The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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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.
Dissertation in PDF format (ISBN 978-952-60-4581-8) [12528 KB]
Dissertation is also available in print (ISBN 978-952-60-4580-1)
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: Very Long Baseline Interferometry, spacecraft tracking, Doppler, radio spectroscopy, space science, interplanetary scintillation
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© 2012 Aalto University
Last update 2012-10-31