Good news, bad news for Sun watchers this week, as our star launched a solar flare even bigger than the one back in May that gave us an amazing display of aurora that dipped down into pretty low latitudes. This was a big one; where the earlier outburst was only an X8.9 class, the one on July 23 was X14. That sure sounds powerful, but to put some numbers to it, the lower end of the X-class exceeds 10^-4 W/m² of soft X-rays. Numbers within the class designate a linear increase in power, so X2 is twice as powerful as X1. That means the recent X14 flare was about five times as powerful as the May flare that put on such a nice show for us. Of course, this all pales in comparison to the strongest flare of all time, a 2003 whopper that pegged the needle on satellite sensors at X17 but was later estimated at X45.

So while the X14 last week was puny by comparison, it still might have done some damage if it had been Earth-directed. As it was, the flare and its associated coronal mass ejection occurred on the far side of the Sun, sending all that plasma off into the void, since pretty much all the planets were on this side of the Sun at the time. That’s the bad news part of this story, at least for those of us who enjoy watching aurora, not to mention the potential for a little doomsday. But fear not; the sunspot region that spawned this monster flare is transiting the far side of the Sun as we speak, and might just emerge with all its destructive potential intact.

Then again, why wait for the Sun to snuff communications when you can just start your own fiber optic apocalypse? Perhaps that was the motivation when saboteurs in France broke into cabinets in several locations on the night of July 28 and 29 to cut fiber cables. These must have been proper cables, since telecomms insiders say it would have taken an axe or angle grinder to cut through them. While the saboteurs were obviously motivated and organized, they appear not to have been familiar enough with the network topology to cause a widespread outage, nor did they succeed in disrupting the Paris Olympics, the most obvious nearby target. Then again, maybe they weren’t looking for that much attention. Probing attack much?

A couple of weeks back we featured a story (third item) about a GMRS system that had a questionable interaction with Federal Communications Commission investigators, resulting in their system of linked repeaters being taken offline. It seemed pretty clear to us at the time that the FCC regulations regarding the General Mobile Radio Service allowed for repeaters, but prohibited linking them together with pretty much any kind of network. Our friend Josh (KI6NAZ) over at Ham Radio Crash Course is weighing in on the issue now, and seems to have come to the same conclusion. However, the FCC didn’t really do themselves or the GMRS community any favors with the wording of 47 CFR §95.1733, which prohibits “Messages which are both conveyed by a wireline control link and transmitted by a GMRS station.” That “wireline” bit seems to be the part GMRS operators latched onto, thinking somehow that this only meant landline telephones and that linking repeaters through the Internet was all good.

A friend of ours once related his plans for the weekend, which included, “Going home, flipping on cable, and turning on CSPAN.” He knew this was pretty sad, and even had a name for it: “Loser Entertainment Television”, or LET. We’re not sure what other channels were on his LET list, but if NASA TV had been available at the time, we’re pretty sure he would have included it. Sadly, or luckily depending on your viewpoint, NASA is shutting down their cable channel in a couple of weeks. You say you had no idea that NASA had a cable channel? We didn’t either — we haven’t had cable or satellite service in at least a decade now — so don’t feel too bad. Our condolences if NASA TV was a part of your life, but you can at least take comfort that much of the same content will still be available on the NASA+ streaming service, which we also didn’t know was a thing. Are we so out of touch?

And finally, if you need something to play with during these dog days of (northern hemisphere) summer, you could do worse than React Flight Tracker, and open-source 3D visualizer for everything that flies. And we mean everything; not only does it track civil and military aviation globally, it also shows the obit of everything from satellites in LEO to dead comms birds in parking geosynchronous parking orbits. You can even zoom way out and see bits of space flotsam like boosters and fairing out about halfway to the Moon. The nice thing about it is the Google Earth-like interface, which gives you a unique perspective on flight. We always knew that the best path from Istanbul to Seattle was (almost) over the North Pole, but seeing it on a 3D globe really brings the point home. It’s also interesting to watch planes from Tokyo to Frankfurt skirting around Russian airspace. Have fun.

Ever since the beginning of the Space Age, the inner planets and the Earth-Moon system have received the lion’s share of attention. That makes sense; it’s a whole lot easier to get to the Moon, or even to Mars, than it is to get to Saturn or Neptune. And so our probes have mostly plied the relatively cozy confines inside the asteroid belt, visiting every world within them and sometimes landing on the surface and making a few holes or even leaving some footprints.

