Chinese Spy Balloon Over the US: An Aerospace Expert Explains How the Balloons Work and What They Can See

By Iain Boyd, professor of aerospace engineering sciences at the University of Colorado Boulder. Originally published at The Conversation

The U.S. military shot down what U.S. officials called a Chinese surveillance balloon off the coast of South Carolina on Feb. 4, 2023. Officials said that the U.S. Navy planned to recover the debris, which is in shallow water.

The U.S. and Canada tracked the balloon as it crossed the Aleutian Islands, passed over Western Canada and entered U.S. airspace over Idaho. Officials of the U.S. Department of Defense confirmed on Feb. 2, 2023, that the military was tracking the balloon as it flew over the continental U.S. at an altitude of about 60,000 feet, including over Malmstrom Air Force Base in Montana. The base houses the 341st Missile Wing, which operates nuclear intercontinental ballistic missiles.

The next day, Chinese officials acknowledged that the balloon was theirs but denied it was intended for spying or meant to enter U.S. airspace. U.S. Secretary of State Antony Blinken said that the balloon’s incursion led him to cancel his trip to Beijing. He had been scheduled to meet with Chinese Foreign Minister Qin Gang on Feb. 5 and 6.

The Pentagon has reported that a second suspected Chinese balloon was seen over Latin America. On Feb. 4, officials told reporters that a third Chinese surveillance balloon was operating somewhere else in the world, and that the balloons are part of a Chinese military surveillance program.

Monitoring an adversary from a balloon dates back to 1794, when the French used a hot air balloon to track Austrian and Dutch troops in the Battle of Fleurus. We asked aerospace engineer Iain Boyd of the University of Colorado Boulder to explain how spy balloons work and why anyone would use one in the 21st century.

What is a spy balloon?

A spy balloon is literally a gas-filled balloon that is flying quite high in the sky, more or less where we fly commercial airplanes. It has some sophisticated cameras and imaging technology on it, and it’s pointing all of those instruments down at the ground. It’s collecting information through photography and other imaging of whatever is going on down on the ground below it.Why would someone want to use a spy balloon instead of just using spy satellites?

Satellites are the preferred method of spying from overhead. Spy satellites are above us today, typically at one of two different types of orbit.

The first is called low Earth orbit, and, as the name suggests, those satellites are relatively close to the ground. But they’re still several hundred miles above us. For imaging and taking photographs, the closer you are to something, the more clearly you can see it, and this applies to spying as well. The satellites that are in low Earth orbit have the advantage that they’re closer to the Earth so they’re able to see things more clearly than satellites that are farther away.

The disadvantage these low Earth orbit satellites have is that they are continually moving around the Earth. It takes them about 90 minutes to do one orbit around the Earth. That turns out to be pretty fast in terms of taking clear photographs of what’s going on below.

The second type of satellite orbit is called geosynchronous orbit, and that’s much farther away. It has the disadvantage that it’s harder to see things clearly when you’re very, very far away. But they have the advantage of what we call persistence, allowing satellites to capture images continuously. In those orbits, you’re essentially overlooking the exact same piece of ground on the Earth’s surface all the time because the satellite moves in exactly the same way the earth rotates – it rotates at the exact same speed.A balloon in some ways gets the best of those. These balloons are much, much closer to the ground than any of the satellites, so they can see even more clearly. And then, of course, balloons are moving, but they’re moving relatively slowly, so they also have a degree of persistence. However, spying is not usually done these days with balloons because they are a relatively easy target and are not completely controllable.

What types of surveillance are spy balloons capable of?

I don’t know what’s on this particular spy balloon, but it’s likely to be different kinds of cameras collecting different types of information.

These days, imaging is conducted across different regions of the electromagnetic spectrum. Humans see in a certain range of this spectrum, the visible spectrum. And so if you have a camera and you take a photograph of your dog, that’s a visible photograph. That’s one of the things spy aircraft do. They take regular photographs, although they have very good zoom capabilities to be able to magnify what they’re seeing quite a lot.

But you can also gather different kinds of information in other parts of the electromagnetic spectrum. Another fairly well-known one is infrared. If it’s nighttime, a camera operating in the visible part of the spectrum is not going to show you anything. It’s all going to be dark. But an infrared camera can pick up things from heat in the dark.

How do these balloons navigate?

Most of these balloons literally go where the wind blows. There can be a little bit of navigation, but there are certainly not people aboard them. They are at the mercy of whatever the weather is. They sometimes have guiding apparatus on them that change a balloon’s altitude to catch winds going in particular directions. According to reports, U.S. officials said the Chinese surveillance balloon had propellers to help steer it. If this is confirmed, it means that its operator would have much more control over the path of the balloon.

What are the limits to a nation’s airspace? At what altitude does it become space and anybody’s right to be there?

There is an internationally accepted boundary called the Kármán Line at 62 miles (100 kilometers) altitude. This balloon is well below that, so it is absolutely, definitely in U.S. airspace.

Which countries are known to be using spy balloons?

The Pentagon has had programs over the last few decades studying what can be done with balloons that couldn’t be done in the past. Maybe they’re bigger, maybe they can go higher in the atmosphere so they’re more difficult to shoot down or disable. Maybe they could be more persistent.

The broad interest in this incident illustrates its unusual nature. Few people would expect any country to be actively using spy balloons these days.

