Attack Of The Atomic Oxygen

May 28, 2026 by Al Williams 19 Comments

While designing anything for operation in space has its challenges, there is at least one thing that is more of a problem for objects in Earth orbit than for deep-space probes: atomic oxygen. We like oxygen because we need it to live, but it is also highly reactive as a single atom. Luckily, on Earth, most of what we breathe is O₂. [Space Daily] talks about the challenges of the International Space Station dealing with the “space weather” of atomic oxygen in low Earth orbit.

Part of the problem is that even when we know better, we tend to think of the atmosphere coming to an abrupt end and space being a hard vacuum. But in reality, the atmosphere gradually dissipates, and at “only” 400 km above the Earth, the Space Station is really flying through a very thin atmosphere.

To compound the problem, this is above the ozone layer, so the Sun’s UV light rips O₂ into single oxygen atoms. Over time, these free oxygen atoms can affect many parts of a spacecraft exposed to them. Engineers first noticed that materials recovered from spacecraft had more damage and changes to material properties on the pieces facing the direction of travel. NASA has spent years testing different materials by mounting trays of different material samples outside the ISS.

Carbon-based polymers take a big hit from atomic oxygen exposure. Polymide film is frequently used, but it erodes with exposure. Carbon composites also lose mass. Other materials change in other ways. For example, an optical surface may roughen with exposure.

The usual answer is to over-design for mission objectives or to cover certain polymers with coatings like silicon dioxide or aluminum oxide, which are not as reactive to free oxygen. For a long-duration mission like the ISS, you may have to pay special attention to the materials in use. Very low satellites also need special care, as there is more oxygen in lower orbits.

There are other effects, too, such as extreme thermal cycles, debris strikes, and other indignities that space-traveling materials must withstand. But in deep space, atomic oxygen is a rare issue. Until, at least, we go somewhere else that has a lot of oxygen.

Decoding The Tianwen-2 Sample Return Mission’s Telemetry Signal

May 27, 2026 by Maya Posch No comments

China’s Tianwen-2 asteroid sample return mission launched on 28 May of 2025 and is scheduled to arrive at its target – near-Earth asteroid 469219 Kamo’oalewa – in June 2026. This gives folk back on Earth plenty of time to listen in on the probe’s communication with its home base, such as [Daniel Estévez] who recently had a poke at this telemetry as captured by the Dwingeloo radio telescope in the Netherlands.

With not a lot of public information on its trajectory it’s a hard probe to track, but now that it’s nearing its destination there’s an obvious part of the sky to aim for. This is X-band telemetry, broadcast at 8428.19 MHz, with the same basic modulation as its predecessor Tianwen-1.

Where it differs is in the coding, with Tianwen-2 also using concatenated coding, but having a frame length that’s better suited to submitting full Reed-Solomon codewords and does not require omitting bytes to make things awkwardly fit.

After analyzing the telemetry data itself, there doesn’t seem to be anything exciting contained within this capture. This does seem to be as expected considering that the probe is still in its coast phase where it doesn’t have to do much and likely is in a low-power state most of the time. Once its orbital insertion burn begins is when this knowledge can likely be used to track the mission in fine-grained detail, which is an event that we’re definitely looking forward to.

Figuring Out What James Webb’s Mysterious Little Red Dots Are

May 26, 2026 by Maya Posch 16 Comments

After the James Webb Space Telescope (JWST) began operations in 2022, it soon made a tantalizing discovery in the form of mysterious red dots: small, red-tinted astronomical objects of unknown origin and composition. So far well over 300 of such little red dots (LRDs) have been identified, with many theories on what they are. Fortunately the Chandra X-ray Observatory recently added some more clues as detailed in an accompanying paper.

Current theories include them being a form of primordial galaxy, or a supermassive black holes embedded in a dense gas cloud. The LRD discussed in the paper with the designation 3DHST-AEGIS-12014 was found to emit X-rays unlike other LRDs. By comparing the data between JWST and Chandra for this LRD it lends credence to the theory that these LRDs are a transitional phase as a supermassive black hole ingests the material of said gas cloud.

X-rays produced during this can sometimes make it out of the gas cloud, after which we can observe it. If that’s the case, these LRDs should cease to exist the moment the black hole has consumed enough of the cloud, which is something that we may be able to find evidence for if we’re lucky.

