The DoD (or the NRO) had this tech in the 80s? Wasn’t this SAR originally in the form of ground penetrating radar invention for finding nukes in ground siloes?
Also used to track submerged submarines by detecting ocean surface disturbances caused by the underwater wake of the submarine. Same benefits: works at night and through cloud cover.
Almost any depth. A big steel tube is going to displace water. Once you have some baseline measurements (of known underwater landforms), then small imperceptible variations would stick out.
Not possible. The uncertainty of bathymetry in areas only mapped using gravity is larger than the dimensions of a sub.
Even in very well mapped areas, think of the effort in the Indian ocean to find MH370, this would require the assumption that the sub is moving, which is not always the case, e.g. if the sub halts propulsion and drifts with a current.
Well yes, it's the surface disturbance of the underwater wake that they are detecting. So the sub has to be moving under its own power.
But there is no need for high resolution and the wake of the sub stands out starkly even with a large field of view. So I'm not sure it can evade detection by halting propulsion and drifting. The point at which it halted would be known and it would be detected as soon as it restarted, unless it was carried by an unknown current far enough to be out of view of the satellite.
The infamed laser on Tu 142 was said to get to only get to 50m, but that was a "direct imager" which relied on direct reflection, and seventies-eighties era technology.
Newer ones are directly sensing density, and temperature changes in the seawater by sensing Raman shift, and are supposedly much better. No known data in public of course.
Tracking submerged boats from space is the holy grail of ASW, and as best as I can tell it doesn't work outside littoral zones (where sometimes you can optically detect the sub) and contrived tests. It has been tried with SAR, blue/green lasers, IR, all kinds of stuff, and luckily it doesn't work in the real world.
When it does, it will be massively destabilizing as it places the "invulnerable" second strike capability that guarantees deterrence against peer states at risk.
> When it does, it will be massively destabilizing as it places the "invulnerable" second strike capability that guarantees deterrence against peer states at risk.
It never been such to begin width, at least by the late cold war, some portion of missile subs were reliably tailed by adversaries without any high tech trickery.
North Korea, Russia, and China each already have more submarines than USA, and would have no problem to put 10 subs to tail each Ohio.
Tailing some portion of missile subs won't do - a single missile sub is an existential threat so deterrence isn't destabilized until the adversary can credibly eliminate all of them within ~10 minutes.
It takes a nuclear sub to trail a nuclear sub. NK and China have exclusively, and primarily (respectively) diesel subs. These have to surface and run their engines to charge batteries. They cannot make 20+ knots submerged for long, and they cannot track deeply submerged submarines from the surface. Surfacing and running diesels would make their presence known. They cannot range far from port, and certainly cannot track missile boats under the arctic ice.
Russia has a sufficiently large nuclear fleet, but it is outdated and probably outclassed by US technology. There is probably greater disparity between the powers than existed during the cold war, at which time deterrence was credible.
This is cool tech and there are new players entering this field with even better capability. The Clinton era laws of optical resolution restrictions seems silly now with this tech in the commercial marketplace.
And just because they have that capability, doesn't mean they can "legally" use it. The posted article says that it can do a better resolution than that 50cm, but didn't specify how much better.
ICEYE's website says high res (25cm) imaging is commercially available. Even has some sample 25cm res images available for download at the bottom of this page (I have not downloaded so can't vouch for it) https://www.iceye.com/satellite-data/blog/new-benchmark-in-i...
That's right. The article says "...other SAR satellites on the market can only get down to around five meters" which isn't true if the story I linked is accurate.
I wonder how intense those microwaves are in a room being scanned. Presumably it's also possible to jam these scans, but it seems that doing so would invoke the wrath of the fcc.
In the 9ghz range, does that mean a sub-1mm wire mesh could mitigate this? Asking for a hypothetical house renovator friend.
Thompson's adage of when the going gets weird, the weird turn pro suggests that the tinfoil hat crowd could be able to corner the emerging domestic Faraday cage market.
Big in home decoration fashion next year, upside down pyramids hanging from the ceiling. (edit: my bad, a corner reflector would have 3 corners at the base, not 4 as a pyramid would)
The entire premise of the synthetic aperture is that the transmission and reception are distant from each other, but a corner reflector will reflect back to the location of the transmission - i.e. it will entirely miss the receiver.
