Comment by phainopepla2
15 hours ago
> Satellites can definitely do things, but they're not magical and people can track where they're looking and just... sail in a different direction
I know nothing about this really, so forgive my ignorance.
Assuming a carrier is found and tracked by a satellite in the ocean, how could it possibly escape the satellite's detection before being targeted by a drone or some other type of munition? If the ship starts sailing in a different direction, the people (or AI) tracking via satellite would notice and adjust, right?
I believe satellites are usually in an orbit. They can’t follow an carrier for example. The satellites may be in a constellation that can track the carrier. That is why anti-satellites weapons have been developed. E.g., a jet fighter flies straight up and then fires a long range missile.
https://www.esa.int/Enabling_Support/Space_Transportation/Ty...
https://en.wikipedia.org/wiki/Anti-satellite_weapon
Do you think a carrier can very far in the couple of hours it takes for a satellite to orbit around the Earth?
A carrier can likely get far enough to generate a miss. Missiles and drones have very limited sensors so in order to hit anything another platform has to cue them with a fairly precise target location. In other words, an adversary like China would need to have enough satellites, submarines, and/or patrol aircraft to maintain a continuous target track long enough to make a decision, launch the weapons, and have them fly out to the target. Current thinking is that China could probably do this inside the first island chain but would struggle to put the pieces together further out in the open Pacific Ocean.
If the carrier is aware of the overflight (and I assume the USN isn't run by complete idiots), it can adjust course after the overflight. And at 30 knots, can be 100s of miles away from its initial location when the satellite returns.
Now satellite constellations make it harder, since their numbers limit this strategy. But currently, none of the know systems utilize SAR like the LEO satellites, so they wouldn't function well in bad weather. They'd have to rely on optics which can be severely degraded.
A typical LEO optical satellite has maybe a 60km swath at high resolution. And it isn't just a couple of hours - an orbit doesn't go over the same spot every two hours. You only may get 1-2 passes a day with a given type of constellation.
China would be using their Yaogan-41 (geostationary) to try to track, which might work, in good weather, during daytime, IF the carrier group was south of Japan (it's equatorial). Carriers deliberately transit through weather, strike groups disperse broadly and use decoy behavior in wartime, and a geostationary optical satellite won't know which blip is the carrier and which is a support ship 50km away.
Every night, you lose the carrier group and have to find it again in the morning, if you can. Usually you can't, even with China's layered approach using optical, SAR, ELINT, and OTH radar.
My understanding is to track something like a carrier the satellite has to be in low earth orbit. Those circle the earth about every two hours. So it is not so much the carrier outruns the satellite; it is the satellite outruns the carrier.
https://eos.com/blog/types-of-satellites/
I don't believe parent is right, but satelites don't stay in one place unless they're on the equator, because otherwise they have to be moving. This means that you need many satelites to maintain coverage of a single spot.
I don't know how many military satelites China has, but I would have assumed it would be sufficient to cover the pacific sufficiently to find an aircraft carrier. (the obvious caveat here being clouds, which are fairly common over the ocean)
The JWST has a 6.5 meter mirror. The largest (known) spy satellites have a mirror of ~3m diameter. At GEO (geostationary orbit) that would provide an imaging resolution of about 7 meters. An aircraft carrier is about 337x76 meters. So from geostationary altitudes, a satellite similar to a KH-11 would see an American aircraft carrier as a blob of about 48 "pixels". This is probably enough signal to track all aircraft carriers around the globe in real time. It would have a field of view roughly the size of Houston (50x50 miles) and would have enough electricity from solar panels to power reaction wheels to stay pointed at carrier groups indefinitely. (~15-year lifespan would be limited by xenon supply for ion thrusters that keeps the satellite in GEO orbit)
The Chinese Yaogan-41 satellite is in geostationary orbit and might have a mirror in the 4m range.
https://www.csis.org/analysis/no-place-hide-look-chinas-geos...
> It would have a field of view roughly the size of Houston (50x50 miles)
Wait, what?
Like, this is a whole bunch of extremely unreliable numbers being stacked on top of each other to reach an unsupported conclusion, but how is a 50 square mile field of view supposed to find something in the middle of the pacific?
2 replies →
> but satelites don't stay in one place
What?
> unless they're on the equator
What?
> because otherwise they have to be moving
What?
It was admittedly a bit sloppy. The more accurate version (IANAKSPP, I am not a kerbal space program player) would be that the only way to maintain a satelite in one position (without expending an infeasible amount of energy) is to position it above the equator and sync its speed with the Earth's rotation, allowing it to stay in a single position above the Earth. Satelites always have to be moving fast enough such that the centripetal force is sufficient to counteract the Earth's gravitational pull, otherwise they would fall back onto the planet.
Some quick Googling implies China has satellites capable of tracking shipping via radar from geostationary orbit. I'm not really convinced that aircraft carriers can hide these days?
Those satellites KNOW where the freighters are going, and check in every day on progress. They aren't looking for something that's intentionally sailing in an unpredictable direction (with no radio emissions in wartime).