But there’s still one place within this warm and familiar neighborhood that remains mysterious and relatively unvisited: the Sun. That seems strange, since our star is the source of all energy for our world and the system in general, and its constant emissions across the electromagnetic spectrum and its occasional physical outbursts are literally a matter of life and death for us. When the Sun sneezes, we can get sick, and it has the potential to be far worse than just a cold.

While we’ve had a succession of satellites over the last decades that have specialized in watching the Sun, it’s not the easiest celestial body to observe. Most spacecraft go to great lengths to avoid the Sun’s abuse, and building anything to withstand the lashing our star can dish out is a tough task. But there’s one satellite that takes everything that the Sun dishes out and turns it into a near-constant stream of high-quality data, and it’s been doing it for almost 15 years now. The Solar Dynamics Observatory, or SDO, has also provided stunning images of the Sun, like this CGI-like sequence of a failed solar eruption. Images like that have captured imaginations during this surprisingly active solar cycle, and emphasized the importance of SDO in our solar early warning system.

Living With a Star

In a lot of ways, SDO has its roots in the earlier Solar and Heliospheric Observer, or SOHO, the wildly successful ESA solar mission. Launched in 1995, SOHO is stationed in a halo orbit at Lagrange point L₁ and provides near real-time images and data on the sun using a suite of twelve science instruments. Originally slated for a two-year science program, SOHO continues operating to this day, watching the sun and acting as an early warning for coronal mass ejections (CME) and other solar phenomena.

Although L₁, the point between the Earth and the Sun where the gravitation of the two bodies balances, provides an unobstructed view of our star, it has disadvantages. Chief among these is distance; at 1.5 million kilometers, simply getting to L₁ is a much more expensive proposition than any geocentric orbit. The distance also makes radio communications much more complicated, requiring the specialized infrastructure of the Deep Space Network (DSN). SDO was conceived in part to avoid some of these shortcomings, as well as to leverage what was learned on SOHO and to extend some of the capabilities delivered by that mission.

SDO stemmed from Living with a Star (LWS), a science program that kicked off in 2001 and was designed to explore the Earth-Sun system in detail. LWS identified the need for a satellite that could watch the Sun continuously in multiple wavelengths and provide data on its atmosphere and magnetic field at an extremely high rate. These requirements dictated the specifications of the SDO mission in terms of orbital design, spacecraft engineering, and oddly enough, a dedicated communications system.

Geosynchronous, With a Twist

Getting a good look at the Sun for space isn’t necessarily as easy as it would seem. For SDO, designing a suitable orbit was complicated by the stringent and somewhat conflicting requirements for continuous observations and constant high-bandwidth communications. Joining SOHO at L₁ or setting up shop at any of the other Lagrange points was out of the question due to the distances involved, leaving a geocentric orbit as the only viable alternative. A low Earth orbit (LEO) would have left the satellite in the Earth’s shadow for half of each revolution, making continuous observation of the Sun difficult.

To avoid these problems, SDO’s orbit was pushed out to geosynchronous Earth orbit (GEO) distance (35,789 km) and inclined to 28.5 degrees relative to the equator. This orbit would give SDO continuous exposure to the Sun, with just a few brief periods during the year where either Earth or the Moon eclipses the Sun. It also allows constant line-of-sight to the ground, which greatly simplifies the communications problem.

Science of the Sun

The main body of SDO has a pair of solar panels on one end and a pair of steerable high-gain dish antennas on the other. The LWS design requirements for the SDO science program were modest and focused on monitoring the Sun’s magnetic field and atmosphere as closely as possible, so only three science instruments were included. All three instruments are mounted to the end of the spaceframe with the solar panels, to enjoy an unobstructed view of the Sun.

