📍 Your Location

Enter a city or use geolocation

🛸 Select Satellite

Next Visible Pass

Time Until Pass

— : — : —

Set location to calculate

📋 Upcoming Passes

Set your location to predict passes

🌍 Live 3D Globe

ISS

—Latitude

—Longitude

—Altitude

—Velocity

Satellite

Your Location

Orbit path

Pass arc

Drag to rotate

▸ Orbital Mechanics — How Fly-Bys Work

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Why Satellites Stay Up

Satellites aren't fighting gravity — they're falling around it. At ~7.7 km/s, they fall toward Earth just as fast as Earth's surface curves away. The ISS completes one orbit every ~92 minutes at 408 km altitude.

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Inclination & Visibility

The ISS orbits at 51.6° inclination, meaning it passes over every location between 51.6°N and 51.6°S latitude. Starlink satellites use multiple inclinations (43°, 53°, 70°, 97°) to cover the entire globe.

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When Can You See It?

The satellite must be in sunlight while you're in darkness — typically 1–2 hours after sunset or before sunrise. The ISS can reach magnitude –5.9, brighter than Venus, moving at ~1° per second across the sky.

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Two-Line Elements (TLE)

Each satellite's orbit is described by a Two-Line Element set — a standardized format encoding inclination, RAAN, eccentricity, mean motion, and more. This app uses them with a Keplerian propagator to predict where each satellite will be.

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Elevation Angle

A pass is visible if the satellite rises above 10° elevation from your horizon. Higher passes (above 45°) are longer and brighter. The azimuth (compass direction) tells you exactly where to look in the sky.

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Starlink Trains

Shortly after launch, Starlink satellites fly in a tight formation — a "train" of bright dots crossing the sky. SpaceX's mega-constellation of 6,000+ satellites at 550 km altitude passes over most locations several times a day.

▸ Frequently Asked Questions

How accurate are these predictions?+

Pass times are predicted using a Keplerian orbital propagator with TLE data — accurate to within 1–2 minutes over a 24-hour window. For real-time precision, the TLEs should be refreshed regularly. The tool uses embedded TLEs (fetching fresh data when available) that represent typical orbital parameters.

What does "max elevation" mean?+

Max elevation is the highest angle above your horizon the satellite reaches during its pass. 90° = directly overhead. Passes above 40° are excellent (long, bright), 20–40° are good, and below 20° are brief and low. Even a 10° pass is visible on a clear dark night.

Why can't I see it on every pass?+

Visibility requires three things: (1) the satellite must pass over your location, (2) it must be in sunlight (not in Earth's shadow), and (3) you must be in twilight or darkness. Many passes happen during daylight hours when the satellite's reflected light is invisible against the bright sky.

Can I see Starlink satellites?+

Yes — individual Starlinks reach around magnitude 3–5 (faintly visible to the naked eye), while freshly-launched trains can be spectacularly bright. SpaceX has added sun visors to reduce brightness after astronomers raised concerns about light pollution.

What direction should I look?+

The pass table shows the maximum azimuth — the compass bearing (N=0°, E=90°, S=180°, W=270°) where the satellite is highest. A good tip: stand outside 2 minutes early to let your eyes adjust to the dark, then watch the sky in that direction for a steady, non-blinking light moving steadily across the sky.