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Dissertation in PDF Format %FQBSUNFOUPG3BEJP4DJFODFBOE&OHJOFFSJOH " /# BM (&3ŗŗ.#(3ŗ ,.#)(ŗ) ŗ."ŗ/(#0,-ŗ"-ŗ(ŗ U P % ,Z -./#ŗ0(ŗ.")/!"ŗ."ŗ*)--##&#.#-ŗ,ŗ % ŗ ) #)ŗ-*.,)-)*3ŗ /(&#'#.ŗ!#0(ŗ."ŗ/,,(.ŗ."()&)!#-ąŗ & ."ŗ,-)/,-ŗ(ŗ."ŗ.#'Ąŗ)ŗ)*.#'#-ŗ."ŗ ,ŗ& /-ŗ) ŗ,-)/,-ąŗ."ŗ .-<")0#ŗ,#)ŗ (ŗ-*ŗ-#(ŗ .&-)*ŗ(ŗ."ŗ2#-.#(!ŗ ŗ*,)--#(!ŗ 0Z +/#*'(.ŗ1,ŗ2*&)#.ŗ.)ŗ-./3ŗŗ,)ŗ -ŗ 0,#.3ŗ) ŗ-*ŗ*"()'(Ąŗ"#-ŗ."-#-ŗ 1#."ŗ ŗ,#)ŗ '*"-#4-ŗ.1)ŗ /('(.&ŗ-*.-ŗ) ŗ #) ,#)ŗ-.,)()'3Ćŗ,#)ŗ-*.,)-)*3ŗ) ŗ ŗ-* .&-)*-ŗ ),ŗ)&,ŗ &-.#&ŗ)#-ŗ(ŗ,#)ŗ-#(ŗ-./#-ŗ . 1#."ŗ*&(.,3ŗ-*, .ŗ#(ŗ."ŗ)&,ŗ ,) 3-.'Ąŗ"ŗ,-,"ŗ'ŗ/-ŗ) ŗ."ŗûþĚ - 3-.'ŗ,-,"ŗ ) '.,ŗ,#)ŗ.&-)*ŗ) ŗ."ŗ .-<")0#ŗ,#)ŗ *3ŗ(ŗ-* )-,0.),3ŗ(ŗ) ŗ).",ŗ ŗ(.((ŗ.)ŗ )(/.ŗ,!/&,ŗ)-,0.#)(-ŗ) ŗ*&(.-ŗ(ŗ *&(.,3ŗ-*, .Ąŗ"ŗ1),%ŗ#(&/ŗ."ŗ ŗ- (VJGSÀ.PMFSB$BMWÀT 0&)*'(.ŗ) ŗ(1ŗ ŗ",1,ŗ # -3-.'-ąŗ*,)--#(!ŗ(ŗ(&3-#-ŗ-) .1,ąŗ ( (ŗ#'*,)0'(.ŗ) ŗ."ŗ)-,0.#)(-ŗ ŗ1 #. *#*&#(Ąŗ " ŗ ŗ,#) ŗ. & - ) * -ŗ -ŗ ) ,ŗ) & ,ŗ3-. 'ŗ, - , " 9HSTFMG*aefiab+ 9HSTFMG*aefiab+ *4#/ #64*/&44 *4#/ QEG &$0/0.: *44/- *44/ "35 *44/ QEG %&4*(/ "3$)*5&$563& " B "BMUP6OJWFSTJUZ M U 4DIPPMPG&MFDUSJDBM&OHJOFFSJOH 4$*&/$& P %FQBSUNFOUPG3BEJP4DJFODFBOE&OHJOFFSJOH 5&$)/0-0(: 6 XXXBBMUPGJ OJ W $304407&3 F S T %0$503"- J %0$503"- U %*44&35"5*0/4 Z %*44&35"5*0/4 Aalto University publication series DOCTORAL DISSERTATIONS 42/2012 Radio spectroscopy and space science with VLBI radio telescopes for Solar System research Guifré Molera Calvés Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Electrical Engineering for public examination and debate in Auditorium S1 at the Aalto University School of Electrical Engineering (Espoo, Finland) on the 27th of April 2012 at 12 noon. Aalto University School of Electrical Engineering Department of Radio Science and Engineering Metsähovi Radio Observatory Supervisor Professor Martti Hallikainen Instructor Doctor Sergei Pogrebenko, JIVE, the Netherlands Preliminary examiners Doctor Kaj Wiik, Tuorla Observatory, University of Turku, Finland Doctor Alan R. Whitney, MIT/Haystack radio observatory, USA Opponent Doctor Franco Mantovani, Istituto di RadioAstronomia, Italy Aalto University publication series DOCTORAL DISSERTATIONS 42/2012 © Guifré Molera Calvés ISBN 978-952-60-4580-1 (printed) ISBN 978-952-60-4581-8 (pdf) ISSN-L 1799-4934 ISSN 1799-4934 (printed) ISSN 1799-4942 (pdf) Unigrafia Oy Helsinki 2012 Finland The dissertation can be read at http://lib.tkk.fi/Diss/ Abstract Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto.fi Author Guifré Molera Calvés Name of the doctoral dissertation Radio spectroscopy and space science with VLBI radio telescopes for Solar System research Publisher School of Electrical Engineering Unit Department of Radio Science and Engineering Series Aalto University publication series DOCTORAL DISSERTATIONS 42/2012 Field of research Radio astronomy Manuscript submitted 15 December 2011 Manuscript revised 22 March 2012 Date of the defence 27 April 2012 Language English Monograph Article dissertation (summary + original articles) Abstract Only a tiny fraction of the universe has been studied even though the possibilities are unlimited given the current technologies, the resources and the time. To optimize the use of resources, the Metsähovi antenna and the existing VLBI processing hardware were exploited to study a broad variety of space phenomena. The research began with radio spectroscopy of the celestial bodies of our Solar System. Every object emits certain spectral signatures at several radio frequencies depending on its chemical molecules. Earth-based observations of the emitted radio spectral signal help to determine the composition of the structure and atmosphere of the planets. A unique method for processing the data captured by VLBI radio telescopes for radio spectroscopy purposes was developed during this work. Although the initial research focused on planetary bodies, it later shifted to the spacecraft motion. This new aim included studying ground support to planetary and deep-space mission spacecraft with VLBI radio telescopes, which opened up possibilities for collaboration between space agencies and radio astronomers. In addition, with VLBI phase-referencing, a high accuracy estimation of the spacecraft state vectors could be obtained. These new tools provide an opportunity for studying a broad variety of physical processes, including the dynamics of planetary atmospheres, geodynamical diagnostics of the interior of planets, fundamental physics effects of spacecraft motion and solar wind characterization. For instance, we organised a VLBI tracking session of Venus Express that involved 10 antennae and it estimated the spacecraft position with a precision of few hundred metres. The most interesting physical process for further investigation was the characterisation of the solar