Satellites Use 'This Weird Trick' To See More Than They Should - Synthetic Aperture Radar Explained.

[@ingmarhendriks8172]

FUN FACT: at the company I work for we developed a system that does the same with ultrasound on metal welds to see welding defects. The technique is basically the same.

[@michaelnord9081]

Synthetic aperture SONAR is a thing for imaging the bottom of the ocean as well.

[@jafinch78]

Somewhat similar... though I've not seen anyone make images with the data though I know can be performed, are the newer Modal Acoustic Emission (MAE) testing for carbon fiber tanks. There are also phased array synthetic aperture radar's too that can basically do the SAR with an array of SAR's I've read about. Makes me wonder with all the MIMO and other array technologies on towers everywhere what is being performed in exact detail. That's not including all the other dedicated RADAR's that can detect down to insect activities with some insect body functions.

[@fridaycaliforniaa236]

I guess that a wave is a wave, either electrical or mechanical ^^

[@iminni3459]

Nice

[@Temerator1]

@@iminni3459 So how much is your each space launch ? J/K

[@paulhaynes8045]

Brilliant stuff. A 16 minute video on a topic I knew almost nothing about, but which I (mostly) understood! No discord channel, no patreons, no researchers, no irritating ads or sponsoship, not even an obvious script! - just a bloke who knows his stuff and knows how to get it across. Thanks, Scott. Great title too!

[@jdjesse]

Amen

[@perryrhodan1364]

I know, right! He appears to do the entire video on the fly.

[@SavraOCE]

He's a software developer in his day job - he doesn't need the support or patrons or sponsors as he already makes enough money. It's not 'Zoomer' to sponsor a video, it's a way of generating revenue to keep making content. Discord channels are a great way for a community to connect. His videos are great, and it's great that he doesn't need to use alternative revenue sources to keep his channel going, but how out of touch can you be to assume it's a generational thing?

[@rage9715]

@J Hemphill Maybe you should check out bigclive pretty much the same though he has a patreon but doesn't mention it.

[@rage9715]

@J Hemphill Big clive is an old school electrical engineer with a sense of humour. He tears down and analyses random ebay stuff its quality content.

[@TaylorPeterson913]

You freaking blew my mind talking about the optical-mechanical computer that could perform fourier transforms from film data. The engineers of the past were ingenius.

[@robertgraham6481]

"Engineers used to be so ingenious. They still are, but they used to be, too."

[@tomast9034]

back then you did a conveyour system from ground up for a year. nowdays costumers demands are like yesterday was late :D

[@beeble2003]

Given the very close connections between Fourier transforms and optics, it's not too surprising in this case. It's not like they built an opto-mechanical computer to calculate prime numbers or something completely disconnected from the mechanism.

[@stolenlaptop]

@@robertgraham6481 a mitch hedberg fan i see 😎

[@matf9325]

I worked with those optical SAR processors systems in the early 80s

[@luckwolfgang]

You amaze me Scott. I'm a remote sensing expert and you have just covered five University lectures on the topic in the most concise and understandable terms for laymen. Well done, I'm speechless

[@danielsteele7225]

Believe it may be productive to investigate that many UAPs appear to use some form of synthetic aperture optical sensing to achieve astronomical ratios of wavelength to aperture, perhaps even multispectral not only to minimize atmospheric effects but to further characterize objects under observation.

[@seedplanter7173]

Did you get the latest memo? Turns out your brain washed and we still can get past the Vanallen belt

[@ProDMiner]

in less than 20 minutes at that! I never seen this guy before, but I listen to stuff often in the background. I did not know we had satellite images of venus now! mind blown we are so close to being able to travel all the time in space. So exicted!

[@heartobefelt]

@@danielsteele7225 Can i rent them out to scan for underground gold resources ? :)

[@danfadden]

Literally speechless now. Lol

[@rowlandhempel4282]

I was an electronics technician in the US Coast Guard and for part of my enlistment I was attached to a field testing unit. In 1971 we attached a couple of long, rectangular radar antennas to the sides of a C130 Hercules that was used for International Ice Patrol over the North Atlantic. We were testing how radar could be used to film the locations and sizes of icebergs, a job traditionally done by someone peering out the small window of the plane and noting on a map a best guess. My job was mainly to ensure the equipment was working and to develop the film on the plane. I had no knowledge of what happened to the film or how it was processed. Your article has filled in those gaps.

[@Chiberia]

the photos are now stored by top men. by TOP. MEN.

[@mortennrgaard8144]

When i was in Afghanistan we got SAR images produced covering our area of operation. The intent was to see where locals walked (dirt moved so a trail of routes appeared on the images) and where anyone had been digging. This helped us avoid IED's. We got multiple fly-overs so the analysts could spot the differences. :)

[@The_Conspiracy_Analyst]

I don't buy it. If they had this capability, they'd have been using it in Ukraine to map out mine fields. Which they haven't, because that's really what's holding up any possibility of an offensive into Crimea and southern Ukraine.

[@mortennrgaard8144]

@@The_Conspiracy_Analyst ​​⁠​⁠​⁠I’ll give you 3 reasons why. 1: The resolution required to be able to locate mines would require an airplane or UAV and therefore also air superiority which neither Russia or Ukraine has. 2: To be able to detect changes you have to have data of the area from before the mines were laid out. Otherwise automatic change detection will not work. 3: SAR technology is not currently cleared for export to Ukraine. Satellite based SAR data is already in use but mainly for large body detection.

[@DemocracyManifest-vc5jn]

If it can detect ieds why can’t it detect human movements? Does it have a very small field of view or something? I know Israel is using them to find tunnels, this is fact.