The U.S. flew many balloons over the Soviet Union in the 1940s and 1950s, and those were eventually replaced by the high-altitude spy airplanes, the U-2s, and they were subsequently replaced by satellites.I’m sure a number of countries around the world have periodically gone back to reevaluate: Are there other things we could do now with balloons that we couldn’t do before? Do they close some gaps we have from satellites and airplanes?

What does that say about the nature of this balloon, which China confirmed is theirs?

China has complained for many years about the U.S. spying on China through satellites, through ships. And China is also well known for engaging in somewhat provocative behavior, like in the South China Sea, sailing close to other nations’ boundaries and saber-rattling. I think it falls into that category.

The balloon doesn’t pose any real threat to the U.S. I think sometimes China is just experimenting to see how far they can push things. This isn’t really very advanced technology. It’s not serving any real military purpose. I think it’s much more likely some kind of political message.

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90 comments

  1. Stephen

    Generally a good article.

    Thanks for posting and it clarifies I think that this incident was a big fuss over nothing. An excuse to cancel Blnken’s visit.

    Surely, if there is tension then talking is a good idea? His pretext for not going to Beijing is disingenuous at best and resonates of school playground politics: “we don’t want to talk to him”.

    Love the comment about China being prepared to be provocative too. Obviously, the US never acts that way. Butter does not melt in its mouth.

    1. John R Moffett

      I still find it shocking that anyone in the US believes the government’s account… about anything. Fool me a thousand times appears to be the mindset of some Americans. Obviously, it is a weather balloon. That is what most balloons are used for. Obviously, satellites are what governments use to surveil. I don’t understand why Americans still believe the nonsense the government pumps out. How many times do you have to find out they lied to you before you stop trusting them???

        1. paddy

          aerostats with rudimentary radars have been protecting the border and coasts against small planes flying in drugs for years…..

          my favorite aerostat kerfuffle is the us army’s now shelved: Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System, or JLENS

          after failing its test and being terminated (the us army is the only service that does terminations*) the aerostat was set up at aberdeen proving ground doing ‘missions’ over the dc beltway.

          one blustery night in 2015 the thing broke its tether and dragged out power lines al the way to gettysburg!

          the pix looks like the air force may be playing with it!

          *why the army still has bradley and abram…..

        2. podcastkid

          “…and could eventually be used to track hypersonic weapons.”

          At mach 15 or whatever seems the tracker would have to be higher up to get a meaningful view of the whole arc. And what good would it do??

      1. Brianf

        It’s the United States of Amnesia. Truly incredible. It could just be a weather ballon and to think that Chinese human intel is not on the ground in USA is ridiculous. This narrative promotion is all you need to know that it probably isn’t true at all.

    2. Michael.j

      I’m sorry, but I have to contradict the author.

      Anyone with first hand experiences with fluid dynamics will see the absurdity in the most common narrative, ie “Spy Balloon”, due the impossibility of controlling such a bulbous object in high winds.

      If you’ve sailed in even a moderate breeze, navigated a boat on the ocean, paddled across a windy lake, bicycled on a windy day, or flown light aircraft, this story becomes implausible, due to difficulty in generating enough power to overcome prevailing winds or tides. This problem becomes even more pronounced when the object being propelled does not have a aerodynamic shape conducive for going against the prevailing winds.

      The short story is that you cannot control the path of a balloon in any sizable wind.

      A quick look at earth.nullschool.net will tell you that the current winds at the specified latitude are running between 50-100 mph. How exactly are you going to plough through that with a balloon?

      Another argument is that you are closer to the earth. That is true, but given the fact that you cannot control where you are, you have that much more atmosphere to penetrate to see at such an acute angle. As anyone knows, the atmosphere is the a huge impediment to clear vision.

      I’m sorry, this is a story about narrative control gone amok, and a failure of the search engines to find anything that is not a “SPY BALLOON”. My internet searches yesterday yielded nothing that did not give credence to this absurd narrative.

      I find the lack of common sense quite depressing. I just hope the people who are in control of the nukes have keener minds.

      1. Angie Neer

        Yes, the mainstream coverage of this has been appallingly bad, but you’re unreasonably projecting that onto this author. Of course you can’t just drive a balloon through a high wind, but he made no such claim.

        1. Hatuxka

          More unreasonable would be presuming at the outset that this was a spy balloon. That wins the unreasonable sweepstakes here.

      2. tbob

        Actually, there’s a company located in Sioux Falls, SD that manufactures several models of controllable balloons for the US Military. They’re balloon-within-balloon design with solar panels to power instrumentation and propulsion units.

        Last year, on FlightRadar24, I tracked a balloon released by our military (in conjunction with their armed forces) from the Philippines cross the Pacific, enter the continental US north of San Francisco and return to earth in a very large area of vacant farmland between Ft. Riley, KS and (you guessed it) Sioux Falls, SD.

        I was able to track that balloon because its transponder was broadcasting its location and altitude (lot of high-flying commercial traffic up there). Wonder if the Chinese “private airship” had a transponder operating and, if not, why not?

        There’s a lot we still don’t know about this.

        1. podcastkid

          Wouldn’t want to totally discount Boyd’s last sentence. Whatever I write here–all conceivable military purposes can best be offset by changing belligerent US policy.

