IRCB S73-7 Satellite Found After Going Untracked For 25 Years

May 12, 2024 by Maya Posch 26 Comments

When the United States launched the KH-9 Hexagon spy satellite into orbit atop a Titan IIID rocket in 1974, it brought a calibration target along for the ride: the Infra-Red Calibration Balloon (IRCB) S73-7. This 66 cm (26 inch) diameter inflatable satellite was ejected by the KH-9, but failed to inflate into its intended configuration and became yet another piece of space junk. Initially it was being tracked in the 1970s, but vanished until briefly reappearing in the 1990s. Now it’s popped up again, twenty-five years later.

As noted by [Jonathan McDowell] who tripped over S73-7 in recent debris tracking data, it’s quite possible that it had been tracked before, but hidden in the noise as it is not an easy target to track. Since it’s not a big metallic object with a large radar cross-section, it’s among the more difficult signals to reliably pick out of the noise. As can be seen in [Jonathan]’s debris tracking table, this is hardly a unique situation, with many lost (XO) entries. This always raises the exciting question of whether a piece of debris has had its orbit decayed to where it burned up, ended up colliding with other debris/working satellite or simply has gone dark.

For now we know where S73-7 is, and as long as its orbit remains stable we can predict where it’ll be, but it highlights the difficulty of keeping track of the around 20,000 objects in Earth orbit, with disastrous consequences if we get it wrong.

Institutional Memory, On Paper

May 11, 2024 by Elliot Williams 18 Comments

Our own Dan Maloney has been on a Voyager kick for the past couple of years. Voyager, the space probe. As a long-term project, he has been trying to figure out the computer systems on board. He got far enough to write up a great overview piece, and it’s a pretty good summary of what we know these days. But along the way, he stumbled on a couple old documents that would answer a lot of questions.

Dan asked JPL if they had them, and the answer was “no”. Oddly enough, the very people who are involved in the epic save a couple weeks ago would also like a copy. So when Dan tracked the document down to a paper-only collection at Wichita State University, he thought he had won, but the whole box is stashed away as the library undergoes construction.

That box, and a couple of its neighbors, appear to have a treasure trove of documentation about the Voyagers, and it may even be one-of-a-kind. So in the comments, a number of people have volunteered to help the effort, but I think we’re all just going to have to wait until the library is open for business again. In this age of everything-online, everything-scanned-in, it’s amazing to believe that documents about the world’s furthest-flown space probe wouldn’t be available, but so it is!

It makes you wonder how many other similar documents – products of serious work by the people responsible for designing the systems and machines that shaped our world – are out there in the dark somewhere. History can’t capture everything, and it’s down to our collective good judgement in the end. So if you find yourself in a position to shed light on, or scan, such old papers, please do! And then contact some nerd institution like the Internet Archive or the Computer History Museum.

Tokyo Atacama Observatory Opens As World’s Highest Altitude Infrared Telescope

May 6, 2024 by Maya Posch 5 Comments

Although we have a gaggle of space telescopes floating around these days, there is still a lot of value in ground-based telescopes. These generally operate in the visible light spectrum, but infrared ground-based telescopes can also work on Earth, assuming that you put them somewhere high in an area where the atmosphere is short on infrared-radiation absorbing moisture. The newly opened Universe of Tokyo Atacama Observatory (TAO) with its 6.5 meter silver-coated primary mirror is therefore placed on the summit of Cerro Chajnantor at 5,640 meters, in the Atacama desert in Chile.

This puts it only a few kilometers away from the Atacama Large Millimeter Array (ALMA), but at a higher altitude by about 580 meters. As noted on the University of Tokyo project site (in Japanese), the project began in 1998, with a miniTAO 1 meter mirror version being constructed in 2009 to provide data for the 6.5 meter version. TAO features two instruments (SWIMS and MIMIZUKU), each with a specific mission profile, but both focused on deciphering the clues about the Universe’s early history, a task for which infrared is significantly more suitable due to redshift.

The Computers Of Voyager

May 6, 2024 by Dan Maloney 71 Comments

After more than four decades in space and having traveled a combined 44 billion kilometers, it’s no secret that the Voyager spacecraft are closing in on the end of their extended interstellar mission. Battered and worn, the twin spacecraft are speeding along through the void, far outside the Sun’s influence now, their radioactive fuel decaying, their signals becoming ever fainter as the time needed to cross the chasm of space gets longer by the day.

