Transcript Satellite Orbit Determination with the Global Educational

Satellite Orbit Determination with the
Global Educational Network for Satellite Operations
AMSAT-UK Colloquium 2010
Ivo Klinkert, PA1IVO
Satellite Orbit Determination with GENSO
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Project Overview
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MSc project Computer Science
Nice combination of part-time study and hobby besides daily job
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'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
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Orbit Determination with GENSO
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Is GENSO able to create TLEs by itself?
Problem statement of the research project
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GENSO not designed for orbit determination
Uses prediction based on TLEs, does not measure
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GENSO has a lot of resources, connected together
Collect many low-accuracy observations
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No operational GENSO available during research
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Orbit Determination Problems for Project
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No distance measurements possible
No direct angle measurements possible
No direct frequency measurements possible
Doppler shift should give speed relative to ground station
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Relatively low-profile ground stations
In principle un-calibrated measurements
Low-profile with respect to orbit determination
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Simulation Model of GENSO (1)
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Simulation model required
Testing of orbit determination methods
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Simulation of satellite reception by GENSO
Ground stations, antennas, receivers, satellite, reception,…
Combination of theory and practice (thanks to many HAMs)
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SGP4 to simulate satellite position and speed
Integration of existing SGP4 Java library (thanks to Dave G4DPZ)
One SGP4 instance to simulate 'real' orbit
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Configurable
Different experiments can be performed
Too many parameters to do all combinations!
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Simulation Model of GENSO (2)
Ground stations – based on Delfi-C3 RX reports (thanks!)
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Simulation Model of GENSO (3)
Simulation model system architecture
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Orbit Determination Algorithms (1)
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Two different methods/algorithms for my project
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First method: 'Static mode' orbit determination
No initial information about orbit
Based on ground track reconstruction principle
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Second method: ‘tracking mode' orbit determination
Some signals will be received with the initial TLE
Based on artificial intelligence search principle
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Orbit Determination Algorithms (2)
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Simplification: circular orbit
No determination of argument of perigee and eccentricity
For LEO orbits only a small error
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Based on reception of satellite signals only
Most generic approach, a satellite will at least transmit some data
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Many other were considered, but not used
AFC, discriminator readings, SDRs, …
 Only basic equipment
Unmodified IC-910H/TS-2000/…., standard antennas
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Central entity for orbit determination 'control'
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Static Mode Orbit Determination – Principles (1)
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Insufficient information to track satellite
Only frequency of satellite is known
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Wait for satellite to pass over
Antennas up, fixed receiver frequency: 'static'
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Observations measure 'position' and time
Averaging of observations, average point-in-time
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The orbit is reconstructed
Reconstruction based on ground track reconstruction
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Static Mode Orbit Determination – Principles (2)
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One observation filtered out per pass
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Longitude correction
For rotation of the Earth
For nodal regression (in iterations)
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Static Mode Orbit Determination – Principles (3)
Uncorrected
Satellite Orbit Determination with GENSO
Longitude-corrected
(inclination visible)
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Static Mode Orbit Determination – Principles (4)
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Orbital period
Find multiple time period between nearly the same locations
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Inclination
Projection of rotated
observations
Least-squares fit
 RAAN / MA
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Static Mode Orbit Determination: Results
After 2 days, TLEs are obtained
that could be used to track satellites with GENSO.
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Tracking Mode Orbit Determination (1)
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Usable TLE is available
Ground stations track the satellite
Following with antenna and receiver: 'tracking'
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Trial-and-error hill-climbing search
By varying orbital parameters in TLEs
Mutual influences on parameter values
One parameter searched at a time
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Different ground stations test different TLEs
Smart quality measurement
Comparison between predicted and the real observations
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Tracking Mode Orbit Determination (2)
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Tracking Mode Orbit Determination (3)
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Tracking Mode Orbit Determination: Results
After 5 to 7 days, reception quality between 90 and 100%,
except for some low inclination orbits.
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Conclusions and Future Work
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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
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Test when GENSO gets operational
Adapt to real-world behavior of GENSO
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Acknowledgements
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ESA
For the organization and sponsoring of GENSO
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People from GENSO
For good discussions and the work done so far
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Radio amateurs from AMSAT
For good discussions and advices. Thanks folks!
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AMOLF
For support in time, money, and offering flexibility
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Family
For support now and in the past
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Questions?
Thesis at: http://www.xs4all.nl/~ivok/genso-ou/ThesisOrbitDetermination.pdf
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