Satellite Orbit Determination with GENSOpage: 1 of 21 Satellite Orbit Determination with the Global Educational Network for Satellite Operations AMSAT-UK Colloquium 2010 Ivo Klinkert, PA1IVO

Satellite Orbit Determination with GENSOpage: 2 of 21 Project Overview MSc project Computer Science Nice combination of part-time study and hobby besides daily job 'Two alternative approaches to orbit determination' Orbit determination because: 1. 'NORAD‘ might stop providing TLEs 2. Scientifically interesting 3. Help during LEOP (not exactly topic of my research)  Based on GENSO ground station network Will work with any collection of amateur radio like ground stations

Satellite Orbit Determination with GENSOpage: 3 of 21 Orbit Determination with GENSO Is GENSO able to create TLEs by itself? Problem statement of the 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 GENSOpage: 4 of 21 Orbit Determination Problems for Project No distance measurements possible No direct angle measurements possible No direct frequency measurements possible Doppler shift should give speed relative to ground station Relatively low-profile ground stations In principle un-calibrated measurements Low-profile with respect to orbit determination

Satellite Orbit Determination with GENSOpage: 5 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, satellite, reception,… Combination of theory and practice (thanks to many HAMs) SGP4 to simulate satellite position and speed Integration of existing SGP4 Java library (thanks to Dave G4DPZ) One SGP4 instance to simulate 'real' orbit Configurable Different experiments can be performed Too many parameters to do all combinations!

Satellite Orbit Determination with GENSOpage: 6 of 21 Simulation Model of GENSO (2) Ground stations – based on Delfi-C3 RX reports (thanks!)

Satellite Orbit Determination with GENSOpage: 7 of 21 Simulation Model of GENSO (3) Simulation model system architecture

Satellite Orbit Determination with GENSOpage: 8 of 21 Orbit Determination Algorithms (1) Two different methods/algorithms for my project First method: 'Static mode' orbit determination No initial information about orbit Based on ground track reconstruction principle Second method: ‘tracking mode' orbit determination Some signals will be received with the initial TLE Based on artificial intelligence search principle

Satellite Orbit Determination with GENSOpage: 9 of 21 Orbit Determination Algorithms (2) Simplification: circular orbit No determination of argument of perigee and eccentricity For LEO orbits only a small error Based on reception of satellite signals only Most generic approach, a satellite will at least transmit some data Many other were considered, but not used AFC, discriminator readings, SDRs, …  Only basic equipment Unmodified IC-910H/TS-2000/…., standard antennas Central entity for orbit determination 'control'

Satellite Orbit Determination with GENSOpage: 10 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 Reconstruction based on ground track reconstruction

Satellite Orbit Determination with GENSOpage: 11 of 21 Static Mode Orbit Determination – Principles (2) One observation filtered out per pass Longitude correction For rotation of the Earth For nodal regression (in iterations)

Satellite Orbit Determination with GENSOpage: 12 of 21 Static Mode Orbit Determination – Principles (3) Uncorrected Longitude-corrected (inclination visible)

Satellite Orbit Determination with GENSOpage: 13 of 21 Static Mode Orbit Determination – Principles (4) Orbital period Find multiple time period between nearly the same locations Inclination Projection of rotated observations Least-squares fit  RAAN / MA

Satellite Orbit Determination with GENSOpage: 14 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 GENSOpage: 15 of 21 Tracking Mode Orbit Determination (1) 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 Mutual influences on parameter values One parameter searched at a time Different ground stations test different TLEs Smart quality measurement Comparison between predicted and the real observations

Satellite Orbit Determination with GENSOpage: 16 of 21 Tracking Mode Orbit Determination (2)

Satellite Orbit Determination with GENSOpage: 17 of 21 Tracking Mode Orbit Determination (3)

Satellite Orbit Determination with GENSOpage: 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 GENSOpage: 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 GENSOpage: 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. Thanks folks! AMOLF For support in time, money, and offering flexibility Family For support now and in the past

Satellite Orbit Determination with GENSOpage: 21 of 21 Questions? Thesis at: