Sunday, February 25, 2024

On The Big X-class Solar Flares & the AT&T Blackout

Last week saw the strongest solar flares of solar cycle 25 and the strongest since the great solar storms of Sept. 2017.  The X6.3 solar flare erupted from sunspot AR3590 on Feb. 22 @ 2234 UT or 5:34 PM EST.  What was unique about this strong flare was that there was no Coronal Mass Ejection (CME) with it, and the charged particles from a CME are most likely to cause a geomagnetic storm when they reach Earth.  No such storm has occurred.  The flare itself produced some ionization in the upper reaches of the ionosphere and caused some brief radio propagation issues.  SpaceWeather.com included this plot of signal strengths at 20 MHz, submitted by Jim Tegerdine from Roseburg, Oregon:

Image credit to Jim Tegerdine.

"I was monitoring radio transmissions at 20 MHz when all the signals started to fade," says Tegerdine. "At the peak of the flare (2234 UT), the signal strength was near zero."

Tegerdine's chart recorder plot shows that the fading began about 10 minutes before the flare's peak, giving him an early warning of what was about to happen. After reaching the nadir of signal strength, the blackout persisted as a "deep fade" for more than 20 minutes. In total, there was loss of signal for about a half an hour.

The rule of thumb with disturbances like this is that lower HF frequencies suffer more attenuation for longer periods than frequencies like 20 MHz.  I'd be completely unsurprised to hear that the 3.5 or 7.0 MHz were blacked out for longer than a half hour.

Sunspot AR3590 is close to the center of the sun's Earth-facing side, while moderately high in latitude and among the first, if not THE first, naked-eye sunspot of cycle 25.  It's wider than 10 Earth diameters and relatively easy to see, although I feel obligated to say not to look at the sun without something like Eclipse glasses - dark enough film to reduce the brightness down to safe levels.  If you have a welding helmet, you're there.  In previous sunspot cycles I would catch a glimpse of big spots on the way into work this time of year, when the rising sun might be behind clouds dense enough to make looking at the sun painless.  

Image credits as shown in the image.

AR3509 has the magnetic configuration that makes more flares possible as it goes through its second week of rotation with the sun. No one can predict the strength of potential flares, at least with much accuracy, but NOAA is putting the chances of at least an X1 flare at 30% through the next 48 hours.  I view that as just a bit more trustworthy than the local fortune teller.  (You know - the gypsy with the gold-capped tooth.)

There was a lot of speculation that the blackout some cellular providers experienced on the 22nd, particularly AT&T, was caused by that X6.3 flare.  People who study these things were quick to point out that without a CME to bring charged particles to Earth, that was pretty unlikely.  By the next day, AT&T was saying, "sorry - our bad" and taking responsibility for the whole mess.  "Anonymous sources" said it was a software update that went wrong.  Today, I've gotten an email and text messages from AT&T (they're my phone service provider) saying they're giving everyone a credit on our bills to compensate for no service while it was down.

"Based on our initial review, we believe that today's outage was caused by the application and execution of an incorrect process used as we were expanding our network, not a cyber attack," AT&T said on its website last night. "We are continuing our assessment of today's outage to ensure we keep delivering the service that our customers deserve."

I've seen some messages that say other providers had issues, but with the way all those networks are interconnected I can't say they couldn't have affected other providers.

To err is human but to really screw things up requires software.



Saturday, February 24, 2024

My Ham Radio Upgrade Is Close to Ready to Implement

Back in December I started the story of upgrading my ham station to allow it do much more than just what the radio allows, by upgrading the computer and putting a Software Defined Radio (SDR) in line.  Yes, relying on a relatively cheap SDR (an Airspy R2) instead of the much more valuable HF to 6m radio that's the heart of my station.  The Airspy SDR and the software that guys are using gives a tremendous advantage.  It allows you to monitor (in this case) seven different frequencies across the ham band you're tuned to, while the receiver itself only allows you to listen to two frequencies. 

Consider this display:

The SDR is running on seven different frequencies.  Some of them are conventional Single Sideband (SSB) voice (50.125 and 50.140 MHz); most of them are the modern digital modes (50.313, 50.260, 50.275, 50.318, and 50.323 MHz).  As the operator, we can listen to SSB voice audio, or CW (Morse code - CW is for Continuous Wave - none of these are tuned to frequencies where CW is more commonly used) and run several instances of the software used for the digital modes.  An important thing to know is that I still have only one transmitter so it's impossible to have more than one contact going at a time; the advantage of this is that it replaces listening all day to one frequency and not hearing the guys 100 kHz away in the same band. 

The hardware that I've needed to acquire to implement this is depicted in this drawing, which I've revised about a billion and six times and am now just about ready to put it in place.  

This started out as a way to determine how many and which kind of cables I needed to get and then became more involved.  The key piece of hardware is an SDR Switch from SDRSwitch.com; the specific one pictured here is his 0 -70 MHz RXin RXout Switch.  The box on the top left is what I call the back panel, which is all low frequency control signals in and out using RCA connectors, also called phono plug connectors.  The biggest box on the top right is all BNC female connectors.  My various notes there are reminders to myself about what cables I have, the four BNC male to BNC male cables I needed to buy or build (and did), the adapters I need in various places and so on.  In a few places I note the existing cable used.

The obviously professional radio drawing at the left is from the user manual for my main rig, an Icom IC-7610.

The last piece I needed to get for this was the LNA - in the square box between the Front Panel and the Splitter at top right.  I bought a kit from Down East Microwave, a relatively well-known VHF to microwave accessory seller.  It was all surface mount components, but they weren't the tiniest of the standard packages and I thought it was relatively easy to build.  I wouldn't recommend it if you've never done surface mount soldering.

This is close to ready to integrate into the station now, except for two little things.  The 12V DC wire to the switch; Anderson Power Poles to RCA Plug, and put a phono plug on the power wires on the LNA.


EDIT 2-25-24 at 0900 EST:  The first link in the post wasn't working and I didn't test it before hitting the Post button. 



Friday, February 23, 2024

The IM-1 Story You Haven't Heard

Everyone has heard that Intuitive Machines Odysseus lunar lander and IM-1 mission has successfully landed on the moon.  Unless you've been digging, you probably haven't heard that the mission went through a phase of being doomed, then a MacGyver-like last minute fix that restored the mission and achieved the landing.  Eric Berger at Ars Technica has the story, and as I've often done, I'll pull a couple of paragraphs and recommend you Read The Whole Thing.

There was high drama and plenty of intrigue on Thursday evening as Intuitive Machines attempted to land its Odysseus spacecraft in a small crater not all that far from the south pole of the Moon. About 20 minutes after touchdown, NASA declared success, but some questions remained about the health of the lander and its orientation. Why? Because while Odysseus was phoning home, its signal was weak.