Yes, completely sure. Corner reflectors are used to calibrate SARs by providing fixed bright ground points. I've also seen SAR imagery where unintentional corner reflectors (in this case, a building) completely washed out the image at that location.
It's true that the SAR antenna has moved a little bit by the time the transmitted signal is received. However, the signal is moving significantly faster than the satellite - with a 600km orbit, velocity is ~8km/s - so the roundtrip time is maybe 0.04s, meaning the satellite has moved 320m. That's about 0.2 degrees from the point of view of the reflector.
The synthetic aperture is not just the distance covered in the round trip of a single chirp, but the distance covered during the imaging process. A SAR typically produces chirps constantly (in the tens to hundreds of Hz) and digitises the responses. All of the energy of all those responses can then be combined to form the image.
If the corner reflector is in a fixed location, every chirp will have a spike in the response corresponding to that location.
or a whole bunch of small corner cube reflectors (such as you would see attached to a sailboat mast for intentional greater radar visibility) in a grid like array.
I think this is a balance. Being the only house in the area that can't be seen into might get you more attention someone being able to see you in your underwear at a 50cm x 50cm resolution.
Unless you live underground, then you'll just look like the rest of the ground.
EDIT: On a more general case, I wonder how expensive and feasible it would be to cover the roof/ceiling and walls with an array of 9ghz emitting "pixels" with the wire mesh behind that. Then show the satellites whatever image you want. Make it look like funny stuff is going on inside for their own amusement.
Wouldn't be able to account for the different angles the satellite might take pictures from, though. Unless you track it.
The satellite is looking at the of flight and intensity of the reflected signal, not 'color'. It's basically monochrome. You can make your ceiling either very massive or very conductive to reduce the signal reflected, or install a corner reflector in the attic to overwhelm the sensor with its own high-intensity signals (like taking a photo in a mirror with the flash on).
Mike: "Hey Bob, what's up with this one house in this neighborhood? We aren't able to get a look in side."
Bob: "Hmmm, anyone preventing us from getting a look means they are subversive. Get a no-knock warrant to investigate that location. Only illicit activities can be taking place there."
In this case, being "invisible" actually makes you more suspicious which only brings their attention upon you that much more intense.
Combine this technology with the launch cadence and pricing of SpaceX and the implications are astounding.
First of all, security. If your opponent has that kind of capability, you cannot meaningfully deploy tanks or any other vehicles anymore. Even infantry will suffer massively once the resolution goes up a notch. On a much smaller level, one could easily detect brake-in attempts on unguarded property.
Second, industrial espionage. Want to know how much the competition buys/sells? Plug this data into some form of image recognition.
Third, government control. From traffic over demonstrations to "unsocial" behavior, governments at the municipal level could easily inspect "their" people and control their behavior much more efficiently.
Worth noting that we don't know what most spy satellites are, but the US has revealed that it has had a constellation of 5 satellites like this since about 2000. So this is bringing the technology into the civilian sphere with an API 'only'.
But yeah, I agree with you about the potential. Also, presumably a constellation imaging the same location from multiple angles could synthesize a super high resolution 3D image?
I thought tanks and infantry were already basically done against equiv-tech opponents. They are not sufficiently mobile to dodge the various smart weaponry we have available today.
Just look at the Syrian civil war or the Russian invasion of the Ukraine. In both cases, Russia deployed (various quantities of) conventional forces and overwhelmed their (more or less) equally equipped opponents with tanks, vehicles, and infantry by employing better organization, tactical and strategical mobility and, to some degree, air superiority. In both cases, live satellite images at the tactical level would have made such an offensive practically impossible.
Hrm. I don't know enough about the exact makeup of those offenses, but it seems to me that Russia is at least a tier above the other two countries you mentioned in terms of military capability. Especially, it seems like Russia has much more ability to project power via long range guided weapons, and that Russia would be able to establish air superiority over the other two countries if they did try to take the fight to the sky.
As those offesive technologies advanced, so too have the countermeasures.
Another part is that you have equal-weight matchups occurring at each level. Your expensive and highly capable platforms will be busy targeting the adversarial platforms that pose the most threat to them (usually expensive systems as well), leaving less time/resources to commit to the lower weight targets. For example, you're not going to get as much air support from either side if the planes are dealing with each other.