But still, they soldier on, humanity’s furthest-flung outposts and testaments to the power of good engineering. And no small measure of good luck, too, given the number of nearly mission-ending events which have accumulated in almost half a century of travel. The number of “glitches” and “anomalies” suffered by both Voyagers seems to be on the uptick, too, contributing to the sense that someday, soon perhaps, we’ll hear no more from them.

That day has thankfully not come yet, in no small part due to the computers that the Voyager spacecraft were, in a way, designed around. Voyager was to be a mission unlike any ever undertaken, a Grand Tour of the outer planets that offered a once-in-a-lifetime chance to push science far out into the solar system. Getting the computers right was absolutely essential to delivering on that promise, a task made all the more challenging by the conditions under which they’d be required to operate, the complexity of the spacecraft they’d be running, and the torrent of data streaming through them. Forty-six years later, it’s safe to say that the designers nailed it, and it’s worth taking a look at how they pulled it off.

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The History Of The World’s First Planetarium

May 6, 2024 by Al Williams 14 Comments

It shouldn’t be a surprise that the idea of a planetarium originated with an electrical engineer, [Oskar von Miller] from the Deutsches Museum in Munich. According to [Allison Marsh] in IEEE Spectrum, he thought about the invention in 1912 as a way to demonstrate astronomical principles to the general public. While it seems obvious today that you can project the night sky onto a dome, it was a novel thought in 1912. So novel that the Carl Zeiss company first told [von Miller] to take a hike. But they eventually reconsidered and built the first planetarium, the Model I.

The engineer for Zeiss was a mechanical engineer by the name of [Walther Bauersfeld]. He was familiar with mechanical devices — orreries — that tracked the motion of the stars and planets. The goal was to translate those movements into a moving projection of light.

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Building A Rocket Engine From Scratch

May 5, 2024 by Al Williams 14 Comments

There is a reason building a rocket engine is harder than most things you want to build. If you are building, say, a car, your goal is to not have it explode. If you are building a bomb, you want that to explode. But a rocket engine needs to explode just enough and not a bit more. That’s tough, as [Ryan Kuhn] discovered. He’s behind ABL’s E2 rocket, a LOX/kerosene engine for small vehicle launches. You can catch a video of the engine’s qualification tests below.

[Ryan] shares many of the problems encountered from many problems, each requiring finetuning of the design. True, there are plenty of publicly available NASA documents about what works and doesn’t work for rocket engines, but that can only take you so far. You can’t learn to bowl by reading about bowling, and you can’t design a successful rocket on paper just by reading about what others have done.

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Welcome Back, Voyager

April 27, 2024 by Elliot Williams 59 Comments

In what is probably the longest-distance tech support operation in history, the Voyager mission team succeeded in hacking their way around some defective memory and convincing their space probe to send sensor data back to earth again. And for the record, Voyager is a 46-year old system at a distance of now 24 billion kilometers, 22.5 light-hours, from the earth.

While the time delay that distance implies must have made for quite a tense couple days of waiting between sending the patch and finding out if it worked, the age of the computers onboard probably actually helped, in a strange way. Because the code is old-school machine language, one absolutely has to know all the memory addresses where each subroutine starts and ends. You don’t call a function like do_something(); but rather by loading an address in memory and jumping to it.

This means that the ground crew, in principle, knows where every instruction lives. If they also knew where all of the busted memory cells were, it would be a “simple” programming exercise to jump around the bad bits, and re-write all of the subroutine calls accordingly if larger chunks had to be moved. By “simple”, I of course mean “incredibly high stakes, and you’d better make sure you’ve got it right the first time.”

In a way, it’s a fantastic testament to simpler systems that they were able to patch their code around the memory holes. Think about trying to do this with a modern operating system that uses address space layout randomization, for instance. Of course, the purpose there is to make hacking directly on the memory harder, and that’s the opposite of what you’d want in a space probe.

Nonetheless, it’s a testament to careful work and clever software hacking that they managed to get Voyager back online. May she send for another 46 years!