But after what the spacecraft and its developer, Houston-based Intuitive Machines, went through earlier on Thursday, it was a miracle that Odysseus made it at all.

The landing attempt was delayed by about two hours after mission controllers had to send a hastily cobbled together, last-minute software patch up to the lander while it was still in orbit around the Moon. Patching your spacecraft's software shortly before it makes its most critical move is just about the last thing a vehicle operator wants to do. But Intuitive Machines was desperate.

Desperate and with no alternatives designed for just this sort of situation.

Earlier on Thursday, the company realized that its navigation lasers and cameras were not operational.  As an autonomous probe, Odysseus was designed by Intuitive Machines to use cameras onboard for two purposes.  First, to compare terrain images to a stored database, to help the lander decide where it is and second to look for smaller things like boulders or unknown things to avoid when it came time to land.  The lasers were used as altimeters.  The combination provided what IM refers to as terrain-relative and hazard-relative navigation.

Without those sensors, Odysseus was blind.  Not just blind, but hopelessly blind without a seeing eye dog or cane.

Without these rangefinders, Odysseus was going to faceplant into the Moon. Fortunately, this mission carried a bunch of science payloads. As part of its commercial lunar program, NASA is paying about $118 million for the delivery of six scientific payloads to the lunar surface.

One of these payloads just happened to be the Navigation Doppler Lidar experiment, a 15-kg package that contains three small cameras. With this NDL payload, NASA sought to test out technologies that might be used to improve navigation systems in future landing attempts on the Moon.

The only chance Odysseus had was if it could somehow tap into two of the NDL experiment's three cameras and use one for terrain-relative navigation and the other for hazard-relative navigation. So, some software was hastily written and shipped up to the lander. This was some true MacGyver stuff. But would it work?

You know the answer to that big question now, but watching the landing was a bit different.  Earlier in the day, I'd watched some videos from IM and knew that they expected the software to take 15 seconds to radio back that it had landed, and Tim Crain - mission director and co-founder of the company - had said, "those are the longest 15 seconds of your life."  It was more like 15 minutes.  Alright, 10 minutes that felt like 15 when Crain said the lander was sending a faint signal back to Earth, adding, “we’re not dead yet.”

This morning, IM updated the mission webpage at 8:18 CST, saying:

Odysseus is alive and well. Flight controllers are communicating and commanding the vehicle to download science data. The lander has good telemetry and solar charging. We continue to learn more about the vehicle’s specific information (Lat/Lon), overall health, and attitude (orientation).

Odysseus took this selfie while passing over the near side of the Moon, after lunar orbit insertion on February 21.  Image credit: Intuitive Machines 

In this morning's update to the mission web page, they also added, “Intuitive Machines CEO Steve Altemus will participate in a press conference later today to discuss this historic moment.” So far, that page hasn't been updated but I expect there will be a press conference as described. Note that it said NASA paid $118 million to send six experiments to the moon as part of its CLPS program (Commercial Lunar Payload Services).  NASA also paid Astrobotics for a ride to the moon on their Peregrine lander that didn't make it also as a part of CLPS. 

Final words to Eric Berger:

So why is NASA supporting such risky ventures?

The space agency believes that private companies will eventually get the hang of flying vehicles to the Moon. And once the service becomes more routine, it will cost NASA a fraction of the price it would pay for traditionally developed lunar services. In essence, then, NASA is taking some short-term risks for some long-term gains. It looks like one of those risks paid off Thursday.



Thursday, February 22, 2024

Blue Origin Pulls a Shocker - or Two

The Blue Origin news shocked me.  You might remember the early January story about a mechanical mock-up of their New Glenn rocket being on the pad at Cape Canaveral Space Force Station and it getting lots of press coverage despite the hardware being prominently labeled "NOT FOR FLIGHT."  They've done themselves one better.  

On Wednesday, engineers rolled a full-scale New Glenn rocket, partially made up of flight hardware, to launch complex 36 on CCSFS for ground testing. 

The first New Glenn launch is almost certainly at least six months away, and it may not even happen this year. In the last few years, observers inside and outside the space industry have become accustomed to the nearly annual ritual of another New Glenn launch delay. New Glenn's inaugural flight has been delayed from 2020 until 2021, then 2022, and for now, is slated for later this year.

But it feels different now. Blue Origin is obviously moving closer to finally launching a rocket into orbit.

On the face of it, this makes me think about some of the things discussed back in December about Bezos Saying the quiet part out loud in a two hour interview with podcaster Lex Fridman to talk about Amazon, Blue Origin, his business practices, and more.

During the interview, Bezos candidly acknowledged this. "Blue Origin needs to be much faster, and it's one of the reasons that I left my role as the CEO of Amazon a couple of years ago," he said. "I wanted to come in, and Blue Origin needs me right now. Adding some energy, some sense of urgency. We need to move much faster. And we're going to."

Part of the efforts Bezos has been putting in included hiring Blue's new CEO Dave Limp, to push that effort to move faster, and be more decisive.  It seems the staff has gotten the memo and that December article about the mock-up being at the pad is evidence of that.  Not just the mock-up but mounting a test article second stage to a flight-rated first stage and testing mechanical fits and interconnections at the pad. 

The New Glenn on the pad at LC-36 is flight hardware and it will be subjected to all the tests required to prepare a vehicle for launch.  

Getting New Glenn to the launch pad is a major milestone for Blue Origin. This is undoubtedly a turning point for the privately funded New Glenn program, but there is a lot left to do before the rocket is ready to fly.

The next step will involve "several demonstrations of cryogenic fluid loading, pressure control, and the vehicle's venting systems," Blue Origin said. According to a report published by Aviation Week, Blue Origin will load this particular test vehicle with cryogenic liquid nitrogen as a stand-in for the super-cold methane and liquid oxygen propellants used by the first stage booster on an actual launch. The upper stage won't be loaded during this upcoming Integrated Tanking Test (ITT).

Dave Limp, Blue Origin's new CEO, left, and founder Jeff Bezos observe the New Glenn rocket on its launch pad Wednesday at CCSFS.  Image credit: Jeff Bezos via Instagram.

New Glenn has been easy to ignore because it has been like a twin of SLS in being consistently late.  The first flight of the heavy-lift rocket has been talked about and missed every year since 2020 and is being talked about for later this year -- with a lot of people saying it will be 2025.  While we may smirk at the small launch startups and say, "nice, but they've never made orbit," Blue Origin has never made orbit either. That means New Glenn may be the oldest rocket design - on paper - that has never flown. 