Of the three science packages, the Extreme UV Variability Experiment, or EVE, is the only instrument that doesn’t image the full disk of the Sun. Rather, EVE uses a pair of multiple EUV grating spectrographs, known as MEGS-A, and MEGS-B, to measure the extreme UV spectrum from 5 nm to 105 nm with 0.1 nm resolution. MEGS-A uses a series of slits and filters to shine light onto a single diffraction grating, which spreads out the Sun’s spectrum across a CCD detector to cover from 5 nm to 37 nm. The MEGS-A CCD also acts as a sensor for a simple pinhole camera known as the Solar Aspect Monitor (SAM), which directly measures individual X-ray photons in the 0.1 nm to 7 nm range. MEGS-B, on the other hand, uses a pair of diffraction gratings and a CCD to measure EUV from 35 nm to 105 nm. Both of these instruments capture a full EUV spectrum every 10 seconds.

To study the corona and chromosphere of the Sun, the Atmospheric Imaging Assembly (AIA) uses four telescopes to create full-disk images of the sun in ten different wavelengths from EUV to 450 nm. The 4,096 by 4,096 sensor gives the AIA a resolution of 0.6 arcseconds per pixel, and the optics allow imaging out to almost 1.3 solar radii, to capture fine detail in the thin solar atmosphere. AIA also visualizes the Sun’s magnetic fields as the hot plasma gathers along lines of force and highlights them. Like all the instruments on SDO, the AIA is built with throughput in mind; it can gather a full data set every 10 seconds.

For a deeper look into the Sun’s interior, the Helioseismic and Magnetic Imager (HMI) measures the motion of the Sun’s photosphere and magnetic field strength and polarity. The HMI uses a refracting telescope, an image stabilizer, a series of tunable filters that include a pair of Michelson interferometers, and a pair of 4,096 by 4,096-pixel CCD image detectors. The HMI captures full-disk images of the Sun known as Dopplergrams, which reveal the direction and velocity of movement of structures in the photosphere. The HMI is also capable of switching a polarization filter into the optical path to produce magnetograms, which use the polarization of light as a proxy for magnetic field strength and polarity.

Continuous Data, and Lots of It

Like all the SDO instruments, HMI is built with data throughput in mind, but with a twist. Helioseismology requires accumulating data continuously over long observation periods; the original 5-year mission plan included 22 separate HMI runs lasting for 72 consecutive days, during which 95% of the data had to be captured. So not only must HMI take images of the Sun every four seconds, it has to reliably and completely package them up for transmission to Earth.

While most space programs try to leverage existing communications infrastructure, such as the Deep Space Network (DSN), the unique demands of SDO made a dedicated communications system necessary. The SDO communication system was designed to meet the throughput and reliability needs of the mission, literally from the ground up. A dedicated ground station consisting of a pair of 18-meter dish antennas was constructed in White Sands, New Mexico, a site chosen specifically to reduce the potential for rainstorms to attenuate the Ka-band downlink signal (26.5 to 50 GHz). The two antennas are located about 5 km apart within the downlink beamwidth, presumably for the same reason; storms in the New Mexico desert tend to be spotty, making it more likely that at least one site always has a solid signal, regardless of the weather.

To ensure that all the downlinked data gets captured and sent to the science teams, a complex and highly redundant Data Distribution System (DDS) was also developed. Each dish has a redundant pair of receivers and servers with RAID5 storage arrays, which feed a miniature data center of twelve servers and associated storage. A Quality Compare Processing (QCP) system continually monitors downlinked data quality from each instrument aboard SDO and stores the best available data in a temporary archive before shipping it off to the science team dedicated to each instrument in near real-time.

The numbers involved are impressive. The SDO ground stations operate 24/7 and are almost always unattended. SDO returns about 1.3 TB per day, so the ground station has received almost 7 petabytes of images and data and sent it on to the science teams over the 14 years it’s been in service, with almost all of it being available nearly the instant it’s generated.

As impressive as the numbers and the engineering behind them may be, it’s the imagery that gets all the attention, and understandably so. NASA makes all the SDO data available to the public, and almost every image is jaw-dropping. There are also plenty of “greatest hits” compilations out there, including a reel of the X-class flares that resulted in the spectacular aurorae over North America back in mid-May.

Like many NASA projects, SDO has far exceeded its planned lifespan. It was designed to catch the midpoint of Solar Cycle 24, but has managed to stay in service through the solar minimum of that cycle and into the next, and is now keeping a close watch on the peak of Solar Cycle 25.