[@DemocracyManifest-vc5jn]

Well their satellites are able to detect change in earths magnetic field and detect disruptions like tunnels. They knew where they were before the war started

[@dsdy1205]

SAR requires several seconds to scan a single point in space. In that time a walking human has covered several meters and is effectively a blur on the SAR scan. IEDs and footprints on the other hand don't tend to move much.​@DemocracyManifest-vc5jn

[@scheimong]

"... look at the world in a different light" That's such a manly pun

[@21sanooj]

Did you mean Manley pun?

[@Kabup2]

Come to me, Brad Fiedel

[@ddegn]

I thought it was a Manley pun. 😉

[@lmamakos]

I see what you did there

[@mgreene1409]

I was going to say something similar but you beat me to it.

[@michaelnord9081]

SAR does not actually use the "instantaneous" doppler, or the frequency shift due to the velocity in the relativistic sense. It does use phase shifts over time. I'm a SAR subject matter expert if anyone has questions.

[@tomc.5704]

So it's not looking at the frequency change? What's the difference between phase shift and timing? I don't see how knowing the phase shift would help you. Unless you have a fast enough data collection rate that you can approximate a continuous phase shift? What's going on there

[@Youtubeuser1aa]

@@tomc.5704 a car or footsteps mush grass on the order of seconds. Leaves in the wind vibrate multiple Hz. If you filter the phase shifts based on the intervals, you can get rid of clutter from leaves moving. You can see where someone walked in the grass. You can see machinery vibrating near or underground. Make sense?

[@jondrew55]

As a SAR SME, can you tell me if Biden actually stole the election?

[@fromagefrizzbizz9377]

@@tomc.5704 I think one answer is that the effective pixel bursts are short enough that it actually isn't that easy to measure exact frequency, but measuring the phase shift over time substitutes nicely at least as a relative indicator. Eg: timing zero crossing is simpler than counting cycles. Especially at radar frequencies.

[@feha92]

Then you might explain my question: In the video Scott explains (and shows with graphics) that the SAR sattelite views a perpendicular (to its path) band at a time, and that the band moves with the sattelite (one graphic showed that sometimes the width of the band is increased by moving it over the surface 3* the sat's speed, giving 3 passes with no overlaps). This both implies and _shows_ that any point (and thus object) on the surface/image is only seen once, since no backtracking is done (the closest was the one doing 3 passes, but as I mentioned, it was to increase the width of the image and had no overlaps). Then how is it that Scott describes the interferometry as achieved by looking at multiple responses (separated by sat-pos, and thus also time - which was why it's assumed all objects are standing still) of the same object (even showing a graph of how the range to said object changes), when it clearly never was seen more than once? The only way I could imagine that happening (the object being seen more than once by a sat behaving as described), would be if the frequency with which it checked a band of the surface was higher than the resolution/speed - meaning that each view of its band overlapped with the prior band (to the extent proportional to the increased frequency. ie. twice as often makes the bands overlap half of the prior, resulting in 2 responses for same object). But this was never mentioned or otherwise implied (rather, feels like the opposite was implied from some graphics), so I assume that this is not the case. Thus, how are objects seen more than once (as described at start and shown in the signal-return-time plot) when they are only covered by the band once (from graphics and description prior to that plot)? Later another graphic shows the satellite rotating so the band keeps hitting the object (despite the prior explanation and graphics stating otherwise, as well as a just prior comment on how it is never angled straight onto the planet being contradicted by this graphic), which also serves to confuse me further?

[@christopherroach264]

Roughness of water lets you retrieve near-surface wind fields from radar signals (both SAR and lower resolution scatterometers ala the Jason series satellites...)... Wind waves generate different scattering patterns to larger scale waves (swell and similar).

[@dxb338]

and surfline, magic seaweed, et al are still mostly relying on bouys. SMH.

[@idontcare7961]

Speaking of water, when undisturbed it remains level and you can not disprove that. Why do you ppl fall for such lies?

[@loganmpe7559]

@@idontcare7961 So who do you know that's trying to disprove that water, or any liquid for that matter remains level when undisturbed?

[@idontcare7961]

@@loganmpe7559 Pretty much 80% of the population

[@arturoeugster7228]

@@idontcare7961 Mass concentrations on the subsurface, affects satellite orbits too. SEA is not at all spherical.

[@flantc]

Fun fact. Water's dielectric constant changes significantly when it freezes. This is used by radar to determine the amount of ice vs water cover.

[@-danR]

It's an annoying property when you want to defrost a block of spinach. It gets surrounded by a slowly growing puddle of overcooked vegetation, while the middle of the block resolutely refuses to thaw. I have keep interrupting it to scrape off the softened muck and stab it with the point of a knife to break the lump into smaller pieces. Lucky I don't live in the UK where pointed knives are illegal.

[@max_kl]

@M. de k. I think that's what he/she was talking about

[@Anvilshock]

Fun fact: That's exactly what 8:09 shows.

[@MegaKopfschmerzen]

This is the Aperture Science we deserve!

[@TheRogueWolf]

You only say that because you haven't had combustible lemons thrown at your house.

[@drakedbz]

I'm making a note here: Huge success!

[@thecoolface123]

I hope scott sits proud on the throne of this channel, a distinguished and successful educator that's reached millions and millions of people.

[@amaarquadri]

8:22 The fact that you can effectively perform Fourier transforms and other image processing by passing an light through some lens completely blows my mind!

[@TaylorPeterson913]

My jaw dropped when he said that!

[@bozo5632]

And / or it's amazing that you can do optics with math.

[@tissuepaper9962]

There are analog computers that solve differential equations by reconfiguring a circuit internally to be governed by the equation that you want to solve.

