Practical Realization of a Reference System for Earth Dynamics by Satellite Methods

1975 ◽  
Vol 26 ◽  
pp. 341-380 ◽  
Author(s):  
R. J. Anderle ◽  
M. C. Tanenbaum
Keyword(s):  
Reference Frame ◽  
Polar Motion ◽  
Pole Position ◽  
Control Points ◽  
Significant Information ◽  
Crustal Motion ◽  
Average Reference ◽  
Future Data ◽  
Existing Data

AbstractObservations of artificial earth satellites provide a means of establishing an.origin, orientation, scale and control points for a coordinate system. Neither existing data nor future data are likely to provide significant information on the .001 angle between the axis of angular momentum and axis of rotation. Existing data have provided data to about .01 accuracy on the pole position and to possibly a meter on the origin of the system and for control points. The longitude origin is essentially arbitrary. While these accuracies permit acquisition of useful data on tides and polar motion through dynamio analyses, they are inadequate for determination of crustal motion or significant improvement in polar motion. The limitations arise from gravity, drag and radiation forces on the satellites as well as from instrument errors. Improvements in laser equipment and the launch of the dense LAGEOS satellite in an orbit high enough to suppress significant gravity and drag errors will permit determination of crustal motion and more accurate, higher frequency, polar motion. However, the reference frame for the results is likely to be an average reference frame defined by the observing stations, resulting in significant corrections to be determined for effects of changes in station configuration and data losses.

scholarly journals Observing UT1-UTC with VGOS

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Rüdiger Haas ◽  
Eskil Varenius ◽  
Saho Matsumoto ◽  
Matthias Schartner
Keyword(s):  
Standard Deviation ◽  
Reference Frame ◽  
Earth Rotation ◽  
Space Observatory ◽  
International Earth Rotation ◽  
Onsala Space Observatory ◽  
X Band ◽  
First Results

AbstractWe present first results for the determination of UT1-UTC using the VLBI Global Observing System (VGOS). During December 2019 through February 2020, a series of 1 h long observing sessions were performed using the VGOS stations at Ishioka in Japan and the Onsala twin telescopes in Sweden. These VGOS-B sessions were observed simultaneously to standard legacy S/X-band Intensive sessions. The VGOS-B data were correlated, post-correlation processed, and analysed at the Onsala Space Observatory. The derived UT1-UTC results were compared to corresponding results from standard legacy S/X-band Intensive sessions (INT1/INT2), as well as to the final values of the International Earth Rotation and Reference Frame Service (IERS), provided in IERS Bulletin B. The VGOS-B series achieves 3–4 times lower formal uncertainties for the UT1-UTC results than standard legacy S/X-band INT series. The RMS agreement w.r.t. to IERS Bulletin B is slightly better for the VGOS-B results than for the simultaneously observed legacy S/X-band INT1 results, and the VGOS-B results have a small bias only with the smallest remaining standard deviation.

scholarly journals Evaluation of hydrological and cryospheric angular momentum estimates based on GRACE, GRACE-FO and SLR data for their contributions to polar motion excitation

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Justyna Śliwińska ◽  
Jolanta Nastula ◽  
Małgorzata Wińska
Keyword(s):  
Angular Momentum ◽  
Spherical Harmonic ◽  
Polar Motion ◽  
Spectral Band ◽  
Water Storage ◽  
Terrestrial Water Storage ◽  
Terrestrial Water ◽  
High Consistency ◽  
Polar Motion Excitation

