On the prospects of a future GNSS constellation on the global terrestrial reference frame

2020 ◽  
Author(s):  
Susanne Glaser ◽  
Grzegorz Michalak ◽  
Rolf Koenig ◽  
Benjamin Maennel ◽  
Harald Schuh
Keyword(s):  
Reference Frames ◽  
Time Synchronization ◽  
Orbital Plane ◽  
Satellite System ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Terrestrial Reference Frames ◽  
Earth Rotation Parameters ◽  
The Impact

<p>Global terrestrial reference frames (TRFs), as one of the most important geodetic products, currently miss the imperative requirements of 1 mm accuracy and 1mm/decade long-term stability. In this study, the prospects of a future Global Navigation Satellite System (GNSS) to improve global TRFs is assessed by simulations. The future constellation, named “Kepler”, is proposed by the German Aerospace Center DLR in view of the next generation Galileo system. In addition to a contemporary Medium Earth Orbit (MEO) segment with 24 satellites in three orbital planes, Kepler consists of six Low Earth Orbit (LEO) satellites in two near polar planes, all carrying long-term stable optical clocks. The MEO satellites in one orbital plane and the LEO and MEO satellites in different planes are connected with optical two-way inter-satellite links (ISLs) as the innovative key feature. The ISLs allow very precise range measurements and time synchronization (at the picosecond-level) between the satellites. Different simulation scenarios are set up to evaluate the impact of the Kepler features on the TRF-defining parameters origin and scale as well as on the Earth rotation parameters (ERPs). The origin of a Kepler-only TRF improves considerably by factors of 8, 8, and 43 in X, Y, and Z direction, respectively, w.r.t. a Galileo-only solution. The scale realized by a Kepler-TRF shows improvements of 34% w.r.t. Galileo-only. In a combination with simulated observations of Very Long Baseline Interferometry the impact on multi-technique TRFs is assessed as well. The ERPs of both techniques are combined as global ties and benefits especially on the determination of UT1-UTC are expected.</p>

scholarly journals ИССЛЕДОВАНИЕ ПОДХОДОВ К ПОСТРОЕНИЮ ОРБИТАЛЬНОЙ ВЫЧИСЛИТЕЛЬНОЙ СЕТИ СПУТНИКОВОЙ СИСТЕМЫ ИНТЕРНЕТА ВЕЩЕЙ

2019 ◽  
pp. 138-151
Author(s):  
Михаил Ефимович Ильченко ◽  
Теодор Николаевич Нарытник ◽  
Владимир Ильич Присяжный ◽  
Сергей Владимирович Капштык ◽  
Сергей Анатольевич Матвиенко
Keyword(s):  
Internet Of Things ◽  
Computer Network ◽  
Fog Computing ◽  
Orbital Plane ◽  
Satellite System ◽  
Low Earth Orbit ◽  
The Internet ◽  
Earth Orbit ◽  
Distributed Satellite ◽  
The Internet Of Things

There are considered issues of building a Low-Earth-Orbit Satellite System designed to provide the Internet of Things services and adapted to the features of the services and systems of the Internet of Things. The considered system provides the creation of the necessary telecommunication infrastructure based on the Low-Earth-Orbit Broadband Access Satellite System and places Computational Facilities into the Low-Earth-Orbit for to ensure the processing of Internet of Things devices and systems information, and perform computations. The architecture of a “Distributed Satellite” was chosen to construct the telecommunications part of the Internets of Things Satellite System. The chosen architecture allows, on the one hand, to ensure the full functionality of complex telecommunication systems, and on the other hand, to use spacecraft of the form factor nano-satellite / cub-sat. The using of the cube-sat spacecraft for development of the satellite-based system allows to significantly reduce the cost of development of the system and the time of the system deploying. A promising direction in the development of the Internet of Things systems is the implementation of the concept of “Fog Computing” for processing Internet of Things information. To implement “Fog Computing”, it was proposed to include into the composition of each “Distributed Satellite” a separate Satellite-Computer and to build an Orbital Distributed Network based on Satellite-Computers. The issues of the inter-satellite connectivity are considered taking into account ensuring the connection between Satellites-Computers in the framework of the Orbital Distributed Computer Network using inter-satellite links between Distributed Satellites, the characteristics of the orbital construction of the Satellite System Constellation. It was proposed to create and deploy the Distributed Localized Database based on the Orbital Distributed Computer Network, for to ensure the continuous provision of Internet of Things services, taking into account the movement of spacecraft in the orbital plane and the rotation of the Earth. It was shown the direction of transmission of the operational part of a Localized Distributed Database. Proposals are made on the distribution of the excess computational load arising in certain regions of the satellite telecommunications system's service area, involving the resource of neighboring satellite computers in its orbital plane and neighboring orbital planes. An algorithm is proposed for moving the excess computational load to the polar and oceanic regions.

