Where - A Software for geodetic Analysis

2020 ◽  
Author(s):  
Ingrid Fausk ◽  
Michael Dähnn ◽  
Ann-Silje Kirkvik
Keyword(s):  
Reference Frame ◽  
Software Package ◽  
Very Long Baseline Interferometry ◽  
Terrestrial Reference Frame ◽  
Test Phase ◽  
Laser Ranging ◽  
Operational Analysis ◽  
Long Baseline ◽  
Analysis Center ◽  
To Receive

<p><em>Where</em> is a software package developed by the Norwegian Mapping Authority (NMA). The software will provide a useful contribution to the International Terrestrial Reference Frame, by analysis of data from Very-long-baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR).</p><div><em>Where</em> is written in Python, and is taking advantage of well-tested code like the SOFA and IERS libraries. The architecture is easily maintainable and extendable. Python makes it easy to write, and utilizes external libraries written in faster languages.</div><div> </div><div>Both the NMA and the Instituto Geografico Nacional, Spain, are in a test phase of deliveries of VLBI analysis results to the IVS with the <em>Where</em> software. After some improvements of the software, we will also deliver analysis results to the ILRS. Our goal is to receive full status as operational analysis center for both VLBI and SLR, and to contribute to ITRF2020.</div><div> </div><div>Sharing and cooperating with other institutions is made possible by making <em>Where</em> an open source project on GitHub.</div>

scholarly journals Erratum to: Determination of a terrestrial reference frame via Kalman filtering of very long baseline interferometry data

2016 ◽  
Vol 90 (12) ◽  
pp. 1329-1329 ◽  
Author(s):  
Benedikt Soja ◽  
Tobias Nilsson ◽  
Kyriakos Balidakis ◽  
Susanne Glaser ◽  
Robert Heinkelmann ◽  
...  
Keyword(s):  
Reference Frame ◽  
Kalman Filtering ◽  
Very Long Baseline Interferometry ◽  
Terrestrial Reference Frame ◽  
Long Baseline

scholarly journals Geocentric Terrestrial Reference Frame Accuracy: DSN Spacecraft Tracking and VLBI/Lunar Laser Ranging

1988 ◽  
Vol 128 ◽  
pp. 115-120 ◽  
Author(s):  
A. E. Niell
Keyword(s):  
Reference Frame ◽  
Terrestrial Reference Frame ◽  
Spin Axis ◽  
Laser Ranging ◽  
Lunar Laser Ranging ◽  
Deep Space Network ◽  
Long Baseline ◽  
Lunar Laser ◽  
Spacecraft Tracking ◽  
Geocentric Coordinates

From a combination of 1) the location of McDonald Observatory from Lunar Laser Ranging, 2) relative station locations obtained from Very Long Baseline Interferometry (VLBI) measurements, and 3) a short tie by traditional geodesy, the geocentric coordinates of the 64 m antennas of the NASA/JPL Deep Space Network are obtained with an orientation which is related to the planetary ephemerides and to the celestial radio reference frame. Comparison with the geocentric positions of the same antennas obtained from tracking of interplanetary spacecraft shows that the two methods agree to 20 cm in distance off the spin axis and in relative longitude. The orientation difference of a 1 meter rotation about the spin axis is consistent with the error introduced into the tracking station locations due to an error in the ephemeris of Jupiter.

scholarly journals Determination of a terrestrial reference frame via Kalman filtering of very long baseline interferometry data

2016 ◽  
Vol 90 (12) ◽  
pp. 1311-1327 ◽  
Author(s):  
Benedikt Soja ◽  
Tobias Nilsson ◽  
Kyriakos Balidakis ◽  
Susanne Glaser ◽  
Robert Heinkelmann ◽  
...  
Keyword(s):  
Reference Frame ◽  
Kalman Filtering ◽  
Very Long Baseline Interferometry ◽  
Terrestrial Reference Frame ◽  
Long Baseline

scholarly journals Commision 19: Earth Rotation (Rotation de la Terre)

1991 ◽  
Vol 21 (1) ◽  
pp. 169-186
Keyword(s):  
Reference Frame ◽  
Earth Rotation ◽  
Very Long Baseline Interferometry ◽  
International Association ◽  
High Accuracy ◽  
Terrestrial Reference Frame ◽  
International Earth Rotation Service ◽  
Long Baseline ◽  
Compact Sources ◽  
Celestial Reference Frame

The period has been marked by the start of the new International Earth Rotation Service (IERS), which benefits from a tight cooperation between astronomers, geodesists, and specialists in satellite geodesy, as well as meteorologists. The scope of the IERS covers not only the Earth’s rotation per se, but also the conventional terrestrial reference frame, of direct interest to the International Association of Geodesy, and a high accuracy (0.001”) celestial reference frame based on extragalactic compact sources observed in Very Long Baseline Interferometry. The IERS conventional celestial reference frame is consistent with the FK5 within the uncertainties of the latter (0.04”). The IERS Standards (1989) which contain the current best estimates of astronomical models and constants are used in many fields of astronomy and geodesy.

