SEARCH · Search NASA

Results for “Earth Orientation space-geodetic”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

35 records · Page 2

All sources NASA NTRS DOE OSTI

NASA NTRS2004

Combinations of Earth Orientation Measurements: SPACE2003, COMB2003, and POLE2003

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the global positioning system have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2003, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28.0, 1976 to January 31.0, 2004 at daily intervals and is available in versions whose epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2003 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2003, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20.0, 1962 to January 31.0, 2004 at daily intervals and which is also available in versions whose epochs are given at either midnight or noon, and (2) POLE2003, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900 to January 21,2004 at 30.4375-day intervals.

Gross, Richard S.↗

NASA NTRS2005

Combinations of Earth Orientation Measurements: SPACE2004, COMB2004, and POLE2004

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the global positioning system have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2004, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to January 22, 2005, at daily intervals and is available in versions whose epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2004 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2004, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to January 22, 2005, at daily intervals and which is also available in versions whose epochs are given at either midnight or noon, and (2) POLE2004, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to January 20, 2005, at 30.4375-day intervals.

Gross, Richard R.↗

NASA NTRS2004

Combinations of Earth orientation measurements : SPACE2003, COMB2003, and POLE2003

Gross, Richard↗

NASA NTRS2009

Combinations of Earth orientation measurements : SPACE2007, COMB2007, and POLE2007.

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2007, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to March 29, 2008, at daily intervals and is available in versions whose epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2007 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2007, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to March 29, 2008, at daily intervals and which is also available in versions whose epochs are given at either midnight or noon; and (2) POLE2007, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to March 22, 2008, at 30.4375-day intervals.

Gross, R. S.↗

NASA NTRS2010

Combinations of Earth orientation measurements : SPACE2008, COMB2008, and POLE2008

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2008, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to July 2, 2009, at daily intervals and is available in versions whose with epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2008 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2008, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to July 2, 2009, at daily intervals and which areis also available in versions whose with epochs are given at either midnight or noon; and (2) POLE2008, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 22, 2009, at 30.4375-day intervals..

Gross, R. S.↗

NASA NTRS2006

Combinations of Earth Orientation Measurements: SPACE2005, COMB2005, and POLE2005

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, by very long baseline interferometry, and by the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2005, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to January 7, 2006, at daily intervals and is available in versions whose epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2005 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2005, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to January 7, 2006, at daily intervals and which is also available in versions whose epochs are given at either midnight or noon; and (2) POLE2005, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to December 21, 2005, at 30.4375-day intervals.

laser ranging↗

NASA NTRS1996

Combinations of EOP Measurements: COMB95 and POLE95

A Kalman filter has been used to combine independent measurements of the Earth's orientation taken by optical astrometry and the space-geodetic techniques of LLR, SLR, VLBI, and GPS.

Kalman filter Kalman Earth's orientation LLR SLR V↗

NASA NTRS1998

Combinations of EOP Measurements: COMB97 & POLE97

A Kalman filter has been used to combine independent measurements of the Earth's orientation taken by optical astrometry and the space-geodetic techniques of LLR, SLR, VLBI, and GPS.

EOP measurements Kalman filter Earth orientation E↗

NASA NTRS2005

Combinations of Earth orientation measurements: SPACE2004, COMB2004, and POLE2004

Gross, Richard S.↗

NASA NTRS1996

Combinations of Earth Orientation Measurements: SPACE94, COMB94, and POLE94

A Kalman filter has been used to combine independent measurements of the Earth's orientation taken by the space-geodetic observing techniques of lunar laser ranging, satellite laser ranging, very long baseline interferometry, and the Global Positioning System. Prior to their combination, the data series were adjusted to have the same bias and rate, the stated uncertainties of the measurements were adjusted, and data points considered to be outliers were deleted. The resulting combination, SPACE94, consists of smoothed, interpolated polar motion and UT1-UTC values spanning October 6.0, 1976, to January 27.0, 1995, at 1-day intervals.

