ISS on 145.800 MHz: SSTV pictures from orbit and ARISS school contacts

What you hear

During an SSTV event, the warble of a picture coming down from orbit: about two minutes of tone that wanders between 1500 and 2300 Hz with a click at the start of every line, then two minutes of silence, then the next picture, for days on end. The pictures come in series of a dozen, commemorating a flight, an anniversary or a programme, each with a number and a caption; a pass gives you two or three, one usually cut by the horizon. The mode is nearly always PD120, 126 seconds a picture, chosen because it survives noise well.

During a school contact, a voice in FM: an astronaut answering, one after another, the questions of a class somewhere under the footprint, ten minutes until the station sets. You hear only the space side; the pupils speak on the uplink, which a receiver far from the school does not hear, so the answers come as a monologue with gaps. Between events and contacts the frequency is quiet, with the odd casual call from a crew member on a free evening.

Who transmits and why

ARISS, Amateur Radio on the International Space Station, a volunteer programme run with the space agencies since the station's first years, with amateur radio equipment in the Columbus module and in the Russian service module. Its stated purpose is education: the school contacts let children talk to a person in orbit with a handheld radio and a wire antenna, and the SSTV series give thousands of listeners a picture from space they received themselves. The events are announced a few days ahead on the ARISS pages, with the dates and the mode; the school contacts are published there too, with the time and the school's location.

When and where to listen

The station rises four to six times a day from any place between about 60 degrees north and south, each pass up to ten minutes, in groups an hour and a half apart; its footprint is about 2000 kilometres in radius. SSTV events run for three to ten days, several times a year, with pictures on every pass over every continent, so the only requirement is a receiver with 2 metres inside the footprint at the time. School contacts happen once or twice a week somewhere in the world; the downlink is audible across the whole footprint, so a contact with a school in Italy is heard from a receiver in Germany or Poland. The Doppler shift on 2 metres, about 3.5 kHz, is small enough for FM and for the SSTV decoder to cope with.

In ShackDeck

Station catalogue → ISS → ISS: SSTV pictures and school contacts. When you click, the program asks where the station is at that moment, looks for a public receiver with 2 metres inside its footprint, takes the nearest one, tunes it to 145.800 MHz, sets the SSTV mode and starts the decoder; no receiver, antenna or account of your own is needed. The picture builds on screen line by line as the sound arrives, goes into the gallery when it is done and can be saved as a PNG; a picture that starts before the station rises comes out with its top missing, which is normal. For a school contact switch the mode to FM, the frequency is the same. When the station is out of reach of every receiver, 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 track and footprint, the passes of the next 24 hours and a bell for ten minutes before.