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


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


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


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


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!



Ground stations – based on Delfi-C3 RX reports (thanks!)



Simulation model system architecture


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


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'


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



One observation filtered out per pass

Longitude correction For rotation of the Earth

For nodal regression (in iterations)



Uncorrected Longitude-corrected(inclination visible)



Orbital period Find multiple time period between nearly the same locations

Inclination Projection of rotated

observations

Least-squares fit

RAAN / MA


Static Mode Orbit Determination: Results

After 2 days, TLEs are obtainedthat could be used to track satellites with GENSO.


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


Tracking Mode Orbit Determination: Results

After 5 to 7 days, reception quality between 90 and 100%,except for some low inclination orbits.


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


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


Questions?

Thesis at: http://www.xs4all.nl/~ivok/genso-ou/ThesisOrbitDetermination.pdf

satellite orbit determination with gensopage: 1 of 21 satellite orbit determination with the global...

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