Improving geodetic VLBI: UT1 accuracy, latency of results, and data quality monitoring

Minttu Uunila

Improving geodetic VLBI: UT1 accuracy, latency of results, and data quality monitoring

Julkaisun otsikon käännös: Geodeettisen VLBI:n kehittäminen: UT1:n tarkkuus, tulosten viiveellisyys ja datan laadun monitorointi

Minttu Uunila

Tutkimustuotos: Doctoral Thesis › Monograph

Abstrakti

Modernissa geodesiassa avaruustekniikoilla on tärkeä rooli. Kolme tärkeintä tekniikkaa ovat globaali satelliittipaikannusjärjestelmä (Global Navigation Satellite System, GNSS, mukaan lukien Global Positioning System, GPS), satelliittilaser (Satellite Laser Ranging, SLR) ja pitkäkantainterferometria (Very Long Baseline Interferometry, VLBI). Seuraavan sukupolven geodeettinen VLBI-järjestelmä, VLBI2010, kattaa kaiken antenneista data-analyysiin. Yksi tärkeimmistä vaatimuksista on analyysin automatisointi, jonka avulla tulokset on mahdollista saada 24 tunnin sisällä korrelloinnista. Tässä väitöskirjassa kansainvälisen geodesian ja astrometrian VLBI-palvelun (International VLBI Service for geodesy and astrometry, IVS) intensiivisessioiden analysointi on automatisoitu sekä Vienna VLBI Software -ohjemistoon (VieVS) lisätään puuttuvia esianalyysivaiheita. Goddard Space Flight Centerin (GSFC) ylläpitämä Calc/Solve-ohjelmisto on yleisimmin käytössä oleva geodeettisen VLBI:n analyysityökalu. Jotta tuloksiin ei tulisi systemaattista virhettä, kun käytetään vain yhtä ohjelmistoa, uudemman VieVS:in tuloksia verrattiin Solven tuloksiin. VieVS antaa tarkempia dUT1-tuloksia, kun taas Solven napavariaatiotulokset olivat tarkempia kuin VieVSin. Jotta VLBI2010-tarkkuusvaatimukset voitaisiin täyttää, tutkittiin dUT1-tuloksia IVS:n INT1-sessioista. Oletuksena oli, että lähteiden sijainti taivaalla kahta teleskooppia yhdistävän viivan keskipisteestä nähtynä vaikuttaa parametriin ja sen virheeseen. Tutkimuksessa todettiin, että ne sessiot, joissa kohteet olivat mahdollisimman kaukana toisistaan, tuottivat tarkimmat tulokset. Väitöskirjatutkimuksessa kirjoitettiin VHDL-firmware niin kutsuttuja 'zero baseline correlation' -testejä varten, joiden avulla voidaan tutkia VLBI-datan laatua.

Julkaisun otsikon käännös	Geodeettisen VLBI:n kehittäminen: UT1:n tarkkuus, tulosten viiveellisyys ja datan laadun monitorointi
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Hallikainen, Martti, Vastuuprofessori Tornikoski, Merja, Ohjaaja Poutanen, Markku, Ohjaaja, Ulkoinen henkilö
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-5179-6
Sähköinen ISBN	978-952-60-5180-2
Tila	Julkaistu - 2013
OKM-julkaisutyyppi	G4 Monografiaväitöskirja

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http://urn.fi/URN:ISBN:978-952-60-5180-2

