Satellite Orbit Determination with the Global Educational Network for Satellite Operations Master Project Presentation Open University of the Netherlands – Faculty of Computer Science Ivo Klinkert 19 July 2010, Utrecht

Satellite Orbit Determination with GENSO page: 2 of 21 Outline Presentation Introduction - Cubesats, low-Earth satellite orbits and reception, GENSO Problem statement - The need for orbit determination with GENSO Orbit determination methods - Simulation model - Two different strategies, and the results Conclusions and future work Questions Cubesat in space

Satellite Orbit Determination with GENSO page: 3 of 21 Educational Satellites: Cubesats Small - 10 x 10 x 10 cm - According to cubesat standard Low transmission power - Comparable to the power of a mobile phone Built by university students No example available here, but.... Compass-1 cubesat

Satellite Orbit Determination with GENSO page: 4 of 21 Low-Earth Satellite Orbits (1) Relatively low orbits km above the Earth, orbits are almost circular Satellites orbit fast, 14 times a day around the Earth - With less speed the satellites would fall back to Earth Satellites are only 'visible' for short periods of time - 6 to 8 times a day, for maximum 15 minutes, for one observer The orbits are 'described' by orbital parameters - Size and shape, orientation relative to Earth - Position of the satellite in the orbit in time - Four parameters for the methods in this research

Satellite Orbit Determination with GENSO page: 5 of 21 Low-Earth Satellite Orbits (2) Example orbital parameter: Inclination Inclination 40° - 60° - 80°

Satellite Orbit Determination with GENSO page: 6 of 21 Receiving Low-Earth Orbit Satellites

Satellite Orbit Determination with GENSO page: 7 of 21 GENSO (1): Characteristics Global Educational Network for Satellite Operations - A unique global radio network, using the internet as the backbone 24-hour-a-day communication with a satellite - Solves traditional communication problem Cooperation universities and radio amateurs - Rich variety of ground stations, low-profile Built by students, coordinated by ESA

Satellite Orbit Determination with GENSO page: 8 of 21 GENSO (2): Principle world-wide coverage

Satellite Orbit Determination with GENSO page: 9 of 21 The Need for Orbital Parameters Orbital parameters defined in Two-Line Elements set - Also called TLEs Provided free of charge, uncertain for the future - By NORAD (North American Aerospace Defense Command) Without a TLE, a satellite becomes useless! - No/outdated information about position and speed - Like going by train without knowing the station and timetable

Satellite Orbit Determination with GENSO page: 10 of 21 Orbit Determination with GENSO Is GENSO able to create TLEs by itself? - Problem statement of this research project GENSO not designed for orbit determination - Uses prediction based on TLEs, does not measure GENSO has a lot of resources, connected together - Collect many low-accuracy observations No operational GENSO available during research

Satellite Orbit Determination with GENSO page: 11 of 21 Simulation Model of GENSO (1) Simulation model required - Testing of orbit determination methods Simulation of satellite reception by GENSO - Ground stations, antennas, receivers, satellites, Combination of theory and practice Integration of existing orbit prediction library - Same as GENSO uses Configurable - Different experiments can be performed

Satellite Orbit Determination with GENSO page: 12 of 21 Simulation Model of GENSO (2) Simulation of ground stations

Satellite Orbit Determination with GENSO page: 13 of 21 Orbit Determination: Phases

Satellite Orbit Determination with GENSO page: 14 of 21 Static Mode Orbit Determination – Principles (1) Insufficient information to track satellite - Only frequency of satellite is known Wait for satellite to pass over - Antennas up, fixed receiver frequency: 'static' Observations measure 'position' and time - Averaging of observations, average point-in-time The orbit is reconstructed - Algorithm for every orbital parameter - Correction for rotation of the Earth

Satellite Orbit Determination with GENSO page: 15 of 21 Static Mode Orbit Determination – Principles (2) Uncorrected Longitude-corrected (inclination visible)

Satellite Orbit Determination with GENSO page: 16 of 21 Static Mode Orbit Determination: Results After 2 days, TLEs are obtained that could be used to track satellites with GENSO.

Satellite Orbit Determination with GENSO page: 17 of 21 Tracking Mode Orbit Determination - Principles Usable TLE is available Ground stations track the satellite - Following with antenna and receiver: 'tracking' Trial-and-error hill-climbing search - By varying orbital parameters in TLEs Different ground stations test different TLEs Smart quality measurement - Comparison between the prediction and the real observations

Satellite Orbit Determination with GENSO page: 18 of 21 Tracking Mode Orbit Determination: Results After 5 to 7 days, reception quality between 90 and 100%, except for some low inclination orbits.

Satellite Orbit Determination with GENSO page: 19 of 21 Conclusions and Future Work Proof-of-concept for orbit determination with GENSO Methods developed for entire lifetime of satellite Not as accurate as NORAD, but sufficient Static mode better than tracking mode - But during tracking mode reception of data is possible Test when GENSO gets operational Adapt to real-world behavior of GENSO

Satellite Orbit Determination with GENSO page: 20 of 21 Acknowledgements ESA - For the organization and sponsoring of GENSO People from GENSO - For good discussions and the work done so far Radio amateurs from AMSAT - For good discussions and advices AMOLF - For support in time, money, and offering flexibility Family - For support now and in the past

Satellite Orbit Determination with GENSO page: 21 of 21 Time for Questions