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Satellite passes

Amateur satellites in low Earth orbit circle the Earth in about 100 minutes, so each pass over you lasts only minutes. See the next passes over your grid square, where to point your antenna, and the frequencies to tune as Doppler shift moves them.

Passes are computed in your browser. Your location is read only if you press the button below, and it never leaves this page.

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Apply it

  • A dual-band handheld can work the FM satellites. Open the squelch (SO-50 transmits about 250 mW), tilt the antenna to match the satellite’s elevation, and tune the 70 cm downlink from about 10 kHz high to 10 kHz low as the pass goes on; a dual-band Yagi or log periodic beats a whip (AMSAT FM guide).
  • Use only the power you need: AMSAT says 5 W from a handheld with a directional antenna is generally enough from horizon to horizon (AMSAT good operating practices), and too much uplink power blocks other users (T8B02).
  • On linear satellites keep a constant frequency at the satellite; tuning by hand, tune the radio on the higher band, where the Doppler shift is larger (AMSAT, The One True Rule).
  • Check AMSAT’s status page before a pass. Satellites switch modes, run on schedules and fail, and the published frequencies change with them.
  • Learn more in Working amateur satellites.

How it works

  • Orbits come from CelesTrak’s amateur satellite group and are propagated with SGP4, using satellite.js, a port of the reference code in Vallado et al., Revisiting Spacetrack Report #3. This site’s tests compare it with five of the paper’s reference results, for two of its test objects.
  • A download is reused for two hours, as CelesTrak asks, and the age shown is the time it actually arrived. Following CelesTrak’s rules for automated clients, a 403 or 404 answer stops requests for two hours, and any other error answer, or data the page cannot read, stops automatic requests until you choose to try again. When no answer arrives at all, usually because you are offline, the page tries again by itself after 10 minutes, doubling the wait each time up to two hours.
  • Passes, azimuth and elevation are computed in your browser for the center of your grid square at sea level. Times are shown in UTC and in your device’s time zone.
  • A signal from a satellite approaching you arrives higher in frequency and from one moving away arrives lower (NASA). The tool uses the range rate v between you and the satellite: the received frequency is f √((1 − v/c)/(1 + v/c)) (OpenStax).
  • The uplink correction is the frequency to transmit so the satellite hears its published uplink. A linear transponder mixes its input with a local oscillator (E2A03); on an inverting one, the uplink and downlink shifts partly cancel (E2A02), which the chart shows as the drift of your own signal.
  • A US station transmitting to a satellite is an Earth station, which 47 CFR 97.209(b) limits to certain bands and segments. Where the full correction would carry the signal past a segment edge, the suggested transmit frequency is held at the edge, taking an FM voice signal as 16 kHz wide (16K0F3E) and an SSB voice signal as 3 kHz wide, from the examples in 47 CFR 2.202. Where an uplink is outside every segment, as AO-7’s mode B uplink is, the tool says a US station may not transmit on it.
  • Frequencies are from AMSAT’s FM and linear satellite lists, matched to catalog numbers with SatNOGS DB where CelesTrak uses another name. Satellites on AMSAT’s lists whose orbits are not in CelesTrak’s amateur group are not included.
  • The footprint on the map is the area from which the satellite is above the horizon, on a spherical Earth.

Learn more: Working amateur satellites

Sources: A New Way to Obtain GP Data (CelesTrak); Revisiting Spacetrack Report #3 (AIAA 2006-6753) (CelesTrak); satellite.js (satellite.js project); Basics of Space Flight, Chapter 6: The Doppler Effect (NASA); University Physics Volume 3, 5.7 Doppler Effect for Light (OpenStax); Live FM Satellites (updated July 10, 2026) (AMSAT); Live Linear Satellites (updated March 24, 2026) (AMSAT); AMSAT Live OSCAR Satellite Status (AMSAT); Getting Started with the FM Satellites (PDF) (AMSAT); FM Satellites: Good Operating Practices (PDF) (AMSAT); The One True Rule for Doppler Tuning (AMSAT); AO-91 (updated April 27, 2025) (AMSAT); AO-91 Commissioned, Declared Open for Amateur Use (November 2017) (AMSAT); Basics of Space Flight, Chapter 5: Planetary Orbits (NASA); SatNOGS DB satellite records (Libre Space Foundation); 47 CFR 97.209, Earth station (eCFR); 47 CFR 97.301, Authorized frequency bands (eCFR); 47 CFR 2.202, Bandwidths (eCFR); 2026-2030 Technician question pool (NCVEC Question Pool Committee); 2024-2028 Extra Class question pool (NCVEC Question Pool Committee)

Practice the exam questions: T8 Signals and Emissions (Technician), E2 Operating Procedures (Amateur Extra)

Found something wrong or out of date? Report a problem with this tool on GitHub (a public issue; nothing is sent until you submit it there).