Mixed Signals
Any sufficiently advanced information is indistinguishable from noise
Friday 5 July 2002, 3:41 PM
Rupert Goodwins' Diary
Monday 1/07/2002
Did you know the skies are full of amateur radio satellites? Well, not full -- but there are around thirty of them up there, all put into orbit for free by piggybacking on commercial or scientific launches. Hams like me use them to relay signals across the globe: it's great fun scrambling up on Hampstead Heath with a portable transmitter, pointing the aerial upwards and shouting at the skies -- and that's what I was doing, officer, honest.
This has been going on for an amazingly long time -- the first Oscar (Orbiting Satellite Carrying Amateur Radio, natch) went up in 1961, just four years after Sputnik. Oscar 7 was launched in late 1974, and ran happily until 1981. Then silence -- until 21 June, 2002, when a Norfolk radio amateur, Pat Gowen, was tuning around the amateur satellite bands and heard a burst of morse code on an unexpected frequency. It was Oscar 7, come back to life and merrily chirping from the heavens.
The signals it was sending back described its internal conditions, which were surprisingly healthy. Turns out it died because its rechargeable batteries short-circuited; twenty years later, one of the batteries then went open circuit. The solar panels, no longer shorted out, could power the spacecraft electronics again and normal service was resumed. It only works in the sunlight, but when it's there it's very happy. And so are the radio amateurs.
There's one small quirk. The frequencies the satellite is designed to use are no longer allocated to space communications. They're in the amateur bands, and so people are using Oscar 7 to relay their signals with only a small guilty feeling, but it's still a tiny bit naughty.
In this case, there's no problem. But the question is -- how much space junk up there retains the power to switch itself back on as it gets older and goes wrong? At the end of their useful lives, satellites are often pushed out to a parking orbit and told to shut up, but as they age they can forget what they were told and revert to a second childhood -- and if they're transmitting on a band now used for something else, the results could be most uncomfortable.
Tscha. Every day, a new disaster waiting to happen. I'm getting back to my radios and monitoring the heavens... (145.975MHz, if you want to listen for Oscar 7)
Did you know the skies are full of amateur radio satellites? Well, not full -- but there are around thirty of them up there, all put into orbit for free by piggybacking on commercial or scientific launches. Hams like me use them to relay signals across the globe: it's great fun scrambling up on Hampstead Heath with a portable transmitter, pointing the aerial upwards and shouting at the skies -- and that's what I was doing, officer, honest.
This has been going on for an amazingly long time -- the first Oscar (Orbiting Satellite Carrying Amateur Radio, natch) went up in 1961, just four years after Sputnik. Oscar 7 was launched in late 1974, and ran happily until 1981. Then silence -- until 21 June, 2002, when a Norfolk radio amateur, Pat Gowen, was tuning around the amateur satellite bands and heard a burst of morse code on an unexpected frequency. It was Oscar 7, come back to life and merrily chirping from the heavens.
The signals it was sending back described its internal conditions, which were surprisingly healthy. Turns out it died because its rechargeable batteries short-circuited; twenty years later, one of the batteries then went open circuit. The solar panels, no longer shorted out, could power the spacecraft electronics again and normal service was resumed. It only works in the sunlight, but when it's there it's very happy. And so are the radio amateurs.
There's one small quirk. The frequencies the satellite is designed to use are no longer allocated to space communications. They're in the amateur bands, and so people are using Oscar 7 to relay their signals with only a small guilty feeling, but it's still a tiny bit naughty.
In this case, there's no problem. But the question is -- how much space junk up there retains the power to switch itself back on as it gets older and goes wrong? At the end of their useful lives, satellites are often pushed out to a parking orbit and told to shut up, but as they age they can forget what they were told and revert to a second childhood -- and if they're transmitting on a band now used for something else, the results could be most uncomfortable.
Tscha. Every day, a new disaster waiting to happen. I'm getting back to my radios and monitoring the heavens... (145.975MHz, if you want to listen for Oscar 7)
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