          Could be all kinds of these things float over all the time, and this time the MICIMATT Complex just decided to create some hooplah about it? But consider: an underwater drone could launch a cruise missile. Ranges of such may increase in the future, but detailed terrain maps would be needed (to put in the missile’s “TERCOM” brain). For whatever maps more details may be needed, fields around power lines, cell towers, heat from various buildings…I’m just conjecturing. It would be a lot of info, and from there it would go to satellites, and from satellites eventually to ground where it’s processed (as with sonobuoy info). The maps get more detailed. Doesn’t have to be an intentional “political message”; it could be a practical thing and a message at the same time (don’t know if usually they can remotely let the helium out before they get near us or not). All of this would just be one more reason to scale down the brinksmanship now.

          Only thing I can think of, while I do think 99 out of a hundred it was just a stray weather balloon.

  2. Strontium-90

    The reporting about balloongate has been horrible, with newspapers here in Europe suggesting surveillance of stationary underground missile silos. Say what? Unpacking the Pentagon’s extreme paranoia and the Mighty Wurlizter’s bad-faith campaign requires a historical perspective. It’s the telemetry: https://muller.lbl.gov/teaching/physics10/Roswell/USMogulReport.html

    That, and undermining any move toward de-escalation before it happens.

    1. Bugs

      That’s really interesting. Especially the fun Roswell connection. So the Chinese could have been up to something like gathering ultra precise targeting information, or even listening operations? Cool.

  3. Alex V

    A more likely sensor system than cameras is electronic intelligence gathering, specifically for military transmitters and radars. Satellites can be used for this purpose as well, but a balloon is a better platform since it moves much slower and therefore can gather far more data. The solar panel boom would also function well as a mount for antennas. The longer the boom, the easier it is to do triangulation, and also increases the number of frequencies one could work over since you could have larger antennas.

    There have been some reports of propellers. I’m guessing these aren’t for propulsion, but for changing the direction the antenna is pointing, again for triangulation of signals.

    The number of solar panels are probably required to power all the equipment for sensing, and for a data relay.

    Some mention was made of the military taking preventative measures against surveillance. This was likely turning off radars and transmitters, or changing what they transmit, not covering up or moving equipment to prevent picture taking.

    I’m not going to take a firm position it was a spy balloon, just presenting some technical arguments for why it could be. The technology we’ve been able to see from pictures also doesn’t rule out the official Chinese explanation of a civilian scientific platform.

  4. digi_owl

    And it’s gone, thanks to an F-22.

    Was it here or on some other site that pointed out that this seemed very similar to Google’s Project Loon, that had high altitude balloons flying from Florida all the way to somewhere in Africa by simply riding the various air currents at different altitudes.

    Also, how long before this gets combined with city wide flying video surveillance that has been performed for a number of years already?

    That said, at least USA has yet to pop an airliner for accidentally entering US airspace, though they did down an Iranian one down in the Gulf back in the 80s.

    Oh, and the timeline of spy flights over USSR leaves out the SR-71.

    1. The Rev Kev

      I read that they did not want to chance a clean miss with a ground-based missile which was why they used an F-22. And that what was used was a Sidewinder missile as it could be heat guided. So they approached from the side of the balloon facing the sun as it would be heated the most and then it was Fox 2 away. And that was why that pilot got so close – to get an unmistakable lock on the heat coming off that balloon.

      I have listened to crowds watching this on the ground and you would think that it was Luke Skywalker taking out the Death Star. All over a damn balloon. They had this “expert” in a pin-stripe suit on the telly this morning in Oz and this female presenter asked him a very good question. That what if it did turn out to be a simple weather balloon when they retrieved that package. The guy laughed and then changed the subject. Maybe they should have just sent up Lawnchair Larry-

      https://en.wikipedia.org/wiki/Lawnchair_Larry_flight

      1. hpreddi

        so a high-altitude balloon lure with a satcom enabled elint package engaged an f-22/sidewinder and was shot down. “mission-accomplished”

        1. ambrit

          Since the ‘damage’ was already done, as in any competent spy agency would have ‘real time’ data links to such a device, then shooting down the aerostat was purely theatre.
          Also, just how much did the balloon and it’s cargo cost the Chinese versus how much the F-22 flight and sidewinder missile cost America?
          This calls for a cost to benefits analysis, since everything else in this, the “Most Perfect of Neo-liberal Paradises” is valued solely in financial terms.

          1. The Rev Kev

            Here is one estimate-

            U.S. F-22: $44,000 per flight hour of maintenance costs.
            Jet fuel: $10,000.
            Aim9x Sidewinder Block II: $399,500
            Total to American taxpayer: $453,500
            Humiliation of balloon already completing its mission and photographing/transmitting all data on U.S. most sensitive nuclear sites: Priceless

            1. tevhatch

              Humiliation of balloon already completing its mission and photographing/transmitting all data on U.S. most sensitive nuclear sites that’s been available for ages already: Priceless indeed.

              To be on target for a site visit would mean flooding the sky with these balloons, at best it’s just doing signal intel. My bet is it’s checking the weather prior invasion of Canada and maybe USA. No sense spending all that useless fed deposit notes buying immigrant visas to Canada and USA without checking out the real weather. Best protection against being nuked too, after all why would China want to nuke cities which demographically are becoming part of Asia.