AbstractIn geodesy, a key application of data from the Gravity Recovery and Climate Experiment (GRACE), GRACE Follow-On (GRACE-FO), and Satellite Laser Ranging (SLR) is an interpretation of changes in polar motion excitation due to variations in the Earth’s surficial fluids, especially in the continental water, snow, and ice. Such impacts are usually examined by computing hydrological and cryospheric polar motion excitation (hydrological and cryospheric angular momentum, HAM/CAM). Three types of GRACE and GRACE-FO data can be used to determine HAM/CAM, namely degree-2 order-1 spherical harmonic coefficients of geopotential, gridded terrestrial water storage anomalies computed from spherical harmonic coefficients, and terrestrial water storage anomalies obtained from mascon solutions. This study compares HAM/CAM computed from these three kinds of gravimetric data. A comparison of GRACE-based excitation series with HAM/CAM obtained from SLR is also provided. A validation of different HAM/CAM estimates is conducted here using the so-called geodetic residual time series (GAO), which describes the hydrological and cryospheric signal in the observed polar motion excitation. Our analysis of GRACE mission data indicates that the use of mascon solutions provides higher consistency between HAM/CAM and GAO than the use of other datasets, especially in the seasonal spectral band. These conclusions are confirmed by the results obtained for data from first 2 years of GRACE-FO. Overall, after 2 years from the start of GRACE-FO, the high consistency between HAM/CAM and GAO that was achieved during the best GRACE period has not yet been repeated. However, it should be remembered that with the systematic appearance of subsequent GRACE-FO observations, this quality can be expected to increase. SLR data can be used for determination of HAM/CAM to fill the one-year-long data gap between the end of GRACE and the start of the GRACE-FO mission. In addition, SLR series could be particularly useful in determination of HAM/CAM in the non-seasonal spectral band. Despite its low seasonal amplitudes, SLR-based HAM/CAM provides high phase consistency with GAO for annual and semiannual oscillation.

scholarly journals Delineating the Polarized and Unpolarized Parton Structure of the Nucleon

2015 ◽  
Vol 37 ◽  
pp. 1560053
Author(s):  
Pedro Jimenez-Delgado
Keyword(s):  
Parton Distribution ◽  
Distribution Functions ◽  
Distribution Analysis ◽  
Coupling Constant ◽  
Parton Distribution Functions ◽  
Careful Treatment ◽  
Future Data ◽  
The Impact

Reports on our latest extractions of parton distribution functions of the nucleon are given. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of the nucleon.

On the Inadequacy of existing Data for determining the Rate of Mortality among Select Lives

1854 ◽  
Vol 4 (1) ◽  
pp. 1-9
Author(s):  
William Spens
Keyword(s):  
First Year ◽  
Sufficient Data ◽  
Existing Data ◽  
Selection Of ◽  
The Way

I. While so much improvement has recently taken place in the arrangement and construction of various tables for facilitating calculations founded on existing data, very little has been done in the way of investigating and correcting the data themselves; and it is feared that the question of the rate of mortality among select lives is still involved in the greatest doubt and obscurity.II. It is not proposed in the present paper to go farther than to show that the rate of mortality, during the first year of selection, of select assured lives is so materially different from what it has hitherto been represented, as to lead to the inference that the data from which the erroneous deduction has been made cannot be true data for the ascertainment of the value of selection. To investigate the rate of mortality of select lives at separate ages, I conceive to be of the utmost importance for the elucidation of truth, and the proper direction of sanatory inquiries; but I do not consider that sufficient data at present exist for the determination of this, and these can only be obtained by a united inquiry. I shall be very happy if the present observations have any effect in hastening such an investigation, which sooner or later must be entered upon.

Dynamic Error Analysis of Measurement While Drilling Using Variable Geomagnetic In-Field Referencing

SPE Journal ◽  
2018 ◽  
Vol 23 (06) ◽  
pp. 2327-2338 ◽  
Author(s):  
Hojjat Kabirzadeh ◽  
Elena Rangelova ◽  
Gyoo Ho Lee ◽  
Jaehoon Jeong ◽  
Ik Woo ◽  
...  
Keyword(s):  
Reference Values ◽  
Dynamic Error ◽  
Directional Drilling ◽  
Average Reference ◽  
Marquardt Algorithm ◽  
Measurement While Drilling ◽  
The Difference ◽  
Dip Angle ◽  
Forward And Inverse Modeling

