Lost Moon Found: The Satellite That Came Back to Life

The late 1950s and early 1960s were a tumultuous time in world history. The Cold War between the East and the West was in full-swing, driving the new fields of nuclear weapons and space exploration and giving the period its dual monikers of “Atomic Age” and “Space Age.”

Changes in these fields often went hand in glove, with developments in one requiring responses in the other. In 1958, the US conducted nuclear tests in the Pacific that effectively destroyed the ionosphere over the test site and shut down high-frequency communications to places like Hawaii and New Zealand. The strategic implications of this were clear, and the US began looking for ways for the military to reduce its reliance on HF communications and ionospheric skip by using space-based assets to communicate at much higher frequencies.

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Portable Classroom Upgrade: Smaller, Cheaper, Faster

[Eric] at MkMe Lab has a dream: to build a cheap, portable system that provides the electronic infrastructure needed to educate kids anywhere in the world. He’s been working on the system for quite a while, and has recently managed to shrink the suitcase-sized system down to a cheaper, smaller form-factor.

The last time we discussed [Eric]’s EduCase project was as part of his Hackaday Prize 2016 entry. There was a lot of skepticism from our readers on the goals of the project, but whatever you think of [Eric]’s motivation, the fact remains that the build is pretty cool. The previous version of the EduCase relied on a Ku-band downlink to receive content from Outernet, and as such needed to stuff a large antenna into the box. That dictated a case in the carry-on luggage size range. The current EduCase is a much slimmed-down affair that relies on an L-band link from the Inmarsat satellites, with a much smaller patch antenna. A low-noise amp and SDR receiver complete the downlink, and a Raspberry Pi provides the UI. [Eric]’s build is just a prototype at this point, but we’re looking forward to seeing everything stuffed into that small Pelican case.

Yes, Outernet is curated content, and so it’s not at all the same experience as the web. But for the right use case, this little package might just do the job. And with a BOM that rings up at $100, the price is right for experimenting.

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Retrotechtacular: FAX as a Service in 1984

If you tell someone these days to send you something via FAX, you are likely to get a look similar to the one you’d get if you asked them to park your horse. But in 1984, FAX was a mysterious new technology (well, actually, it wasn’t, but it wasn’t yet common to most people).

fed-ex_zapFedEx–the people who got famous delivering packages overnight–made a bold move to seize a new market: Zapmail (not to be confused with the modern mass mailing service). The idea was simple (you can see a commercial for it in grainy VHS splendor, below): Overnight is great but sometimes you need something sent across the country now. A FedEx driver picks up your documents, carries them to a FedEx office. There the documents FAX to another FedEx office where another driver delivers the printed copy. The process took two hours to get a paper document from one side of the continent to another.

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HFSat and The All-HF Amateur Radio Satellite Transponder

One facet of the diverse pursuit that is amateur radio involves the use of amateur radio satellites. These have a long history stretching back to the years shortly after the first space launches, and have been launched as “piggy-back” craft using spare capacity on government and commercial launches.

Though a diverse range of payloads have been carried by these satellites over the years, the majority of amateur radio satellites have featured transponders working in the VHF and UHF spectrum. Most often their links have used the 2m (144 MHz) and 70cm (430MHz) bands. A few have had downlinks in the 10m (28MHz) band, but this has been as far as they have ventured into the HF spectrum.

A new cubesat designed and built by trainees at the US Naval Academy promises to change all that, because it will feature an all-HF transponder with a 15m (21MHz) uplink and a 10m downlink. To that end it will carry a full size 10m wire dipole antenna. The 30KHz wide transponder is an inverting design intended to cancel out the effects of Doppler shift. In their write-up they provide a fascinating description of many aspects of cubesat design, one which should be of significant interest beyond the world of amateur radio.

If the subject of amateur radio in space interests you, have a look at our series on the matter, first covering the OSCAR satellites, and then our recent feature on its use in manned missions.

[via Southgate ARC]

Modest Motor Has Revolutionary Applications

Satellites make many of our everyday activities possible, and the technology continues to improve by leaps and bounds. A prototype, recently completed by [Arda Tüysüz]’s team at ETH Zürich’s Power Electronics Systems Lab in collaboration with its Celeroton spinoff, aims to improve satellite attitude positioning with a high speed, magnetically levitated motor.

Beginning as a doctoral thesis work led by [Tüysüz], the motor builds on existing technologies, but has been arranged into a new application — with great effect. Currently, the maneuvering motors on board satellites are operated at a low rpm to reduce wear, must be sealed in a low-nitrogen environment to prevent rusting of the components, and the microvibrations induced by the ball-bearings in the motors reduces the positioning accuracy. With one felling swoop, this new prototype motor overcomes all of those problems.

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Hackaday Prize Entry: Reverse GPS

Every time you watch a SpaceX livestream to see a roaring success or fireball on a barge (pick your poison), you probably see a few cubesats go up. Everytime you watch a Soyuz launch that is inexplicably on liveleak.com before anywhere else, you’re seeing a few cubesats go up. There are now hundreds of these 10 cm satellites in orbit, and SatNogs, the winner of the Hackaday Prize a two years ago, gives all these cubesats a global network of ground stations.

There is one significant problem with a global network of satellite tracking ground stations: you need to know the orbit of all these cubesats. This, as with all Low Earth Orbit deployments that do not have thrusters and rarely have attitude control, is a problem. These cubesats are tumbling through the rarefied atmosphere, leading to orbits that are unpredictable over several months.

[hornig] is working on a solution to the problem of tracking hundreds of cubesats that is, simply, reverse GPS. Instead of using multiple satellites to determine a position on Earth, this system is using multiple receiving stations on Earth’s surface to determine the orbit of a satellite.

The hardware for [hornig]’s Distributed Ground Station Network is as simple as you would expect. It’s just an RTL-SDR TV tuner USB dongle, a few antennas, a GPS receiver, and a Raspberry Pi connected to the Internet. This device needs to be simple; unlike SatNogs, where single base station in the middle of nowhere can still receive data from cubesats, this system needs multiple receivers all within the view of a satellite.

The modern system of GPS satellites is one of the greatest technological achievements of all time. Not only did the US need to put highly accurate clocks in orbit, the designers of the system needed to take into account relativistic effects. Doing GPS in reverse – determining the orbit of satellites on the ground – is likewise a very impressive project, and something that is certainly a contender for this year’s Hackaday Prize.

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GNU Radio for Space (and Aircraft)

GOMX-3 is a CubeSat with several payloads. One of them is a software defined radio configured to read ADS-B signals sent by commercial aircraft. The idea is that a satellite can monitor aircraft over oceans and other places where there no RADAR coverage. ADB-S transmits the aircraft’s ID, its position, altitude, and intent.

The problem is that ADS-B has a short-range (about 80 nautical miles). GOMX-1 proved that the signals can be captured from orbit. GOMX-3 has more capability. The satellite has a helical antenna and an FPGA.

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