            2. Luc Verbeurgt

              This is only half the cost for bringing the balloon down. Now the marines have to dive and bring it in. Then some labs have to examine the debry. Whatever they find, the end result will always be a “spy balloon”, just like the Iraqi WMD.

    2. Spudbuster

      Recall flight 707 with over 100 civilians on board flying into Russian air space. The Russians shot it down killing all on board. This is a bit different being a simple balloon. Not worthy of a half million dollar sidewinder missile or all the bulls___ media coverage.

  5. Fazal Majid

    The U-2 or SR-71 (and presumably whatever replaced them) can fly well above the 66,000ft altitude of this balloon, but the balloon can loiter, which would be useful for sustained electronic surveillance, e.g. traffic analysis. ICBM silos in Montana wouldn’t be the target, though, NORAD and Space Force in Cheyenne Mountain or similar sites would.

    1. Polar Socialist

      On the other hand, U-2 or SR-71 can be precisely over the target at a precise time, whereas the balloon can be hundreds of miles off course without no means of correcting it’s course. The high-and-fast flying airplanes are hard to shoot down even if you where they are whereas the balloon and it’s equipment is relatively easy to capture.

      A balloon actually sucks for spying.

      1. Vodkatom

        “A ballon actually sucks for spying”

        That the balloon’s path can’t be controlled is a good Occam’s razor for a not serious spy attempt. I’m open to the idea that, even if it was a weather ballon, it’s possible it was released just to troll us.

        I can’t believe this is a topic of national conversation. Though I’ve had a good chuckle. At least until I realize later this was the cases belli of world war 3.

      2. Spudbuster

        Recall flight 707 with over 100 civilians on board flying into Russian air space. The Russians shot it down killing all on board. This is a bit different being a simple balloon. Not worthy of a half million dollar sidewinder missile or all the bulls___ media coverage.

        1. Spudbuster

          A sidewinder missile to take down a fifty dollar weather balloon. I have an old single shot 22 that could pop the Balloon. LoL. Just need a fly by.

          1. tevhatch

            Considering the closing speed, that would be interesting to watch… from the ground, preferable located where the aircraft would not go down in case of a collision.

    2. TimmyB

      This ballon cannot and did not “loiter.” It drifted with the wind, which is why it was shot down over the Atlantic Ocean.

  6. ambrit

    America is presently using what it calls ‘aerostats’ to carry out spying on the public here at home. Basically medium sized blimps carrying an array of surveillance devices, I remember reading about one that “got away” over the Atlantic states.
    See: https://www.defensenews.com/air/2015/10/28/jlens-spy-blimp-on-the-ground-after-journey-over-pennsylvania/
    Several are being used for “defensive” surveillance in support of American troops overseas. One is, I believe, presently floating above the American power projection base at al-Tanf in southern Syria.
    For China to ‘float’ a big surveillance balloon over America does indeed sound like a “message” to the US. The flight path shown goes over the right place, and at about the proper altitude to detonate an EMP device for maximum disruptive effect on American telecommunications, computing data storage, and other electromagnetic systems.
    Would America consider the use of an EMP device, which generally utilizes an atomic explosion to do it’s work on a mass scale, in the atmosphere above “the Heartland” as a first strike, and thus reason enough to initiate an intercontinental ballistic missile strike? The nutters in Washington are acting crazy enough to do exactly that and then scoot off to their doomsday bunkers.
    All deities help us. We are ‘ruled’ by fools and psychos.

    1. Carolinian

      Go camp at Rockhound State Park in southern New Mexico and you will see a tethered balloon–not unlike those WW2 barrage balloons–hanging over the nearby hills. It is watching the southern border with cameras and this is part of the talked about electronic wall.

      So yes balloons–that 18th century invention–are part of the MIC/ICE toolkit.

    2. tevhatch

      If China was to detonate an EMP, it would mostly just do economic harm at first, as military communications are shielded with EMP in mind, but it almost certainly would start a nuclear exchange and then to all out nuclear war. That means they would have to be religious nuts, which they are not. Your remark on some of the religious nutters in American uniforms wanting to get to heaven early may be correct.

      1. playon

        This is especially true for the nutters in the US Air Force… see the film “Constantine’s Sword”.

  7. DJG, Reality Czar

    Thanks for this post. It clarifies that the balloon was taking pictures–as if the U.S. of A. isn’t using technology to gobble up enormous amounts of internet traffic…

    We’re all shocked to find out that the “intelligence community” is making another attempt at justifying its existence.

    Further: The selective outrage from Washington is, errrr, whiny.

    Allow me to note that Antony Blinken, who seems to have a highly inflated sense of his worth, is currently canceling trips over some balloon buffoonery and so far as we know is still “not talking” to Sergei Lavrov, Russian foreign minister. Aside from his general vibe of “banality of evil,” I am now detecting a certain vibe of drama-queenery.

    Does everything in U.S. life have to be endless high school? Now there are nukes. I will assume that none of the Blinkens in the elite and in the administration will wake up till it is too late (if ever). Maybe that is what history is–a saga of horrible decisions made by ambitious people lacking insight, lacking perspective.

    1. Darthbobber

      It doesn’t quite clarify that. The author talks about characteristics of “spy” balloons generally, and simply assumes that this balloon was one. What precise equipment this one actually carried they won’t know yet. And we’ll never know, though we may be told.