It's capable of lifting payloads to orbit of nearly 100,000 pounds, which ranks it above ULA's Vulcan Centaur and behind SpaceX's Falcon Heavy.  It has been designed with reuse in mind, with a target of 25 missions at minimum, with the first stage intended to land on an offshore recovery ship much like the Falcon 9.  At more than 320 feet tall, New Glenn is roughly the same height as the SLS rocket and nearly as tall as the Saturn V used in the Apollo program.  Only the Starship/Super Heavy towers above it.

Because of that "launch was talked about and missed every year since 2020" history, I'm not inclined to give them the benefit of doubt and say New Glenn will launch this year, although if you read that linked article at Ars Technica, you may come away thinking they will make it this year.  I'll be happy for them and interested in watching the first launch, but "I'll believe it when I see it." 

Did I say two shockers?

Making news yesterday is that it appears Blue Origin is going to be the buyer of United Launch Alliance

Blue Origin, the rocket company owned by Amazon founder Jeff Bezos, has emerged as the sole finalist to buy United Launch Alliance.

The sale is not official, and nothing has been formally announced. The co-owners of United Launch Alliance (ULA), Lockheed Martin and Boeing, have yet to comment publicly on the sale of the company, which, until the rise of SpaceX, was the sole major launch provider in the United States. They declined again on Wednesday.

I find it interesting that Bezos is on record selling $2.4 billion in Amazon stock and, in his mandatory securities filings, disclosed that he could sell an additional $8 billion to $9 billion in stock over the next 12 months.  While there's no real quoted price to buy ULA, industry speculation is that it would be sold for somewhere around 2 to $3 billion.  How convenient.  He can buy ULA with some cash he figuratively recovered from between his sofa cushions. 



Wednesday, February 21, 2024

Thursday the 22nd 5:30 PM EST

Thursday afternoon at 5:30 PM EST  is the targeted time for the landing of Intuitive Machines IM-1 Odysseus mission near the lunar south pole.  This morning at 9:20 CST, IM posted an update on the Lunar Orbit Insertion maneuver. (The time was updated later on the 21st)

Odysseus completed its scheduled 408-second main engine lunar orbit insertion burn and is currently in a 92 km circular lunar orbit. Initial data indicates the 800 m/s burn was completed within 2 m/s accuracy.

After traveling over 1,000,000  km, Odysseus is now closer to the Moon than the end-to-end distance driving across Space City, Houston, TX.

Over the next day, while the lander remains in lunar orbit, flight controllers will analyze the complete flight data and transmit imagery of the Moon.

Odysseus continues to be in excellent health. We expect to continue to provide mission updates at least once a day on X and the IM-1 Mission web page, where we intend to host a live stream for landing coverage.

That link above is the Mission web page to keep an eye on for the live stream of the landing.  

If all goes according to plan, Intuitive Machines will be the first private company to land on the moon, and will mark the first American soft lunar landing since Apollo 17 in December of 1972, just over 51 years ago. 

The first private company to attempt a lunar landing was Japan's iSpace, with their Hakuto-R in April of 2023, but it didn't successfully land.  India became the fourth national space program to land on the moon with their Chandrayaan-3 mission last August.  Don't forget Astrobotic's Peregrine lander that had a fuel leak after launch last month and never got as close to trying to land as Hakuto-R.  

Odysseus' original landing target was Oceanus Procellarum, or 'Ocean of Storms', the largest basaltic plain visible on the western edge of the visible side of the moon.  That was changed to Malapert A, a small impact crater about 190 miles (300 kilometers) from the moons' south pole.

Instead, Malapert A is a relatively flat and safe region located within the heavily cratered southern highlands on the side of the moon visible from Earth, NASA officials said in a statement announcing the new landing site in May 2023.

"The decision to move from the original landing site in Oceanus Procellarum was based on a need to learn more about terrain and communications near the lunar south pole, which is expected to be one of the best locations for a sustained human presence on the moon," NASA officials said in the statement.

"Landing near Malapert A also will help mission planners understand how to communicate and send data back to Earth from a location that is low on the lunar horizon."

A map of the area coded for elevations: blue are lowest through greens and reds to the highest in brown and then gray at Mons Mouton, bottom left.  Malapert is at the bottom center.  Image credit, Intuitive Machines.

I'll be trying to watch this one tomorrow. 



Tuesday, February 20, 2024

Intuitive Machines IM-1 Looking Good for Landing Attempt

In the "no news is good news" category, since last Thursday's (very) early morning launch of Intuitive Machines IM-1 Odysseus moon lander mission, everything has gone by the book and not made news.   Odysseus completed two engine burns in deep space on Feb. 16 and Feb. 18 and is sailing on the right course through space, the company said on X. If you go to that link, the graphic in this post is an animated .gif, although the only things you'll see moving are the shadow/light area on the right and some reflections at top left.

The stakes go up again Wednesday the 21st when the engines will burn for Lunar Orbit Insertion, a critical milestone which controllers are calling "Odysseus' largest challenge to date." The exact time for that hasn't been announced and the burn will occur on the far side of the moon, so out of radio contact.  It's the biggest velocity change of all the maneuvers to date, changing velocity 800-900 m/s (note the one described above was a 21 m/s change).  I have to assume the exact number will be calculated based on the speed and trajectory as known some time before the attempt.  


Source: Intuitive Machines on X

This lander mission is part of NASA's Commercial Lunar Payload Services program or CLPS. The 12 payloads on board Odysseus include six NASA instruments.  CLPS aims to fly NASA science payloads to the moon on a set of private landers, to scout ahead of Artemis missions. 

[Odysseus'] landing site is a tiny crater roughly 190 miles (300 kilometers) from the moon's south pole, about where NASA hopes to place astronauts later in the 2020s under the agency's Artemis program of lunar exploration. Artemis 3 is now scheduled to make the historic landing in 2026 or so, following a recent delay for several technical reasons.

Back in early January, it was announced that the first Artemis landing on the moon, Artemis 3, would be delayed until 2026 due to technical problems discussed at that link.

Odysseus, whose mission is known as IM-1, is the second CLPS mission to fly in 2024. Astrobotic flew the Peregrine lander into space on Jan. 8 on board the first launch of United Launch Alliance's Vulcan Centaur rocket

While its launch went well, a fuel leak aboard Peregrine forced controllers to aim the lander instead for a controlled destruction in Earth's atmosphere on Jan. 18.



Monday, February 19, 2024

SpaceX Moving to Take Over Another Cape Launch Complex

Sometime "No Later Than this summer" United Launch Alliance will launch the last Delta IV Heavy mission from Cape Canaveral's Space Launch Complex 37 (SLC-37).  This is one of the largest launch pads on the Cape - which it needs to be to handle Delta IVs - originally built to handle the Saturn 1 and 1B back in the 1960s.  After eight flights of those rockets, it sat unused until the 1990s when Boeing converted it to handle the Delta IV.  That was before Boeing merged with Lockheed Martin to form ULA and the Delta IV became a ULA vehicle.