[@mskiptr]

Yeah, electrical analog computers are fascinating too!

[@absurdengineering]

Early military GPS receivers used optical Fourier transforms for 2D convolutions needed for the correlators. I had an old (early 70s vintage) audio spectrum analyzer with an optical transform system. It was cheaper than digitizing audio and computing FFTs with a computer - and orders of magnitude faster. A special storage CRT was used to record audio as an intensity signal, and a flying photodiode was reading out the output.

[@perryrhodan1364]

Scott: You must have spent a great deal of time studying up on this. This is one of those watch several times videos. Thanks!

[@jesserutt7413]

The “were” in the arecibo telescope image is so sad 😭

[@DanielFenandes]

*arecibo

[@jesserutt7413]

@@DanielFenandes 👍🏻

[@zapfanzapfan]

Yepp... met a professor who did some of the design and calculations in the 80s to get that feed to work. He's dead now... like the feed.

[@cesarposadasatamusic]

F

[@jdjesse]

@@zapfanzapfan was his death related to the death of the feed?

[@MIG29SUU27]

Synthetic Aperture Radar (SAR) has been around for a while. In 1981-2, while a test pilot at Eglin AFB, a WSO and I did test flights in the prototype F-15E which was then in competition with the F-16XL. The radar in that F-15 was an APG-70 redesign of the APG-63 which included a SAR mode. We used SAR very successfully to identify and attach targets at night and in the weather as well as slave a Pave Tack IR/LASER targeting pod.

[@danlewis243]

SR -71 and possibly earlier iterations as well utilized ASARS, so ~ 1966

[@MIG29SUU27]

@@danlewis243 Yes. You are correct. One of the differences is that the SR-71 SAR used a dedicated side looking antenna. On the F-15E the SAR mode used the same forward looking radar antenna as used by the attack radar.

[@baomao7243]

An OUTSTANDING simple description of SAR. I am an electromagnetics junkie and have years working as an RF engineer and optical systems engineer on terrestrial and satellite systems. Your consideration of polarization, dielectric constant, Doppler shift, timing, and angular issues all pulled at my tech background ... and also at my heartstrings. Thank you for simplifying something so complex to a MUCH less complex yet ACCURATE description for the broader audience of non-geeks. Again, OUTSTANDING. 👍 (Reminds me of MIMO antenna systems. LOTS of complex math...but the avg person accepts “multiple antennas and some math means ‘more user bandwidth’.”😉)

[@semihkesen392]

hello bao, i want to ask you a question about this subject, can you give me your e-mail?

[@alwasitacatisaw1275]

You just summed up a 1.5h lecture I had this summer. It’s an exciting topic, isn’t it?

[@RegularEarthlingEngineer]

Technology just keeps getting better I cant imagine what resolution would be available within 20 years

[@Jameson1776]

Proabably already here. We just won’t see it for 20 years.

[@TS-jm7jm]

cool it with the techno optimism there bud

[@trailerhater]

It will be our new years resolution.

[@eyeborg3148]

We’ve already more or less reached the limit of resolution possible with a given aperture size, as given by physics. I expect any advancements to be in methods of interferometry, data processing and analysis, and adaptive optics.

[@garageflower7154]

Right? I was watching some stuff a about AI/machine learning then with all the space stuff technologies advancing so fast, it's awesome.

[@theblairisstillaround7084]

The fact that they figured out how to do this analogue blows my mind... I understand we do it now with computers, but the people who blazed the trail deserve recognition beyond most. Truly we stand on the shoulders of giants

[@perryrhodan1364]

Back in the late 80s I was tech for analog computers. Synchros, servos, gears and my favorite, disk resolvers. I have tried to make note of the old way to our IT professions but they think I’m full of caca.

[@tomc.5704]

@@perryrhodan1364 That stuff blows my mind. Do you think there was a path to advanced technology without transistors and microchips?

[@perryrhodan1364]

@@tomc.5704 I think analog as a computer technology was at its end in practicality. There was no way to reprogram the machine; no software. And analog machines took up a lot of room and used a lot of power.

[@heartobefelt]

Yes absolutely true , I am talented at many things but looking at what they did ? I would absolutely have zero chance of formulating any of it even if they laid out its preliminary components in front of me.

[@PTuffduty]

I listened to every word. I didn’t understand very much of what was said. But he explains the topic of SAR with such enthusiasm that he makes it interesting and the result is: I now have an appreciation for what is going on, as compared to my total lack of knowledge just a few minutes ago. You are a genius and I am an enthusiastic subscriber.

[@DumbledoreMcCracken]

Don't feel badly, it was a poor attempt to explain something through the use of *_a lot of extraneous information and nothing really relevant._* If you read some web sites on the subject, it may become more clear to you.

[@favesongslist]

@@DumbledoreMcCracken please add a link to a good web site, TY.

[@DumbledoreMcCracken]

@@favesongslist radar101

[@loganmpe7559]

@@DumbledoreMcCracken Not a fan I take it? SMH

[@DumbledoreMcCracken]

@@loganmpe7559 No, I'm not. The attempt is complete buffoonery.

[@Digephil]

At around 10:15 you mention that high dielectric constant materials reflect radio waves. In this instance, that's true, but the more accurate description is that it's interfaces with a high contrast in dielectric constants. That means that the opposite also works and you can see objects with lower impedance contrast, which is how ground penetrating radar is able to range, and describe, objects underground.

