance of short-periodic gravity signals are analyzed, in view of their capabilities to retrieve gravity field information with short latencies to be used for societally relevant service applications, such as water management, groundwater monitoring, and forecasting of droughts and floods.</p>

scholarly journals Athanasius Kircher and Terrestrial Magnetism: The Magnetic Map

2020 ◽  
Vol 7 (2) ◽  
pp. 166-184
Author(s):  
Agustín Udías, S.J.
Keyword(s):  
Magnetic Field ◽  
Terrestrial Magnetism ◽  
The Earth ◽  
Magnetic Declination ◽  
Athanasius Kircher ◽  
Different Sources ◽  
The Magnetic Field

Athanasius Kircher paid special attention to magnetism, more specifically terrestrial one, in his work Magnes sive de arte magnetica. Other Jesuits of his time, such as Garzoni and Cabeo, also wrote on this subject. Kircher studied in particular magnetic declination and its possible use to determine geographical longitudes. At his time, this was an important subject for long sea journeys. First, he collected a large number of observations of magnetic declination from different sources in three tables and two lists with a total of 518 values, among them forty-three made by Jesuits. Kircher proposed that a magnetic map could be made based on these observations, but he did not do it. From Kircher’s observations a map of magnetic declination has been drawn and it is presented here. Kircher discussed the causes of declination and presented a model for the origin of the magnetic field of the Earth, which differed from that proposed by Gilbert. Kircher finally considered magnetism as a cosmic force with its origin in God.

scholarly journals Keplerian consequences of an impact on an asteroid and their relevance for a deflection demonstration mission

2006 ◽  
Vol 2 (S236) ◽  
pp. 417-426 ◽  
Author(s):  
Andreas Rathke ◽  
Dario Izzo
Keyword(s):  
Measurement Accuracy ◽  
Radial Component ◽  
Line Of Sight ◽  
Optimal Planning ◽  
Short Term ◽  
Secular Changes ◽  
The Earth ◽  
Asteroid Deflection ◽  
New Formulation ◽  
Asteroid Orbit

AbstractWe investigate upon the change of an asteroid orbit caused by an impact. We find that, given the assumption of two dimensional motion, the asteroid displacement may be described by an analytic and explicit expression that is the vectorial sum of a radial component and a component along the asteroid velocity. The new formulation bridges the gap between the study of short-term effects, using numerical methods and the analytic study of secular changes of the asteroid orbit. The relation of the method to the established formulations is described and the known results are derived as limiting cases.The application of the new method for the performance evaluation of an asteroid deflection demonstration mission is illustrated. In such a mission the measurement of the change of the asteroid orbit by an impact will be conducted by radio-ranging to a spacecraft orbiting the deflected asteroid. Hence the measurement will primarily be sensitive to the deflection projected onto the Earth-asteroid line of sight. We discuss how the new formulation of the deflection can conveniently be employed for the estimation of the measurement accuracy and the optimal planning of a deflection demonstration mission.

scholarly journals Sequential modelling of the Earth's core magnetic field

2020 ◽  
Author(s):  
Guillaume Ropp ◽  
Vincent Lesur ◽  
Julien Baerenzung ◽  
Matthias Holschneider
Keyword(s):  
Magnetic Field ◽  
Prior Information ◽  
Spatial Scales ◽  
Model Parameters ◽  
The Core ◽  
The Earth ◽  
Temporal And Spatial ◽  
Different Sources ◽  
Original Approach ◽  
Modelling Approach

Abstract We describe a new, original approach to the modelling of the Earth's magnetic field. The overall objective of this study is to reliably render fast variations of the core field and its secular variation. This method combines a sequential modelling approach, a Kalman filter, and a correlation based modelling step. All sources that most significantly contribute to the field measured at the surface of the Earth are modelled. Their separation is based on strong prior information on their spatial and temporal behaviours. We obtain a time series of model distributions which display behaviours similar to those of recent models based on more classic approaches, particularly at large temporal and spatial scales. Interesting new features and periodicities are visible in our models at smaller time and spatial scales. An important aspect of our method is to yield reliable error bars for all model parameters. These errors, however, are only as reliable as the description of the different sources and the prior information used are realistic. Finally, we used a slightly different version of our method to produce candidate models for the IGRF-13.

scholarly journals Tomography of the Solar Wind using Interplanetary Scintillation

2000 ◽  
Vol 179 ◽  
pp. 445-446 ◽  
Author(s):  
Divya Oberoi ◽  
A. Pramesh Rao
Keyword(s):  
Solar Wind ◽  
Solar Surface ◽  
Line Of Sight ◽  
Weighted Sum ◽  
The Sun ◽  
Interplanetary Scintillation ◽  
The Earth ◽  
Compact Radio Source ◽  
Different Sources ◽  
Inner Heliosphere

Extended AbstractInterplanetary scintillation (IPS) measurements are sensitive to a weighted sum of the properties of solar wind (SW) along the line-of-sight (los) to a distant compact radio source. Mapping alosback to the surface of the Sun provides information of the sites of origin of the SW sampled by thelos. By observing different sources, lines-of-sight can be so chosen that they sample overlapping regions of Solar surface. In addition, the rotation of the Sun causes the long lived features in the SW to co-rotate, much like the twirling skirt of a ballerina, presenting different perspective views to the Earth based observers. These properties raise the possibility that systematic IPS observations can be inverted to give the maps of density and the velocity of the SW in the inner heliosphere, using techniques similar to tomography.

