Satellite Pass Tracker & TLE Orbital Predictor
Track visible satellite passes for Hubble, Tiangong, Starlink, and NOAA, parse TLE orbital elements, and calculate radio Doppler shifts.
Hubble Space Telescope (HST)
Tiangong Space Station (CSS)
| Satellite | Next Visible Pass | Max Elevation | Visual Brightness | TLE Action |
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Two-Line Element (TLE) Format Parser
Paste standard NORAD/NASA TLE orbital sets to extract inclination, eccentricity, and orbital period.
Satellite Radio Doppler Shift Calculator
Calculate frequency deviation caused by orbital relative velocity for amateur satellite downlink reception.
Fundamentals of Satellite Pass Prediction
Spotting satellites requires understanding celestial mechanics, lighting geometry, and coordinate horizons. Satellites in low Earth orbit race through orbits in roughly 90 to 100 minutes at altitudes between 300 and 1,000 kilometers.
Apparent Magnitude
Astronomical magnitude is inverse logarithmic. A satellite of magnitude -2 is over 15 times brighter than magnitude +1.
Polar vs Inclined Orbits
NOAA weather satellites use ~98° sun-synchronous polar orbits, passing near the poles on every orbit to survey the whole globe.
Zenith Elevation
Passes crossing 90° overhead experience the shortest atmospheric path length and are maximally bright compared to low-horizon transits.
About this tool
How to use it
- Select a satellite target from the catalog (Hubble Space Telescope, Tiangong Station, Starlink trains, NOAA Weather satellites).
- Choose your observer location or enter geographic coordinates to calculate upcoming overhead passes.
- Inspect maximum elevation (zenith angle), visibility magnitude (apparent brightness), and compass trajectory (e.g., NW to SE).
- Switch to the TLE Decoder tab and paste any standard two-line element set to inspect orbital inclination, eccentricity, and period.
- Use the Radio Doppler Shift Calculator to predict VHF/UHF frequency drifts for amateur satellite tracking.
Why it matters
Thousands of operational satellites orbit in Low Earth Orbit (LEO), reflecting sunlight down to ground observers during dawn and dusk passes. Enthusiasts, ham radio operators, and astrophotographers need accurate overhead pass predictions, TLE orbital parameter parsing, and radio Doppler frequency corrections to track satellites across the night sky.
When to use it
Use when planning evening satellite spotting sessions, predicting Starlink satellite train visibility, receiving weather images from NOAA polar-orbiting satellites, or tracking the Tiangong space station.
Common questions
What is a Two-Line Element (TLE) set?
A TLE is a standardized data format used by NORAD and NASA containing orbital parameters (epoch, inclination, eccentricity, mean motion) that allow mathematical models like SGP4 to compute a satellite's position at any given timestamp.
Why do satellites look brighter at dawn and dusk?
Satellites do not generate their own light. They are visible only when the ground observer is in darkness while the satellite in orbit is still illuminated by direct sunlight.
How does radio Doppler shift affect satellite tracking?
Because LEO satellites travel at over 7 km/s relative to ground stations, incoming radio frequencies shift upward as the satellite approaches and downward as it recedes. Ham radio operators adjust receiver frequencies dynamically to maintain clear signals.
Does this pass tracker work offline?
Yes! The tool incorporates an embedded database of major earth observation, science, and communication satellites with real-time Keplerian orbital prediction algorithms that run locally in your browser.