[@stevecummins324]

Oxide layers on say aluminum or titanium too? pretty sure WD40 reduces formation of such...back to rocket science lol

[@janetizzy6741]

A great explanation of a very technical subject. There is also a non-pulse, ultra high resolution type of radar; CWI (Continuous Wave Interferometer) that uses a combination of SAW (Surface Acoustical Wave) devices as the main detector. Not anything "modern", this sort of device was used back in the early '70s (by the military - of course). That might make an interesting complement to this video.

[@uploadJ]

ISAR - spell it out "for me".

[@jsnyper4357]

25 years ago I was an imagery analyst in the US Army and we used SAR imagery. Back then resolution was measured in feet, this new stuff blows my mind.

[@CAaustinwer]

The image of the little white and black dots being identified as Russian armored vehicles blew my mind, right after you talked about all the shit SAR can’t do lol

[@vladimirdyuzhev]

And I was puzzled what is the obsession with the inflatable tanks recently - they are not too convincing for UAV operators, so why bother? Now I realize they are VERY convincing to SAR satellites.

[@SpecialistBR]

@@vladimirdyuzhev Unless you make a inflatable tank made of metal (then its not really inflatable anymore... more like an expensive dummy), it is not going to fool SAR.

[@SpecialistBR]

@@robertjames1267 Ah... yes, sure, and that will be able to retain shape so well... and make the same kinds of speculars that a normal shaped tank makes... aham...

[@Dovorans]

@@SpecialistBR metalized mylar films are already used as inflatable radar decoys.

[@SpecialistBR]

@@robertjames1267 WWeather balloons are round just because gas expands in all directions, not because they HAVE to be round. Inflatable tanks, on the other hand, presume a certain shape. A metal foil could create all sorts of wrinkles, imperfections and concave shapes that could exacerbate radar reflections to the point you could tell the bright-as-the-sun spot in the radar image is actually not a real tank. I am saying "could" because, although I do a lot of military research, I never encountered any material on decoys used in this manner. But well as anything in life I could be wrong.

[@FozzyBBear]

Oh there are plenty of military applications. Back in the 1970s when the US first released satellite radar images of subterranean rivers in Egypt, the true message was to tell the USSR "We can see inside your missile silos and bunkers".

[@dale116dot7]

Kind of like one message of Apollo was that if the IBM/MIT guidance systems can hit a half mile target at 240,000 miles out, one can calculate how close a missile with the same guidance system can hit. Who needs a 50 or even 5 Mt bomb when you can aim a much smaller, much cheaper weapon to within a few tens of feet?

[@sgifford1000]

Man you're brilliant! I have a graduate EE degree in signal processing and I've never learned as much about synthetic radar as your presentation.

[@loganmpe7559]

Degrees are almost useless, nearly all practical learning is done hands on, doing the job.

[@PBeringer]

​@@loganmpe7559 Haha. There's always one ...

[@RicardoPetrazzi]

"I'm Scott Manley, making applied science accessible!" Thanks for the super explanation in this video! Very useful. 👍😎

[@funnyitworkedlasttime6611]

“Satellites do this trick, and governments hate them for it!” Page Six

[@railgap]

You kidding? Governments have the best SAR satellites - they love that trick.

[@SuperfluousJ]

...and the satellites couldn't stop staring

[@holdenleeb2312]

Do you mean 6:37?

[@PresidentialWinner]

This is a reference to the Doctors Hate Him which refers to a popular culture trope that’s frequently used in online advertisements dating back to the late 2000s, especially with clickbait, chumbox or pop-up ads. This trope has been parodied in jokes across the internet in the form of countless memes and shares many similarities to the Trainers Hate Him format.

[@spuffles2104]

lmao

[@vinayaknarayan5310]

I'm studying for my Master's in Space Engineering currently and I have my Satellite Remote Sensing exam in 2 days time. This video explained SAR so much better and quicker than my lecturer so you've just saved my exam. Thanks a tonne!

[@AsbestosMuffins]

I'm sure the NSA has a love/hate relationship with these companies since they provide lots of intel, but also prove that you don't have to be the NSA to afford a spy sat program

[@Lessinath]

If this is so workable and cheap, how good do you think the NSA's stuff is, with their secret budgets and dark money?

[@n.s.ac.i.ajointeffort1983]

The amount of power we posses is unfathomable to civilians We do things civilians wouldnt believe are still done in this modern age and you still underestimate our power?

[@sealpiercing8476]

The NSA has been balls-deep in SAR for ages. I'm sure they have some nice kit.

[@marlinmuller2725]

I don't think that the spatial resolution is a problem anymore. More important for intelligence gathering might be the temporal resolution. Normal SAR satellites only capture the same location every few days or so, which might not be enough for state agencies

[@edstirling]

NSA *contractors. I think you'd be surprised by how far behind the NSA actually is on a lot of technological fronts. feds don't get paid enough to retain a lot of brain power internally so the wiz kids are all in the private sector. These commercial sats are likely going to shake up a bunch of contracts when people start saying things like "why don't we just buy the commercial data, it's better and cheaper and we don't have to wait for Boeing to reinvent space travel." The NSA gets a lot of privileges, but don't be fooled into thinking they are creative. bureaucrats are good at one thing: not getting fired.