      1. tevhatch

        If you are not given hard facts (vs. CNN/FauxNews spin), then is most surely isn’t a spy balloon, at least as far as military spying goes. They are not going to advertise spending money and media spin on a weather balloon.

        1. tevhatch

          Saturday evening Garland Nixon predicted they would shoot the balloon down where it could not be recovered by non-state actors, probably the ocean, ambiguity serving their purpose.

  8. Louis Fyne

    1. The US media’s fearmongering and lack of circumspection is going help push the US to WW3 one day over Taiwan and/or Senkoku (Japanese rocks near Taiwan).

    The US had a secret military space shuttle (X-37) roam the world in low-earth orbit for months on end which likely did more real military work than this balloon by magnitudes. A d don’t forget Francis Powell….who probably most under-35s have never heard of.

    2. A potent hypothetical military use of balloons is as intelligence-survellience over a war theatre. Say the US-China fight in Taiwan, a hypothetical swarm of balloons over Taiwan and the South China Sea can give panopticon-like real-time monitoring for the entire combat zone and beyond.

    When the US Navy retrieves the balloon, it’ll prob have ordinary commercial-grade cameras and sensors, just like research balloon.

    But it prob. had a dual-use mission to get data on how balloons travel in real conditions.

    1. Michaelmas

      Louis Fyne: The US had a secret military space shuttle (X-37) roam the world in low-earth orbit for months on end which likely did more real military work than this balloon by magnitudes.

      What do you mean ‘had’? The US has a couple of X-37Bs, both still operational though on Earth at the moment since the last mission finished in November last year.

      They deploy and re-deploy US satellites, among other things. Though there’s no reason that, for all we know, that some of the orbital capability they’re deploying couldn’t be nuclear weapons.

    2. Daniil Adamov

      I’m marginally still under 35, and I do know Gary Francis Powers. Then again he was shot down over my city…

  9. doug

    Will the ‘top gun’ that was able to win that ‘dog fight’ gets Congressional Medal of Honor?
    And yes, DJG, endless HS from our leaders, and perhaps that way forever? Hopefully history treats Blinken poorly.

    1. Stephen

      Tom Cruise will make a blockbuster film about it.

      The only appropriate film though would be of the Mel Brooks or National Lampoons variety.

  10. Not Again

    I want to know what our vaunted Space Force was up to during this “First Chinese Assault on America”! (See, Biden really is like FDR and Pearl Harbor is now in Montana.)

    What’s the point of having a totally useless branch of the Armed Forces if they aren’t getting any camera time? It obvious that there’s a total lack of funding here. The defense contractors are missing an opportunity to do good for America and themselves. Go Space Force Go!

  11. farmboy

    “Since “Chinese Spy Balloon” is trending: In 1945, the crew of USS New York spotted a sphere that they thought might be a Japanese balloon weapon. The captain ordered it shot down but none of the guns could score a hit. Finally, a navigator realized they were attacking Venus.” source US Naval Institute.
    this time it was real, spy balloons over hanford

    1. LifelongLib

      Last year a couple of stratospheric balloons released by a U.S. company were in the sky over Honolulu. They did look planet-like to the naked eye but when I first saw them it seemed too late in the morning for that. Through binoculars I could see the spherical shapes. So confusing a balloon with a planet (or vice-versa) is not so far-fetched.

  12. JMW Turner

    There is an internationally accepted boundary called the Kármán Line at 62 miles (100 kilometers) altitude. This balloon is well below that, so it is absolutely, definitely in U.S. airspace.

    This is incorrect. The Kármán line is a physical concept, not a legal one. The upper limit of sovereign airspace is not defined by international law. In fact there are proposals to treat the 18-160km zone as a transitional region of reduced sovereignty akin to EEZs.

    https://iaass.space-safety.org/wp-content/uploads/sites/24/2021/07/IAASS-near-space-the-quest-for-a-new-legal-frontier.pdf

    > Legally however, it is an indistinct region where it is not clear whether the operations that take place are covered by aviation or space conventions and treaties, in particular with reference to the freedom of overflight that applies to space orbital operations

    Also:

    > Although outer space is free, if states are allowed to claim vertical sovereignty up to the point where orbital dynamics are possible, other states will be precluded from having free access to space

    > John A. Johnson, General Counsel of [NASA] and [of USAF], said in 1964 “there should therefore be no legal basis for protesting, merely on grounds of unpermitted presence, the overflight of national territory by ascending and descending spacecraft, regardless of altitude.”

    https://scholar.smu.edu/cgi/viewcontent.cgi?article=1126&context=jalc

    Also see:

    https://aviation.stackexchange.com/questions/43439/is-there-a-height-limit-to-national-airspace

    https://en.wikipedia.org/wiki/Air_sovereignty

      1. JMW Turner

        60,000 feet is just above 18km

        Referred to by different authors by various names, this region is called Near Space for the purpose of this paper and is tentatively defined as extending from airspace Flight Level 600, approximately 18 km,10 the practical upper limit of airspace, to 160 km above sea level,11 the practical lower perigee for an orbiting satellite.

  13. Rip Van Winkle

    1. From China’s perspective this was literally a trial balloon as a test of U.S. military and political reaction to same.