An interesting alliance seems to be forming to try to get SpaceX to take over the complex and modify it to launch Starships.  The obvious one is SpaceX themselves; they're in the process of building a second Starship launch facility at Boca Chica. This would give them two launch pads here in Florida; the current one at Pad 39A and SLC-37.  The one you might not expect is that the Department of Defense and the US Air Force apparently want this, too.  

The environmental review for SpaceX's proposal to take over Space Launch Complex 37 (SLC-37) at Cape Canaveral is getting underway now, with three in-person public meetings and one virtual meeting scheduled for March to collect comments from local residents, according to a new website describing the plan.

Then, federal agencies, led by the Department of the Air Force, will develop an environmental impact statement to evaluate how Starship launch and landing operations will affect the land, air, and water around SLC-37, which sits on Space Force property on the Atlantic coastline.

It's worth noting that an Environmental Impact Statement (EIS) is a tougher hurdle than the "Environmental Assessment" SpaceX went through to obtain the rights to launch in Texas. It's possible that the EIS could take years to complete.  According to a source at the Orlando Sentinel, republished at Phys.org

So the EIC is considering three options.

One is to transition Space Launch Complex 37 after it supports the final United Launch Alliance Delta IV Heavy rocket mission, expected to fly this summer.

The second is to construct a new launch pad called Space Launch Complex 50 that would be located between SLC 40 and SLC 37 on currently undeveloped land.

The final option is to do nothing.

The next steps in the EIS process will be a series of four public meetings around the Merritt Island home of the CCSFS in the cities of Cocoa, Titusville and Port Canaveral along with an online virtual meeting, according to the EIS website. These meetings are already scheduled for March 5-7 and 12.

With the understanding that the EIS could take years to complete, this has to be regarded as something interesting we can't do much about.  We don't - can't - know if or when this could happen, but it's looking increasingly likely we will see the world's most powerful rocket launch from the Cape.  For the first time since Apollo 17's Saturn V in December of 1972. 

This 2014 photo shows a Delta IV Heavy being readied for launch at SLC-37, Cape Canaveral Space Force Station.  NASA Photo by Kim Shiflett.



Sunday, February 18, 2024

It's My 14th Blogiversary

Sorta.  As I say every year, my very first day of blogging was ackshually February 21, 2010, which happened to be the third Sunday of the month.  Since weekends are more quiet days, and the 21st hardly ever works out to be a Sunday, I've always marked the anniversary as the third Sunday of February. Today.  

(Gratuitous celebratory image found just doing a search for 14th Anniversary, and when I went to the website to link back to them I got an error message.)  BTW, these anniversary symbols serve a purpose when I'm looking for old images to reuse.  If I can find the first time I used it, the anniversary posts are markers in the calendar to look around.  Those of you who use Blogger probably already know this.

As always, I thank you for stopping by. It's hard to know how many people stop by to read by Blogger's stats. Over the last month, views per day stayed in the 1500 range, going up at the start of February to above 2000/day. The last couple of weeks have had days over 3000. That said, a couple of times in the last six months Google must have changed their way of counting, or some spyware went out of control or something odd because it was saying over 5,000/day with a couple of peaks over 15,000. 

This will be post 4,819 and at my typical one post/day, I'll hit 4,900 in about 80 days, or early in May.  The 5,000th post will be in mid-August.  My least favorite time of year.

If you've read down this far, what are you doing? Just kidding. Double thanks.



Saturday, February 17, 2024

The Ham Radio Series 42 - What's All This Noise Figure Stuff Anyway?

Right now a lot of you are saying you never heard of a noise figure, so what am I talking about?  People who have some familiarity with receivers for VHF, UHF and higher are probably more likely to have heard the term because it tends to be talked about more as you go higher in the spectrum.  At lower frequencies, like HF radios and even things like VHF handie-talkies, people still tend to talk about sensitivity, using measurements of the signal power (or voltage) to achieve a certain Signal to Noise ratio or SNR, literally signal power divided by noise power; S/N.  Sometimes instead of an SNR, you'll see SINAD, which is the desired signal to noise and adds distortion to the noise term. 

Noise figure can be talked about for complete receivers or single circuits.  It's a way of describing how much noise a component or circuit degrades the SNR of the signal going through it.  How much noise it adds to the signal as it goes through it.  

NF = (SNRout)/(SNRin)

Everything has a noise figure.  For a passive circuit, the NF is reciprocal of the gain.  An attenuator (pad) with 3dB of attenuation or 3dB of loss means it had a gain of negative 3.  That means the NF of a 3dB pad is 3dB. When you buy an amplifier, the specifications will generally include the NF.  To design for a noise figure and verify that what you've created performs as you intended is "beyond the scope of this discussion." 

In receiver design, it has become increasingly common to cascade constant impedance circuit elements or blocks.  With the exception of some cable TV systems, which operate at 75 ohms, receivers tend to be designed as 50 ohm systems.  To determine the overall gain of a system, and the signal levels at any stage is trivially easy.  You add dB of gain and use negative numbers for the gain of a stage with loss (like a filter, cable or pad).  

Gain Total = G1 + G2 + G3 + ... Gn

Noise figure is a bit more complex.  The equation is well-known but can get a bit long in a hand calculator or spreadsheet.  Named after the guy who first derived it, Harald Friis, the Friis equation is:

The 1, 2, 3, etc, are the stage numbers, so the cascade NF is always greater than the first stage's NF, F1.  You can see the value of F at any stage is the sum of that first NF, and the stage's NF divided by the product of the gains to that point.  Important note: these numbers are the linear gain and noise figure numbers, not expressed in decibels.  

This is a vivid reminder to minimize losses before the first amplifier because you'll never get a better NF than that first stage.  Since loss in all coaxial cables goes up with frequency, to reduce the losses before the first amplifier, a very common approach is to put the first stage of amplification, and downconversion at the antenna's feedpoint.  The downconversion is to change to an easier frequency to handle with less loss in the cable.

How about some practical stuff?  This is how you might compare the signal you measured to be required to get 10 dB SNR to what the math says you should get:

That would be like CW, just a carrier in a 500Hz BW and -133 dBm is a small signal.  You might think you need a half microvolt, or a less.  The number is much less: it's .05 microvolt or 50 nanovolts.  If the receiver is in a quiet room connected directly to a signal generator, you should get that.  This old post might be helpful.  As should this chart that's in it.