scholarly journals Determination of precise Galileo orbits using combined GNSS and SLR observations

GPS Solutions ◽  
2020 ◽  
Vol 25 (1) ◽  
Author(s):  
Grzegorz Bury ◽  
Krzysztof Sośnica ◽  
Radosław Zajdel ◽  
Dariusz Strugarek ◽  
Urs Hugentobler
Keyword(s):  
Orbit Determination ◽  
Reference Frames ◽  
Semimajor Axis ◽  
Precise Orbit Determination ◽  
Orbital Plane ◽  
Normal Equation ◽  
Terrestrial Reference Frames ◽  
Formal Error ◽  
Combined Solution ◽  
The Impact

Abstract Galileo satellites are equipped with laser retroreflector arrays for satellite laser ranging (SLR). In this study, we develop a methodology for the GNSS-SLR combination at the normal equation level with three different weighting strategies and evaluate the impact of laser observations on the determined Galileo orbits. We provide the optimum weighting scheme for precise orbit determination employing the co-location onboard Galileo. The combined GNSS-SLR solution diminishes the semimajor axis formal error by up to 62%, as well as reduces the dependency between values of formal errors and the elevation of the Sun above the orbital plane—the β angle. In the combined solution, the standard deviation of the SLR residuals decreases from 36.1 to 29.6 mm for Galileo-IOV satellites and |β|> 60°, when compared to GNSS-only solutions. Moreover, the bias of the Length-of-Day parameter is 20% lower for the combined solution when compared to the microwave one. As a result, the combination of GNSS and SLR observations provides promising results for future co-locations onboard the Galileo satellites for the orbit determination, realization of the terrestrial reference frames, and deriving geodetic parameters.

scholarly journals Earth rotation variations observed by VLBI and the Wettzell “G” ring laser during the CONT17 campaign

2019 ◽  
Vol 50 ◽  
pp. 9-15 ◽  
Author(s):  
Sigrid Böhm ◽  
Matthias Schartner ◽  
André Gebauer ◽  
Thomas Klügel ◽  
Ulrich Schreiber ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Ring Laser ◽  
Polar Motion ◽  
Reference Frames ◽  
Reference Value ◽  
Terrestrial Reference Frames ◽  
Earth Rotation Parameters ◽  
Sparse Networks ◽  
The Impact ◽  
Earth Rotation Variations

Abstract. The VLBI (Very Long Baseline Interferometry) technique can provide the full set of parameters needed for the transformation between celestial and terrestrial reference frames with high accuracy. Yet it has some limitations regarding temporal resolution and continuity, and the accuracy of the resulting Earth Orientation Parameters (EOP) varies depending on the network geometry. In this work we explore the benefit of combining VLBI observations with the measurements of the large ring laser gyroscope “G” in Wettzell for deriving highly resolved ERP (Earth Rotation Parameters, i.e. polar motion and universal time variations, δUT1). We examine the observations collected by two simultaneously operating VLBI networks during the 15 d of the CONT17 campaign. These two networks, of 14 globally distributed telescopes each, were designed for the estimation of Earth rotation variations, for which reason the resulting hourly ERP are appointed as benchmark in this investigation. To evaluate the advantage of a VLBI and ring laser combined solution, we create degraded versions of the original networks, containing only six stations. The ERP derived from those sparse networks and from the VLBI sparse plus ring laser solutions are then compared in terms of differences to the reference values. It should certainly be considered that these are relative numbers, since they are also determined by the number and selection of the stations remaining in the sparse networks. The root mean square of the difference to the benchmark is reduced by 24 % in case of δUT1 from one network. The polar motion yp component from the same network moves 14 % closer to the reference value due to the inclusion of the ring laser data. The impact on xp and on all ERP from the other network ranges between 2 % and 9 %. The research again confirms the feasibility and also the potential gain of a combined evaluation of VLBI and ring laser observations, but the full capacity of such a sensor fusion will emerge once the ring laser gyroscopes reach a level of accuracy similar to VLBI.

scholarly journals Effects of long-term exposure to the low-earth orbit environment on drag augmentation systems

2021 ◽  
Author(s):  
Zaria Serfontein ◽  
Jennifer Kingston ◽  
Stephen Hobbs ◽  
Susan A. Impey ◽  
Adrianus I. Aria ◽  
...  
Keyword(s):  
Low Earth Orbit ◽  
Earth Orbit

scholarly journals Assessment of BeiDou differential code bias variations from multi-GNSS network observations