Of course that is highly generalized as the whole system works as an interdependent mesh.
Maybe? I feel like most of the countries at the top present tech levels could not really absorb the kinds of infantry and mechanized losses that would ensue if they tried to have an actual ground war. Guided rocket artillery, cruise missiles, airstrikes, etc. seem capable of killing infantry in numbers that would not be politically acceptable. This is to say nothing of the losses that could be inflicted with strategic weaponry (either nuclear or non-nuclear) in a total war. This is part of why I don't expect any future direct wars between world powers.
"Guided rocket artillery, cruise missiles, airstrikes, etc. seem capable of killing infantry in numbers that would not be politically acceptable."
Even infantry to infantry conflicts against a peer-like adversary would result in unacceptable losses for today's society.
"This is part of why I don't expect any future direct wars between world powers."
I somewhat agree with that. I think it could be possible in a scenario similar to that video game (Solid Snake?) where countries fight each other in highly mechanized/autonomous fashion - limited loss of life, but high economic costs until one collapses. But yeah, probably more likely to be a cyber war or cold war scenario. Technically we are in a loose proxy war with Russia based on what's going on in Syria.
> governments [...] could easily inspect "their" people
Governments can now spy on their people via old fashioned surveillance: wire-tapping, informants, social media analysis, etc. If a nation has the checks and balances to prevent that, then it's very likely they'll be able to prevent satellites peeking into your home. If not, it could potentially be another tool in their oppression toolkit, but not terribly efficient compared to the mountains of tools they already have, like traffic light CCTV cameras, highway tollbooths, tracking of credit card payments, tracking of internet-connected personal devices, etc, etc.
There may not be specific laws preventing this sort of surveillance because it is unknown. Sure, you could have it considered as a general 4th ammendment violation which would protect the general population. You'll still have it used against small numbers of high-value targets.
I think the main thing preventing widespread use is that once you start using these technologies on a larger scale, then people can identify it's capabilities (making it less effective, especially against the highest value targets) and also creating public backlash once a sufficient number of 'normal' people have been targeted (without getting 'disappeared').
Even if there were laws would they bother to comply? I’m still shocked by how little people understand what Snowden exposed about what the NSA is already doing - if you are concerned about these satellites you should be even more concerned about the other crap already going on that we KNOW the NSA has been lying about.
I'd bet someone could pretty easily build an alarm that goes off every time one of these things is looking at you. That radar blast has got to be massive. This definitely couldn't be a 24/7 thing from those satellites. I wonder how much radar time one of those things has before it needs to recharge/refuel.
Power usage isn't necessarily huge. I worked on a SAR satellite a few years ago with a total RF power of <1kW.
It's pulsed as well - you send an RF "chirp" at a sub-1kHz pulse frequency. Depending on imaging mode the average power draw is probably in the 500W-1kW range.
That had a much larger resolution (6m rather than 50cm), but the resolution is a function of frequency and antenna design as much as power.
The SAR concept essentially creates an image by sending out a known RF chirp and then, for each pixel of the image, correlating the response with the expected signal from that pixel. That correlation means that even if the received signal is below the noise floor you can create an image.
Efficiency of solar panels on satellites is about 40%. That means ~ 700W/m2 if correctly oriented. That's quite a lot of power, even if you stay 50% of the time in night while orbiting Earth. So no need for huge panels usually. (Updated : more like 40%, not 50%)
As an EE, I consider it important to understand that nothing at any level in your technology stack from silicon to SAAS to smartphones is black magic. This is just an application of the physics of high frequency
electromagnetic signals.
I haven't personally done work with SAR, but I imagine it's much the same as dealing with EMI/EMC in PCB development: extend Maxwell's equations from a simple case to the general principle, simulate, test, and tune. I'd have to go back to my textbook and review to figure out the exact mechanisms and the limiting factors for resolution and power, I think I have Johnson's "High Speed Digital Design: A Handbook of Black Magic" on a shelf around here somewhere...
Likely wood, concrete would probably attenuate a fair amount but still penetrate.
Modern glass-walled office buildings with metallic coating for UV and thermal insulation would probably reflect or attenuate the signal enough to be unusable. Walls with metal lattice in them (plaster, stucco) might also be difficult to penetrate.