    2. From U.S. Empire perspective this was Mathias Rust landing in Red Square a couple of years before the collapse of the decrepit and hollowed-out Soviet Union. Too bad Payne Stewart’s corpse wasn’t piloting the balloon, as the Air Force would have been right on it.

    3. From my perspective it reminded me of a favorite Jules Verne-based movie from 60 years ago, Mysterious Island and a Three Stooges short from 80 years ago, Spook Louder, where Curley is being chased around a haunted house by a balloon with a face drawn on it hooked to the back of his coat and a maniacal laugh in the background. That’s where Blinken and Sullivan are at.

  14. NotTimothyGeithner

    Breaking News: President Biden has demanded all copies of “The Red Balloon” be destroyed to protect the children from communists.

  15. lyman alpha blob

    Little Marco Rubio has it all figured out! – https://www.yahoo.com/gma/rubio-says-china-sent-balloon-141039993.html

    “They did this on purpose. They understood that it was going to be spotted, they knew the U.S. government would have to reveal it, that people were gonna see it over the sky. And the message they were trying to send is what they believe internally, and that is that the United States is a once-great superpower that’s hollowed out, it’s in decline,” Rubio told ABC “This Week” co-anchor Jonathan Karl.

    The Chinese probably have a decent sense of humor. I doubt that their plan was to demonstrate the US as so jingoistically paranoid that they’d scramble a fighter jet to shoot down a freakin’ balloon, but I bet they and the rest of the world are having a few good belly laughs about it right now. But if Rubio is correct as to Chinese intentions, well mission accomplished! It would be difficult for the US govt. to come off looking more stupid and inept than they have here.

  16. Mike from Jersey

    There is one thing that the article missed – gravitational bias factors.

    The earth’s gravitational field is not uniform. Areas with larger deposits of heavier elements will have greater mass and thus generate greater gravitational effects. These differing gravitational effects (though small) will affect the trajectory of ballistic missiles. These are called gravitational bias factors. Ballistic missiles utilize “accelerometers” to adjust the trajectory of missiles during parts of the missile’s flight to keep them on target. But they cannot anticipate specific areas of gravitational bias over the lands controlled by a foreign power. So, although modern ballistic missiles have tremendous accuracy, they cannot account for gravitational bias factors in the nation of the proposed strike. It could be (I don’t know) that China was mapping gravitational bias factors in order to help calibrate ballistic missiles.

    On the other hand, it could have just been a weather balloon.

    1. wendigo

      When you are using a primary pressure standard involving rotating weights you use local gravitation as part of it’s calibration. Gravity maps are available on the internet, such as the Bouguer Gravity Map Grid.

      1. Mike from Jersey

        You are right about Bouguer Gravity Maps, but I am not sure that you could use those corrections at the altitudes that the missiles would be coming in, due the the effects of the interaction of multiple gravitational biases.

        The last time I checked, I know that many analysts did not believe that estimates of circular areas of probability of impact were accurate due to gravitational bias factors.

        Maybe they have overcome that since then.

  17. David in Santa Cruz

    This past Thursday Andrei Martyanov linked to Larry Johnson’s analysis of all the NORAD pearl-clutching:

    I think the Chinese are testing the definition of what constitutes acceptable overhead surveillance and may be trying to create a predicate for destroying our satellites if we go after their balloons.

    For me as a person who relies on GPS and Starlink every day, this is a rather alarming state of affairs. We know that the Russians and the Chinese have been jamming GPS signals for years — but the recent “heroic” American Military-Industrial Complex assistance to “Ukraine” has been utilizing GPS and Starlink for guidance and coms.

    As I understand it, the American military machine would be instantly rendered impotent without GPS . China and Russia clearly have the technical expertise and orbital hardware to knock down the satellite guidance systems that the U.S. MIC depends on for navigation and weapons guidance. However, there has been an open question under international law whether satellites are fair game for a shoot-down.

    Now they have been provided the answer. Biden, Blinken, and Austin are idiots…

    1. David in Santa Cruz

      Just drive Johnson’s point home the failing New York Times now reports that:

      “We solemnly protest the U.S. action, and retain the right to use the necessary means to deal with similar circumstances,” the [Chinese ] Defense Ministry said in its two-sentence statement.

      As we are discussing here, is there a functional difference under international law, and not the Rules-based Order (whatever that is), between a balloon dangling sensors flying at 55 miles altitude and a satellite dangling sensors in orbit at 60? None.

      To reiterate, the Chinese military is perfectly capable of putting up a satellite that can do just as good a job of spying as the white balloon, if not better. That slowly drifting balloon was dangling an invitation for Biden, Blinken, and Austin to set the precedent for shooting down other peoples’ “eyes in the sky.”

      What’s sauce for the goose is sauce for the gander. It may not happen today. It may not happen tomorrow. But the U.S. goose is cooked…

      1. marku52

        USN has been practicing celestial navigation with sextants for years now, because in some areas Russian jamming makes GPS useless.

        Also according to Black Mountain Analysis, the Russians have been practicing troop movements with Glonass turned off, as they also anticipate a space war taking out sat nav.

        I have an old optical transit in the closet, just in case surveying gets to be a thing again. It’s a lovely piece of kit, completely pointless in the age of GPS.

