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Asteroid Tomography by Utilizing Nanosatellites

Tampere University
Location Tampere
Via remote connection
28.8.2020 13.00–15.00
LanguageEnglish
Entrance feeFree of charge
Tohtori
In the last 10 years, utilization of nanosatellites has gained popularity in Low Earth Orbit (LEO) applications via the CubeSat standard. They have been an important part of so called new space economy, where larger and larger objectives in space can be achieved with low-cost, off-the-shelf electronics.

While CubeSats have remained for research and technology development purposes, the science-oriented space missions have utilized larger spacecraft. One such mission was the European Space Agency’s (ESA’s) Rosetta mission, which reached comet 67P/Churyumov–Gerasimenko in August 2014. An integral part of the mission was to attempt a radio tomography experiment, where the interior structure of the comet would have been mapped via radar signals. This thesis considers utilization of CubeSat-scale spacecraft to attempt to recover the interior structure of a small Near-Earth Asteroid (NEA). This has not been attempted before. During this thesis project, ESA selected CubeSats to fly on the Hera mission to asteroid Didymos. One of these CubeSats will include a radar instrument based on the one on Rosetta and its lander, Philae.

The thesis of M.Sc. (Tech.) Mika Takala extends the previous work of the Inverse Problems research group in Tampere University in simulating radio wave propagation within the asteroid via Finite-Difference Time Domain (FDTD) method as well as using the full wave measurement data in state of the art mathematical inversion strategies to recover the interior structure of the asteroid. Here, the focus is on investigating the effects of the measurement strategy and noise to the inversion results, improving the speed and accuracy of the method by using a multiresolution approach, and extending the modeling domain to make it possible to performthe simulations when the transmitting and receiving spacecraft are in far field, outside the finite element mesh based simulation domain. Important aspect of the work includes utilization of state-oftheart Graphics Processing Units (GPUs) which make it possible to accelerate the simulations both locally and in a calculation cluster.

A CubeSat feasibility study called Deep Interior Scanning CubeSat (DISCUS) was performed during the thesis project with the project collaborators. The goal of DISCUS is to fly a CubeSat to a NEA and perform the measurements, store the data and send the data back to Earth. The study includes analysis of currently available CubeSat hardware with realistic performance parameters, analysis of the mission parameters and the potential target asteroids, and realistic orbital parameters to perform the measurements on-site. DISCUS concept was later extended for a space mission called Asteroid In-situ Interior Investigation - 3way (Ai3), which was proposed for ESA’s F-class mission call in summer of 2018. While Ai3 was not selected, it was one of the six proposals on the second round of the process. The general interest towards studies of NEAs indicate that NEAs remain important for science, planetary protection purposes, as well as commercial companies, which motivates further studies in the topic.

The doctoral dissertation of M.Sc. (Tech.) Mika Takala in the field of information technology titled Asteroid Tomography by Utilizing Nanosatellites will be publicly examined in the Faculty of Information Technology and Communication Sciences at Tampere University starting at 4 o'clock p.m. The Opponent will be Professor Erik Asphaug from University of Arizona. The Custos will be Professor Sampsa Pursiainen.

The event can be followed via remote connection. If the remote connection does not work properly, you may also follow the dissertation defence here.

The dissertation is available online at
http://urn.fi/URN:ISBN:978-952-03-1651-8