Friday, February 16, 2024

Voyager 1 is Still Not Well

Back in early December, NASA/JPL released some grim news on the status of Voyager 1, now well past the solar system in interstellar space.  As I said at the time, it seemed a lot like a stroke, or perhaps Alzheimer's disease.  While the probe seemed to take commands, it only responded with incoherent ramblings.  

The Voyagers are now in the 46th year of their four year missions and are the two probes that have gone farthest from Earth and are still in routine contact with controllers on the ground.  Light travel to Voyager 1 is over 22 and a half hours each way.  That means to send it a command that would generate a response and get that response back to Earth together take over 45 hours - just short of two full days.  That puts a premium on really understanding what you're going to transmit and knowing what the expected results could be.  

As of Feb. 6, NASA said the team remains working on bringing the spacecraft back to proper health. "Engineers are still working to resolve a data issue on Voyager 1," NASA's Jet Propulsion Laboratory said in a post on X (formerly Twitter). "We can talk to the spacecraft, and it can hear us, but it's a slow process given the spacecraft's incredible distance from Earth."

It helps to know that Voyager has three computer systems on board, together called the Flight Data System (FDS), and engineers working on the problem have concluded it's what they call the telecommunications unit (TMU). When it was developed five decades ago, Voyager's Flight Data Subsystem was an innovation in computing. It was the first computer on a spacecraft to make use of volatile memory. Each Voyager spacecraft launched with two FDS computers, but Voyager 1's backup FDS failed in 1981, according to Dodd. There's only so much capacity for backups of critical systems, they can't fly three of everything, and Vger has been working without a backup for 42 years.

As a result, no science or engineering data is being sent back to Earth.  They've been troubleshooting this  issue since early December and while they haven't fixed it, they're focused on the TMU.  

Then, in early February, Suzanne Dodd, Voyager project manager at NASA's Jet Propulsion Laboratory, told Ars Technica that the team might have pinpointed what's going on with the FDS at last. The theory is that the problem lies somewhere with the FDS' memory; there might be a computer bit that got corrupted. Unfortunately, though, because the FDS and TMU work together to relay information about the spacecraft's health, engineers are having a hard time figuring out where exactly the possible corruption may exist. The messenger is the one that needs a messenger.

Suzanne Dodd also said, "It would be the biggest miracle if we get it back. We certainly haven't given up. There are other things we can try. But this is, by far, the most serious since I’ve been project manager." 

The only signal Voyager 1's Earthbound engineers have received since November is a carrier tone, which basically tells the team the spacecraft is still alive. There's no indication of any other major problems. Changes in the carrier signal's modulation indicate Voyager 1 is receiving commands uplinked from Earth.

Artist’s illustration of one of the Voyager spacecraft. Credit: Caltech/NASA-JPL

My inner photographer insists that I point out that image is entirely artistic license. Or outright fiction, you can choose the word you'd like. At 22 light hours from the sun there won't be light out there.  There are no clouds of stars out there to give that pretty blue and purple backlighting. The sun itself would be brighter than the distant stars, but you could stare at it without harming your eyes.  In short, it would be pitch black out there and Voyager would be undetectable.  Invisible. Which doesn't make a pretty picture.

Voyager project manager Dodd makes some mention of the lurking, harshest reality of all.  At 46, Voyager is inescapably approaching end of life.  There may not be a fix for this, and if there is, another worse problem might be right behind this one.  The absolute best possible outcome is that they fix it and get another few years of data out of Voyager 1.



Thursday, February 15, 2024

What's A Day Between Friends?

In the big picture view, the three launches I had posted about taking place on Valentine's Day all took place and all were successful.  All that happened was they shifted in the times and the order in which they launched. Does that really matter? Who's counting? 

Instead of starting just after midnight Wednesday morning with the launch of the IM-1 mission to the moon, followed by the USSF-124 mission about 16-1/2 hours later in the late afternoon and then a Starlink mission from Vandenberg on Wednesday night, the order got jumbled.  The USSF-124 mission was first at the listed time, (5:30 PM ET on Wednesday); the IM-1 mission went to second at 1:05 AM ET after its 24 hour delay and the final mission was the Starlink 7-14 mission from Vandenberg Space Force Base at 7:34 PM ET after its delay.  Notice how it was all three launches in about a 26 hour span rather than the original 24 hours.  Again; does that really matter?  

The last launch was their 15th launch of the year. This is the 7th week. That works out to them getting around 110 to 115 for the year, when their stated goal was higher. That's the only negative I see here.

An added historic note was that the last of those three was the 300th Falcon 9 mission - although there's some influence there of who counts the missions or which missions count (note: Wikipedia shows it as 300).  The NASA Spaceflight narrators for that mission discuss that briefly in the opening few minutes of their hour-long coverage. I think we've posted before that every mission SpaceX flies is some sort of record. 

I think they're so far ahead of everybody else's number of consecutive missions without a failure that it's going to be a long time until that record gets challenged.



Wednesday, February 14, 2024

Two One Out of Three Isn't That Good

Of the three SpaceX launches for today listed last night, only one has been successful.  The launch of the USSF-124 mission went successfully at its scheduled 5:30 PM EST.  Video here.  

Conditions in the backyard were great and we were able to follow it visually until after Main Engine Cut Off and Second Engine Start but not as far as we can see night launches.  The entry burn of the booster to wipe off much of its velocity was suddenly visible and bright against the evening's blue sky.  The Landing Zone on the KSC is below our horizon so a booster landing is always invisible to us.

The previous launch, last night's attempt at launching the Intuitive Machines IM-1 lunar lander, was scrubbed 90 minutes before the scheduled 12:57 AM liftoff.  The probe was unique in requiring liquid oxygen and liquid methane to be loaded a few hours before the launch.  It required SpaceX to modify the ground support equipment at Pad 39A, which made it the only pad of the two on the Cape that could handle this launch.  That, in turn, led to the delays because of other missions that could only launch from Pad 39A, like the manned AX-3 mission.  

It's currently scheduled for Thursday morning the 15th at 1:05 AM EST.  

An excellent and succinct summary was posted as a comment to last night's post by Malatrope this afternoon. 

"It's not trivial to load the liquid oxygen and liquid methane into the vehicle," said Bill Gerstenmaier, vice president of build and flight reliability for SpaceX.

The company had to modify the second stage of the Falcon 9 rocket to add propellants onto the Nova C lander at the launch pad shortly before liftoff. SpaceX and Intuitive Machines completed two tests of this new procedure over the weekend. It's a complex process, and during the countdown, SpaceX actually controls six valves on the lunar lander to ensure the integrity of the fueling process. Despite the tests, a non-nominal methane temperature reading observed late Tuesday night scrubbed the first launch attempt a couple of hours before the planned liftoff early Wednesday.

