4 ms·

How much data can you get from 150-300km away?

by bitL 7y ago

Robotbeat 7y ago
Depending on wavelength, if you've got a ~meter aperture for taking pictures and you're 200km away, you should be able to see ~10cm details. But one got as close as 20km (in which case, 1cm details...): https://twitter.com/planet4589/status/1223420130576818176 https://twitter.com/planet4589/status/1223420130576818176
- monadic2 7y ago
  Surely at that resolution atmospheric noise would dominate, even at 20km (which is crazy close for a satellite, right? There’s non negligible atmospheric drag at that height).
  - 0xTJ 7y ago
    Assuming that there's even 1% as much atmosphere up there, 20km is like 200m, making some very rough assumptions that I'm not sure are substantiated. If you've got a big camera, you can make out a huge amount of detail. At 20km, with the advanced technology that you'd assume is on this thing, they'd be able to see a lot.
    - aaron695 7y ago
      > Assuming that there's even 1% as much atmosphere up there I think it's way less than .00000000001% ~0%
  - wcoenen 7y ago
    > atmospheric noise would dominate, even at 20km 20 km distance between the satellites, not 20 km altitude! Those satellites actually have an elliptical orbit with an altitude between 276 km and 1010 km.
    - Robotbeat 7y ago
      Huh, why are you downvoted? This is absolutely correct. There's effectively no atmosphere up there for optical purposes.
ceejayoz 7y ago
https://en.wikipedia.org/wiki/KH-11_Kennen https://en.wikipedia.org/wiki/KH-11_Kennen > KH-11s are believed to resemble the Hubble Space Telescope in size and shape, as the satellites were shipped in similar containers. Their length is believed to be 19.5 meters, with a diameter of up to 3 meters. More than is publicly known, at the very least. With no atmosphere, a small telescope is gonna give you a pretty good look at that distance.
- twic 7y ago
  They resemble space telescopes enough that the NRO gave NASA a couple of leftovers: https://en.wikipedia.org/wiki/2012_National_Reconnaissance_Office_space_telescope_donation_to_NASA https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...
  - DuskStar 7y ago
    Not just those - IIRC Hubble's mirror diameter was changed to 2.4m at least partly so that they could use NRO tooling.
zelon88 7y ago
Considering USA 245 is gathering data on targets that are 42,000km away I'd be willing to venture that they can gather a lot at 300km. Perhaps they can use this for signals intelligence as well.
- DuskStar 7y ago
  USA 245 is gathering data on targets from about 300km to 1000km away - it'd be pretty hard to see individual structures from geosync. Here's the orbit info: https://www.heavens-above.com/orbit.aspx?satid=39232 https://www.heavens-above.com/orbit.aspx?satid=39232
- joshvm 7y ago
  USA 245 is an Earth observation satellite, its apogee is only about 1000 km. 42,000km would be for a geostationary satellite. But yes, 300km is pretty close in space. Since you have no issue with atmospheric distortion, the optics become a lot more simple. This is quite a small satellite - "mini fridge" someone said, which does limit what you can put in it. 300km is a fair distance away and you'd need an enormous focal length to resolve small features on the other spacecraft. It's possible they just want to test how well they can track another satellite. For a Hubble class telescope (~50k mm focal length) you'd get around 20cm resolution for a 4MP sensor. A more general way, since we don't know what sensor is onboard, would be to calculate the diffraction limit for the largest mirror you could put on the satellite (sibling comment suggested 1 m, which is about 1 arcsecond at 540nm). That works out to 20cm at 300km, or about 1cm at 20km. Of course you still need the focal length and sensor to make this useful. I guess you could compare Trump's images of the Iranian launch site which were taken at a similar distance, but with a much larger satellite.
deleted 7y ago
[deleted]
throwaway5752 7y ago
Maybe they can visually infer where it's oriented and what it's monitoring. Perhaps they can use infrared to detect heat when it's maneuvering or motors are active. Maybe unshielded electronics are sending off trace EMR.
- 14 7y ago
  In my mind I thought exactly that monitor orientation and see what it is pointing at. On a second wild thought I said perhaps once that close they launch a tiny space drone that flies up to the other satellite to push buttons or whatever function it would have.
  - throwaway5752 7y ago
    It could also just be a weapons platform. A lot of the space based scenarios end up denying capabilities for both sides (fine for the attacker if there is asymmetry in capabilities, but not so much here). But if it can attach to the target and push it out of orbit and into the atmosphere without a debris cloud?
wyldfire 7y ago
SIGINT? Does this thing intentionally or unintentionally radiate anything that could be intercepted?