wind along the propagation path. The phase fluctuations on the signal allowed us to study essential parameters of the interplanetary scintillations, such as the phase scintillation index, bandwidth of scintillations or spectral broadening and their dependence on the solar elongation, distance to the target, celestial position of the spacecraft and radio telescopes. A scintillation and electron density model as a function of solar elongation was developed based on the data collected during two years. This model is powerful for improving the accurate determination of the spacecraft state vectors. Keywords VLBI, spacecraft tracking, Doppler, radio spectroscopy, space science, interplanetary scintillation ISBN (printed) 978-952-60-4580-1 ISBN (pdf) 978-952-60-4581-8 ISSN-L 1799-4934 ISSN (printed) 1799-4934 ISSN (pdf) 1799-4942 Location of publisher Espoo Location of printing Helsinki Year 2012 Pages 216 The dissertation can be read at http://lib.tkk.fi/Diss/ Preface I have been working as a post-graduate student at the Metsähovi radio ob- servatory since spring 2006. Because of my incorporation with the VLBI group, I have been collaborating with several international projects in the field of the space science and radio astronomy using VLBI telescopes. First, I want to express my deep gratitude to the thesis advisor and mentor, Dr. Sergei Pogrebenko, who has provided support, guidance and interesting opportunities over the years. I would like to thank my col- leagues at Metsähovi for offering a good working environment, strong col- laboration and support. I would like to acknowledge the CASPER group at UC Berkeley who welcomed me to their group and provided a place for writing the dissertation. I would like to express my appreciation for the supervisor Prof. Martti Hallikainen, the director of Metsähovi Prof. Merja Tornikoski and the two pre-examiners that supervised this disser- tation, Dr. Kaj Wiik and Dr. Alan R. Whitney. I’m also grateful to Megan, Giuseppe, Sergei, Leonid, Neville and Anna for the language help and everyone who have contributed directly or indirectly on this thesis. I wish to thank my parents Roser and Angel, and my brother Guillem for all the love and support they have given me. I also want to thank all my friends for the relaxing times after the work. Last but not least, I want to thank my wife Anna for the innumerable hours helping with the thesis and for being the most awesome thing in my life. This thesis has been financially supported by the European Commis- sion via the EXPReS project and the Academy of Finland via the From ultra-rapid data transfer into science - a near real-time VLBI application project. Helsinki, March 28, 2012, I Preface II Contents Preface .................................. I Contents ................................. III List of Figures .............................. VII List of Tables .............................. XI 1. Introduction ............................. 1 1.1 Background ........................... 1 1.2 Technical development ..................... 2 1.3 Scientific purpose ........................ 3 1.4 Outline of the thesis ...................... 4 1.5 Contribution of the author ................... 4 2. Fundamentals of radio spectroscopy and VLBI ......... 7 2.1 Microwave spectroscopy .................... 7 2.1.1 Interstellar microwave spectroscopy ......... 7 2.1.2 Radio spectral line .................... 8 2.1.3 Masers ........................... 10 2.2 Space radio science ....................... 11 2.2.1 Radio wave propagation ................. 13 2.2.2 Propagation in the interplanetary plasma ...... 16 2.3 Radio interferometer ...................... 20 2.3.1 Radio interferometer system . ........... 20 2.3.2 Very Long Baseline Interferometry .......... 24 2.3.3 Current radio interferometers . ........... 27 3. Digital Back Ends .......................... 29 3.1 Introduction ........................... 29 3.2 Implementation of VLBI hardware . ............ 31 3.2.1 New VLBI Data Acquisition System ......... 34 3.3 VLBI software applications .................. 39 3.4 iBOB designs/firmware ..................... 41 III Contents 3.5 Conclusions ........................... 45 4. Radio spectroscopy in the Solar System . ............ 47 4.1 Introduction ........................... 47 4.2 Water search in the Solar System .............. 49 4.2.1 Introduction ....................... 49 4.2.2 Materials and methods ................. 51 4.2.3 Data processing and analysis ............. 56 4.2.4 Kronian results ..................... 57 4.2.5 W75N maser results ................... 61 4.3 Dicarbon sulphide search in the Solar System ....... 64 4.4 Lightning discharges on Mars . .............. 68 4.4.1 Observations ......................
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