The mystery head trauma suffered by U.S. diplomats comes to mind when discussing active-scanning satellite technology. The commerical product seems not so above-board based on the use cases discussed.
> Another innovation, he says, is the resolution at which Capella’s satellites can collect imagery. Each pixel in one of the satellite’s images represents a 50-centimeter-by-50-centimeter square, while other SAR satellites on the market can only get down to around five meters. When it comes to actually discerning what you’re looking at from space, that makes a huge difference.
If that's what is available to civilians, I'd like to see what 2020 spy satellites can do.
IIRC, the conclusion at the time was that that particular image was taken by an NRO KH-11 satellite - roughly equivalent to a Hubble Space Telescope pointed at earth and definitely not SAR.
Supposedly this was taken by a KH-11 Block 4 (USA-224) which means this is cutting edge as of 2005. We're currently on Block 5 as of 2018.
The biggest secrets within US Reconnaissance Satellites isn't really optical clarity anymore, it is their capabilities in other spectrums (and have supported at least infrared for 30+ years, but with signals intelligence well beyond that since).
> The satellite beams down a powerful 9.65 GHz radio signal toward its target, and then collects and interprets the signal as it bounces back up into orbit.
Years ago there were lots of articles about X-ray backscatter vans, owned by NYPD but probably also other jurisdictions. One of the concerns was you'd never know when they were scanning you and looking inside your car. But of course, though these active systems are invisible to human eyes, they do have to send out pretty strong signals. So I wonder if a kind of sousveillance is possible. Can we have devices that detect the signal being directed at the target, and alarm and publish that info? Both individuals could know if/when they are being imaged, and the public could see some patterns in who they look at. Anyone aware of how hard a detector would be to build?
9.65GHz would be outside the range of most common SDRs, but other than that it would be like detecting any other radio transmission. You would need a sample to know it's the satellite in question and not some other noise on that band, and it would be vulnerable to false positives unless the sample is unique.
All an SDR needs is a frontend LNA and a downconverting mixer (collectively called a LNB). Once the frequency is brought down, all standard SDRs can be used.
You could do this with spectrum analyzers intended for the commercial telecom industry, and a horn antenna with waveguide tuned to the right bands. It's not far off from the frequencies used in the standard FCC Part 101 licensed, 11 GHz FDD band plan for point to point high capacity microwave links.
One of the problems would be that detecting such a thing in an omnidirectional way would be problematic and difficult, the horn antenna described above would have the vast majority of its gain when aimed in one particular azimuth and elevation.
Is anybody else scared as absolute all fuck about this complete dystopia we're going full speed into with not even the slightest of brakes?
At what point are we going to be able to distinguish those who are being always watched from the paranoid schizophrenic?
LOVEINT tells us it's really just a matter of time until we hear of some worker who goes postal after tracking his love interest in everything building they go in.
I’ve often wondered why no commercial satellite provider provides any kind of RF platform. I believe you could tell which power plants and factories are active and at what level from the amount of RF emissions. It seems like you could get lots of valuable information without even decoding any of the signals. Does anyone know why this service has never been offered?
What you’re asking about is essentially why hasn’t anyone started a civilian SIGINT/MASINT company. The main reason is cost and governments. Most civilian devices are compliant to some country’s emission standard, and don’t have a lot of spurious emissions outside of their fundamental frequency, and only use the power necessary to complete their function. Detecting these things from space is crazy hard. When your field of view is wide, you have a ton of similar signals stepping on each other. When your field of view is narrow it takes a lot of time to look at everything. Overcoming these basic problems is why the major powers of the world have to spend billions of dollars to do it. And even if you managed to fund and develop a civilian capability, you have to get permission from a major world power to launch and operate. They don’t like competition- this is why civilian space imagery has limited resolution and why Capella has to limit their resolution. Civilian SIGINT would have to be limited to the point where it has no commercial use. If civilian SIGINT were able to measure activity at factories it could measure activity at military bases and track military movements.
While it would be cool to have the capability, it won’t happen soon. Not because there aren’t people smart enough to solve the technical problems, but because nobody has navigated the political issues. The people with the resources to do so are happy enough with the money they are receiving from the governments of the world.