How much data can you get from 150-300km away?

by bitL 7y ago

How much data can you get from 150-300km away?

Depending on wavelength, if you've got a ~meter aperture for taking pictures and you're 200km away, you should be able to see ~10cm details. But one got as close as 20km (in which case, 1cm details...): https://twitter.com/planet4589/status/1223420130576818176 https://twitter.com/planet4589/status/1223420130576818176

monadic2 7y ago
Surely at that resolution atmospheric noise would dominate, even at 20km (which is crazy close for a satellite, right? There’s non negligible atmospheric drag at that height).
- 0xTJ 7y ago
  Assuming that there's even 1% as much atmosphere up there, 20km is like 200m, making some very rough assumptions that I'm not sure are substantiated. If you've got a big camera, you can make out a huge amount of detail. At 20km, with the advanced technology that you'd assume is on this thing, they'd be able to see a lot.
  - aaron695 7y ago
    > Assuming that there's even 1% as much atmosphere up there I think it's way less than .00000000001% ~0%
- wcoenen 7y ago
  > atmospheric noise would dominate, even at 20km 20 km distance between the satellites, not 20 km altitude! Those satellites actually have an elliptical orbit with an altitude between 276 km and 1010 km.
  - Robotbeat 7y ago
    Huh, why are you downvoted? This is absolutely correct. There's effectively no atmosphere up there for optical purposes.

ceejayoz 7y ago

https://en.wikipedia.org/wiki/KH-11_Kennen https://en.wikipedia.org/wiki/KH-11_Kennen > KH-11s are believed to resemble the Hubble Space Telescope in size and shape, as the satellites were shipped in similar containers. Their length is believed to be 19.5 meters, with a diameter of up to 3 meters. More than is publicly known, at the very least. With no atmosphere, a small telescope is gonna give you a pretty good look at that distance.

twic 7y ago
They resemble space telescopes enough that the NRO gave NASA a couple of leftovers: https://en.wikipedia.org/wiki/2012_National_Reconnaissance_Office_space_telescope_donation_to_NASA https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...
- DuskStar 7y ago
  Not just those - IIRC Hubble's mirror diameter was changed to 2.4m at least partly so that they could use NRO tooling.

zelon88 7y ago

Considering USA 245 is gathering data on targets that are 42,000km away I'd be willing to venture that they can gather a lot at 300km. Perhaps they can use this for signals intelligence as well.

DuskStar 7y ago
USA 245 is gathering data on targets from about 300km to 1000km away - it'd be pretty hard to see individual structures from geosync. Here's the orbit info: https://www.heavens-above.com/orbit.aspx?satid=39232 https://www.heavens-above.com/orbit.aspx?satid=39232
joshvm 7y ago
USA 245 is an Earth observation satellite, its apogee is only about 1000 km. 42,000km would be for a geostationary satellite. But yes, 300km is pretty close in space. Since you have no issue with atmospheric distortion, the optics become a lot more simple. This is quite a small satellite - "mini fridge" someone said, which does limit what you can put in it. 300km is a fair distance away and you'd need an enormous focal length to resolve small features on the other spacecraft. It's possible they just want to test how well they can track another satellite. For a Hubble class telescope (~50k mm focal length) you'd get around 20cm resolution for a 4MP sensor. A more general way, since we don't know what sensor is onboard, would be to calculate the diffraction limit for the largest mirror you could put on the satellite (sibling comment suggested 1 m, which is about 1 arcsecond at 540nm). That works out to 20cm at 300km, or about 1cm at 20km. Of course you still need the focal length and sensor to make this useful. I guess you could compare Trump's images of the Iranian launch site which were taken at a similar distance, but with a much larger satellite.

deleted 7y ago

[deleted]

throwaway5752 7y ago

Maybe they can visually infer where it's oriented and what it's monitoring. Perhaps they can use infrared to detect heat when it's maneuvering or motors are active. Maybe unshielded electronics are sending off trace EMR.

14 7y ago
In my mind I thought exactly that monitor orientation and see what it is pointing at. On a second wild thought I said perhaps once that close they launch a tiny space drone that flies up to the other satellite to push buttons or whatever function it would have.
- throwaway5752 7y ago
  It could also just be a weapons platform. A lot of the space based scenarios end up denying capabilities for both sides (fine for the attacker if there is asymmetry in capabilities, but not so much here). But if it can attach to the target and push it out of orbit and into the atmosphere without a debris cloud?

wyldfire 7y ago

SIGINT? Does this thing intentionally or unintentionally radiate anything that could be intercepted?