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Transcript of Satellite Orbit Determination with GENSOpage: 1 of 21 Satellite Orbit Determination with the Global...
Satellite Orbit Determination with GENSO page: 1 of 21
Satellite Orbit Determination with theGlobal Educational Network for Satellite Operations
AMSAT-UK Colloquium 2010Ivo Klinkert, PA1IVO
Satellite Orbit Determination with GENSO page: 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 GENSO page: 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 GENSO page: 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 GENSO page: 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 GENSO page: 6 of 21
Simulation Model of GENSO (2)
Ground stations – based on Delfi-C3 RX reports (thanks!)
Satellite Orbit Determination with GENSO page: 7 of 21
Simulation Model of GENSO (3)
Simulation model system architecture
Satellite Orbit Determination with GENSO page: 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 GENSO page: 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 GENSO page: 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 GENSO page: 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 GENSO page: 12 of 21
Static Mode Orbit Determination – Principles (3)
Uncorrected Longitude-corrected(inclination visible)
Satellite Orbit Determination with GENSO page: 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 GENSO page: 14 of 21
Static Mode Orbit Determination: Results
After 2 days, TLEs are obtainedthat could be used to track satellites with GENSO.
Satellite Orbit Determination with GENSO page: 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 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. Thanks folks!
AMOLF For support in time, money, and offering flexibility
Family For support now and in the past