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title = "Improving geodetic VLBI: UT1 accuracy, latency of results, and data quality monitoring",

abstract = "In modern geodesy the space-related techniques play an important role. The three most significant of these techniques are the Global Navigation Satellite System (GNSS) that includes the Global Positioning System (GPS), the Satellite Laser Ranging (SLR), and Very Long Baseline Interferometry (VLBI). The next generation geodetic VLBI system, VLBI2010, covers everything from antennas to analysis and is being implemented at VLBI stations globally. One of the key requirements for VLBI2010 is the automation of the data analysis in order to reduce the latency of the results to 24 hours. VLBI is a unique technique for determining the Earth Orientation Parameters (EOP), which are necessary, for example, for navigation satellites. The accuracy of GNSS positioning is related to the accuracy of EOP. Therefore, it is important to measure these parameters with the best possible accuracy and as short latency as possible. In this dissertation the automation of the International VLBI Service for geodesy and astrometry (IVS) intensive sessions is described. In the near future, the Vienna VLBI Software (VieVS) will be implemented with the pre-analysis steps that are currently being developed, the group delay ambiguity resolution and the ionospheric correction. The most commonly used geodetic VLBI analysis software is Calc/Solve that is maintained at the Goddard Space Flight Center (GSFC). So as not to bias the outcome by adopting only one software package, a comparison of Solve and VieVS EOP results was performed. This comparison showed that VieVS analysis appeared to improve the accuracy in the dUT1 result. However, polar motion results were more precise when Solve was used for the analysis. To fulfill the VLBI2010 precision requirements, the effect of source distribution on the dUT1 result accuracy obtained from IVS INT1 experiments was investigated. On the basis of the research conducted in this thesis, the results from the source constellation study show that the accuracy of the dUT1 is affected by the distribution in the sky as seen from the midpoint of a baseline, and will improve when a novel method proposed for scheduling intensive sessions will be implemented. Until now, the sky has been observed from the Kokee Park North direction. Introducing the new concept of observing the sky from a fictitious midpoint of the baseline greatly improves dUT1 accuracy. IVS should take this into consideration, because the accuracy of the results is a significant factor when calculating satellite orbits, for example. VLBI2010 requires shipment of the VLBI data via Internet. Firmware was developed to enable VLBI2010-compatible stations to perform zero baseline correlation tests with the Digital Base Band Converter (DBBC) and FILA10G ethernet board, and thus the stations can check the quality of the data in real-time.",

keywords = "Very Long Baseline Interferometry, VLBI, geodesy, UT1, VHDL, VHSIC Hardware Description Language, g, e, o, d, s, i, a, Very Long Baseline Interferometry, VLBI, geodesy, UT1, VHDL, VHSIC Hardware Description Language",

author = "Minttu Uunila",

year = "2013",

language = "English",

isbn = "978-952-60-5179-6",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "88",

address = "Finland",

school = "Aalto University",

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TY - BOOK

T1 - Improving geodetic VLBI: UT1 accuracy, latency of results, and data quality monitoring

AU - Uunila, Minttu

PY - 2013

Y1 - 2013

N2 - In modern geodesy the space-related techniques play an important role. The three most significant of these techniques are the Global Navigation Satellite System (GNSS) that includes the Global Positioning System (GPS), the Satellite Laser Ranging (SLR), and Very Long Baseline Interferometry (VLBI). The next generation geodetic VLBI system, VLBI2010, covers everything from antennas to analysis and is being implemented at VLBI stations globally. One of the key requirements for VLBI2010 is the automation of the data analysis in order to reduce the latency of the results to 24 hours. VLBI is a unique technique for determining the Earth Orientation Parameters (EOP), which are necessary, for example, for navigation satellites. The accuracy of GNSS positioning is related to the accuracy of EOP. Therefore, it is important to measure these parameters with the best possible accuracy and as short latency as possible. In this dissertation the automation of the International VLBI Service for geodesy and astrometry (IVS) intensive sessions is described. In the near future, the Vienna VLBI Software (VieVS) will be implemented with the pre-analysis steps that are currently being developed, the group delay ambiguity resolution and the ionospheric correction. The most commonly used geodetic VLBI analysis software is Calc/Solve that is maintained at the Goddard Space Flight Center (GSFC). So as not to bias the outcome by adopting only one software package, a comparison of Solve and VieVS EOP results was performed. This comparison showed that VieVS analysis appeared to improve the accuracy in the dUT1 result. However, polar motion results were more precise when Solve was used for the analysis. To fulfill the VLBI2010 precision requirements, the effect of source distribution on the dUT1 result accuracy obtained from IVS INT1 experiments was investigated. On the basis of the research conducted in this thesis, the results from the source constellation study show that the accuracy of the dUT1 is affected by the distribution in the sky as seen from the midpoint of a baseline, and will improve when a novel method proposed for scheduling intensive sessions will be implemented. Until now, the sky has been observed from the Kokee Park North direction. Introducing the new concept of observing the sky from a fictitious midpoint of the baseline greatly improves dUT1 accuracy. IVS should take this into consideration, because the accuracy of the results is a significant factor when calculating satellite orbits, for example. VLBI2010 requires shipment of the VLBI data via Internet. Firmware was developed to enable VLBI2010-compatible stations to perform zero baseline correlation tests with the Digital Base Band Converter (DBBC) and FILA10G ethernet board, and thus the stations can check the quality of the data in real-time.