The launch after the USSF-124 mission was originally scheduled for 7:30 PM EST, 4:30 PST, from Vandenberg SFB. That launch was postponed, then rescheduled for later in the window, and eventually rescheduled for Thursday afternoon at 1:34 p.m. PST, 4:34 EST.  It can be watched live on SpaceX's X (Twitter) account starting about five minutes before launch. 

Screen capture of the one launch from the Space.com video. 

The last thing I mentioned in the lead-in post yesterday was that whenever I do a post about X launches in Y days, things don't tend to work out.  In this case it went from 3 in 1 day to one.  The saying that space is hard is demonstrated yet again. 



Tuesday, February 13, 2024

Turns Out Valentine's Day is Going to Be SpaceX Day

SpaceX has three launches scheduled for Valentine's day in the CONUS.

Screen capture from Next SpaceflightSpace.com has the rundown.

Of course the one on the left is the IM-1 launch we talked about yesterdayThe important part that I looked for but couldn't find to include yesterday is that you can watch it online, with a NASA webcast that will begin at 12:15 a.m. EST (0515 GMT)

SpaceX will follow the IM-1 moon flight with the launch of USSF-124, a classified payload for the U.S. Space Force. That mission is scheduled to lift off at 5:30 p.m. EST (2230 GMT) atop a Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Space Force Station. 

SpaceX is expected to provide a livestream of the military space launch beginning 10 to 15 minutes before liftoff, but the company may cut off the stream shortly after liftoff at its customer's request as has been done in the past for classified missions. You can watch that USSF-124 launch at SpaceX's page on X (formerly Twitter).

Space.com goes on to discuss a Russian launch set for Valentine's Day as well, but doesn't mention the third SpaceX launch of the day, this one from Vandenberg Space Force Base, SLC-4E at 7:30 PM EST or 4:30 PM by Vandenberg's clock.  I'll return to the Russian launch in a minute. 

That's a Starlink launch, which SpaceX has said they'd like to become boring but they still cover those at the previously mentioned page on X.  Coverage typically starts closer to the launch time on these, the 10 to 15 minutes ahead quoted for the USSF-124 is probably right. Narration is pretty much not done for Starlink launches, although some of the alternative coverage sites that show up on YouTube add their own.  It seems having cameras stationed on Vandenberg is more challenging then having them at Cape Canaveral or the Kennedy Space Center.  Starbase Boca Chica is probably the most tolerant of the various cameras.  

The Russian (Roscosmos) launch is the launch of a Progress cargo ship to the International Space Station from Site 31/6 of the Baikonur Cosmodrome in Kazakhstan.  The time on this one is 10:25 PM EST on Valentine's Day, which makes it 0325 UTC on the 15th.  Being on the 15th means it's not a Valentine's Day launch to me, but I include it because Space.Com did

My only hesitation here is that stories like this don't tend to always happen, because anything that causes a reschedule of any one of the three breaks the "X launches in Y days" story.



Monday, February 12, 2024

Tuesday Night/Wednesday Morning

The mission we've been keeping an eye on since at least August of '23 is finally here.  Intuitive Machines' IM-1 is scheduled to lift off on a Falcon 9 from Pad 39A at the Kennedy Space Center on Wednesday morning, Feb. 14, at 12:57 a.m. EST (0557 UTC), sending the robotic Nova-C lander "Odysseus" toward the moon.  As you know, the eastern time zone is the only one in the CONUS in which this launch is on Wednesday, Valentine's Day.  Those of you in California or points farther west will have it progressively earlier in the evening of Tuesday, February 13.  

If all goes according to plan, Odysseus will touch down near the moon's south pole on Feb. 22, pulling off the first-ever private lunar landing.  That race is still going on. 

Odysseus' mission, known as IM-1, includes 12 payloads, half commercial and half NASA science packages. NASA is using this research to get ready for the Artemis program missions that will land astronauts near the moon's south pole, beginning in 2026 or so.

IM-1 is part of the series of low-cost private moon missions that include NASA-funded instruments, which are manifested via the agency's Commercial Lunar Payloads Services (CLPS) program.

The CLPS program is a collection of smaller-company driven, private robotic missions that are each low in cost, with the inevitable tradeoff being fewer backup systems in case of trouble. That was seen clearly in Astrobotic's Peregrine lander mission, the first CLPS mission, last month.  The lander suffered an anomaly as soon as they tried to use its engines, immediately losing the ability to complete the mission.  They tried to get some results out of the mission but ended up looping around the moon, returning to Earth and burning up in the atmosphere on reentry.  

Smaller and cheaper missions allow NASA to test technologies faster than traditional mission planning allows for, emphasized Susan Lederer, CLPS project scientist at NASA's Johnson Space Center in Houston, during a teleconference today (Feb. 12). The high risk is worth it, as "this will allow us to prepare for Artemis more efficiently," with more missions launching more frequently, Lederer said.

Another advantage is the proliferation of landing options if multiple CLPS missions succeed: There's "a far greater number of places you can go to on the moon and the diversity of people involved" if lots of CLPS missions reach the surface, Lederer said.

As a mission intended to prepare for the Artemis moon landings, also set to land at the south pole, the IM-1 mission will experience one of the aspects of landing there that is causing some concern.  The radio signal being beamed back to Earth will be close to the surface of the moon, and that can cause problems.  "The communications can kind of bounce along the terrain, coming and going," Lederer added. "So, having a location that's close to the south pole will help us to start investigating those kinds of things that are happening."

Computer rendering showing the Intuitive Machines' Nova-C lander on the surface of the moon with Earth in the background. (Image credit: Intuitive Machines) (I've never really tried to deep dive on why they have the Columbia sportswear logo on that large panel.  I figure it's got to be some sort of name placement or advertising.)

The CLPS program seems to be reality-based in that they realize they're going to lose some of these missions or even all of them.  They may only have parts of the missions that they can claim were successful, but they're still determined to learn from them.  Whether that's the smartest way to get the information they want, I don't think we can know until all the work is done and the numbers are in.

Additionally, IM-1's equipment will be assessed for how well it performs in the harsh cold of the moon, including components such as solar panels and instruments. But even if that mission or some other CLPS landers don't make it, she emphasized, NASA will proceed with plans for its Artemis 3 mission, which aims to land astronauts near the lunar south pole in September 2026.

"It won't endanger efficiency," Lederer said.



Sunday, February 11, 2024

Tory Bruno Hypes Vulcan After Their Successful First Flight

Space News starts out this article by pointing out that rumors of an impending sale of United Launch Alliance are reaching a crescendo, so I think that's a good thing to keep in mind as you digest this story, based on a presentation CEO Tory Bruno made for ULA at a January 31 SpaceCom conference in Orlando.  In light of some of the things he talked about, it does come across as trying to capture some glory for the company.  And maybe goose the price up a little.

