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Comment by nickff | Hacker News Reader

There is no need for a citation, because it is obviously wrong. If you calculate the angular resolution required to read 16 point font from low Earth orbit, you will find that you need a satellite with a primary mirror much larger than has ever been launched.

In addition to the (currently) unavailable high-resolution imagery which would be required, atmospheric distortion would render any text illedgible, and it seems very unlikely the individual characters would be resolvable. Many of the techniques used to reduce/compensate for atmospheric distortion in telescopic imaging are not possible in Earth observation.

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That said, it's only little off. They may not be able to read the text on your phone, but they can see that you have a phone in your hand.

Also, things will get worse since satellites are not really the future. Solar-powered high-altitude planes that can keep themselves aloft for years are potentially much cheaper to launch and operate, and much more flexible, so I'm guessing this is where things will be heading in the next few years. They may be easier to detect and shoot down, true, but they seem perfect for domestic surveillance ops.

OT but this reminds me of the Mythbusters episode on the U2 plane. Well worth watching if you haven't, and it also nicely displays how amazingly powerful these are for surveillance.

Found a youtube video: https://www.youtube.com/watch?v=iTXnJF5MnHQ

Nice :).

Check that one as well, DARPA's 1.8 gigapixel camera for continous monitoring of, well, small cities from altitudes up to 20 000 feet. And something tells me that's not the real state of the art.

https://www.youtube.com/watch?v=QGxNyaXfJsA

What's the word when something is unbelievably cool and unbelievably scary at the same time?

"Military technology"? :).

>"That said, it's only little off."

It's off by orders of magnitude. KH-11 had/has a 2.4m primary mirror. Wikipedia (correctly) says the following:

>"Assuming a 2.4-meter mirror, the theoretical ground resolution with no atmospheric degradation and 50% MTF would be roughly 15 cm (6 inches). Operational resolution would be worse due to effects of the atmosphere"

16-point typeface is 5.8mm tall, so you probably need at least 0.58mm resolution to read it, and 2mm resolution to separate the characters.

2mm/150mm = 1/75 = 0.013

You need 75x better resolution than KH-11 to resolve characters.

0.58mm/150mm = 0.0038

You need (1/0.0038) 259x better resolution than KH-11 to read 16 point text.

You need ~2-2.5 orders of magnitude better resolution than the largest known earth-imaging satellite can provide, and that is assuming the phone is perpendicular to the satellite with no atmospheric distortion.

Well do consider that Google Maps/Earth don't zoom too much because of security and privacy reasons. If you consider everyday technology that is accessible like https://www.urthecast.com/ and how clear it is then it wouldn't be impossible to get clearer imagery from spy satellites. Maybe not actual text but a blurry view of that 6 inch touch screen.

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