AB - In modern geodesy the space-related techniques play an important role. The three most significant of these techniques are the Global Navigation Satellite System (GNSS) that includes the Global Positioning System (GPS), the Satellite Laser Ranging (SLR), and Very Long Baseline Interferometry (VLBI). The next generation geodetic VLBI system, VLBI2010, covers everything from antennas to analysis and is being implemented at VLBI stations globally. One of the key requirements for VLBI2010 is the automation of the data analysis in order to reduce the latency of the results to 24 hours. VLBI is a unique technique for determining the Earth Orientation Parameters (EOP), which are necessary, for example, for navigation satellites. The accuracy of GNSS positioning is related to the accuracy of EOP. Therefore, it is important to measure these parameters with the best possible accuracy and as short latency as possible. In this dissertation the automation of the International VLBI Service for geodesy and astrometry (IVS) intensive sessions is described. In the near future, the Vienna VLBI Software (VieVS) will be implemented with the pre-analysis steps that are currently being developed, the group delay ambiguity resolution and the ionospheric correction. The most commonly used geodetic VLBI analysis software is Calc/Solve that is maintained at the Goddard Space Flight Center (GSFC). So as not to bias the outcome by adopting only one software package, a comparison of Solve and VieVS EOP results was performed. This comparison showed that VieVS analysis appeared to improve the accuracy in the dUT1 result. However, polar motion results were more precise when Solve was used for the analysis. To fulfill the VLBI2010 precision requirements, the effect of source distribution on the dUT1 result accuracy obtained from IVS INT1 experiments was investigated. On the basis of the research conducted in this thesis, the results from the source constellation study show that the accuracy of the dUT1 is affected by the distribution in the sky as seen from the midpoint of a baseline, and will improve when a novel method proposed for scheduling intensive sessions will be implemented. Until now, the sky has been observed from the Kokee Park North direction. Introducing the new concept of observing the sky from a fictitious midpoint of the baseline greatly improves dUT1 accuracy. IVS should take this into consideration, because the accuracy of the results is a significant factor when calculating satellite orbits, for example. VLBI2010 requires shipment of the VLBI data via Internet. Firmware was developed to enable VLBI2010-compatible stations to perform zero baseline correlation tests with the Digital Base Band Converter (DBBC) and FILA10G ethernet board, and thus the stations can check the quality of the data in real-time.

KW - Very Long Baseline Interferometry

KW - VLBI

KW - geodesy

KW - UT1

KW - VHDL

KW - VHSIC Hardware Description Language

KW - g

KW - e

KW - o

KW - d

KW - s

KW - i

KW - a

KW - Very Long Baseline Interferometry

KW - VLBI

KW - geodesy

KW - UT1

KW - VHDL

KW - VHSIC Hardware Description Language

M3 - Doctoral Thesis

SN - 978-952-60-5179-6

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Improving geodetic VLBI: UT1 accuracy, latency of results, and data quality monitoring

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