8 ms·

Unless something dramatic changes in the field of optics, lenses and how to deal with atmospheric blur at those distances, resolving features smaller than 15-20

Unless something dramatic changes in the field of optics, lenses and how to deal with atmospheric blur at those distances, resolving features smaller than 15-20cm from low earth orbit remains a low probability. Take a look at some youtube videos of a Nikon P1000 at maximum zoom looking through ordinary atmosphere at some distance away for an example. https://www.youtube.com/watch?v=LhQlwKX3LQA https://www.youtube.com/watch?v=LhQlwKX3LQA

IceWreck 6y ago
> Take a look at some youtube videos of a Nikon P1000 at maximum zoom looking through ordinary atmosphere at some distance away for an example. https://www.youtube.com/watch?v=LhQlwKX3LQA https://www.youtube.com/watch?v=LhQlwKX3LQA This is unbelievable.
- giantrobot 6y ago
  While that's an impressive zoom, the camera is moving much slower relative to the targets (~0km/s) than if it were in even a low orbit. It's also imaging people at the extent of its zoom at only a few km away. In orbit it would be hundreds of km from its targets. CubeSats and other small satellites can capture useful imagery but they're not spy satellites. There's optical limits to their capabilities because of their size.
ceejayoz 6y ago
I think the more likely use is supplementing existing facial recognition. Recognize a face on a security camera, then be able to track their movements out and about after that. Before, too, if you store the satellite footage. https://www.buzzfeednews.com/article/christianstork/spy-planes-over-american-cities https://www.buzzfeednews.com/article/christianstork/spy-plan..., but at scale.
- walrus01 6y ago
  Pattern of life analysis correlated with ground based intelligence, where your car goes, where it usually parks in the day and at night, etc. You would need a lot of LEO satellites to approach anything like persistent coverage, however, current sun synchronous things have very long revisit times for any particular site.
  - JulianMorrison 6y ago
    Also clouds kind of get in the way of anything optical - unless it's a drone lower than the cloud level.
londons_explore 6y ago
Atmospheric distortions are worse when looking horizontally though the atmosphere (think marriage on the horizon). It's also only the bottom few miles of atmosphere that is really thick. Looking vertically from 400km up, there actually isn't too much distortion. The limiting factor is making high enough quality lenses and getting enough light onto your sensor without too much diffraction.
- pintxo 6y ago
  But hard to get a face shot from a 90 deg angle, as people tend to focus their attention on the ground rather the sky.
  - saberdancer 6y ago
    You don't need to look from 90 deg angle. Satellites often times scan ahead/behind so they don't always scan at 90 deg angle. Look at this image that is probably from a spy satellite. It's almost at 45 degree angle. https://www.thedrive.com/the-war-zone/29634/trump-tweets-intelligence-image-after-irans-rocket-explosion-and-offers-them-best-wishes https://www.thedrive.com/the-war-zone/29634/trump-tweets-int...
    - pintxo 6y ago
      The previous post argued that the influence of the air is less severe looking straight down. If we now go back to looking at an angle, we are back to square one, the problem of distortion due to the amount of air between the observer and the observed.
  - ta988 6y ago
    If you need that you can send a drone though.
- andreareina 6y ago
  If I'm running the numbers right, then using the Hubble's maximum theoretic angular resolution of 2.8e-7 rad[1], something 400km up would still not resolve features smaller than 11.2cm. That's the absolute best, diffraction-limited case. Don't know how close we are to that on real-world optics. [1] https://opentextbc.ca/universityphysicsv3openstax/chapter/circular-apertures-and-resolution/ https://opentextbc.ca/universityphysicsv3openstax/chapter/ci...
helsinkiandrew 6y ago
Presumably, orientation is also an issue - satellites will tend see tops of heads more than faces full on.
- jl6 6y ago
  The obvious solution: pivot face-recognition algorithms into top-of-head-recognition algorithms.
  - yuliyp 6y ago
    People can comb their hair quite differently

IceWreck 6y ago

> Take a look at some youtube videos of a Nikon P1000 at maximum zoom looking through ordinary atmosphere at some distance away for an example. https://www.youtube.com/watch?v=LhQlwKX3LQA https://www.youtube.com/watch?v=LhQlwKX3LQA This is unbelievable.

giantrobot 6y ago
While that's an impressive zoom, the camera is moving much slower relative to the targets (~0km/s) than if it were in even a low orbit. It's also imaging people at the extent of its zoom at only a few km away. In orbit it would be hundreds of km from its targets. CubeSats and other small satellites can capture useful imagery but they're not spy satellites. There's optical limits to their capabilities because of their size.

ceejayoz 6y ago

I think the more likely use is supplementing existing facial recognition. Recognize a face on a security camera, then be able to track their movements out and about after that. Before, too, if you store the satellite footage. https://www.buzzfeednews.com/article/christianstork/spy-planes-over-american-cities https://www.buzzfeednews.com/article/christianstork/spy-plan..., but at scale.

walrus01 6y ago
Pattern of life analysis correlated with ground based intelligence, where your car goes, where it usually parks in the day and at night, etc. You would need a lot of LEO satellites to approach anything like persistent coverage, however, current sun synchronous things have very long revisit times for any particular site.
- JulianMorrison 6y ago
  Also clouds kind of get in the way of anything optical - unless it's a drone lower than the cloud level.

londons_explore 6y ago

Atmospheric distortions are worse when looking horizontally though the atmosphere (think marriage on the horizon). It's also only the bottom few miles of atmosphere that is really thick. Looking vertically from 400km up, there actually isn't too much distortion. The limiting factor is making high enough quality lenses and getting enough light onto your sensor without too much diffraction.

pintxo 6y ago
But hard to get a face shot from a 90 deg angle, as people tend to focus their attention on the ground rather the sky.
- saberdancer 6y ago
  You don't need to look from 90 deg angle. Satellites often times scan ahead/behind so they don't always scan at 90 deg angle. Look at this image that is probably from a spy satellite. It's almost at 45 degree angle. https://www.thedrive.com/the-war-zone/29634/trump-tweets-intelligence-image-after-irans-rocket-explosion-and-offers-them-best-wishes https://www.thedrive.com/the-war-zone/29634/trump-tweets-int...
  - pintxo 6y ago
    The previous post argued that the influence of the air is less severe looking straight down. If we now go back to looking at an angle, we are back to square one, the problem of distortion due to the amount of air between the observer and the observed.
- ta988 6y ago
  If you need that you can send a drone though.
andreareina 6y ago
If I'm running the numbers right, then using the Hubble's maximum theoretic angular resolution of 2.8e-7 rad[1], something 400km up would still not resolve features smaller than 11.2cm. That's the absolute best, diffraction-limited case. Don't know how close we are to that on real-world optics. [1] https://opentextbc.ca/universityphysicsv3openstax/chapter/circular-apertures-and-resolution/ https://opentextbc.ca/universityphysicsv3openstax/chapter/ci...

helsinkiandrew 6y ago

Presumably, orientation is also an issue - satellites will tend see tops of heads more than faces full on.

jl6 6y ago
The obvious solution: pivot face-recognition algorithms into top-of-head-recognition algorithms.
- yuliyp 6y ago
  People can comb their hair quite differently