The Contribution of LARES to Global Climate Change Studies With Geodetic Satellites

2015 ◽  
Author(s):  
Giampiero Sindoni ◽  
Claudio Paris ◽  
Cristian Vendittozzi ◽  
Erricos C. Pavlis ◽  
Ignazio Ciufolini ◽  
...  
Keyword(s):  
Reference Frame ◽  
Earth Science ◽  
Global Climate ◽  
Temporal Variations ◽  
Terrestrial Reference Frame ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Long Baseline ◽  
Geophysical Processes ◽  
Global Navigation Satellite

Satellite Laser Ranging (SLR) makes an important contribution to Earth science providing the most accurate measurement of the long-wavelength components of Earth’s gravity field, including their temporal variations. Furthermore, SLR data along with those from the other three geometric space techniques, Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS) and DORIS, generate and maintain the International Terrestrial Reference Frame (ITRF) that is used as a reference by all Earth Observing systems and beyond. As a result we obtain accurate station positions and linear velocities, a manifestation of tectonic plate movements important in earthquake studies and in geophysics in general. The “geodetic” satellites used in SLR are passive spheres characterized by very high density, with little else than gravity perturbing their orbits. As a result they define a very stable reference frame, defining primarily and uniquely the origin of the ITRF, and in equal shares, its scale. The ITRF is indeed used as “the” standard to which we can compare regional, GNSS-derived and alternate frames. The melting of global icecaps, ocean and atmospheric circulation, sea-level change, hydrological and internal Earth-mass redistribution are nowadays monitored using satellites. The observations and products of these missions are geolocated and referenced using the ITRF. This allows scientists to splice together records from various missions sometimes several years apart, to generate useful records for monitoring geophysical processes over several decades. The exchange of angular momentum between the atmosphere and solid Earth for example is measured and can be exploited for monitoring global change. LARES, an Italian Space Agency (ASI) satellite, is the latest geodetic satellite placed in orbit. Its main contribution is in the area of geodesy and the definition of the ITRF in particular and this presentation will discuss the improvements it will make in the aforementioned areas.

scholarly journals The Celestial Frame and the Weighting of the Celestial Pole Offsets in the Computation of VLBI-Based Corrections for the Main Lunisolar Nutation Terms

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8276
Author(s):  
Víctor Puente ◽  
Marta Folgueira
Keyword(s):  
Stochastic Model ◽  
Least Squares ◽  
Reference Frame ◽  
Very Long Baseline Interferometry ◽  
Long Baseline ◽  
Celestial Pole ◽  
Two Factors ◽  
Least Squares Adjustment ◽  
Empirical Corrections ◽  
Celestial Reference Frame

Very long baseline interferometry (VLBI) is the only technique in space geodesy that can determine directly the celestial pole offsets (CPO). In this paper, we make use of the CPO derived from global VLBI solutions to estimate empirical corrections to the main lunisolar nutation terms included in the IAU 2006/2000A precession–nutation model. In particular, we pay attention to two factors that affect the estimation of such corrections: the celestial reference frame used in the production of the global VLBI solutions and the stochastic model employed in the least-squares adjustment of the corrections. In both cases, we have found that the choice of these aspects has an effect of a few μas in the estimated corrections.

scholarly journals Impact of network constraining on the terrestrial reference frame realization based on SLR observations to LAGEOS

2019 ◽  
Vol 93 (11) ◽  
pp. 2293-2313 ◽  
Author(s):  
R. Zajdel ◽  
K. Sośnica ◽  
M. Drożdżewski ◽  
G. Bury ◽  
D. Strugarek
Keyword(s):  
Reference Frame ◽  
A Priori ◽  
Terrestrial Reference Frame ◽  
Laser Ranging ◽  
Potential Core ◽  
North East ◽  
The North ◽  
Station Coordinates ◽  
Earth Rotation Parameters ◽  
Variable List

