@phdthesis{Balagurin2022,
  author    = {Balagurin, Oleksii},
  title     = {Designoptimierung von Sternsensoren f{\"u}r Pico- und Nanosatelliten},
  doi       = {10.25972/OPUS-25896},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-258966},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Die Raumfahrt ist eine der konservativsten Industriebranchen. Neue Entwicklungen von Komponenten und Systemen beruhen auf existierenden Standards und eigene Erfahrungen der Entwickler. Die Systeme sollen in einem vorgegebenen engen Zeitrahmen projektiert, in sehr kleiner St{\"u}ckzahl gefertigt und schließlich aufwendig qualifiziert werden. Erfahrungsgem{\"a}ß reicht die Zeit f{\"u}r Entwicklungsiterationen und weitgehende Perfektionierung des Systems oft nicht aus. Fertige Sensoren, Subsysteme und Systeme sind Unikate, die nur f{\"u}r eine bestimme Funktion und in manchen F{\"a}llen sogar nur f{\"u}r bestimmte Missionen konzipiert sind. Eine Neuentwicklung solcher Komponenten ist extrem teuer und risikobehaftet. Deswegen werden flugerprobte Systeme ohne {\"A}nderungen und Optimierung mehrere Jahre eingesetzt, ohne Technologiefortschritte zu ber{\"u}cksichtigen. Aufgrund des enormen finanziellen Aufwandes und der Tr{\"a}gheit ist die konventionelle Vorgehensweise in der Entwicklung nicht direkt auf Kleinsatelliten {\"u}bertragbar. Eine dynamische Entwicklung im Low Cost Bereich ben{\"o}tigt eine universale und f{\"u}r unterschiedliche Anwendungsbereiche leicht modifizierbare Strategie. Diese Strategie soll nicht nur flexibel sein, sondern auch zu einer m{\"o}glichst optimalen und effizienten Hardwarel{\"o}sung f{\"u}hren. Diese Arbeit stellt ein Software-Tool f{\"u}r eine zeit- und kosteneffiziente Entwicklung von Sternsensoren f{\"u}r Kleinsatelliten vor. Um eine maximale Leistung des Komplettsystems zu erreichen, soll der Sensor die Anforderungen und Randbedingungen vorgegebener Anwendungen erf{\"u}llen und dar{\"u}ber hinaus f{\"u}r diese Anwendungen optimiert sein. Wegen der komplexen Zusammenh{\"a}nge zwischen den Parametern optischer Sensorsysteme ist keine „straightforward" L{\"o}sung des Problems m{\"o}glich. Nur durch den Einsatz computerbasierter Optimierungsverfahren kann schnell und effizient ein bestm{\"o}gliches Systemkonzept f{\"u}r die gegebenen Randbedingungen ausgearbeitet werden.},
  subject      = {Sternsensor},
  language  = {de}
}
@article{GrzesikBaumannWalteretal.2021,
  author    = {Grzesik, Benjamin and Baumann, Tom and Walter, Thomas and Flederer, Frank and Sittner, Felix and Dilger, Erik and Gl{\"a}sner, Simon and Kirchler, Jan-Luca and Tedsen, Marvyn and Montenegro, Sergio and Stoll, Enrico},
  title     = {InnoCube — a wireless satellite platform to demonstrate innovative technologies},
  series = {Aerospace},
  volume    = {8},
  journal   = {Aerospace},
  number    = {5},
  issn      = {2226-4310},
  doi       = {10.3390/aerospace8050127},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-239564},
  year      = {2021},
  abstract  = {A new innovative satellite mission, the Innovative CubeSat for Education (InnoCube), is addressed. The goal of the mission is to demonstrate "the wireless satellite", which replaces the data harness by robust, high-speed, real-time, very short-range radio communications using the SKITH (SKIpTheHarness) technology. This will make InnoCube the first wireless satellite in history. Another technology demonstration is an experimental energy-storing satellite structure that was developed in the previous Wall\#E project and might replace conventional battery technology in the future. As a further payload, the hardware for the concept of a software-based solution for receiving signals from Global Navigation Satellite Systems (GNSS) will be developed to enable precise position determination of the CubeSat. Aside from technical goals this work aims to be of use in the teaching of engineering skills and practical sustainable education of students, important technical and scientific publications, and the increase of university skills. This article gives an overview of the overall design of the InnoCube.},
  language  = {en}
}
@phdthesis{Kramer2021,
  author    = {Kramer, Alexander},
  title     = {Orbit control of a very small satellite using electric propulsion},
  isbn      = {978-3-945459-34-8 (online)},
  doi       = {10.25972/OPUS-24155},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-241552},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Miniaturized satellites on a nanosatellite scale below 10kg of total mass contribute most to the number of launched satellites into Low Earth Orbit today. This results from the potential to design, integrate and launch these space missions within months at very low costs. In the past decade, the reliability in the fields of system design, communication, and attitude control have matured to allow for competitive applications in Earth observation, communication services, and science missions. The capability of orbit control is an important next step in this development, enabling operators to adjust orbits according to current mission needs and small satellite formation flight, which promotes new measurements in various fields of space science. Moreover, this ability makes missions with altitudes above the ISS comply with planned regulations regarding collision avoidance maneuvering. This dissertation presents the successful implementation of orbit control capabilities