Looking at the examples of 'ghostly buildings', it seems these are just combining different perspectives as the satellite moves. It isn't actually seeing inside the building, just 3D rendered to look transparent.
10Ghz has (optimistically) a building penetration loss of 25dB [1], with any reflections back also seeing 25dB loss. I don't think this is workable with current satellite power flux density regulations. At least not at 10Ghz.
Edit: the claims to seeing 'individual rooms' are not backed by any examples, but maybe natural corner reflectors could rarely give a return. Still wouldn't be able to see anything within the room.
> “There’s a bunch of gaps in how we’re currently observing Earth from space [...]”
It's weird to hear places that were expected to be private to be called 'gaps' like they should be visible but weren't until we had the technology to fix that.
> Capella launched a platform allowing governmental or private customers to request images of anything in the world
'or private customers' adds to the looming creepiness of our future.
SAR has been around since the 70s and works using the same principles as CT scans (projection slice theorem). Think about observing an image by rotating it and projecting it orthogonally to the rotated direction. Take a bunch of these measurements (basically a radon transform) and then you can invert the process using the back projection algorithm.
The resolution of the image is proportional to the bandwidth of the waveform and the distance traversed by the satellite during the collection process.
This article is a bit of an exaggeration and Capella is certainly not the first or only SAR service.
Note that these 50cm image resolutions are limited by law, not technology. The US military of course has superior technology, and its resolution is unlikely to be limited by statute.
The NRO Topaz satellites are the successful radar development of the two prong Future Imaging Architecture (the optical component failed, which was to be the successor to Keyhole [of which the Hubble Space Telescope is derived]) should be assumed to have capabilities far beyond those of this company.
Capella's competitor Iceye has already achieved 25cm. Physics limitations are even lower than that.
But you are right talking about computing power. SAR work in a very different way from optical imagery and data generation/processing is quite a huge difficulty.
With free flying satellite SAR, the resolution is dependent on how fast the satellite can fly before it gets the return signal, and this is predetermined by orbital velocity.
94 comments
[ 4.7 ms ] story [ 136 ms ] threadEven in very well mapped areas, think of the effort in the Indian ocean to find MH370, this would require the assumption that the sub is moving, which is not always the case, e.g. if the sub halts propulsion and drifts with a current.
But there is no need for high resolution and the wake of the sub stands out starkly even with a large field of view. So I'm not sure it can evade detection by halting propulsion and drifting. The point at which it halted would be known and it would be detected as soon as it restarted, unless it was carried by an unknown current far enough to be out of view of the satellite.
Newer ones are directly sensing density, and temperature changes in the seawater by sensing Raman shift, and are supposedly much better. No known data in public of course.
When it does, it will be massively destabilizing as it places the "invulnerable" second strike capability that guarantees deterrence against peer states at risk.
It never been such to begin width, at least by the late cold war, some portion of missile subs were reliably tailed by adversaries without any high tech trickery.
North Korea, Russia, and China each already have more submarines than USA, and would have no problem to put 10 subs to tail each Ohio.
It takes a nuclear sub to trail a nuclear sub. NK and China have exclusively, and primarily (respectively) diesel subs. These have to surface and run their engines to charge batteries. They cannot make 20+ knots submerged for long, and they cannot track deeply submerged submarines from the surface. Surfacing and running diesels would make their presence known. They cannot range far from port, and certainly cannot track missile boats under the arctic ice.
Russia has a sufficiently large nuclear fleet, but it is outdated and probably outclassed by US technology. There is probably greater disparity between the powers than existed during the cold war, at which time deterrence was credible.
[1] https://apnews.com/press-release/pr-prnewswire/d35f7cb315af0...
"Hello this is the EU, you satellite does not comply with GDPR".
Thompson's adage of when the going gets weird, the weird turn pro suggests that the tinfoil hat crowd could be able to corner the emerging domestic Faraday cage market.
It would also draw a lot of attention to you... So maybe not the best approach if you're trying to hide.
The entire premise of the synthetic aperture is that the transmission and reception are distant from each other, but a corner reflector will reflect back to the location of the transmission - i.e. it will entirely miss the receiver.
It's true that the SAR antenna has moved a little bit by the time the transmitted signal is received. However, the signal is moving significantly faster than the satellite - with a 600km orbit, velocity is ~8km/s - so the roundtrip time is maybe 0.04s, meaning the satellite has moved 320m. That's about 0.2 degrees from the point of view of the reflector.
