Satellite Pass Helper

Summary

Learn how to predict and spot satellite passes (ISS, Starlink, and more) using free tools, and understand key concepts like elevation angle, azimuth, and visual magnitude.

How it works

1. A satellite orbits Earth in a predictable path governed by Keplerian orbital elements updated daily by space-tracking agencies.
2. Pass prediction software (Heavens-Above, Stellarium, SkySafari) takes your GPS coordinates and computes when the satellite's ground track will be visible from your location.
3. The pass is described by a start azimuth/elevation, a peak elevation (the highest point), and an end azimuth/elevation — letting you know exactly where to look.
4. Visual magnitude (brightness) tells you whether the pass will be naked-eye visible; lower numbers (even negative) mean brighter. The ISS frequently reaches -3 to -4 mag.
5. Use the Heavens-Above website or the NASA "Spot the Station" app: enter your location, pick a satellite, and get a table of upcoming passes with all details.
6. On the predicted date and time, face the start compass direction, scan to the given elevation, and watch the satellite track across the sky.

Use cases

• Plan an ISS observation on a clear night.
• Spot a Starlink train shortly after launch.
• Photograph a satellite transit across the Moon or Sun.
• Teach students about orbital mechanics with real-time examples.
• Verify satellite identification for amateur radio (APRS) contacts.
• Find the best viewing window for a high-magnitude flare pass.
• Compare passes for multiple nights to pick the most favorable geometry.
• Understand why two observers 100 km apart see a pass at different times.

Frequently Asked Questions