  18. jackman

    I’m with Rubio–there’s no question at this point that it was clearly a Chinese act of war. And now that we’ve shot it down, I think it’s safe to say that WWIII is over, and we won. China turned out to be not only a paper tiger, but a paper balloon tiger.
    But on a more serious note, the whole episode did reveal a disturbing weakness in our anti-balloon technology which the Armed Services Committee should take up–without delay!

  19. Sue inSoCal

    Thanks for this Conor. I see it as the American collective insanity. Fear! Fear! Fear! Oh dear! Reminiscent of youth — the Russians are coming, get under your desk! Fear has worked very well in the home of the brave. Fear China, fear Russia, you name it, fear it: Excluding huge issues that we really *should* fear such as our own home grown crazies, unstoppable climate destruction, and the uniparty. (There’s more. /s)

  20. scott s.

    I guess this is an alternative to “Open Skies” for which Trump admin terminated US participation. I was assigned to an HQ at one time and as a watch officer we would get notification of a pending flight and had to give notification to our subordinate activities to execute their protocols for over flight.

  21. Pookah Harvey

    So who is this Iain Boyd, professor of aerospace engineering sciences? From his bio at University of Colorado Boulder website:

    Professional Experience
    2019 – Present, Director, Center for National Security Initiatives, CU Boulder Research and Innovation Office
    2017 – 2019, Faculty Director of Government Relations, University of Michigan, Washington, DC

  22. GP

    A Google translation of this: https://www.163.com/dy/article/HSITNN8L05538ZXF.html that Blinken wasn’t wanted.

    1) US just signed up the Philippines for China Encirclement Duty this week.
    2) Biden has a whole new batch of severe sanctions on Huawei.
    3) Blinky wants to give a lecture on China/Russia cooperation.

    So, if these balloons have been transiting the USA for years (Trump, etc), offer no great advantage for spying, this is inflated (pun) by the US to cancel the non-existent China visit as a presumed US initiative.

    There are 3 balloons apparently. Is there anywhere in the USA that isn’t “near” US military installations, or anywhere in the world (beside inside China/Russia) that isn’t “near” US bases?

  23. Cat Burglar

    The balloon took time to get to Montana — what is the chance it was not being monitored by the US the minute it reached a decent altitude over China? By some maps, it appears to have first crossed into US territory near Juneau Alaska before drifting into northern British Columbia — where were US air surveillance and defense assets then? Were there no intergovernmental communications between China and the US then, even though military-to-military links exist? We are beginning to see articles impugning Trump for letting three earlier balloons drift into US airspace, hinting that perhaps he is in China’s pocket, or a poor defender of the nation. I will be reading further coverage with lots of questions — for now, the whole thing stinks of propaganda.

    I remember the Obama staffer, Ben Rhodes, writing that the press were easy to manipulate because the reporters were inexperienced and had no background in what they were reporting on: they would accept anything you’d tell them. As usual, known facts about US surveillance capability is below their sight line, just as it was in the case of the Iraq attack (US airborne ability to detect nuclear materials production), the Russian computer hack (Snowden showed the US has the ability to detect the origin of such attacks), and the Nordstream attack (the Baltic is heavily surveilled) — ignorance in the service of power.

  24. Cat Burglar

    The balloon took time to get to Montana — what is the chance it was not being monitored by the US the minute it reached a decent altitude over China? By some maps, it appears to have first crossed into US territory near Juneau Alaska before drifting into northern British Columbia — where were US air surveillance and defense assets then? Were there no intergovernmental communications between China and the US then, even though military-to-military links exist? We are beginning to see articles impugning Trump for letting three earlier balloons drift into US airspace, hinting that perhaps he is in China’s pocket, or a poor defender of the nation — the poor balloon is already being pressed into service in the next election! I will be reading further coverage with lots of questions — for now, the whole thing stinks of propaganda.

    I remember the Obama staffer, Ben Rhodes, writing that the press were easy to manipulate because the reporters were inexperienced and had no background in what they were reporting on: they would accept anything you’d tell them. As usual, known facts about US surveillance capability is below their sight line, just as it was in the case of the Iraq attack (US airborne ability to detect nuclear materials production), the Russian computer hack (Snowden showed the US has the ability to detect the origin of such attacks), and the Nordstream attack (the Baltic is heavily surveilled) — ignorance in the service of power.

  25. Chet G

    The following two quotes highlight what I consider to be the questionable nature of the article. First,

    A spy balloon is literally a gas-filled balloon that is flying quite high in the sky, more or less where we fly commercial airplanes.

    Aren’t international flights at about 35,000 feet, whereas the balloon was at 60,000. So how does the “more or less” fit in with an “expert” viewpoint? Second,

    China is also well known for engaging in somewhat provocative behavior,

    And that is on behalf of the US which has encircled China with military bases? Oh come on, Iain Boyd is pure establishment.

  26. Deltahedged

    What if the balloon was ‘fake Chinese” for U.S. propaganda of the imminent threat from the PRC?

  27. TimmyB

    This article is garbage. First, it claims that the balloon flew at the altitude airliners fly. No, it was at 60,000 feet, over 20,000 higher than the altitude airliners fly. Then it presupposes this balloon is a spy balloon without any evidence. In closing, it states that this balloon is an example of Chinese saber rattling, like Chinese navy vessels in the South China Sea. Seriously, wtf?