The synthetic aperture is not just the distance covered in the round trip of a single chirp, but the distance covered during the imaging process. A SAR typically produces chirps constantly (in the tens to hundreds of Hz) and digitises the responses. All of the energy of all those responses can then be combined to form the image.
If the corner reflector is in a fixed location, every chirp will have a spike in the response corresponding to that location.
https://www.westmarine.com/WestAdvisor/Selecting-a-Radar-Ref...
Similarly there's monitoring of AIS by Iridium, but pirates and drug lords turn those off.
EDIT: On a more general case, I wonder how expensive and feasible it would be to cover the roof/ceiling and walls with an array of 9ghz emitting "pixels" with the wire mesh behind that. Then show the satellites whatever image you want. Make it look like funny stuff is going on inside for their own amusement.
Wouldn't be able to account for the different angles the satellite might take pictures from, though. Unless you track it.
Bob: "Hmmm, anyone preventing us from getting a look means they are subversive. Get a no-knock warrant to investigate that location. Only illicit activities can be taking place there."
In this case, being "invisible" actually makes you more suspicious which only brings their attention upon you that much more intense.
First of all, security. If your opponent has that kind of capability, you cannot meaningfully deploy tanks or any other vehicles anymore. Even infantry will suffer massively once the resolution goes up a notch. On a much smaller level, one could easily detect brake-in attempts on unguarded property.
Second, industrial espionage. Want to know how much the competition buys/sells? Plug this data into some form of image recognition.
Third, government control. From traffic over demonstrations to "unsocial" behavior, governments at the municipal level could easily inspect "their" people and control their behavior much more efficiently.
But yeah, I agree with you about the potential. Also, presumably a constellation imaging the same location from multiple angles could synthesize a super high resolution 3D image?
Another part is that you have equal-weight matchups occurring at each level. Your expensive and highly capable platforms will be busy targeting the adversarial platforms that pose the most threat to them (usually expensive systems as well), leaving less time/resources to commit to the lower weight targets. For example, you're not going to get as much air support from either side if the planes are dealing with each other.
Of course that is highly generalized as the whole system works as an interdependent mesh.
Even infantry to infantry conflicts against a peer-like adversary would result in unacceptable losses for today's society.
"This is part of why I don't expect any future direct wars between world powers."
I somewhat agree with that. I think it could be possible in a scenario similar to that video game (Solid Snake?) where countries fight each other in highly mechanized/autonomous fashion - limited loss of life, but high economic costs until one collapses. But yeah, probably more likely to be a cyber war or cold war scenario. Technically we are in a loose proxy war with Russia based on what's going on in Syria.
Governments can now spy on their people via old fashioned surveillance: wire-tapping, informants, social media analysis, etc. If a nation has the checks and balances to prevent that, then it's very likely they'll be able to prevent satellites peeking into your home. If not, it could potentially be another tool in their oppression toolkit, but not terribly efficient compared to the mountains of tools they already have, like traffic light CCTV cameras, highway tollbooths, tracking of credit card payments, tracking of internet-connected personal devices, etc, etc.
I think the main thing preventing widespread use is that once you start using these technologies on a larger scale, then people can identify it's capabilities (making it less effective, especially against the highest value targets) and also creating public backlash once a sufficient number of 'normal' people have been targeted (without getting 'disappeared').
https://www.theguardian.com/us-news/2019/aug/02/pentagon-bal...
It's pulsed as well - you send an RF "chirp" at a sub-1kHz pulse frequency. Depending on imaging mode the average power draw is probably in the 500W-1kW range.
That had a much larger resolution (6m rather than 50cm), but the resolution is a function of frequency and antenna design as much as power.
The SAR concept essentially creates an image by sending out a known RF chirp and then, for each pixel of the image, correlating the response with the expected signal from that pixel. That correlation means that even if the received signal is below the noise floor you can create an image.
Presumably solar panels recharge a battery when it can, but continuous operations seem out of the question without some pretty large panels.
Maybe I'm underestimating modern solar panels or something.