2016 ◽  
Vol 34 (2) ◽  
pp. 259-269 ◽  
Author(s):  
S. G. Jin ◽  
R. Jin ◽  
D. Li
Keyword(s):  
Orbital Plane ◽  
Satellite Orbit ◽  
Satellite System ◽  
Global Navigation Satellite Systems ◽  
Dominant Factor ◽  
Earth Orbit ◽  
Navigation Satellite ◽  
Differential Code Bias ◽  
Code Bias ◽  
Gnss Network

Abstract. The differential code bias (DCB) of global navigation satellite systems (GNSSs) affects precise ionospheric modeling and applications. In this paper, daily DCBs of the BeiDou Navigation Satellite System (BDS) are estimated and investigated from 2-year multi-GNSS network observations (2013–2014) based on global ionospheric maps (GIMs) from the Center for Orbit Determination in Europe (CODE), which are compared with Global Positioning System (GPS) results. The DCB of BDS satellites is a little less stable than GPS solutions, especially for geostationary Earth orbit (GEO) satellites. The BDS GEO observations decrease the precision of inclined geosynchronous satellite orbit (IGSO) and medium Earth orbit (MEO) DCB estimations. The RMS of BDS satellites DCB decreases to about 0.2 ns when we remove BDS GEO observations. Zero-mean condition effects are not the dominant factor for the higher RMS of BDS satellites DCB. Although there are no obvious secular variations in the DCB time series, sub-nanosecond variations are visible for both BDS and GPS satellites DCBs during 2013–2014. For satellites in the same orbital plane, their DCB variations have similar characteristics. In addition, variations in receivers DCB in the same region are found with a similar pattern between BDS and GPS. These variations in both GPS and BDS DCBs are mainly related to the estimated error from ionospheric variability, while the BDS DCB intrinsic variation is in sub-nanoseconds.

scholarly journals Detecting Targets above the Earth’s Surface Using GNSS-R Delay Doppler Maps: Results from TDS-1

2019 ◽  
Vol 11 (19) ◽  
pp. 2327 ◽  
Author(s):  
Changjiang Hu ◽  
Craig Benson ◽  
Hyuk Park ◽  
Adriano Camps ◽  
Li Qiao ◽  
...  
Keyword(s):  
Specular Reflection ◽  
Satellite System ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Navigation Satellite ◽  
Reflection Point ◽  
Leo Satellites ◽  
Gnss Reflectometry ◽  
Global Navigation Satellite ◽  
Remotely Sense

Global Navigation Satellite System (GNSS) reflected signals can be used to remotely sense the Earth’s surface, known as GNSS reflectometry (GNSS-R). The GNSS-R technique has been applied to numerous areas, such as the retrieval of wind speed, and the detection of Earth surface objects. This work proposes a new application of GNSS-R, namely to detect objects above the Earth’s surface, such as low Earth orbit (LEO) satellites. To discuss its feasibility, 14 delay Doppler maps (DDMs) are first presented which contain unusually bright reflected signals as delays shorter than the specular reflection point over the Earth’s surface. Then, seven possible causes of these anomalies are analysed, reaching the conclusion that the anomalies are likely due to the signals being reflected from objects above the Earth’s surface. Next, the positions of the objects are calculated using the delay and Doppler information, and an appropriate geometry assumption. After that, suspect satellite objects are searched in the satellite database from Union of Concerned Scientists (UCS). Finally, three objects have been found to match the delay and Doppler conditions. In the absence of other reasons for these anomalies, GNSS-R could potentially be used to detect some objects above the Earth’s surface.

Long-term collision risk prediction for low earth orbit satellite constellations

2000 ◽  
Vol 47 (2-9) ◽  
pp. 707-717 ◽  
Author(s):  
R. Walker ◽  
P.H. Stokes ◽  
J.E. Wilkinson ◽  
G.G. Swinerd
Keyword(s):  
Risk Prediction ◽  
Low Earth Orbit ◽  
Earth Orbit ◽  
Collision Risk ◽  
Satellite Constellations ◽  
Orbit Satellite ◽  
Low Earth Orbit Satellite

On the impact of local ties on the datum realization of global terrestrial reference frames

2018 ◽  
Vol 93 (5) ◽  
pp. 655-667 ◽  
Author(s):  
Susanne Glaser ◽  
Rolf König ◽  
Karl Hans Neumayer ◽  
Tobias Nilsson ◽  
Robert Heinkelmann ◽  
...  
Keyword(s):  
Reference Frames ◽  
Local Ties ◽  
Terrestrial Reference Frames ◽  
The Impact
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