Kalman↗

NASA NTRS1995

Combinations of Earth Orientation Observations: SPACE94, COMB94, and POLE94

A Kalman filter has been used to combine all publicly available, independently determined measurements of the Earth's orientation taken by the modern, space-geodetic techniques of very long baseline interferometry, satellite laser ranging, lunar laser ranging, and the global positioning system. Prior to combining the data, tidal terms were removed from the UT1 measurements, outlying data points were deleted, series-specific corrections were applied for bias and rate, and the stated uncertainties of the measurements were adjusted by multiplying them by series-specific scale factors. Values for these bias- rate corrections and uncertainty scale factors were determined by an iterative, round-robin procedure wherein each data set is compared, in turn, to a combination of all other data sets. When applied to the measurements, the bias-rate corrections thus determined make the data sets agree with each other in bias and rate, and the uncertainty scale factors thus determined make the residual of each series (when differenced with a combination of all others) have a reduced chi-square of one. The corrected and adjusted series are then placed within an IERS reference frame by aligning them with the IERS Earth orientation series EOP (IERS)90C04. The result of combining these corrected, adjusted and aligned series is designated SPCE94 and spans October 6.0, 1976 to January 27.0, 1995 at daily intervals.

SPACE94 COMB94↗

NASA NTRS1994

A Combination of Earth Orientation Data: SPACE93

A combination of independently-determined Earth orientation data has been generated from space-geodetic observations spanning 1976-1993. The approach taken is based upon a Kalman filter that was developed at the Jet Propulsion Laboratory (JPL) for just such a purpose.

lunar laser ranging↗

NASA NTRS1997

Combinations of EOP Measurements: COMB96 & POLE 96

A Kalman filter has been used to combined independent measurements of the Earth's orientation taken by optical astrometry and the space-geodetic techniques of LLR, SLR, VLBI, and GPS.

EOP COMB96 POLE96 Kalman Filter↗

NASA NTRS2012

VLBI: A Fascinating Technique for Geodesy and Astrometry

Since the 1970s Very Long Baseline Interferometry (VLBI) has proven to be a primary space-geodetic technique by determining precise coordinates on the Earth, by monitoring the variable Earth rotation and orientation with highest precision, and by deriving many other parameters of the Earth system. VLBI provides an important linkage to astronomy through, for instance, the determination of very precise coordinates of extragalactic radio sources. Additionally, it contributes to determining parameters of relativistic and cosmological models. After a short review of the history of geodetic VLBI and a summary of recent results, this paper describes future perspectives of this fascinating technique. The International VLBI Service for Geodesy and Astrometry (IVS), as a service of the International Association of Geodesy (IAG) and the International Astronomical Union (IAU), is well on its way to fully defining a next generation VLBI system, called VLBI2010. The goals of the new system are to achieve on scales up to the size of the Earth an accuracy of 1 mm in position and of 0.1 mm/year in velocity. Continuous observations shall be carried out 24 h per day 7 days per week in the future with initial results to be delivered within 24 h after taking the data. Special sessions, e.g. for monitoring the Earth rotation parameters, will provide the results in near real-time. These goals require a completely new technical and conceptual design of VLBI measurements. Based on extensive simulation studies, strategies have been developed by the IVS to significantly improve its product accuracy through the use of a network of small (approx 12 m) fast-slewing antennas. A new method for generating high precision delay measurements as well as improved methods for handling biases related to radio source structure, system electronics, and deformations of the antenna structures has been developed. Furthermore, as of January 2012, the construction of ten new VLBI2010 sites has been funded, with good prospects for one dozen more antennas, which will improve the geographical distribution of geodetic VLBI sites on Earth and provide an important step toward a global VLBI2010 network. Within this paper, the Global Geodetic Observing System (GGOS) of the IAG will also be introduced and the contribution of VLBI to GGOS will be described.