on the pico-satellite class for the first time. This pioneering achievement is demonstrated on the 1U CubeSat UWE-4. A focus is on the integration and operation of an electric propulsion system on miniaturized satellites. Besides limitations in size, mass, and power of a pico-satellite, the choice of a suitable electric propulsion system was driven by electromagnetic cleanliness and the use as a combined attitude and orbit control system. Moreover, the integration of the propulsion system leaves the valuable space at the outer faces of the CubeSat structure unoccupied for future use by payloads. The used NanoFEEP propulsion system consists of four thruster heads, two neutralizers and two Power Processing Units (PPUs). The thrusters can be used continuously for 50 minutes per orbit after the liquefaction of the propellant by dedicated heaters. The power consumption of a PPU with one activated thruster, its heater and a neutralizer at emitter current levels of 30-60μA or thrust levels of 2.6-5.5μN, respectively, is in the range of 430-1050mW. Two thruster heads were activated within the scope of in-orbit experiments. The thrust direction was determined using a novel algorithm within 15.7° and 13.2° of the mounting direction. Despite limited controllability of the remaining thrusters, thrust vector pointing was achieved using the magnetic actuators of the Attitude and Orbit Control System. In mid 2020, several orbit control maneuvers changed the altitude of UWE-4, a first for pico-satellites. During the orbit lowering scenario with a duration of ten days, a single thruster head was activated in 78 orbits for 5:40 minutes per orbit. This resulted in a reduction of the orbit altitude by about 98.3m and applied a Delta v of 5.4cm/s to UWE-4. The same thruster was activated in another experiment during 44 orbits within five days for an average duration of 7:00 minutes per orbit. The altitude of UWE-4 was increased by about 81.2m and a Delta v of 4.4cm/s was applied. Additionally, a collision avoidance maneuver was executed in July 2020, which increased the distance of closest approach to the object by more than 5000m.},
  subject      = {Kleinsatellit},
  language  = {en}
}
@article{KramerBangertSchilling2020,
  author    = {Kramer, Alexander and Bangert, Philip and Schilling, Klaus},
  title     = {UWE-4: First Electric Propulsion on a 1U CubeSat — In-Orbit Experiments and Characterization},
  series = {Aerospace},
  volume    = {7},
  journal   = {Aerospace},
  number    = {7},
  doi       = {10.3390/aerospace7070098},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236124},
  year      = {2020},
  abstract  = {The electric propulsion system NanoFEEP was integrated and tested in orbit on the UWE-4 satellite, which marks the first successful demonstration of an electric propulsion system on board a 1U CubeSat. In-orbit characterization measurements of the heating process of the propellant and the power consumption of the propulsion system at different thrust levels are presented. Furthermore, an analysis of the thrust vector direction based on its effect on the attitude of the spacecraft is described. The employed heater liquefies the propellant for a duration of 30 min per orbit and consumes 103 ± 4 mW. During this time, the respective thruster can be activated. The propulsion system including one thruster head, its corresponding heater, the neutralizer and the digital components of the power processing unit consume 8.5 ± 0.1 mW ⋅μ A\(^{-1}\) + 184 ± 8.5 mW and scales with the emitter current. The estimated thrust directions of two thruster heads are at angles of 15.7 ± 7.6∘ and 13.2 ± 5.5∘ relative to their mounting direction in the CubeSat structure. In light of the very limited power on a 1U CubeSat, the NanoFEEP propulsion system renders a very viable option. The heater of subsequent NanoFEEP thrusters was already improved, such that the system can be activated during the whole orbit period.},
  language  = {en}
}
@techreport{RieglerKayal2022,
  type      = {Working Paper},
  author    = {Riegler, Clemens and Kayal, Hakan},
  title     = {VELEX: Venus Lightning Experiment},
  doi       = {10.25972/OPUS-28248},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-282481},
  pages     = {6},
  year      = {2022},
  abstract  = {Lightning has fascinated humanity since the beginning of our existence. Different types of lightning like sprites and blue jets were discovered, and many more are theorized. However, it is very likely that these phenomena are not exclusive to our home planet. Venus's dense and active atmosphere is a place where lightning is to be expected. Missions like Venera, Pioneer, and Galileo have carried instruments to measure electromagnetic activity. These measurements have indeed delivered results. However, these results are not clear. They could be explained by other effects like cosmic rays, plasma noise, or spacecraft noise. Furthermore, these lightning seem different from those we know from our home planet. In order to tackle these issues, a different approach to measurement is proposed. When multiple devices in different spacecraft or locations can measure the same atmospheric discharge, most other explanations become increasingly less likely. Thus, the suggested instrument and method of VELEX incorporates multiple spacecraft. With this approach, the question about the existence of lightning on Venus could be settled.},
  language  = {en}
}