50 years in SPAAAAACE: Telstar celebrates half-century since launch

World's first active comms satellite stopped bouncing signals in'63

Vid On 10 July 1962, the privately-owned Telstar 1 was blasted into orbit on the back of NASA's Thor-Delta rocket, and despite only working for a year it proved that commercial satellite communications was possible.

Telstar 1 was owned by the US telephony monopoly Ma Bell, and was built in the Bell Telephone Laboratories, though it was a joint project: the French and UK post offices both chucked in some cash as well as expertise and a couple of ground stations to receive the bounced signals. Those signals could, and did, include 600 simultaneous phone calls, and (most importantly of all) a single black-and-white TV stream:

Telstar wasn't the first satellite to bounce radio signals, that was "Courier 1B" from whose name one can identify as a military project, but Telstar was privately owned and thus ushered in a new age of space exploitation that would eventually let us all watch Buffy the Vampire Slayer at seven in the morning.

Arthur C Clarke is often credited with inventing the idea of satellite communications, though in fact his contribution was to point out that three birds in geostationary orbit could provide global coverage. Geostationary orbit is more than 35,000km up, beyond the reach of radios in 1962, so Telstar's orbit peaked at less than 6,000km up and dipped down to less than 1,000km during its two-and-a-half-hour circumnavigation.

That dip is also what caused Telstar's downfall. Its repeated drops into the Van Allen radiation belt did allow the satellite to gather information about the belt (which was part of the plan) but the information it gathered was largely the havoc such radiation plays with electronic circuits. If Wikipedia is to be believed then US nuclear tests at the time had left the Van Allen particularly charged, but either way the satellite failed intermittently for a few months and finally stopped relaying signals entirely in February 1963. However, it remains in orbit to this day, faithfully tracked by the US government as required by international treaties.

Telstar was solar powered, with 3,600 solar cells feeding 19 nickel-cadmium batteries which received a 6GHz signal and retransmitted it with 2.25w of power at 4GHz. The electrics necessary were all suspended by shock-absorbent nylon cords in the middle of the spherical body, which had to spin at 180 rpm for stabilisation (gyroscopes perform the same function on modern satellites, but weren't reliable enough back then).

Even when it was working, Telstar was only over the Atlantic for 20 minutes per orbit, so developers envisioned 20 more satellites filling the gaps for global communications. In fact the radios got better and rockets more powerful, so as Arthur C Clarke had predicted, the vast majority of communication satellites end up in geostationary orbit these days (though they aren't manned, as he had expected them to be).

But geostationary orbit carries with it a latency, as the signal has to travel all that way up and back down again. This is fine for TV broadcasting but irritating when one is making a phone call ... and fatal if you're playing Call of Duty. The vast majority of global communications now takes place over cables draped across the sea bed, and the first of those to cross the Atlantic only worked for three weeks (by which measure Telstar was an overwhelming success).

Alcatel-Lucent, inheritors of Bell Labs' legacy, are celebrating that achievement with a collection of images, information and video, but an equally good tribute is to spend the day watching satellite TV and remembering that Telstar made it possible.

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