Geodesy↗

NASA NTRS2005

Multi-reference evaluation of uncertainty in earth orientation parameter measurements

Uncertainties in polar motion and length-of-day measurements are evaluated empirically using several data series from the space-geodetic techniques of the global positioning system (GPS), satellite laser ranging (SLR), and very long baseline interferometry (VLBI) during 1997-2002. In the evaluation procedure employed here, known as the three-corner hat (TCH) technique, the signal common to each series is eliminated by forming pair-wise differences between the series, thus requiring no assumed values for the 'truth' signal. From the variances of the differenced series, the uncertainty of each series can be recovered when reasonable assumptions are made about the correlations between the series. In order to form the pair-wise differences, the series data must be given at the same epoch. All measurement data sets studied here were sampled at noon (UTC); except for the VLBI series, whose data are interpolated to noon and whose UT1 values are also numerically differentiated to obtain LOD. The numerical error introduced to the VLBI values by the interpolation and differentiation is shown to be comparable in magnitude to the values determined by the TCH method for the uncertainties of the VLBI series. The TCH estimates for the VLBI series are corrupted by such numerical errors mostly as a result of the relatively large data intervals. Of the remaining data sets studied here, it is found that the IGS Final combined series has the smallest polar motion and length-of-day uncertainties.

Combination↗

NASA NTRS2004

On Physical Interpretation of the In-Site Measurement of Earth Rotation by Ring Laser Gyrometers

Large ring laser gyrometers under development have demonstrated the capability of detecting minute ground motions and deformations on a wide range of timescales. The next challenge and goal is to measure the Earth's rotation variations to a precision that rivals that of the present space-geodesy techniques, thus providing an in-situ (and cost effective alternatives of Earth rotation measurement for geophysical research and geodetic applications. Aside from thermal and mechanical instabilities, "undesirable" ground motion and tilt that appear in the signal will need to be removed before any variation in Earth rotation can be detected. Removal of these signals, some of them are larger than the sought rotation signals, has been a typical procedure in many precise geophysical instruments, such as gravimeters, seismometers, and tiltmeters. The remaining Earth rotation signal resides in both the spin around the axis and in the orientation of the axis. In the case of the latter, the in-situ measurement is complementary to the space-geodetic observables in terms of polar motion and nutation, a fact to be exploited.

Chao, B. F.↗

NASA NTRS1986

Plate motions and deformations from geologic and geodetic data

Research effort on behalf of the Crustal Dynamics Project focused on the development of methodologies suitable for the analysis of space-geodetic data sets for the estimation of crustal motions, in conjunction with results derived from land-based geodetic data, neo-tectonic studies, and other geophysical data. These methodologies were used to provide estimates of both global plate motions and intraplate deformation in the western U.S. Results from the satellite ranging experiment for the rate of change of the baseline length between San Diego and Quincy, California indicated that relative motion between the North American and Pacific plates over the course of the observing period during 1972 to 1982 were consistent with estimates calculated from geologic data averaged over the past few million years. This result, when combined with other kinematic constraints on western U.S. deformation derived from land-based geodesy, neo-tectonic studies, and other geophysical data, places limits on the possible extension of the Basin and Range province, and implies significant deformation is occurring west of the San Andreas fault. A new methodology was developed to analyze vector-position space-geodetic data to provide estimates of relative vector motions of the observing sites. The algorithm is suitable for the reduction of large, inhomogeneous data sets, and takes into account the full position covariances, errors due to poorly resolved Earth orientation parameters and vertical positions, and reduces baises due to inhomogeneous sampling of the data. This methodology was applied to the problem of estimating the rate-scaling parameter of a global plate tectonic model using satellite laser ranging observations over a five-year interval. The results indicate that the mean rate of global plate motions for that interval are consistent with those averaged over several million years, and are not consistent with quiescent or greatly accelerated plate motions. This methodology was also used to provide constraints on deformation in the western U.S. using very long baseline interferometry observations over a two-year period.

Jordan, T. H.↗