@phdthesis{Dannemann2015,
  author    = {Dannemann, Frank},
  title     = {Unified Monitoring of Spacecrafts},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-115934},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {Within this thesis a new philosophy in monitoring spacecrafts is presented: the unification of the various kinds of monitoring techniques used during the different lifecylce phases of a spacecraft. The challenging requirements being set for this monitoring framework are: - "separation of concerns" as a design principle (dividing the steps of logging from registered sources, sending to connected sinks and displaying of information), - usage during all mission phases, - usage by all actors (EGSE engineers, groundstation operators, etc.), - configurable at runtime, especially regarding the level of detail of logging information, and - very low resource consumption. First a prototype of the monitoring framework was developed as a support library for the real-time operating system RODOS. This prototype was tested on dedicated hardware platforms relevant for space, and also on a satellite demonstrator used for educational purposes. As a second step, the results and lessons learned from the development and usage of this prototype were transfered to a real space mission: the first satellite of the DLR compact satellite series - a space based platform for DLR's own research activities. Within this project, the software of the avionic subsystem was supplemented by a powerful logging component, which enhances the traditional housekeeping capabilities and offers extensive filtering and debugging techniques for monitoring and FDIR needs. This logging component is the major part of the flight version of the monitoring framework. It is completed by counterparts running on the development computers and as well as the EGSE hardware in the integration room, making it most valuable already in the earliest stages of traditional spacecraft development. Future plans in terms of adding support from the groundstation as well will lead to a seamless integration of the monitoring framework not only into to the spacecraft itself, but into the whole space system.},
  subject      = {Raumfahrzeug},
  language  = {en}
}
@phdthesis{Borchers2020,
  author    = {Borchers, Kai},
  title     = {Decentralized and Pulse-based Clock Synchronization in SpaceWire Networks for Time-triggered Data Transfers},
  doi       = {10.25972/OPUS-21560},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-215606},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2020},
  abstract  = {Time-triggered communication is widely used throughout several industry do- mains, primarily for reliable and real-time capable data transfers. However, existing time-triggered technologies are designed for terrestrial usage and not directly applicable to space applications due to the harsh environment. In- stead, specific hardware must be developed to deal with thermal, mechanical, and especially radiation effects. SpaceWire, as an event-triggered communication technology, has been used for years in a large number of space missions. Its moderate complexity, her- itage, and transmission rates up to 400 MBits/s are one of the main ad- vantages and often without alternatives for on-board computing systems of spacecraft. At present, real-time data transfers are either achieved by prior- itization inside SpaceWire routers or by applying a simplified time-triggered approach. These solutions either imply problems if they are used inside dis- tributed on-board computing systems or in case of networks with more than a single router are required. This work provides a solution for the real-time problem by developing a novel clock synchronization approach. This approach is focused on being compatible with distributed system structures and allows time-triggered data transfers. A significant difference to existing technologies is the remote clock estimation by the use of pulses. They are transferred over the network and remove the need for latency accumulation, which allows the incorporation of standardized SpaceWire equipment. Additionally, local clocks are controlled decentralized and provide different correction capabilities in order to handle oscillator induced uncertainties. All these functionalities are provided by a developed Network Controller (NC), able to isolate the attached network and to control accesses.},
  subject      = {Daten{\"u}bertragung},
  language  = {en}
}