Abstract The Satellite Laser Ranging (SLR) network struggles with some major limitations including an inhomogeneous global station distribution and uneven performance of SLR sites. The International Laser Ranging Service (ILRS) prepares the time-variable list of the most well-performing stations denoted as ‘core sites’ and recommends using them for the terrestrial reference frame (TRF) datum realization in SLR processing. Here, we check how different approaches of the TRF datum realization using minimum constraint conditions (MCs) and the selection of datum-defining stations affect the estimated SLR station coordinates, the terrestrial scale, Earth rotation parameters (ERPs), and geocenter coordinates (GCC). The analyses are based on the processing of the SLR observations to LAGEOS-1/-2 collected between 2010 and 2018. We show that it is essential to reject outlying stations from the reference frame realization to maintain a high quality of SLR-based products. We test station selection criteria based on the Helmert transformation of the network w.r.t. the a priori SLRF2014 coordinates to reject misbehaving stations from the list of datum-defining stations. The 25 mm threshold is optimal to eliminate the epoch-wise temporal deviations and to provide a proper number of datum-defining stations. According to the station selection algorithm, we found that some of the stations that are not included in the list of ILRS core sites could be taken into account as potential core stations in the TRF datum realization. When using a robust station selection for the datum definition, we can improve the station coordinate repeatability by 8%, 4%, and 6%, for the North, East and Up components, respectively. The global distribution of datum-defining stations is also crucial for the estimation of ERPs and GCC. When excluding just two core stations from the SLR network, the amplitude of the annual signal in the GCC estimates is changed by up to 2.2 mm, and the noise of the estimated pole coordinates is substantially increased.

Corrections to the Luni-Solar Precession From Radio Positions of Extragalactic Objects

1990 ◽  
Vol 141 ◽  
pp. 285-292
Author(s):  
H. G. Walter
Keyword(s):  
Pilot Study ◽  
Fixed Points ◽  
Reference Frame ◽  
Apparent Motion ◽  
Very Long Baseline Interferometry ◽  
Confidence Limits ◽  
Independent Observation ◽  
Long Baseline ◽  
Better Than

In an attempt of a realization of the radio reference frame a compilation catalogue of positions is derived from independent observation catalogues of extragalactic objects the coordinates of which had been determined by means of Very Long Baseline Interferometry. The compilation catalogue comprises 209 objects which are divided into a core consisting of 50 objects having mean positional accuracies of 0.5 milliseconds of arc (mas) and an extension with positional accuracies better than 2 mas. Comparison of this catalogue with an independent compilation catalogue led to confidence limits at the 1 mas level. - The compilation catalogue is supposed to represent a static reference frame of fixed extragalactic points. As the epochs of the contributing observations span nearly 10 years it was tried to interpret the apparent motion of the fixed points recognizable in the observation catalogues as an effect of luni-solar precession. The pilot study points at a reduction of the conventional value of about 2 mas per year.

scholarly journals Drift of the Earth’s Principal Axes of Inertia from GRACE and Satellite Laser Ranging Data

2020 ◽  
Vol 12 (2) ◽  
pp. 314
Author(s):  
José M. Ferrándiz ◽  
Sadegh Modiri ◽  
Santiago Belda ◽  
Mikhail Barkin ◽  
Mathis Bloßfeld ◽  
...  
Keyword(s):  
Reference Frame ◽  
Terrestrial Reference Frame ◽  
Satellite Laser Ranging ◽  
Laser Ranging ◽  
Navigation Systems ◽  
Time Varying ◽  
Stationary Case ◽  
Principal Axes ◽  
Initial Location ◽  
Gravity Recovery

The location of the Earth’s principal axes of inertia is a foundation for all the theories and solutions of its rotation, and thus has a broad effect on many fields, including astronomy, geodesy, and satellite-based positioning and navigation systems. That location is determined by the second-degree Stokes coefficients of the geopotential. Accurate solutions for those coefficients were limited to the stationary case for many years, but the situation improved with the accomplishment of Gravity Recovery and Climate Experiment (GRACE), and nowadays several solutions for the time-varying geopotential have been derived based on gravity and satellite laser ranging data, with time resolutions reaching one month or one week. Although those solutions are already accurate enough to compute the evolution of the Earth’s axes of inertia along more than a decade, such an analysis has never been performed. In this paper, we present the first analysis of this problem, taking advantage of previous analytical derivations to simplify the computations and the estimation of the uncertainty of solutions. The results are rather striking, since the axes of inertia do not move around some mean position fixed to a given terrestrial reference frame in this period, but drift away from their initial location in a slow but clear and not negligible manner.

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