A couple of weeks back we featured a story (third item) about a chunk of space jetsam that tried to peacefully return to Earth, only to find a Florida family’s roof rudely in the way. The 700-gram cylinder of Inconel was all that was left of a 2,360-kg battery pack that was tossed overboard from the ISS back in 2021, the rest presumably turning into air pollution just as NASA had planned. But the surviving bit was a “Golden BB” that managed to slam through the roof and do a fair amount of damage. At the time it happened, the Otero family was just looking for NASA to cover the cost of repairs, but now they’re looking for a little more consideration. A lawsuit filed by their attorney seeks $80,000 to cover the cost of repairs as well as compensation for the “stress and impact” of the event. This also seems to be about setting a precedent, since the Space Liability Convention, an agreement to which the USA is party, would require the space agency to cover damages if the debris had done damage in another country. The Oteros think the SLC should apply to US properties as well, and while we can see their point, we’d advise them not to hold their breath. We suppose something like this had to happen eventually, and somehow we’re not surprised to see “Florida Man” in the headlines.

There was a little hubbub this week around the release of a study regarding the safety of autonomous vehicles relative to their meat-piloted counterparts. The headlines for the articles covering this varied widely and hilariously, ranging from autonomous vehicles only being able to drive in straight lines to AVs being safer than human-driven cars, full-stop. As always, one has to read past the headlines to get an idea of what’s really going on, or perhaps even brave reading the primary literature. From our reading of the abstract, it seems like the story is more nuanced. According to an analysis of crashes involving 35,000 human-driven vehicles and 2,100 vehicles with some level of automation, AVs with SAE Level 4 automation suffered fewer accidents across the board than those without any automation. Importantly, the accidents that Level 4 vehicles do suffer are more likely to occur when the vehicle is turning just before the accident, or during low-visibility conditions such as dawn or dusk. The study also compares Level 4 automation to Level 2, which has driver assistance features like lane-keeping and adaptive cruise control, and found that Level 2 actually beats Level 4 in clear driving conditions, but loses in rainy conditions and pretty much every other driving situation.

There’s a strange story coming out of New York regarding a Federal Communications Commission (FCC) enforcement action that seems a little shady. It regards a General Mobile Radio Service (GMRS) repeater system used by the New York State GMRS Alliance. GMRS is sort of a “ham radio lite” system — there’s no testing required for a license, you just pay a fee — that uses the UHF band. Repeaters are allowed, but only under specific rules, and that appears to be where things have gone wrong for the club. The repeater system they used was a linked system, which connected geographically remote repeaters stretching from the far western part of the state near Buffalo all the way to Utica. It’s the linking that seems to have raised the FCC’s hackles, and understandably so because it seems to run counter to the GMRS rules in section 95. But it’s the method of notification that seems hinky here, as the repeater custodian was contacted by email. That’s not typical behavior for the FCC, who generally send enforcement notices by certified snail mail, or just dispense with the paper altogether and knock on your door. People seem to think this is all fake news, and it may well be, but then again, the email could just have been an informal heads-up preceding a formal notice. Either way, it’s bad news for the GMRS fans in upstate New York who used this system to keep in touch along Interstate 90, a long and lonely stretch of road that we know all too well.

Third time’s a charm? We’ll see when sunspot region AR3723 (née AR3697 née AR3664) makes a historic third pass around the Sun and potentially puts Earth in its crosshairs yet again. The region kicked up quite a ruckus on its first pass across the solar disk back in May with a series of X-class flares that produced stunning aurorae across almost all of North America. Pass number two saw the renamed region pass more or less quietly by, although it did launch an M-class flare on June 23 that caused radio blackouts in most of the North Atlantic basin. When AR3723 does peek out from behind the eastern limb of the Sun it’ll be a much-diminished version of its former Carrington-level glory, and will likely be given multiple designations thanks to fragmentation while it was hanging out on the backside. But it could still pack a punch, and even if this particular region doesn’t have much juice left, it sure seems like the Sun has plenty of surprises in store for the balance of Solar Cycle 25.

Somebody made a version of Conway’s Game of Life using nothing but checkboxes, which is very cool and you should check it out.

And finally, we’ve been doing an unexpected amount of automotive DIY repairs these days, meaning we spend a lot of time trolling around for parts. Here’s something we didn’t expect to see offered by a national retailer, but that we’d love to find a use for. If it ever comes back in stock we just might pick one up.