ON THE FIELD DUE TO A VERTICAL LINE SOURCE OF CURRENT GROUNDED TO EARTH

Geophysics ◽  
1938 ◽  
Vol 3 (1) ◽  
pp. 58-62 ◽  
Author(s):  
Solomon Bilinsky
Keyword(s):  
Current Density ◽  
Line Source ◽  
Vertical Component ◽  
Radial Component ◽  
Vertical Line ◽  
Displacement Current ◽  
The Earth ◽  
Density Vector ◽  
Vertical Wire ◽  
A Current

An expression for the current density at any point in the earth due to a current in an infinitely long vertical wire is found for two types of current: (1) Simply periodic, (2) Rectangular impulse. These are given respectively by equations (11) and (13) below, where [Formula: see text] is the horizontal radial component and [Formula: see text] the vertical component of the current density vector at the point (r, z), which is at a distance R from the grounding point. These formulas hold for frequencies not too high or times not too small to allow neglect of the displacement current.

scholarly journals WILL IT BE POSSIBLE TO MEASURE INTRINSIC GRAVITOMAGNETISM WITH LUNAR LASER RANGING?

2009 ◽  
Vol 18 (08) ◽  
pp. 1319-1326 ◽  
Author(s):  
LORENZO IORIO
Keyword(s):  
Orbital Motion ◽  
Radial Component ◽  
Laser Ranging ◽  
The Moon ◽  
Lunar Laser Ranging ◽  
The Earth ◽  
Gravitomagnetic Field ◽  
Lunar Laser ◽  
Short Period ◽  
Orbital Revolution

In this paper we mainly explore the possibility of measuring the action of the intrinsic gravitomagnetic field of the rotating Earth on the orbital motion of the Moon with the lunar laser ranging (LLR) technique. Expected improvements in it should push the precision in measuring the Earth–Moon range to the mm level; the present-day root mean square (RMS) accuracy in reconstructing the radial component of the lunar orbit is about 2 cm; its harmonic terms can be determined at the mm level. The current uncertainty in measuring the lunar precession rates is about 10-1 milliarcseconds per year. The Lense–Thirring secular — i.e. averaged over one orbital period — precessions of the node and the perigee of the Moon induced by the Earth's spin angular momentum amount to 10-3 milliarcseconds per year, yielding transverse and normal shifts of 10-1-10-2 cm yr-1. In the radial direction there is only a short-period — i.e. nonaveraged over one orbital revolution — oscillation with an amplitude of 10-5 m. Major limitations come also from some systematic errors induced by orbital perturbations of classical origin, such as the secular precessions induced by the Sun and the oblateness of the Moon, whose mismodeled parts are several times larger than the Lense–Thirring signal. The present analysis holds also for the Lue–Starkman perigee precession due to the multidimensional braneworld model by Dvali, Gabadadze and Porrati (DGP); indeed, it amounts to about 5 × 10-3 milliarcseconds per year.

scholarly journals Sequential modelling of the Earth's core magnetic field

2020 ◽  
Author(s):  
Guillaume Ropp ◽  
Vincent Lesur ◽  
Julien Baerenzung ◽  
Matthias Holschneider
Keyword(s):  
Magnetic Field ◽  
Prior Information ◽  
Spatial Scales ◽  
Model Parameters ◽  
The Core ◽  
The Earth ◽  
Temporal And Spatial ◽  
Different Sources ◽  
Original Approach ◽  
Modelling Approach

Abstract We describe a new, original approach to the modelling of the Earth's magnetic field. The overall objective of this study is to reliably render fast variations of the core field and its secular variation. This method combines a sequential modelling approach, a Kalman filter, and a correlation based modelling step. All sources that most significantly contribute to the field measured at the surface of the Earth are modelled. Their separation is based on strong prior information on their spatial and temporal behaviours. We obtain a time series of model distributions which display behaviours similar to those of recent models based on more classic approaches, particularly at large temporal and spatial scales. Interesting new features and periodicities are visible in our models at smaller time and spatial scales. An important aspect of our method is to yield reliable error bars for all model parameters. These errors, however, are only as reliable as the description of the different sources and the prior information used are realistic. Finally, we used a slightly different version of our method to produce candidate models for the IGRF-13.

scholarly journals POSSIBILITIES OF LAND ADMINISTRATION DOMAIN MODEL (LADM) IMPLEMENTATION IN NIGERIA

2015 ◽  
Vol II-2/W2 ◽  
pp. 155-163 ◽  
Author(s):  
S. O. Babalola ◽  
A. Abdul Rahman ◽  
L. T. Choon ◽  
P. J. M. Van Oosterom
Keyword(s):  
Domain Model ◽  
Management Information ◽  
Colonial Era ◽  
Essential Information ◽  
Administration System ◽  
Post Colonial ◽  
Land Administration ◽  
The Earth ◽  
Cadastral System ◽  
Different Sources

LADM covers essential information associated components of land administration and management including those over water and elements above and below the surface of the earth. LADM standard provides an abstract conceptual model with three packages and one sub-package. LADM defined terminology for a land administration system that allows a shared explanation of different formal customary or informal tenures. The standard provides the basis for national and regional profiles and enables the combination of land management information from different sources in a coherent manner. Given this, this paper started with the description of land and land administration in Nigeria. The pre-colonial, colonial and post-colonial era with organization structure was discussed. This discussion is important to present an understanding of the background of any improvement needed for the LADM implementation in Nigeria. The LADM, ISO 19152 and the packages of LADM was discussed, and the comparison of the different aspects of each package and classes were made with Nigerian land administration and the cadastral system. In the comparison made, it was discovered that the concept is similar to LADM packages in Nigerian land administration. Although, the terminology may not be the same in all cases. Having studied conceptualization and the application of LADM, as a model that has essential information associated with components of the land administration. Including those on the land, over water as well as elements above and below the surface of the earth and discovered that the standard is suitable for the country. The model can, therefore, be adopted into Nigerian land administration system by mapping in some of the concepts of LADM.

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