5 ms·

It went thru the journalist filter a million times until unrecognizable. The first answer is ICBMs are, now a days, mostly an IR optical thing. The flightpath

by VLM 6y ago

It went thru the journalist filter a million times until unrecognizable. The first answer is ICBMs are, now a days, mostly an IR optical thing. The flightpath of most Russia to US ICBMs would never have passed over the observatory, obviously, but it was a major radar technology research site in the early years.

javajosh 6y ago
>The first answer is ICBMs are, now a days, mostly an IR optical thing. Source? This seems unlikely since ground-based visual tracking would be obscured by e.g. clouds. Is ICBM tracking all space-based and visual? (I can see why IR is useful to detect the initial boost, but it would also seem rather useless to track a small, passive object in freefall).
- rtkwe 6y ago
  They're mostly talking about the initial launch detection which is indeed IR based because it's going to be nearly impossible to hide the signature of a rocket launch of any useful size. After that flight tracking is a lot of different sources like radar.
- pdehaan 6y ago
  DSP and more recently SBIRS are satellite-based systems, both use IR. If you track the missile to the end of it's burn you'll have a pretty good idea of where it's going after that -- ballistic trajectories are fairly predictable. https://en.wikipedia.org/wiki/Defense_Support_Program https://en.wikipedia.org/wiki/Defense_Support_Program https://www.lockheedmartin.com/content/dam/lockheed-martin/space/photo/sbirs/SBIRS_Fact_Sheet_(Final).pdf https://www.lockheedmartin.com/content/dam/lockheed-martin/s...
- ethbr0 6y ago
  > small, passive object in freefall That's probably anomalously hot as it plows back through the atmosphere. I think radar stealth coatings are sufficiently advanced that they swung the balance back in favor of IR for tracking purposes. Historically: it was hard / unknown how to make a flying object that resisted reflecting radar Current: it's hard / unknown how to make a flying object that's resistant to radiating heat
  - javajosh 6y ago
    >as it plows back through the atmosphere. I would assume that if you're tracking it on re-entry that's a little too late.
    - ethbr0 6y ago
      Depends on what you want to do. Launch - early warning, max time, low certainty of trajectory Boost - trajectory and impact refinement Re-entry - terminal maneuvering, impact prediction, terminal interceptor cueing I'd imagine you'd have ground-based sensors for terminal interception refinement, but having a wide angle view to cover highly maneuverable glide vehicles would be useful too.
  - ardy42 6y ago
    > Current: it's hard / unknown how to make a flying object that's resistant to radiating heat There are techniques to reduce infrared signature, though: https://en.wikipedia.org/wiki/Northrop_Grumman_B-2_Spirit#Infrared https://en.wikipedia.org/wiki/Northrop_Grumman_B-2_Spirit#In...
- giantrobot 6y ago
  The IR systems are space-based and look for rocket plumes in the ascent phase. Once a rocket gets above the troposphere there's no clouds to obscure it. It's an intensely bright IR source that easily stands out from the -60°C surrounding atmosphere. Just a second of observing the plume's trajectory will tell the difference between and orbital or ballistic one. Ballistic missiles will also be launched over the poles to travel the shortest distance to their targets. So IR plumes over the North Pole either means Santa's upped his present delivery game or there's an incoming ballistic missile attack.
est31 6y ago
Hmm ok I watched the video someone else linked here, apparently the telescope was used to check for facilities in Russia by checking the reflection of radio waves on the moon. Pretty cool stuff.

by VLM 6y ago

javajosh 6y ago

>The first answer is ICBMs are, now a days, mostly an IR optical thing. Source? This seems unlikely since ground-based visual tracking would be obscured by e.g. clouds. Is ICBM tracking all space-based and visual? (I can see why IR is useful to detect the initial boost, but it would also seem rather useless to track a small, passive object in freefall).

rtkwe 6y ago
They're mostly talking about the initial launch detection which is indeed IR based because it's going to be nearly impossible to hide the signature of a rocket launch of any useful size. After that flight tracking is a lot of different sources like radar.
pdehaan 6y ago
DSP and more recently SBIRS are satellite-based systems, both use IR. If you track the missile to the end of it's burn you'll have a pretty good idea of where it's going after that -- ballistic trajectories are fairly predictable. https://en.wikipedia.org/wiki/Defense_Support_Program https://en.wikipedia.org/wiki/Defense_Support_Program https://www.lockheedmartin.com/content/dam/lockheed-martin/space/photo/sbirs/SBIRS_Fact_Sheet_(Final).pdf https://www.lockheedmartin.com/content/dam/lockheed-martin/s...
ethbr0 6y ago
> small, passive object in freefall That's probably anomalously hot as it plows back through the atmosphere. I think radar stealth coatings are sufficiently advanced that they swung the balance back in favor of IR for tracking purposes. Historically: it was hard / unknown how to make a flying object that resisted reflecting radar Current: it's hard / unknown how to make a flying object that's resistant to radiating heat
- javajosh 6y ago
  >as it plows back through the atmosphere. I would assume that if you're tracking it on re-entry that's a little too late.
  - ethbr0 6y ago
    Depends on what you want to do. Launch - early warning, max time, low certainty of trajectory Boost - trajectory and impact refinement Re-entry - terminal maneuvering, impact prediction, terminal interceptor cueing I'd imagine you'd have ground-based sensors for terminal interception refinement, but having a wide angle view to cover highly maneuverable glide vehicles would be useful too.
- ardy42 6y ago
  > Current: it's hard / unknown how to make a flying object that's resistant to radiating heat There are techniques to reduce infrared signature, though: https://en.wikipedia.org/wiki/Northrop_Grumman_B-2_Spirit#Infrared https://en.wikipedia.org/wiki/Northrop_Grumman_B-2_Spirit#In...
giantrobot 6y ago
The IR systems are space-based and look for rocket plumes in the ascent phase. Once a rocket gets above the troposphere there's no clouds to obscure it. It's an intensely bright IR source that easily stands out from the -60°C surrounding atmosphere. Just a second of observing the plume's trajectory will tell the difference between and orbital or ballistic one. Ballistic missiles will also be launched over the poles to travel the shortest distance to their targets. So IR plumes over the North Pole either means Santa's upped his present delivery game or there's an incoming ballistic missile attack.

est31 6y ago

Hmm ok I watched the video someone else linked here, apparently the telescope was used to check for facilities in Russia by checking the reflection of radio waves on the moon. Pretty cool stuff.