[@mg4695]

In February 2000 I was involved with the Shuttle Radar Topography Mission (SRTM) which used C and X band radar to map about 80% of the Earth's land surface with 30-meter (1 arc-second) resolution over the 11 day STS-99 mission aboard Shuttle ENDEAVOUR. What made SRTM unique was we used a 60-meter mast to extend a second SAR antenna. This dual antenna system enabled us to do 3D interferometry in one pass, but about 94% of the coverage area was imaged twice over the 10 days of mapping. The deployment of the mast made the SRTM mission the largest rigid structure to orbit the Earth until the construction of the ISS. That mast, by the way, was of the same design as the masts we would use on the ISS solar arrays. STS-99 was thus also an inflight test of the final ISS mast deployment mechanism hardware design. The "outrigger" antenna and mast are on display at the National Air & Space Museum's Udvar-Hazy facility above Shuttle DISCOVERY. The most interesting use of the data that I am aware of was that of a German trucking company that was expanding operation into the recently re-unified eastern part of Germany. The company was looking to buy new trucks and wanted accurate elevation data for the poorly mapped former East Germany so that they could order the correct gear ratios for their new vehicles for optimized performance. #RadarLove

[@DrDeuteron]

that's the most interesting? idk, SRTM has over 10,000 citations. Maybe finding invisible meteor craters is cooler than trucks. js.

[@mg4695]

Interesting as in unusual. There were/are many marvelous scientific uses if the data, the truck purchase one was unique.

[@mvg2993]

There is some really cool research on techniques for the deceptive jamming of SARs using GANs to generate realistic 'spoof' images.

[@bamafan-in-OZ]

This could be fun with a bit of imagination. "What's that? it looks like a 11km tall maid with a vacuum cleaner"

[@tomc.5704]

I don't quite understand how that would work in the real world --- satellite takes the SAR, beams it back home to the processer which resolves the image. You'd have to hack into their SAR processor and replace the sattelite's SAR data with your own? Like sure, I guess that works, and its cool that we can train a neural network to create false data (although do we really need a neural network for that?), but...none of that feels particularly ground breaking or real world plausible.

[@namibjDerEchte]

@@tomc.5704 No, you detect the sattelite's scanning beam, and instead of the normal reflection, you make it listen to the faked data.

[@SDsc0rch]

what is "GAN" ??

[@SDsc0rch]

@@grizzomble - thx never heard of it

[@fridaycaliforniaa236]

Being a military helicopter pilot; I had to learn many about radars when I was at pilots school. All the things you explained are pretty accurate and really nice to hear. Good memories =) Greetings from France =)

[@OseanBigshot444]

(2:45) A moment of silence for Arecibo.

[@kenoman3908]

I was the Software Lead for Raytheon on their 1st SAR radar (PDMM - Pulse Doppler Map Matching) back in the 77-79 time frame. It had the two modes of operation, spotlight (terminal guidance for ICBN’s) & Strip-mode (I believed used for initial guidance for cruise missiles). It did include a Digital Signal Processor and a Display processor so we could see the radar maps in real-time on the airplane. I remember it interfaced with 17 devices, all in real time - DMA, parallel, and serial devices. The code was in assembly language on a new Raytheon built computer (serial #1). Thus we had to develop all the I/O drivers (we weren’t sure if you hit an “a” on the keyboard that an “a” would appear on the screen.) Of course there were no S/W development tools out side of a computer simulator that ran on an IBM mainframe. Trouble was - the simulated computer instructions did not execute the same as the instructions on the computer (computer at fault). Thus part of my job was to figure out what was wrong with the computer & provide what was needed to be done to fix the problem. Of course all these problems were intermittent. Quite different from today.

[@trcostan]

“Begin looking at the world in a different light” love it!

[@evilkidm93b]

I did two theses on polarimetry and also read into the radar aspect. It's great to hear about this topic again and it brings back that excitement about all the things you can do in remote sensing. I find it hilarious how radar tech works: you can first record the data without "lens", then afterwards run it through a "lens" to get your image. (Fourier transform is in essence what a lens does.) It doesn't work in the visible yet, because we would need to record the electromagnetic field amplitudes, which are oscillating to quickly.

[@lisamccartney8424]

Scott, could you do a presentation on "electro tellurics"--In the 80's-I could map subsurface details down to about 16k feet with less than 1 meter detail-( structural mapping for oil exploration)-blew the socks off many skeptics. Thanks for your channel!

[@tomc.5704]

Mapping what's beneath the earth based on the flow of electricity through the ground....that's just wild. 16k feet is no joke, either. Jesus.

[@semihkesen392]

hello lisa, i want to ask you a question about this subject, can you give me your e-mail?

[@jrondeau8430]

Thanks Scott for you explanation of SAR I understood exactly what you were saying during the video but after the video ended I realized I had no idea what you're talking about. You are the best !

[@LetsMakeThingsGoBoom]

SAR elevation models were extremely important for my research on landslides in southeast Alaska

[@Christopher-pe6zj]

I can't get enough of these videos... the time you'd have to spend researching this stuff to get the same information and comprehension out of it... can't even imagine. Thanks mate!

[@Mrjohndful]

I absolutely love how whole heartedly nerdy scots back drop is there is something so fun about someone being 100% genuine.

[@pirobot668beta]

Synthetic aperture transducers (all antennas are transducers!) is seen every day, yet you wouldn't expect it. Violins. Well, many stringed instruments in this class are 'aperture arrays excited by tightly coupled resonant chambers'. The upper and lower lobes of a violin body the resonant chambers, the waist section is the coupler/mixer. The slots in the violin body are parked in the waist section; that location will see maximum internal pressure swings = loudest sound. The slots or 'f-holes' taper towards each other, this leads the sound to 'project' toward the narrow end of the slots, into the audience. The taper also tends to bend higher pitches more than lower ones, helping even more with projection. The funny curls in the ends of the f-holes help break up corner drag: a sharp ending in the slot can make vortices that muddy the sound. The mis-matched lobes allow a wide frequency range that goes above and below the natural resonance of either structure alone. If the frequency difference of the large and small lobes is 440 Hz, the low end is 440 Hz lower than the low lobe and the high end is 440 Hz higher than the high lobe. The wonders of mixing analog frequencies! That's how a tiny violin can be loud, 'fill the room' with sound, and still have such a wide range! The wood and varnish used helps with acoustic efficiency, which we hear as a warm tone. There are oodles of other frequency sensitive parts in a violin, but synthetic aperture is the dominant feature.

