4 ms·

Those suffer from the same problem. There's a lot of ocean, and if you don't know where to look then you won't find what you're looking for.

by post-it 7mo ago

joe_mamba 7mo ago
>if you don't know where to look I mean fuck, I can pretty easily find the strait of hormuz on the map, pretty sure intelligence agencies can too and just look there for the carrier. If I can't find the carrier there, then I can plot the course between France and hormuz and do a brute force search over that course taking into account such a ship's relative velocity, since it's not like the carrier is gonna zig-zag through south america and the north pole on its way there to avoid detection. Is what I'm saying something sci-fi?
- gherkinnn 7mo ago
  It is dangerous to believe a problem goes only as deep as one's understanding of it.
  - joe_mamba 7mo ago
    I am always open to corrections from specialists in the field or just any average joes with a different opinion. That's why I keep coming here.
    - burnished 7mo ago
      It is absolutely one of the better benefits of this forum
- blitzar 7mo ago
  > I can pretty easily find the strait of hormuz on the map, pretty sure intelligence agencies can too Seems to have come as a shock to the US government.
Sanzig 7mo ago
Eh, not really. Synthetic Aperture Radar satellites used for marine ship detection have extremely wide sensor swath widths, and ships show up as very bright radar targets against the ocean. Detecting a large ship, even in a very large search area, is almost trivial. Identifying a ship is harder, but not insurmountable. In particular, large ships like aircraft carriers tend to have very identifiable radar signatures if your resolution is high enough.
- throwaway894345 7mo ago
  How do these work? I would think radar would have a very difficult time seeing a ship against the backdrop of the ocean from so high above. Is the satellite bouncing radar waves off the side of the ship as the satellite is near the horizon? Even if you can detect a ship, I'm having a hard time imagining a sufficiently high radar resolution for such a wide sensor swath width at such an extreme range. Is the idea that you locate it with the wide sensor swath and then get a detailed radar signature from a more precise sensor?
  - Sanzig 7mo ago
    SAR operates in side-looking slant geometry. Consider shooting a ray at the ocean at an oblique angle from a satellite: it bounces off and scatters away from you. Hardly any of the energy scatters back towards you. Now, put a ship there. The ray bounces off the surface of the ocean and scatters up into the side of the ship, and from geometry, it's going to bounce off the ship and come straight back towards its original source. You get tons of energy coming back at you. A ship on the ocean is basically a dihedral corner reflector, which is a very good target for a radar. > I'm having a hard time imagining a sufficiently high radar resolution for such a wide sensor swath width at such an extreme range. Is the idea that you locate it with the wide sensor swath and then get a detailed radar signature from a more precise sensor? That's one approach, there are so-called "tip and cue" concepts that do exactly this: a lead satellite will operate in a wide swath mode to detect targets, and then feed them back to a chase satellite which is operating in a high resolution spotlight mode to collect detailed radar images of the target for classification and identification. However, aircraft carriers are big, so I don't think you'd even need to do the followup spotlight mode for identification. As an example, RADARSAT-2 does 35 meter resolution at a 450 km swath for its ship detection mode. That's plenty to be able to detect and identify an aircraft carrier, and that's a 20 year old civilian mission with public documentation, not a cutting edge military surveillance system. There are concepts for multi-aperture systems that can hit resolutions of less than ten meters at 500 km swath width using digital beamforming, like Germany's HRWS concept. tl;dr: Radar works very well for this.

Those suffer from the same problem. There's a lot of ocean, and if you don't know where to look then you won't find what you're looking for.

by post-it 7mo ago

Those suffer from the same problem. There's a lot of ocean, and if you don't know where to look then you won't find what you're looking for.

joe_mamba 7mo ago

>if you don't know where to look I mean fuck, I can pretty easily find the strait of hormuz on the map, pretty sure intelligence agencies can too and just look there for the carrier. If I can't find the carrier there, then I can plot the course between France and hormuz and do a brute force search over that course taking into account such a ship's relative velocity, since it's not like the carrier is gonna zig-zag through south america and the north pole on its way there to avoid detection. Is what I'm saying something sci-fi?

gherkinnn 7mo ago
It is dangerous to believe a problem goes only as deep as one's understanding of it.
- joe_mamba 7mo ago
  I am always open to corrections from specialists in the field or just any average joes with a different opinion. That's why I keep coming here.
  - burnished 7mo ago
    It is absolutely one of the better benefits of this forum
blitzar 7mo ago
> I can pretty easily find the strait of hormuz on the map, pretty sure intelligence agencies can too Seems to have come as a shock to the US government.

Sanzig 7mo ago

Eh, not really. Synthetic Aperture Radar satellites used for marine ship detection have extremely wide sensor swath widths, and ships show up as very bright radar targets against the ocean. Detecting a large ship, even in a very large search area, is almost trivial. Identifying a ship is harder, but not insurmountable. In particular, large ships like aircraft carriers tend to have very identifiable radar signatures if your resolution is high enough.

throwaway894345 7mo ago
How do these work? I would think radar would have a very difficult time seeing a ship against the backdrop of the ocean from so high above. Is the satellite bouncing radar waves off the side of the ship as the satellite is near the horizon? Even if you can detect a ship, I'm having a hard time imagining a sufficiently high radar resolution for such a wide sensor swath width at such an extreme range. Is the idea that you locate it with the wide sensor swath and then get a detailed radar signature from a more precise sensor?
- Sanzig 7mo ago
  SAR operates in side-looking slant geometry. Consider shooting a ray at the ocean at an oblique angle from a satellite: it bounces off and scatters away from you. Hardly any of the energy scatters back towards you. Now, put a ship there. The ray bounces off the surface of the ocean and scatters up into the side of the ship, and from geometry, it's going to bounce off the ship and come straight back towards its original source. You get tons of energy coming back at you. A ship on the ocean is basically a dihedral corner reflector, which is a very good target for a radar. > I'm having a hard time imagining a sufficiently high radar resolution for such a wide sensor swath width at such an extreme range. Is the idea that you locate it with the wide sensor swath and then get a detailed radar signature from a more precise sensor? That's one approach, there are so-called "tip and cue" concepts that do exactly this: a lead satellite will operate in a wide swath mode to detect targets, and then feed them back to a chase satellite which is operating in a high resolution spotlight mode to collect detailed radar images of the target for classification and identification. However, aircraft carriers are big, so I don't think you'd even need to do the followup spotlight mode for identification. As an example, RADARSAT-2 does 35 meter resolution at a 450 km swath for its ship detection mode. That's plenty to be able to detect and identify an aircraft carrier, and that's a 20 year old civilian mission with public documentation, not a cutting edge military surveillance system. There are concepts for multi-aperture systems that can hit resolutions of less than ten meters at 500 km swath width using digital beamforming, like Germany's HRWS concept. tl;dr: Radar works very well for this.