Summary The safe and economical determination of a wellbore trajectory in directional drilling is traditionally achieved by measurement-while-drilling (MWD) methods, which implement magnetic north-seeking sensor packages. Inaccuracies in the determination of well path arise because of random and systematic errors in the measurements of the sensors. Multistation analysis (MSA) and magnetic in-field referencing (IFR) have already demonstrated the potential to decrease the effects of errors because of magnetization of drillstring components along with variable errors caused by irregularities in the magnetization of crustal rocks in the vicinity of wells. Advanced MSA methodologies divide a borehole into several sections and use the average reference values of the total magnetic field, declination, and dip angle for analysis of errors in each section. Our investigations indicate that the variable-reference MSA (VR-MSA) can lead to a better determination of errors, specifically in areas of high magnetization. In this methodology, magnetic reference values are estimated at each station using forward and inverse modeling of surface-magnetic observations from IFR surveys. The fixed errors in magnetometer components are then calculated by minimizing the variance of the difference between the measured and unique estimated reference values at each station. A Levenberg-Marquardt algorithm (LMA) is adopted to solve the nonlinear optimization problem. Examination of this methodology using MWD data confirms more than 20% improvement in well-path-determination accuracy by comparing the results with the corrected path from the conventional MSA method and gyro surveys.

The Dynamics of Atmospherically Driven Intraseasonal Polar Motion

2008 ◽  
Vol 65 (7) ◽  
pp. 2290-2307 ◽  
Author(s):  
Steven B. Feldstein
Keyword(s):  
Excitation Function ◽  
Normal Mode ◽  
Polar Motion ◽  
Stationary Wave ◽  
Pole Position ◽  
Heat Fluxes ◽  
Synoptic Scale ◽  
Zonal Wavenumber ◽  
Polar Motion Excitation ◽  
Winter Hemisphere

Abstract The atmospheric dynamical processes that drive intraseasonal polar motion are examined with National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis data and with pole position data from the International Earth Rotation Service. The primary methodology involves the regression of different atmospheric variables against the polar motion excitation function. A power spectral analysis of the polar motion excitation function finds a statistically significant peak at 10 days. Correlation calculations show that this peak is associated with the 10-day, first antisymmetric, zonal wavenumber 1, normal mode of the atmosphere. A coherency calculation indicates that the atmospheric driving of polar motion is mostly confined to two frequency bands, with periods of 7.5–13 and 13–90 days. Regressions of surface pressure reveal that the 7.5–13-day band corresponds to the 10-day atmospheric normal mode and the 13–90-day band to a quasi-stationary wave. The regressions of pole position and the various torques indicate not only that the equatorial bulge torque dominates the mountain and friction torques but also that the driving by the equatorial bulge torque accounts for a substantial fraction of the intraseasonal polar motion. Furthermore, although the 10-day and quasi-stationary wave contributions to the equatorial bulge torque are similar, the response in the pole position is primarily due to the quasi-stationary wave. Additional calculations of regressed power spectra and meridional heat fluxes indicate that the atmospheric wave pattern that drives polar motion is itself excited by synoptic-scale eddies. Regressions of pole position with separate torques from either hemisphere show that most of the pole displacement arises from the equatorial bulge torque from the winter hemisphere. Together with the above findings on wave–wave interactions, these results suggest that synoptic-scale eddies in the winter hemisphere excite the quasi-stationary wave, which in turn drives the polar motion through the equatorial bulge torque.

scholarly journals Astrometric Programs by the New Hamburg Plate Measuring Machine

1994 ◽  
Vol 161 ◽  
pp. 173-176
Author(s):  
Chr. de Vegt ◽  
L. Winter ◽  
N. Zacharias
Keyword(s):  
Reference Frame ◽  
Northern Hemisphere ◽  
High Accuracy ◽  
Proper Motions ◽  
Sky Surveys ◽  
Unique Data ◽  
Large Sets ◽  
Measuring Machine ◽  
First Time

With the new Hamburg astrometric measuring machine, large sets of plates can be digitized very quickly with submicrometer accuracy. In particular about 2000 plates of the AGK2-catalog, mean epoch 1930, can be remeasured now for the first time to their limiting magnitude, about B = 11. The new AGK2-data therefore will cover practically the whole AC-catalog and TYCHO-stars in the northern hemisphere. All plates will be reduced using the HIPPARCOS results as the reference frame when available in 1996. The new AGK2-data will provide a unique data base for the determination of high accuracy proper motions (about 2 mas/yr) of all TYCHO stars in the northern hemisphere. Furthermore, for the first time a dense reference frame for a final reduction of the Astrographic Catalog (AC) and the large deep sky surveys will be generated by this catalog. The inferior situation in the southern hemisphere will be addressed briefly.

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