This adds just another reason why keeping the Chandra X-ray Observatory mission funded, after it narrowly got saved in 2024.

Spacelab’s Mitra 125 MS

May 24, 2026 by Al Williams 4 Comments

[Ken Shirriff] does some of the most interesting teardowns. This time, he’s looking at a French-built minicomputer called the Mitra 125 MS from around 1980. In particular, it was the computer inside Spacelab, a European lab that could fit in the back of the Space Shuttle.

As you might expect, the computer doesn’t contain a microprocessor. Instead, it is a series of cards and, in this post, [Ken’s] looking at the ALU that allows the computer to perform math operations.

Continue reading “Spacelab’s Mitra 125 MS” →

How Did Apollo Separate?

May 13, 2026 by Al Williams 23 Comments

If you’ve watched a Saturn V launch, you’ve probably seen how a large rocket will often jettison a stage on the way up. There are several reasons for this — there is no reason to haul an empty fuel container, for example. However, you can probably imagine how the separation works. You release something — probably explosive bolts — and gravity pulls the old stage away from you as you climb on the next stage’s engines. But what about on the way back? The command module drops the service module before reentry. [Apollo11Space] has a video explaining just how complicated that was to pull off. You can watch it below.

The main problem? The service module has almost everything you need: oxygen, a big engine, fuel, and electrical generation capability. If you’ve ever seen a real command module, they are tiny. Somehow, you need to get the command module prepared to be on its own for the amount of time it takes to land, and get the service module safely away.

Continue reading “How Did Apollo Separate?” →

Photographing The ISS With A Thrift Store Lens Is Challenging

May 3, 2026 by Zoe Skyforest 8 Comments

There are plenty of photos of the International Space Station out there on the Internet, but taking your own from ground level is a special challenge. [saveitforparts] recently decided to attempt this feat using a $15 thrift store lens.

What a setup! The lens is so big it has its own tripod mount.

The cool thing about the digital photography revolution is that there is a lot of old film gear that can be had for cheap. In this case, [saveitforparts] found a 400 mm Sigma XQ lens with a 2x teleconverter for just $14.99. Paired with an adapter, it sat nicely on a Sony NEX-3 digital camera, ready to try and capture the ISS as it passed overhead.

But as you might imagine, aiming at the space station is not a point-and-shoot job. N2YO.com was used to figure out the best time to try and capture it. [saveitforparts] was able to capture the ISS as a white dot as it passed over, but couldn’t quite get enough zoom to really see the Station in detail. He was able to repeat the feat with a Canon camcorder, but the image was still pretty blobby and didn’t show much. Later attempts involved capturing transits as the ISS passed by the Sun, though the orbiting complex mostly appeared as a small speck.

[saveitforparts] did technically capture the ISS, just not closely enough to see much beyond a dot. It’s not the first time we’ve seen this attempted, though! If you try and capture the ISS with something truly ridiculous, like a Game Boy Camera or Kodak Charmera, you are honor-bound to tell us on the tipsline. Continue reading “Photographing The ISS With A Thrift Store Lens Is Challenging” →

A Guide To CubeSat Mission And Bus Design

April 28, 2026 by Al Williams 9 Comments

If you mention the word bus, you might think of public transportation or, more likely for us, a way to connect things together. But in the satellite world, the bus is the part of a vehicle that supports the payload but isn’t itself the payload. Typically, that means the electric power system, propulsion, radios, and thermal control, among other systems. If you are designing a CubeSat, you will want to read A Guide to CubeSat Mission and Bus Design by [Frances Zhu].

The Creative Commons-licensed book has twelve chapters, ranging from systems engineering — that is, defining what you want to do — to analyzing structures, handling power, setting up communications, and more. Of particular interest to us was the chapter on command and data handling. The final chapters cover software, system integration, and there’s even a chapter on Ethics.

If you want to build a CubeSat or just want to learn more about how satellites actually work, this is a great read. There are videos and other features, too. If you don’t like reading in your browser, you can download an EPUB, PDF, or MOBI near the top of the page.

There are many resources for the want-to-be CubeSat builder. You can even start with an open source design.