Speaking about the much delayed first test flight of the Vulcan Centaur, he said it went exceptionally well, with no issues reported during the countdown or after liftoff.

“That was a perfect mission,” he said of the launch, which placed Astrobotic’s Peregrine lunar lander on a highly elliptical lunar transfer orbit. “Dead nominal flight throughout, and a bullseye insertion in the end.”

That was in contrast with the reputation first launches of new vehicles have, which historically have high failure rates. “I’ve done about three dozen first launches, and generally one of two things happen: either it blows up or it has significant anomalies in flight,” he said. “I have never seen as clean a first launch” as Vulcan.

One of the topics he seems to have spent some time on was their development process.  

“You can fly, fail, fix; nothing wrong with it,” he said. ULA instead took a “rigorous design process: have your failures in ground tests, have them in the computer, have them in the sim lab and have them on paper. That’s how this was done and my guys just did an outstanding job.”

While this can be taken as a mild shot at SpaceX, I think most would agree that it's undoubtedly cheaper to find an error in a simulation than to find it by blowing up a rocket. Experience shows, though, that simulation isn't always "plug and chug" straightforward.  It depends on not only exactly how good the model is that the engineers create to analyze, but how good the simulation programs are.  This is a complex thing to try to summarize, but simulations are not infallible.  Consider the explosion of the Centaur stage last year; that had passed all the simulations. 

It's easier to believe a test flight than a simulation, recognizing that a flight tests one set of conditions and a simulation can test more than one.  There are situations that are mathematically impossible to derive closed-form solutions for and situations where interactions between the huge number of things being simulated lead to unpredictable combinations. 

I suppose it's unavoidable that he also spent some time patting himself and the rest of leadership on their backs.

Another factor, he argued, was a transformation of the company he led after joining the company in 2014. He described the company then as one in crisis, having lost access to Russian-built RD-180 engines used by the Atlas 5 after Russia’s annexation of Crimea as well as competition from SpaceX, which sued the U.S. Air Force to gain access to national security launches that ULA then held a monopoly on.

“A business in that situation might go broke. In fact, most of them do,” Bruno said. He undertook several measures to turn the company around, from reducing costs and changing the company’s product line to more commercial approaches and accepting it will have to compete. “The plan was we were going to shrink and become competitive and then we’re going to grow.”

As we've talked about before, ULA was formed as a joint venture between Boeing and Lockheed Martin in 2006.  The reports are that both companies are considering selling it.  The two names that seem to be at the top of rumor pile are Blue Origin and the private equity fund Cerberus Capital Management.  Blue Origin, of course, is developing a competitor to Vulcan, the New Glenn, but they also sell their BE-4 engines to ULA.  Vulcan is shaping up to be a valuable platform, and their winning portion of National Security launches is an asset for potential buyers to consider.  Bruno stresses that Vulcan can achieve "high energy" orbits that no one else can - yet. 

“When Atlas flies out in about a year, this will be the only high-energy rocket left in the world,” he said, serving “the most critical and important missions, unique missions, for national security.”

That approach, he said, was proven with the NSSL Phase 2 contracts. “There’s a lot of high-energy missions in there and we designed for that,” he said, such as missions that involve direct injection of payloads into geostationary orbit, which he said will be a growing share of both Phase 2 and the upcoming Phase 3 contracts.

“We run about 34% cheaper on a high-energy mission than the other one, SpaceX, does,” he argued. “We put all our bets nine years ago in the right places.”

In addition to those NSSL Phase 2 launches for the government, they also have the Kuiper constellation launches for Amazon - 38 of the booked 70 Vulcan launches are for the private sector. 

ULA Chief Executive Tory Bruno discussed the transformation of his company in a Jan. 31 speech at SpaceCom. Credit: SpaceNews/Jeff Foust



Saturday, February 10, 2024

Time For Our Annual Trip to Orlando

I guess I shouldn't call it an annual trip since we've missed two of the last four years.  On the other hand, everyone missed the first of those two (2021) because there was no hamfest due to the Covidiocy, like 99% of everything else cancelled that year.  Last year was because of my surgery, which was two weeks before the 'fest, but I was under orders not to sit in one place "too long" - like the 90 minute drive each way to where it's held and then home.  Put that way, we've missed making it once.

That's a very roundabout way of saying this weekend is the annual Orlando hamfest.  It was our 41st annual visit to the hamfest, and unlike most years since I retired, we went over today, Saturday, which is always the most crowded day.  It has been cool here, but warmed into the upper 70s and even low 80s as the day went by; I wore a short-sleeved polo shirt and was comfortable all day.  By the time the temperature got into that "the sun is not your friend" range, clouds came along and kept it comfortable.  

As I've said before the Orlando HamCation (real name) is now generally referred to as the second largest in the country behind only Dayton's Hamvention (which is only Dayton in name - it's held in Xenia, Ohio).  Dayton tends to be the one where major products are announced.  Absolutely not related to any of that is we unknowingly attended the last Dayton Hamvention in Dayton, Ohio, in 2016.  I mentioned being there, but that was before it was announced the arena where they held the Hamvention was being torn down.

Two years ago, we were late ordering our tickets and had to pick them up at the show.  This year, we ordered them in time to get the tickets in the mail - we ordered around Christmas.   We got out of the house at a less than optimum time from the standpoint of lines and crowds at the hamfest.  We parked close to as far from the entrance of the main building as it was possible to be and did quite a bit of walking.  Unsurprisingly, it turns out the preparing for last Saturday's 70 mile bike ride does, in fact, making walking a couple of miles over the course of a day rather more tolerable than not doing that bike ride prep. 

Obligatory picture #1, inside the main building looking toward the west end.  Much of the main building is displays from major radio manufacturers like Icom, Kenwood, Yaesu, and Flex, as well as antenna manufacturers and others.  The west half of the building has a couple of larger businesses and some that maybe had "luck of the draw" that got them into that building. 

Obligatory picture #2, the biggest building, dedicated to individuals and smaller businesses that rent indoor tables to sell from.  This is from the west end looking east.  There were vendors selling old model digital cameras for $2 or $3 apiece, the same price as old calculators.  Lots of older model laptops, tablets and computers of all types, along with the obligatory older radios.  Like all of those Icom boxes on the tables closest to the camera.  

As always, a pleasant way to spend the day.  We only ran across a couple of friends and that was when we first walked into the place.  Didn't spend much, just picked up a couple of little things that have their price doubled when you buy them online, once shipping gets added.