Even easier, Capella-1 is in a sun synchronous orbit, so it will always pass overhead at the same local time, at noon or midnight.
https://www.n2yo.com/satellite/?s=43791
As an EE, I consider it important to understand that nothing at any level in your technology stack from silicon to SAAS to smartphones is black magic. This is just an application of the physics of high frequency electromagnetic signals.
I haven't personally done work with SAR, but I imagine it's much the same as dealing with EMI/EMC in PCB development: extend Maxwell's equations from a simple case to the general principle, simulate, test, and tune. I'd have to go back to my textbook and review to figure out the exact mechanisms and the limiting factors for resolution and power, I think I have Johnson's "High Speed Digital Design: A Handbook of Black Magic" on a shelf around here somewhere...
Can anyone tell me if 9.65 GHz waves can penetrate concrete / wood homes?
If commercial satellites have reached this capability, military ones are definitely far ahead.
https://www.dhs.gov/sites/default/files/publications/Radar-T...
If that's what is available to civilians, I'd like to see what 2020 spy satellites can do.
https://www.thedrive.com/the-war-zone/29634/trump-tweets-int...
More like standard optical image(the resolution and details are amazing, if it's a satellite, which is doubtful given the angle).
The biggest secrets within US Reconnaissance Satellites isn't really optical clarity anymore, it is their capabilities in other spectrums (and have supported at least infrared for 30+ years, but with signals intelligence well beyond that since).
Years ago there were lots of articles about X-ray backscatter vans, owned by NYPD but probably also other jurisdictions. One of the concerns was you'd never know when they were scanning you and looking inside your car. But of course, though these active systems are invisible to human eyes, they do have to send out pretty strong signals. So I wonder if a kind of sousveillance is possible. Can we have devices that detect the signal being directed at the target, and alarm and publish that info? Both individuals could know if/when they are being imaged, and the public could see some patterns in who they look at. Anyone aware of how hard a detector would be to build?
One of the problems would be that detecting such a thing in an omnidirectional way would be problematic and difficult, the horn antenna described above would have the vast majority of its gain when aimed in one particular azimuth and elevation.
At what point are we going to be able to distinguish those who are being always watched from the paranoid schizophrenic?
LOVEINT tells us it's really just a matter of time until we hear of some worker who goes postal after tracking his love interest in everything building they go in.
While it would be cool to have the capability, it won’t happen soon. Not because there aren’t people smart enough to solve the technical problems, but because nobody has navigated the political issues. The people with the resources to do so are happy enough with the money they are receiving from the governments of the world.
Looking at the examples of 'ghostly buildings', it seems these are just combining different perspectives as the satellite moves. It isn't actually seeing inside the building, just 3D rendered to look transparent.
10Ghz has (optimistically) a building penetration loss of 25dB [1], with any reflections back also seeing 25dB loss. I don't think this is workable with current satellite power flux density regulations. At least not at 10Ghz.
[1] ITU-R P.2346-1 https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-P.2346-1-201...
Edit: the claims to seeing 'individual rooms' are not backed by any examples, but maybe natural corner reflectors could rarely give a return. Still wouldn't be able to see anything within the room.
It's weird to hear places that were expected to be private to be called 'gaps' like they should be visible but weren't until we had the technology to fix that.
> Capella launched a platform allowing governmental or private customers to request images of anything in the world
'or private customers' adds to the looming creepiness of our future.
The resolution of the image is proportional to the bandwidth of the waveform and the distance traversed by the satellite during the collection process.
This article is a bit of an exaggeration and Capella is certainly not the first or only SAR service.
The NRO Topaz satellites are the successful radar development of the two prong Future Imaging Architecture (the optical component failed, which was to be the successor to Keyhole [of which the Hubble Space Telescope is derived]) should be assumed to have capabilities far beyond those of this company.
https://en.wikipedia.org/wiki/Future_Imagery_Architecture
https://www.space.com/23871-air-force-spy-satellite-launch-n...
https://www.nytimes.com/2007/11/11/washington/11satellite.ht...
^ A very well put together long read from the Times on black world contracting chaos, exemplified by these satellites.
By physics, and computing power.
For any stable circular orbit, a satellite can only fly that fast, and the radio window would only pass so much of radio spectrum.
But you are right talking about computing power. SAR work in a very different way from optical imagery and data generation/processing is quite a huge difficulty.