Amateur satellite passes

Set your location as a locator (FN31pr) or latitude and longitude, or press My location. Choose a satellite to see:

where it is now: azimuth, elevation, range, and the point below it;
a countdown to the next pass (AOS, acquisition of signal) or to the end of this one (LOS);
a sky plot: the horizon is the outer circle and overhead is the centre, with the pass track and the satellite’s position;
every pass in the next 48 hours above your minimum elevation, with the time of closest approach (TCA) and the azimuths where it rises and sets;
the next pass of each satellite with known frequencies (click a row to switch).

Frequencies and Doppler — for the ISS, SO-50, PO-101, AO-91, AO-27, RS-44, FO-29, and AO-7 the table lists uplinks and downlinks. While the satellite is up it shows what to set now: Doppler shifts a 70 cm signal by up to about ±10 kHz and a 2 m signal by about ±3.5 kHz. The correction uses the range rate, f_rx = f(1 − v/c) and f_tx = f / (1 − v/c).

Orbits — two-line element sets (TLEs) for the amateur group are fetched from CelesTrak when the page opens (the only network request) and cached for 12 hours. You can paste your own TLEs instead. Positions use SGP4 via satellite.js 7.1.0 (MIT licence, served from this site; licence at /tools/satellite/LICENSE.md). Element sets more than a week old drift by kilometres; fetch fresh ones before a pass.

⛶ Full screen gives the sky plot the whole screen (with the live position above it) — the browser’s full screen where it is allowed, otherwise a full-window layer (iPhone); it is redrawn as the window changes, and ◫ Panels hides the frequency panel beside it. Escape leaves.

Presenting

A pass board for the shack or a club demonstration: the satellite, a countdown to AOS (or LOS during a pass), azimuth, elevation and range, the sky plot, and the Doppler-corrected frequencies to set. Press ⛶ Present (beside Share link) or F to open it; Esc or F closes it and T switches between dark and light. It goes full screen where the browser allows, otherwise it fills the window, and keeps the screen awake.

Share link copies a URL with the satellite’s NORAD number (sat), location (loc), and minimum elevation (minel). For example ?sat=27607&loc=IO91wm&minel=15 for SO-50 over London.

Sources

Frequencies are from AMSAT’s FM and linear satellite summaries (checked October 2026). Satellites fail, change mode, and run on schedules — check AMSAT live status before you call.

Related: the ham radio toolkit converts locators and finds bearings; antennas designs Yagis for 2 m and 70 cm, and feedline shows how much signal the coax costs at 435 MHz; the RF calculator works out path loss and antennas; orbital mechanics covers Kepler and Hohmann.

Presenting

Sharing

Sources