September 23, 2006 1
Real-Time Satellite Tracking Real-Time Satellite Tracking
and Orbit Prediction with and Orbit Prediction with
GPREDICTGPREDICT
Alexandru Csete (Rovsing A/S)[email protected]
3. International Workshop on Astrodynamics Tools and Techniques
ESTEC, October 2-5, 2006
September 23, 2006 2
Gpredict
• Real-time satellite tracking
– Where is the satellite now?
• Future pass predictions
– Where will the satellite be tomorrow?
• Fast and accurate algorithms (SGP4/SDP4)
• Position, velocity, bearing, visibility, signal properties
• One or more ground stations
• Presents data in tabular or graphical form
• Modular design, portable ANSI C code
• Free/open-source software (GNU GPL)
• Unix/Linux/BSD, Mac, and Windows
September 23, 2006 3
Satellite Tracking
Size and shape
of orbit
Orientation of the
orbit in space
Satellite position
on the orbit path
Time when the
satellite was there
Keplerian Elements
Solve Kepler’s
Equation
+
Corrections
Vector
Calculations
Position of Satellite
Current Date and Time
Latitude and longitude
of ground station
Azimuth and
elevation from
ground station
to satellite
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SGPx/SDPx Algorithms
• Gravitational models of Earth (1959-1980)
• Solve Kepler’s equation for orbital motion
• SGPx: Near-Earth objects (period < 255 min)
• SDPx: SGPx + deep space perturbations, e.g. Sun and
Moon
• SGP, SGP4/SDP4, and SGP8/SDP8
• Input: Orbital elements at t0 generated and published on
the web by NORAD
• Orbital elements must be updated periodically
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Initial Orbital Elements
• Also known as Keplerian Elements or TLE
• Size, shape, and orientation of the orbit
• Satellite position on the orbit at t0
• Average atmospheric drag
ISS (ZARYA)
1 25544U 98067A 06252.44258404 .00014635 00000-0 96907-4 0 6335
2 25544 51.6331 113.4131 0011142 320.8285 104.5775 15.75745231446454
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Gpredict Design
User Interface
Input Data
BackendSGP4/SDP4
EngineDriver
Satellite Data
at time t0
Ground Station
Data (Lat,Lon)Time
Future Pass
Predictions
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Map View
• Which satellite is where at any given time
• Shows footprints and covered areas
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List View
• Details about many satellites
• Automatically sorts itself
• User can show/hide each column individually
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Polar View
• Also known as Radar View
• Shows satellites within range
• Sky track (path)
• Radio Amateurs love this
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Single-Satellite View
• Shows details about one satellite at
a time
• Good to show many details
• Better performance than the list
view
• User can show/hide each data field
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Modules: Combination of Views
• Group satellites and ground stations into separate
“workspaces”
• Include up to 3 views (map, list, …)
• Individual configuration
• Many modules at the same time
• Module States: Docked, window or full-screen
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Modules: Combination of Views
Map + List
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Modules: Combination of Views
List + Polar + Single-Sat
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Modules: Combination of Views
Map + Polar + List
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Modules: Combination of Views
List + 2 ! Single-Sat
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Live Demo
September 23, 2006 17
Future Plans
• Automatic update of orbital elements
• Automatic control of communication equipment
• More prediction gadgets
• Mobile “ground” stations
• Formalise plug-in infrastructure
– More algorithms and user interface modules
• External hooks
• Simulated real-time
• Embedded devices
– PDA, car navigation computers, …
• Fix bugs
September 23, 2006 18
Summary
• Real-time satellite tracking
• Future pass predictions
• Runs “out of the box”
• High quality anti-aliased graphics
• Many customisation options
• Nice playground to test algorithms
• Modular Design
• Clean, portable ANSI C code
• Free/open-source (GNU GPL)
• Unix/Linux/BSD, Mac, and Windows
September 23, 2006 19
Summary
• Real-time satellite tracking
• Future pass predictions
• Runs “out of the box”
• High quality anti-aliased graphics
• Many customisation options
• Nice playground to test algorithms
• Modular Design
• Clean, portable ANSI C code
• Free/open-source (GNU GPL)
• Unix/Linux/BSD, Mac, and Windows
Use it
September 23, 2006 20
Summary
• Real-time satellite tracking
• Future pass predictions
• Runs “out of the box”
• High quality anti-aliased graphics
• Many customisation options
• Nice playground to test algorithms
• Modular Design
• Clean, portable ANSI C code
• Free/open-source (GNU GPL)
• Unix/Linux/BSD, Mac, and Windows
Use it
Enjoy it
September 23, 2006 21
Summary
• Real-time satellite tracking
• Future pass predictions
• Runs “out of the box”
• High quality anti-aliased graphics
• Many customisation options
• Nice playground to test algorithms
• Modular Design
• Clean, portable ANSI C code
• Free/open-source (GNU GPL)
• Unix/Linux/BSD, Mac, and Windows
Use it
Enjoy it
Explore it
September 23, 2006 22
Summary
• Real-time satellite tracking
• Future pass predictions
• Runs “out of the box”
• High quality anti-aliased graphics
• Many customisation options
• Nice playground to test algorithms
• Modular Design
• Clean, portable ANSI C code
• Free/open-source (GNU GPL)
• Unix/Linux/BSD, Mac, and Windows
Use it
Enjoy it
Explore it
Learn from it
September 23, 2006 23
Summary
• Real-time satellite tracking
• Future pass predictions
• Runs “out of the box”
• High quality anti-aliased graphics
• Many customisation options
• Nice playground to test algorithms
• Modular Design
• Clean, portable ANSI C code
• Free/open-source (GNU GPL)
• Unix/Linux/BSD, Mac, and Windows
Use it
Enjoy it
Explore it
Learn from it
Enjoy freedom
September 23, 2006 24
Availability
http://groundstation.sf.net/gpredict
Questions?