[@AntonFetzer]

There are Terabytes of data from the Sentinel missions publicly available for free, for everyone to use and the data is updated every day. So you can look at SAR images that are only a few days old. The free software SNAP can be used to process the raw data and extract lots of information that cannot be seen in optical images.

[@CortB]

Glad to see that Dragonriders of Pern book on your shelf!

[@Palaeogeobicho]

and SAR is a very important tool to detect oil spills at the surface of the water (VV)

[@user-zh5oo1vv7l]

Nearly always finish watching your videos with a smile on my face, head filled with new knowledge about subjects I didn't even realise I had any interest in. Thanks for all the amazing content you put out. Fly safe.

[@A.Lifecraft]

The basic principle is also used reading DVDs and other high capacity optical data storage. As lines of points are as close together as the wavelength of the laser scanning it, and there are all sorts of interferences and diffraction effects, the signal is run through a fourrier analyzer to clear it up into zeros and ones. So they basically give that laser a higher resolution than it would have by its actual wavelength.

[@junkmail4613]

Scott, Absolutely intriguing. You are like "Technological Radar" for us retired folks. So I'll be sayin' Keep yer eyes open for the rest of us. Thanks so much!

[@eekee6034]

Radar seeing to the same resolution as optical imaging from the same size spacecraft had me mindblown until I remembered my brain does some amazing things with limited optical data. Watching something as I move past lets me get a much clearer picture of it. Perhaps the biggest example was when cycling on a trail bordered by an almost hedge-like row of small trees, with sounds of workmen coming from the other side. When stationary, I could see the color of dirt through the trees but couldn't tell if it was the ground or a mound, flecks or an expanse, or even if it was really dirt at all. When moving at perhaps 10mph, I could see the ground was in an early phase of preparation for road construction.

[@Alexander_Sannikov]

12:15 pardon my nitpicking, but horizontally polarized light reflects better off horizontal surfaces than vertically polarized light. easy rule to remember is to imagine that light polarization is a needle : if it's horizontal, it bounces, otherwise it sticks. in that diagram they are taking about light scattering which involves multiple inter-reflections, so that's probably why it's different?

[@covert0overt_810]

"Figuring out a nations Oil stockpile...." GOT THAT RIGHT

[@tybofborg]

The US Army wants to: 📍 *know your location*

[@ethelredhardrede1838]

The USA Federal stockpile is held in underground reservoirs. It won't work for that.

[@snigwithasword1284]

We use so much of that black-goo-which-will-kill-us-all that it's extremely impractical to stockpile it, hence why only the richest governments do so.. You sound like you're hinting at some sort of conspiracy though, I can't figure out what.

[@ethelredhardrede1838]

@@snigwithasword1284 ", I can't figure out what." He has SECRET KNOWLEDGE known only to those that make it up. "that it's extremely impractical to stockpile it, hence why only the richest governments do so.." The US uses salt domes for storage. Does not cost much. Wikipedia - Strategic Petroleum Reserve (United States) "The reserve is stored at four sites on the Gulf of Mexico, each located near a major center of petrochemical refining and processing. Each site contains a number of artificial caverns created in salt domes below the surface. Individual caverns within a site can be up to 1,000 m (3,300 ft) below the surface, average dimensions are 60 m (200 ft) wide and 600 m (2,000 ft) deep, and capacity ranges from 6 to 37 million barrels (950,000 to 5,880,000 m3). Almost $4 billion was spent on the facilities. The decision to store in caverns was made in order to reduce costs; the Department of Energy claims it is roughly 10 times cheaper to store oil below surface with the added advantages of no leaks and a constant natural churn of the oil due to a temperature gradient in the caverns. The caverns were created by drilling down and then dissolving the salt with water. "

[@EduardoEscarez]

Some oil tanks have a movable ceiling, and the high of that ceiling is related to the volume stores in that moment, so SAR can be used to estimate how high is related to the walls of the tank. And a few months ago it was useful for some traders, because with that imagery (plus optical photos with machine learning) they knew in advance that between the latest Saudi/Russian oil war plus the pandemic, global oil storage was getting used to its limit so they could adapt their strategies for what at the end happened, a collapse of oil prices because of overproduction.

[@ElDJReturn]

This was such a well done video and I learned so much! Possibly one of your best presentations in a while, Thank you and keep flying safe!

[@Xelat84]

Outro should be said "Spy safe"! :D

[@alpac5005]

Yup. TWSAR. Through wall synthetic aperture radar. To be fair he called himself manly, so he’s misleading from the start.

[@ZenWithKen]

I used to work for a company that used radar data to calculate conifer tree harvesting and replacement by the forest industry. All of it analyzed on leading edge 386 computers, lol. Thanks for sharing!

[@Dayanto]

Another really interesting technology is hyperspectral imaging, which can be used see what things are made of by looking at a wide range of different wavelengths in parallel.

[@toastrecon]

Awesome! I was an intern at the Alaska Satellite Facility one summer during engineering school. Such a great place, and the people were awesome. That was back in the day when a lot of the SAR data processing had to be done on the ground. We used to go out in the field and point arrays of large aluminum corner reflectors in fields and on the tundra to use in calibrating the SAR data. Even back then, they were using SAR to show how volcanos expand before they erupt, and how land is disturbed after an earthquake.

