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An Advanced Approach to Satellite Software and Communication Based on SmartOS and Compass Protocol: Design, Implementation, and Test on the Picosatellite Platform UWE
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The launch of UWE-3 in 2013 and the experience of preceding Universität Würzburg Experimentalsatellit (UWE) projects have provided many lessons on the communication of the ground station with the satellite.To date, direct communication with subsystems, either from ground or from another subsystem, is not possible. Also several fields of the current protocol, the Missionlink protocol, are not needed any more. However, the need for other fields and functionalities emerged. Analyzing the protocol requirements and existing protocols revealed the need for a new protocol design.This thesis develops Compass, a novel protocol for networks of space-based systems and ground stations with real-time capabilities and the functionality for Ground Station Internet Access Points.A small overhead is required to account for the limited data rate of the space link. Compass offers a minimum overhead of five bytes which is less than for the other analyzed protocols. Additionally, large packets can be split into multiple, smaller fragments independently from the service using Compass.Compass protocol enables a uniform communication inside and between the systems using it. The dynamic address length allows for large networks of ground stations and satellites while being compact for intra-satellite communication. The metadata field can contain further information allowing for added functionalities without altering the Compass protocol definition.Performing formation flight with satellites requires the participating systems to periodically exchange data. The real-time capability of Compass protocol allows the protocol handler to detect the time correlation of received packets on the transport layer without the need for time synchronization. The predefinition of a dedicated Internet service allows a ground station to function as a Ground Station Access Point, providing Internet access to every satellite using Compass protocol.Flow bytes, a new variable-length code compression scheme for integers as well as strings, increases flexibility while decreasing overhead. The performance of flow bytes as well as Compass implementation was benchmarked and it was ascertained that they do not limit the data rate.The UWE program has to cope with the growing complexity of the software. The Small Modular Adept Real-Time Operating System (SmartOS) allows for a modular built-up system, thus clearing the code structure and facilitating the enhancement of the software through new software modules. An elaborated resource management and small footprint conform with the scarce resources available to space-based systems. The communication via Compass was implemented on the OBDH of UWE-3 using SmartOS and inside the existing environment on the ground station.

Place, publisher, year, edition, pages
2016. , 96 p.
Keyword [en]
Technology, compass, uwe, communication, software, satellite, smartos
Keyword [sv]
URN: urn:nbn:se:ltu:diva-58606Local ID: f301e1b4-20f5-4f69-b02e-ef024e8b40c0OAI: diva2:1031994
Subject / course
Student thesis, at least 30 credits
Educational program
Space Engineering, master's level
Validerat; 20160407 (global_studentproject_submitter)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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