Parcae: A Trio Of Spy Satellites

Did you ever hear of a satellite called Parcae (pronounced like park-eye)? If you haven’t, don’t feel bad—it was, after all, a top-secret project only revealed in July 2023. [Ivan Amato] not only heard about it, but also wrote a fascinating peek into the cloak-and-dagger world of cold-war spy satellites for this month’s IEEE Spectrum.

According to [Ivan], the satellite helped the United States to keep track of Russian submarines and was arguably the most capable orbiting spy platform ever. Or, at least, that we get to hear about.

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Testing At Scale

We’ve said it before: building one-offs is different from building at scale. Even on a small scale. There was a time when it was rare for a hobbyist to produce more than one of anything, but these days, access to cheap PC boards makes small production runs much more common. [VoltLog], for example, is selling some modules and found he was spending a lot of time testing the boards. The answer? A testing jig for his PC board.

Big factories, of course, have special machines for bulk testing. These are usually expensive. [VoltLog] found a place specializing in creating custom test jigs using 3D printing.

They also have some standard machines. He did have to modify his PCB to accommodate special test points. He sent the design files to the company, and they produced a semi-custom testing jig for the boards in about a month.

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Your VAX In A Cloud Is Ready

For many people of a certain age, the DEC VAX was the first computer they ever used. They were everywhere, powerful for their day, and relatively affordable for schools and businesses. These minicomputers were smaller than the mainframes of their day, but bigger than what we think of as a computer today. So even if you could find an old one in working order, it would be a lot more trouble than refurbishing, say, an old Commodore 64. But if you want to play on a VAX, you might want to get a free membership on DECUServe, a service that will let you remotely access a VAX in all its glory.

The machine is set up as a system of conferences organized in notebooks. However, you do wind up at a perfectly fine VAX prompt (OpenVMS).

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DIY Strontium Aluminate Glows In The Dark

[Maurycyz] points out right up front: several of the reagents used are very corrosive and can produce toxic gasses. We weren’t sure if they were trying to dissuade us not to replicate it or encourage us to do so. The project in question is making strontium aluminate which, by the way, glows in the dark.

The material grows strongly for hours and, despite the dangers of making it, it doesn’t require anything very exotic. As [Maurycyz] points out, oxygen and aluminum are everywhere. Strontium sounds uncommon, but apparently, it is used in ceramics.

For the chemists among us, there’s an explanation of how to make it by decomposing soluble nitrate salts. For the rest of us, the steps are to make aluminum hydroxide using potassium alum, a food preservative, and sodium hydroxide. Then, it is mixed with nitric acid, strontium carbonate, europium, and dysprosium. Those last elements determine the color of the glow.

A drying step removes the acid, followed by dissolving with urea and water. The heat of the reaction wasn’t enough to form the final product, but it took time with an oxy-propane torch to form blobs of strontium aluminate. The product may not have been pure, because it didn’t glow for hours like commercial preparations. But it did manage to glow for a few minutes after light exposure.

We try to limit our chemistry to less toxic substances, although ferric chloride can make a mess. You could probably track down the impurities with a gas chromatograph. What we really want is a glow-in-the-dark car antenna.

Time-of-Flight Sensors: How Do They Work?

With the right conditions, this tiny sensor can measure 12 meters

If you need to measure a distance, it is tempting to reach for the ubiquitous ultrasonic module like an HC-SR04. These work well, and they are reasonably easy to use. However, they aren’t without their problems. So maybe try an IR time of flight sensor. These also work well, are reasonably easy to use, and have a different set of problems. I recently had a project where I needed such a sensor, and I picked up a TF-MiniS, which is a popular IR distance sensor. They aren’t very expensive, and they work serial or I2C. So how did it do?

The unit itself is tiny and has good specifications. You can fit the 42 x 15 x 16 mm module anywhere. It only weighs about five grams — as the manufacturer points out, less than two ping-pong balls. It needs 5 V but communicates using 3.3 V, so integration isn’t much of a problem.

At first glance, the range is impressive. You can read things as close as 10 cm and as far away as 12 m. I found this was a bit optimistic, though. Although the product sometimes gets the name of LiDAR, it doesn’t use a laser. It just uses an IR LED and some fancy optics.

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Robotics Class Is Open

If you are like us, you probably just spin up your own code for a lot of simple projects. But that’s wasteful if you are trying to do anything serious. Take a robot, for example. Are you using ROS (Robot Operating System)? If not — or even if you are — check out [Janne Karttunene] and the University of Eastern Finland’s open-source course Robotics and ROS 2 Essentials.

The material is on GitHub. Rather than paraphrase, here’s the description from the course itself:

This course is designed to give you hands-on experience with the basics of robotics using ROS 2 and Gazebo simulation. The exercises focus on the Andino robot from Ekumen and are structured to gradually introduce you to ROS 2 and Docker.

No prior experience with ROS 2 or Docker is needed, and since everything runs through Docker, you won’t need to install ROS 2 on your system beforehand. Along the way, you’ll learn essential concepts like autonomous navigation and mapping for mobile robots. All the practical coding exercises are done in Python.

Topics include SLAM, autonomous navigation, odometry, and path planning. It looks like it will be a valuable resource for anyone interested in robotics or anything else you might do with ROS.

If you want a quick introduction to ROS, we can help. We’ve seen a number of cool ROS projects over the years.

Forgotten Internet: UUCP

What’s Forgotten Internet? It is the story of parts of the Internet — or Internet precursors — that you might have forgotten about or maybe you missed out on them. This time, we’re looking at Unix-to-Unix Copy, more commonly called UUCP. Developed in the late 1970s, UUCP was a solution for sending messages between systems that were not always connected together. It could also allow remote users to execute commands. By 1979, it was part of the 7th Edition of Unix.

Ken Thompson and Dennis Ritchie may have used UUCP on a PDP-11 like this one. (Photo via Computer History Museum/Gwen Bell)

Operation was simple. Each computer in a UUCP network had a list of neighbor systems. Don’t forget, they weren’t connected, so instead of an IP address, each system had the other’s phone number to connect to a dial up modem. You also needed a login name and password. Almost certainly, by the way, those modems operated at 300 baud or less.

If a computer could dial out, when someone wanted to send something or do a remote execution, the UUCP system would call a neighboring computer. However, some systems couldn’t dial out, so it was also possible for a neighbor to call in and poll to see if there was anything you needed to do. Files would go from one system to another using a variety of protocols.

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