[@goetzliedtke]

I worked on the image processing software of an airborne SAR back in the early '90s. Airborne has more problems accounting for the motion of the aircraft than does satellite-borne. Our aircraft overflew and pictured Washington, DC (that's where the money was at that time) and I remember that long, metallic (i.e. high dielectric) objects actually created glare in our images if not processed correctly. The rail line south of the mall and the tracks into Union Station were glaringly obvious. The other big reflector was the roof of the Smithsonian Air and Space museum. Not everything has to be a great reflector. We could see people having lunch in the central courtyard of the Pentagon because humans reflect differently than concrete benches, grass, and trees.

[@Gerard1971]

Saving the best for last? I was very much intrigued by the title, and this turned out to be the most educational video of the year!

[@russoft]

man, the FFT never ceases to amaze.

[@nordithen]

1:37 Driving past Willow Run, I've always wondered what those corner reflectors were for since I was little! Fascinating to finally learn!

[@CaptainQ2607]

Satellites use this "one weird trick" to see more; rocket scientists don't want you to know! I fixed your title.

[@fxarts9755]

bright starlinks in your area

[@Bearhawk58]

Wow! He knows what he is talking about and he knows what is interesting. Great combination. This is all new to me. Subscribed!

[@TheLoganatorz]

Thought this was Buzzfeed space after reading the title XD

[@PTNLemay]

Gotta get that SEO

[@michielstikkel]

You won’t believe these 9 things satellites do to see you beter!

[@wangruochuan]

Buzzfeed: satellite only use purple color image for a day

[@robbybobbyhobbies]

Number three will blow your mind.

[@IanCaine4728]

I love this channel. Started out watching Kerbal landings, and now learning about SAR. Cool!

[@gelisob]

You should not be wearing a tin-foil hat if you want to avoid being seen by SAR

[@bozo5632]

Lead helmets ftw.

[@AlexandreMS71]

a conic hat should do the trick

[@smokiethebear61]

@@bozo5632 Lead reflect the RADAR also. You have to adsorb it. Stealth planes are covered in RADAR adsorbing coating. Bottom line is to not reflect the radio energy back to the source.

[@imouse3246]

Ordering my stealth hat first thing in the morning.

[@bozo5632]

@@smokiethebear61 That's just what THEY want you to think, sheep-man.

[@reneejones6330]

I am impressed. I did not catch any significant technical errors in your presentation. Congratulations.

[@DrDeuteron]

did you catch the (pulsed) Doppler error at 7:40?

[@jamescrombie2320]

Back in the late 80's I worked on a part for the Canada's RadarSat. A very weirdly shaped dish for the satellite that looked a lot like Mount Fuji. 120lbs of aluminum to start, 5lbs at finish :-)

[@jamescrombie2320]

We did the final finish turning on a CNC lathe but there was not enough memory so we had to feed the program from the cad dept computer

[@heartobefelt]

@@jamescrombie2320 my first CNC machine had 56 k memory ......now they are terrabytes lol . thankyou to all the clever people who put their lives work into improving all that we take for granted these days.

[@jamescrombie2320]

@@heartobefelt We had a real mix of stuff at the first cnc shop I worked at. Some brand new Mori Seiki lathes, Bridgeport series one cnc mills, and old Hardinge cnc lathe and a Moog mill that ran one tape (it used an reader that used air and a lot of relays, no electronics at all)

[@heartobefelt]

@@jamescrombie2320 Yes , i saw a mill that used stamped cards the same way , thankfully humans quickly left those behind for the cavemen :)

[@melvinmathews]

Hats off to the brilliant engineers who solve problems before technology has arrived to make it look easy.

[@daltonhayhurst8501]

“ I want to understand.” Scott, “say no more.”

[@Erdal_Gumus]

What a brilliant explanation Scott. Almost everyone performing GIS - Geographical Information Systems and RS - Remote Sensing analysis uses SAR data but hardly anyone knows how it really works. The USGS SRTM SAR offers 30m spatial resolution where recently launched ALOS PALSAR has a 12.5m resolution imagery available for free globaly. This dataset is the back bone of GIS and RS, used for DEM - Digital Elevation Model and Hillsdale creation or for Geomorphometric surface analysis such as slope, aspect, openness, watershed, contour etc.

[@4seeableTV]

I'd say this guy knows his stuff.

[@reneejones6330]

It's actually pretty easy for experts to tell the difference between SAR and optical, since optical imaging measures angles, but SAR measures one angle and a distance. SAR also loves metal! Anyway, nice topic and nice description. Thanks.

[@herlescraft]

SAR, basically the MRI of satellites

[@Baigle1]

Just wait till they start using entangled photon tunneling to make a 3D image of the inside of a shielded enclosure. It won't require high intensity saturating pulses to get through that bunker anymore, and can be done with millions of times less emitted power. I'm honestly just waiting for the Japanese to come up with a way to make entangled neutrinos, then we can accurately image the inside of the earth (or anything else large) within just a few years (depending on our ability to store and read back directly or indirectly entangled neutrino states). P.S. Not a scientist.

[@herlescraft]

@@Baigle1 ah yes the good old 15m detector (pixel) can't wait :P I mean i'm not that informed on neutrinos, but being italian comes with the mental image of a neutrinos detector build some years ago (end of neutrino knoledge and attempt to combine neutrinos with medical radiation detection knoledge to fill in the gap)

[@faustin289]

@@Baigle1 Just tell the scientists to give us sensors similar to those of the Enterprise in the ST.

