ISS on 143.625 MHz: cosmonauts talking to mission control

What you hear

A human voice from orbit, in Russian, in ordinary narrow FM: a cosmonaut reporting to mission control, reading back a procedure, asking about a schedule, answering a question. You hear only the space side; the ground talks on another path, so the pauses mid-sentence are the controller speaking. The traffic is working traffic, short and formal, with the occasional laugh or a few words to a family on a quiet evening. The audio is clean, cleaner than most terrestrial repeaters: between the station's antenna and the receiver there is nothing but four hundred kilometres of nearly empty space.

A session lasts as long as the station stays within reach of the Russian ground stations, five to ten minutes, then the frequency goes silent until the next pass. The frequency moves as the station comes and goes: on 2 metres the Doppler shift is about 3.5 kHz, high as the station rises and low as it sets, which an FM receiver takes in its stride.

Who transmits and why

The crew of the Russian segment, through the radio of the Zvezda module, on the channel the Russian side calls VHF-1. It is the primary voice link to the control centre in Korolyov near Moscow, used whenever the station is over the ground stations in Russia, in the clear as it has been since the days of Mir. A backup channel exists on 130.167 MHz. The American segment is different: it talks to Houston through relay satellites high above, and nothing of that reaches a receiver on the ground.

This is not an amateur frequency and the traffic is not meant for the public, but it is sent openly and a receiver only listens. In most countries receiving an open transmission is legal; what the rules may limit is passing its content on. Know the rules where you live.

When and where to listen

The station circles the Earth every 93 minutes on an orbit inclined 51.6 degrees, so from any place between about 60 degrees north and south it rises four to six times a day, in groups an hour and a half apart, each pass up to ten minutes; its footprint, the circle from which it is above the horizon, is roughly 2000 kilometres in radius. The voice comes only when the crew is working and the station is over Russia or eastern Europe: in practice the daytime and evening passes by Moscow time, more on working days than at weekends. From central Europe the sessions are heard on passes that cross Poland, the Baltic and Ukraine; from Russia on nearly every daytime pass. A receiver within the footprint that covers 143 MHz is all that is needed; a vertical antenna is enough on a high pass.

In ShackDeck

Station catalogue → ISS → ISS: cosmonauts and mission control. When you click, the program asks where the station is at that moment, looks for a public receiver with the frequency inside its footprint, takes the nearest one, tunes it to 143.625 MHz in FM and tells you which receiver the station is over; no receiver, antenna or account of your own is needed. If the station is over an ocean or a region without receivers, the program says where it is and when the next pass over your own location begins, from the locator in the settings. The Satellites tab shows the ISS on the map with its track and footprint, the passes of the next 24 hours with rise, maximum elevation and set, a sky plot, and its transmitters with the Doppler-corrected downlink next to a Listen link; a bell there reminds you ten minutes before a pass.