AOS · LOS · Sky plot · Doppler
Amateur satellite passes
When can you work the ISS, SO-50, RS-44 or AO-7 from your station? Enter your grid square, coordinates or a US callsign to list upcoming passes: rise and set times, where to point, how high they climb, a sky plot, and the Doppler shift on the downlink. Orbits come from current CelesTrak elements and are computed with SGP4 in your browser.
Upcoming passes
Tap a pass for its sky plot and Doppler. Times are your device's local time () with UTC beneath. Rise/set are at the geometric horizon (0°).
Pass
Looking up: centre is overhead, edge is the horizon, north at top, east at right.
| UTC | Az | El | Range | Range rate | Doppler | Tune RX to |
|---|
Frequencies
From AMSAT's Live FM Satellites (updated 10 Jul 2026) and Live Linear Satellites (updated 24 Mar 2026) pages, as retrieved 1 Oct 2026. Satellites come and go and transponders get switched off: check the AMSAT status page for recent reports before you key up. MHz; the ISS crossband repeater, for example, is listed by AMSAT but isn't always on.
| Satellite | Uplink | Downlink | Notes |
|---|
How it works
Orbital elements are CelesTrak's general-perturbations (GP) data for the “amateur” group, which includes the ISS, downloaded in OMM/JSON form. They're kept on this device for 4 hours; CelesTrak only refreshes them every 2 hours (and the underlying US Space Force data changes only a few times a day), so the page never asks more often than that. The Elements column shows how old each satellite's element set is. Predictions are usually good to within seconds to a minute with elements a day or two old, and drift as the elements age, especially for low satellites like the ISS that are slowed by drag or boosted by engine burns.
Orbits are propagated with SGP4, the model the element sets are made for, using satellite.js, a port of Vallado's reference code that reproduces his published verification vectors. SGP4's output (TEME frame) is rotated to Earth-fixed by Greenwich mean sidereal time. Azimuth and elevation are from your position on the WGS-84 ellipsoid at sea level: azimuth from true north, elevation geometric (refraction lifts objects near the horizon by about half a degree, so real rise is a few seconds earlier and set a few seconds later). Passes are found by stepping every 60 s and refining rise, set and the highest point to a fraction of a second; a pass is listed if its highest point reaches your minimum elevation.
Doppler. With the satellite's velocity in Earth-fixed coordinates, the range rate is ṙ = ρ·ρ̇/|ρ| (negative while it approaches). The downlink you hear is frx = ftx × (1 − ṙ/c), c = 299 792.458 km/s. Approaching satellites sound high, receding ones low; on the uplink the correction is the other way round. For linear transponders we use the centre of the passband.
Location from a callsign uses FCC data from callook.info, geocoded from the mailing address, so it's approximate. A few kilometres makes no practical difference to pass times.
- Orbital elements: CelesTrak (Dr T.S. Kelso), GP data from the US Space Force; formats and usage guidance: GP data formats.
- D.A. Vallado, P. Crawford, R. Hujsak, T.S. Kelso, “Revisiting Spacetrack Report #3”, AIAA 2006-6753 (paper, code and test vectors).
- WGS-84: a = 6378.137 km, f = 1/298.257223563, ω = 7.292115×10⁻⁵ rad/s (NGA TR8350.2).
- Frequencies: AMSAT FM and linear satellite lists; status: AMSAT live status.