  28. Piotr Berman

    February 5, 2023 at 5:26 pm
    The balloon took time to get to Montana — what is the chance it was not being monitored by the US the minute it reached a decent altitude over China? By some maps, it appears to have first crossed into US territory near Juneau Alaska before drifting into northern British Columbia — where were US air surveillance and defense assets then?

    State run scientific projects, like on in USA managed by Columbia University with launching in Texas experiment with scientific balloon technology, and there were many balloons so far that flew for up to 300 days, hence going around the Earth many time, up to ten? and of course over most of possible countries, especially large ones like USA, China, Russia and Canada. Nobody objected because each time, it was JUST A BALLOON. Since the balloon was quite a bit larger than a pinhead, upon approaching air bases in Alaska it was surely identified. Airplanes near Juneau should be ready to scramble fast enough to shoot down balloon over Canada with only wolves, grizzlies etc. to be mildly in danger. But it was JUST A BALLOON. So a report was sent to a proper higher command at that was that.

    Until someone leaked the report with ensuing hilarity, hysterics, posturing, the works. At that point, the largest threat to the Administration was that the balloon could circulate around the globe, as many long-lasting stratospheric balloons did before, and RETURN. GOP could even try impeachment over it, and surely “Biden is WEAK” would be repeated incessantly.

    About spying equipment being on the balloon or not, non-Chinese do not know and do not care. Allegedly another balloon was spotted over Costa Rica. No reports on panic and fury down there. American do not know either, but they chose to be furious.

    1. Cat Burglar

      IIRC, the Canadian Air Force handles air defense for the Southeast Alaskan Coast, where the balloon first crossed US territory. But US planes could have come south from the bases in central Alaska, too.

      Whatever sensors were being carried by the balloon were emitting signals. One report said the US sent three RC-135s to monitor whatever was being transmitted — so they know exactly if it is a research project or spying, they just aren’t going to show us the evidence.

    2. Hatuxka

      It’s not hard to randomly drift over a US military installation, having as many as we do. Why would the Biden/Blinken clown show not seize the opportunity to play this up?

  29. Geoffrey

    It seems to me that there is more here then seems to be conventionally assumed. Surely an aspirant power like China has more control over its technology than to allow a diplomatic incident (which this morning (Monday 6th) China says has severely damaged US-Sino relations, to occur? Surely if a balloon is drifting into contenscious territory – and China does not want it to – it could be brought down gently into the sea, (and picked up by one of its ships if needs be)? Aren’t the Chinese being just as disingenuous as the US in saying its ‘just a weather balloon’, as the US said of the innocence of Pelosi’s visit? As the US has – predictably – shot it down, surely the US should now think twice about sending more ‘innocent’ planes and visitors to Taiwan? And given the gravity of the world situation, and knowing that the US is going to visit war on it in due course, why would China wait for the US to choose its time and opportunity (for kenetic hostilities to begin) and not try to upset US plans by upping the ante in at a time an manner of its (China’s) choosing. The one thing that might derail the headlong movement to WW3 is the US being faced with a two front war before it is ready.
    I might add that the incident my be a warning that WW3 will visit directly on the US mainland, and the US is no longer protected by its geographic isolation….

  30. Retired, Cynical, Scared S**tless

    If it weren’t for the nukes on both sides, this would be brilliant farce, kind of a Mouse that Roared situation, or the Simpsons episode (Sideshow Bob’s Last Gleaming, Season 7) where the USAF Harriers couldn’t shoot down a biplane because it was travelling so slowly.

    If it were a real spy balloon, one would think the Pentagon would have intercepted it much more quickly, and devised a plan to recover it as undamaged as possible. Waiting days while the balloon continued its spying mission would seem to be criminally incompetent. Then they destroyed it over the ocean so only wreckage remains and they can make up anything about what was really on it.

    Hoping that Xi has a sense of humour and launches 99 red ones next.

    Or just one, that looks like Principal Skinner.

  31. elkern

    This whole thing is hysterical; indeed, the real story IS the hysteria. Bowen Yang’s portrayal of the Balloon on the SNL cold open was likely more accurate than most “news” coverage.

    I wouldn’t argue with the implication in the OP that whatever info the balloon gathered would be seen by some Chinese equivalent of the NSA; our alphabet-soup security agencies gather info from wherever they can get it, theirs would too. But even if the primary purpose was taking pictures of whatever it passed over, China must have learned MUCH more from our insane reaction to the balloon:

    – USA really has gone bananas; the inmates really do run the asylum.
    – USA doesn’t have technical capability to grab a balloon out of the sky (had to shoot it down & dredge it up)

    OTOH, maybe this just what the Deep State *wants* China to think!!!!! :)

  32. Hatuxka

    Press TV had a segment with two interviewees one of whom related that China was not informed of any visit by Blinken. So supposedly a cancellation of an upcoming visit was for show to add false gravity to this off course weather balloon incident.

  33. Michael Wakefield

    I don’t know about anyone else, but spy balloons might make an interesting bio weapon deployment system. Call me a conspiracy theorist or whatever you like – IDK.

    The Pentagon chose to use an AIM9X Sidewinder missile to take out the balloon. definitely caused a lot of smoke!

    It would be interesting to note where the previous balloons have been sighted and correlate any COVID variant outbreaks in those locations.

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