Out of the world service

14/10/1995
Down To Earth

THE British Broadcasting Corporation (BBC) has made history by broadcasting what are thought to be the first radio programmes to be picked up in deep space. Two 15-minute news-and-current-affairs programmes in Spanish for the Americas, BBC Primera Hora (now BBC International) and Via Libre, were detected by a National Aeronautics and Space Agency (NASA) spacecraft more than 200,000 kilometres from the Earth in November 1994. Details have been given in BBC Worldwide in July 1995.

The signal was picked up by scientific investigators Michael Desch and Michael Kaiser Of NASA's Goddard Space Flight Center in Greenbelt, Maryland, USA. Desch takes up the Story: "NASA's WIND spacecraft was launched last November and carried a radio astronomy instrument called WAVES, designed to observe naturally occurring planetary and solar radio phenomena at a low radio frequencies."

Wares detects humanmade signals from Earth-based transmitters around the globe. Usually what is observed at a given time and frequency is the combined effect of transmissions from the commercial short-wave and amateur broadcast stations 'visible' to the spacecraft. Because almost the entire hemisphere of Earth is visible, this can amount to a lot of stations.

However, on November 17, WAVES detected a highly unusual radio signal. Around midday on 6.15 MHZ observing conditions were ideal as there were no solar storms and all humanmade interference was at higher frequencies. The only signal being recorded near 6 MHZ was 'cosmic background', the radio noise that is always present.

Abruptly at 1300 GMT the receiver signal jumped by a factor of over 1,000 and remained high for exactly 30 min- utes. At 1330, the output fell back to cosmic background a sharply as it had risen. No similar signal enhancements were recorded on the receiver's adjacent channels.

Most naturally occuring radio emissions turn on and off gradually and when they are 'on' the signal is quite erratic, whereas the 6.15 MHZ signal stayed well above the cosmic background for extended intervals. The signal was also extremely narrowband; most natural emissions are broadband.

We were fairly sure the signal was humanmade and from a single broad- cast station on Earth: but which one? We could not pinpoint the source using direction-finding.

Using one of the short-wave guides we were able to find a regularly schedules broadcast which matched the time and frequency of our reception exactly. It was a BBC broadcast to Central America from a relay station in Dalany, California."

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