Mysteries in polar orbit – space's oldest working hardware still keeps its secrets

It's never aliens, but it could be underground TV repair techs

Opinion The oldest functional off-Earth space hardware? Well, that is a great question for those into pub quizzes, aka bar trivia. 1977's Voyagers hold some impressive records beside those golden discs, just not that one. Any guesses?

Astronomers are still bouncing range-finding lasers off the reflectors left on the Moon by Apollo 11, but fancy mirrors hardly count.

Nope. The best contender is from 1974 and wasn't even launched by NASA or the Soviets. It's still in orbit, still functioning remarkably well, it celebrates its 50th birthday this month, and, lastly, has the suitably prize-winning name of Oscar. 

Its full name is AMSAT-OSCAR 7, known to its friends as Oscar 7, and it is remarkable for many reasons – not least of which are two great mysteries that may never be resolved. For a tiny box built on a budget that shames shoestrings for their conspicuous wealth, it pioneered some amazing technologies, got amazingly lucky more than once, and repaired itself after two decades of being dead (perhaps). 

Start with the luck. The Oscar in Oscar-7 stands for Orbiting Satellite Carrying Amateur Radio, and it was – is – the seventh of its kind. It cost around $60,000 in 1974 money (see PDF) to build, and as The World Radio News pointed out at the time "was built on evenings and weekends by volunteers, many of whom are involved professionally in the aerospace industry." It added: "A comparable satellite commercially built would cost two million dollars."

The hardware weighs just 28.6 kg, and is an octagon covered in solar cells, about half a meter tall, and with spikes sticking out. Its mission, which was planned for either five or ten years depending on sources, was to relay ham radio signals over an area roughly the size of the continental US, and if you've got a ham radio license you can use it right now, orbit permitting.

To build and launch anything for that kind of coin needed volunteers, exceptionally smart thinking, and donated parts. We may have Arduinos in space in 2024, even if nobody knows why, but 50 years ago it was all custom unobtanium.

So Oscar-7 scored several big pieces of luck: firstly, it was given a rechargeable battery used as a test item for a long-forgotten lunar orbiter, and spare solar cells found in a NASA Earth observation satellite program. The battery was space-rated with a limited number of charging cycles before it died, and most solar cells are also limited life, being degraded by radiation. These ones were designed to go through the Van Allen belt and had an unknown lifetime.

Another great piece of luck was the project team, which was scattered around the world in universities, agencies and companies. Time and resources were donated, cadged or constructively shoehorned into theses, all coordinated without even email, and with some brilliant engineering.  The spacecraft had to be in a permanently controlled spin for thermal management and had to be permanently aligned to Earth, but moving parts were out, let alone control jets. Alignment was taken care of by strapping large magnets to align with the Earth's magnetic field, and four antennas made out of cut-up metal tape measures were painted black on one side and white on the other. Arranged as a propeller, the pressure of sunlight would make them act as solar sails, as long as that arrangement also worked for the radio side. It did. 

Ah yes, the radio side. With a 1,000 km orbit and a power budget of 12-14 watts - less than a three amp USB charger, the satellite's transmitters had to be exceptionally efficient to have any chance of being usable by ordinary radio hams with ordinary radio ham gear. That design pioneered ideas still in use today in digital mobile comms. Then there were telemetry, control, beacon and data transmission systems, all touched with genius, all deliciously documented in a [PDF] 50th anniversary paper.

Moreover, it all worked. Launched on November 15th, 1974 and activated a few days later, it wired superbly for six years and six months before, cell by cell, the battery failed, shorting out the solar cells and turning off Oscar-7 for good in June 1981. So far, as expected – and then we hit two intertwined mysteries. 

The first mystery is unambiguously attested. In 2002, 21 years after the satellite died, a British radio ham picked up telemetry signals proclaiming it had returned to life. One of the shorted cells in the battery had somehow gone open circuit, letting all the power from those fortuitously robust solar cells to flow back into the electronics. Oscar 7 worked again, providing it was in sunlight, and since it's in a polar orbit that rarely dips into eclipse, that's most of the time. The problem? Those kinds of batteries never do that. They stay short circuited. This one didn't, and nobody knows why. 

The second mystery or theory also says Oscar-7 came back to life, only this time claiming the revival happened mere months after it went to sleep in the summer of 1981. In December of that year, the Polish Communist Party declared martial law in that country due to widespread protests by the Solidarity organization. This included confiscating all two-way radio equipment and aggressively controlling the telephone system. In response, a network of scientists, engineers and technicians in universities and television repair shops started building clandestine equipment and used it to organize protests and strikes across regions, until martial law was rescinded in 1983. It was one of the big triggers for the collapse of the Soviet Union, and is well documented. So, what to make of claims (Polish) that the clandestine radio network somehow "reactivated" Oscar-7 and used it within Poland and to communicate with the West?

On the one hand, it made sense to use the kit if you could. Uplinks to ham satellites can be highly portable and much more difficult to detect and locate than terrestrial transmission that is powerful enough to cover a country directly. Reception can be very discreet, and it would be politically difficult to jam an international amateur radio satellite that serves all of Europe. If you could, you certainly would, and the reports are clear that the authorities knew it was happening and were very unhappy. On the other hand, it's incredibly unlikely that a working Oscar-7 would go unnoticed by the rest of the world. Tens of thousands of contacts had been made before the satellite went to sleep in 1981, and by the time it did, Oscar-8 had been launched – so there were plenty of hams still using the satellite frequencies. 

That, perhaps, is the best explanation, that the underground were using Oscar-8 – and the Oscar-7 story was deliberately or accidentally elided with it, or clandestine satcomms was a story too good to not pass on, no matter what its origins. More research is definitely needed. It's highly unlikely any amount of research will reveal the magic of the seemingly "self-repairing" power system. It's no mystery that damn fine, committed, passionate engineering had to be behind a system that appears to be able to sleep in orbit for more than two decades and then wake up as if nothing had happened. Laptop designers, please note. ®