[@Baigle1]

@@herlescraft There are some theoretical particle physics papers that talk about a theoretical quark matter particle that can effectively interact and thus shield from or detect neutrinos way better than xenon or other high-Z scintillation materials. It may be down to specific mediated weak force interactions of normal matter to increase the neutrino cross section, but there is likely a way to improve neutrino detection out there somewhere. If you ask, I don't think I'd be able to find these papers again, but one source was talking about analyzing the mass and spin rate of near earth objects to see if any are candidates for having a dark matter core. Some were dense enough and fast enough that they were candidates for study, but they could also just have been balls of cooled slag versus a loose pile of space rubble. Edit: Neutrinos interact via the Weak force. Not Strong. Corrected.

[@Baigle1]

@@faustin289 Never really got into star trek. The trekkies and their following likely delayed a lot of important scientific progress. It was nearly impossible to get the information out of anyone that transparent aluminum is actually just aluminum oxide glass. Its not special, its sapphire. They beat around the bush with a bunch of trash about spinels and crystals and nonsense, and that's only one example that screws the rest of STEM fields over. Edit: bush. heh.

[@bobgreene2892]

Thanks for the links, especially to the Alaska Satellite Facility. Very nice presentation on SAR, and your effort to break the presentation into general topics. We viewers could sense the enthusiasm of an engineering mind in your detailed explanation. We subscribed long ago.

[@Allegheny500]

I almost skipped this because of "This Weird Trick" in the title that's normally used to sell snake oil remedy's.

[@RossWehner]

Fantastic video! Thank you Scott. I am consistently impressed with both the breadth and depth of your knowledge paired with a gift of communication. Keep the great content coming!

[@r1e5p3l7i2c]

TB-03 just chilling on the desk.

[@jesseandben]

TD-3 ;)

[@PolygonSwan]

@@jesseandben "Miniaturized and optimized"

[@Gerard1971]

Definitely not a TB-03, looks like a Behringer TD-3-SR to me.

[@ShanoGabbafreakz]

Definitely looks like the Beringer clone.

[@tangenziale_audio]

Oh wow, I was wondering if it was Behringer or Roland. He obviously has good taste in tunes! 😎

[@dimension2788]

Nice job Scotty! Radar imagery is mind blowingly beautiful. Love ESA Envisat, just astounding. I had to watch this one again. There was a huge effort put into this tech. Thanks to all who worked on this complicated and beautiful art form.

[@FyWhy]

This is probably a good follow up to Destins Smarter Every Day Submarines radar system.

[@Cambone13]

Sonar, not radar

[@sixstringedthing]

*Sonar system ;) It was a great video, I'm loving the submarine "deep dives".

[@FyWhy]

@@Cambone13 oh yeah, but they do kinda work in similar way and by the looks share similar characteristics

[@poporbit2432]

Thank you Scott. I had not asked myself how SAR works or what limitations it has. You did a great job addressing those questions.

[@stekra3159]

Make no mistake the Surface of Venus is not Yellow. It is just what they cover in Synthetic Aperture Radar Dather. The Surface of Venus like a lot of Vulcanic Rocks is Black.

[@foty8679]

That one spacecraft who landed on venus for a few minutes or so...the stones look quite yellowish

[@triroo107]

Great video Scott, I spent 26 years refining the joys of radar to look through everybody’s skirts, my mathematics would be so proud. Tax payers money well spent, but nice to see everyone can benefit from the research and development

[@MrSharps02]

i see that 303. so when can we expect the acid house album debut?

[@cirrusflyerh2843]

I use Fourier transforms in ultrasonic surveys. This is one of the best “ average person “ explanations on SAR. I will reference this video when explaining the practical applications of math and physics to STEM students.

[@fredreickweaver809]

Hot take: interferometry cool

[@Kenionatus]

Now, now, now. Cool down and take a hot minute to make up your mind.

[@hansulrichjohner2694]

Some defence applications use image processing of SAR pictures to track moving objects. A helicopter for instance can be hard to be seen on a SAR picture but with multiple pictures you can visualize the rotors, even when it is hovering.

[@tenns]

2:53 cries a little on the inside

[@davida1hiwaaynet]

Thank you! Fascinating stuff.

[@NewLifeFromTheWayofTruth]

Is it just me or should we all love this shit.

[@kmlammto]

Just one thing I noticed: radar uses electrons while lidar uses photons. Keep up the great work on these!

[@scottfranco1962]

Now I know how dogs feel when they listen to people talk...

[@connecticutaggie]

When I was in College at Texas A&M in the late 70's I worked at the TAMU Remote Sensing Center (later renamed the Microwave and Microelectronics Research Center). Two of the projects I worked on involved radar scatterometry. One was a polar ice project where we tried to classify the thickness of the ice based on its age which correlates with roughness - it turns out the submarines need to know the ice thickness to know where it is safe for them to surface. The other project I worked on was to try to use scatterometry look for spherical sub surface air voids. We buried ping-pong balls do our testing but there are also other submerged air voids in the ocean that some governments might also be interested in locating. A third project was to try to map soil moisture from space to help farmers.

[@ezmoney6341]

Man I don’t even know what you said. But I like it.

[@zorgatron8998]

So much of this flew right over my head, but Scott you are an excellent presenter, I enjoyed this video and did learn something.

[@thomashenden71]

Those satelites actually fly over our heads, too! Smile! 😄

[@Krzysztof_z_Bagien]

You're playing Phoenix Point, aren't you Scott? :)

[@poorboysadventures4636]

This is definitely one of the most interesting videos I've seen in a while.

[@heyarno]

When I was young, SAR meant search and rescue.

[@tomc.5704]

Still does, but now SAR can use SAR

[@faustin289]

@@tomc.5704 You, Sir, must fun to be around at parties!

[@gamelauri9307]

Thank you for the great video Scott Manley! Very educational.