Friday, February 9, 2024

Strongest X-Flare of Cycle 25 Erupted Today

It wasn't pointed at Earth, so all effects observed so far and all predicted are pretty mild, but sunspot group AR3575 burped out an X3.4 class solar flare and Coronal Mass Ejection (CME) this morning at 1314 UTC or 8:14 AM EST.  Group AR3575 had rotated around the sun's limb in the last 48 hours so it was pointed at over 90 degrees away from Earth.  NASA's Solar Dynamics Observatory (SDO) recorded the extreme ultraviolet flash:


While instruments in space don't all have this handicap, the instruments that measured the flare's strength could have had their readings reduced by its position over the limb of the sun so it's the realm of possibility that this flare was stronger than X3.4.  The previous strongest flare of cycle 25 was an X2.8 flare on Thursday, Dec. 14.  

This morning's flare triggered a warning of an S2 or Moderate Solar Radiation Storm.  NOAA lists these characteristics of an S2 storm. 

Biological: Passengers and crew in high-flying aircraft at high latitudes may be exposed to elevated radiation risk.
Satellite operations: Infrequent single-event upsets possible.
Other systems: Small effects on HF propagation through the polar regions and navigation at polar cap locations possibly affected.

Space.com has a video that shows the eruption in several parts of the spectrum, viewable here.  

As we move toward or through the peak of cycle 25, this sort of thing is more likely than a year ago.  This is the sun today as posted on SpaceWeather.com, and there's an obvious, big sunspot group in the southern hemisphere (3576) that has the magnetic configuration to produce more flares and CMEs. 

For my fellow hams, solar terrestrial indices have been good, with solar flux in the 180s and K index has remained low until the last 3 hour window of the 9th, when it popped up to K=3.  I've heard nothing even remotely like the conditions that brought in New Zealand and Australia on 6m (50 MHz) a couple of weeks ago.



Thursday, February 8, 2024

OK, Who Had Central Florida Earthquake for 2024?

I thought I was coming up with a once in a lifetime story back in 2020 when I wrote a piece "Who Had Florida Earthquake On Their 2020 Card?"  Last night, we had another earthquake, only this time much closer to my home. 

When we got up this morning, Mrs. Graybeard opened up Firefox as she usually does to the USGS latest earthquakes website. We were stunned to see a report of magnitude 4.0 quake 163 km east of Cape Canaveral or just over 100 miles offshore.  The time is reported as 0348UTC on the 8th, or 10:48PM EST - approximately five to ten minutes after I fell asleep last night.  While the number of people responding to the USGS page's "Did you feel it?" query was in the low 30s before 8:00 AM this morning, this evening it shows 162 people reported feeling it, including people well inland.

The quake had no effect on SpaceX's launch of NASA's PACE satellite, which went off successfully at 1:33 AM EST, just under three hours later.  I've seen no references to anything done due to the quake.

The 2020 quake I talked about was in the extreme NW corner of Florida, pretty much on the Florida/Alabama state line and far closer to Mobile, Alabama than well-known panhandle cities like Panama City Beach.  That NW corner area had reported ten other earthquakes in the previous year.  A report I saw that went away quickly from a news source this afternoon said that the closest quake to last night's was off St. Augustine, about 100 miles north of last night's and about 20 years ago.

Florida is a big state, and is often thought of as three different states: the very southernmost part from the keys through around Lake Okeechobee, the central part from the Lake up to around where the Suwanee river meets the gulf coast, then the panhandle area that stretches 370 miles east to west.  The western part of the panhandle is on Central time; the dividing line is west of Tallahassee, close to the west side of the Apalachicola Forest. 

As with the 2020 quake, nobody was hurt and no damage was reported, but it still brought the same idea to mind:


Revised version of the meme in the 2020 post. 



Wednesday, February 7, 2024

India's Chandrayaan-2 Moon Orbiter Catalogs Solar Flares

Not just any solar flares, a new kind first described in the 1980s.  The kind of solar flares that we see the most pictures and video loops of are fast, dramatic events.  These occur when the magnetic field lines of the sun tangle, or cross, then snap and reconnect around sunspots. These outflows of radiation are the ones you hear talk of doom coming from; when strong enough, they can damage satellites and even affect the power and communication infrastructure on the ground.  

The new kind of solar flares don't release energy as quickly and then slowly dissipate.  Until Chandrayaan-2 began observing these flares, around 100 had been observed.  That's 100 since the 1980s.  Using Chandrayaan-2's lunar orbiter, a team of researchers detected 1,400 such slow-rising flares in three years.  

"There was a consensus in the solar physics community, since the early 2000s, that most solar flares are these rapidly rising intensities, followed by a slow decay," Aravind Bharathi Valluvan, team leader and an astrophysics graduate student at the University of California, San Diego, told Space.com. "However, what my research, along with my team, has shown is that not all solar flares follow that pattern."

Valluvan explained that the solar science community had overlooked slower-rising flares, or "hot thermal" flares because computer algorithms used to detect solar flares in observational data have focused on fast-rising, or "impulsive" flares. Impulsive flares are defined as covering the maximum area they possibly can in under half their lifespan. 

"We did not do that, and instead took a more general approach. What we saw is that there are a lot more slow-rising flares, and it's not an insignificant subset. In fact, they form a quarter of all flares," they continued. "So, we need to be studying hot thermal flares as a separate population. Currently, our understanding about these slower type flashes is quite limited."

As is often the case, the more these hot thermal flares are studied the more questions arise.  To begin with, the magnetic reconnection process that's believed to generate both impulsive flares and hot thermal flares is rapid, which should give rise to a rapid energy release as well. Which says that it might be the climb of the flare's ejected material through the suns photosphere that's different, instead of the way the flare is created.  

Rapid-rising impulse flares are associated with temperatures of around 18 million degrees Fahrenheit (10 million degrees Celsius). But slow-rising flares get their moniker "hot thermal flares" because they are associated with even greater temperatures of up to 54 million degrees Fahrenheit (30 million degrees Celsius).

Another significant conclusion of the the lunar orbiter's observations is that there are no "medium" speed flares between the faster impulse flares and the slower hot thermal flares.  Trying to understand that seems like an important step. 

There are more things to study.  A question researchers puzzle over is why the solar corona is hotter than the sun's "surface," or photosphere.  Not just "hotter" but hundreds of times hotter, despite being closer to the sun's fusion core.

"Why is the atmosphere hotter than the surface of the sun? That is something that solar flares have always been hypothesized as a solution for, but we never found evidence for this," Valluvan concluded. "These new types of flashes could be a potential resolution for this coronal heating mystery. And that is one of the things that I am most excited about."

"On July 2nd (2314 UT), giant sunspot AR3354 exploded, producing a long duration X1-class solar flare. NASA's Solar Dynamics Observatory (SDO) recorded the extreme ultraviolet flash."  From the July 3, 2023 post about that flare.