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Ask HN: Which is the most powerful satellite camera directed towards earth?

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21–30 of 45 posts

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#21
I worked a earth imaging system (EIS) back in the 1990s. I didn't have security clearance (almost got it and realized it had no benefit to me but a bunch of crap I'd have to do, or not do/say, so I passed).

I'm pretty sure that the satellites at the time could read 3 inch newspaper print under the right conditions which happened rarely.

I've got a tack sharp 600mm Canon lens and it's sort of useless for a lot of stuff. If there is any haze, heat, dust, whatever, in the air, all that expense glass sees is that instead of what you want to see.

That note aside, it was a fun project. I was the I/O guy, I did this work:

http://www.nfsv4bat.org/Documents/ConnectAThon/1996/bds.pdf

and I got Seagate to redesign part of their 9gb (I think, might have been 2 or 4g) barracudas. I've got a benchmark in lmbench that shows how the disk performs as a function of seek distance, looks like this:

http://mcvoy.com/lm/bitmover/disks/seek.gif

The lower edge of the band is what you get if you seek and get to the track just as the sector you want is to about to pass under the head; the upper edge of the band is what you get if the sector had just passed under the head; the height of the band is a rotational delay; and those outliers? In this case I think they were either bad blocks or I don't know.

But when you ran this benchmark on two drives, mounted in a rack right next to each other, you got tons and tons of outliers which blew any chance we had of meeting the performance metrics. I bitched at Seagate and they hemmed and hawed and finally admitted there might be a problem with their internal mounts.

The problem was that their mounts were so useless that the vibration caused by one head moving vibrated the drive next to it enough that the other drive's head didn't settle properly and you blew a rev waiting for it to get where it needed to be.

Seagate redid the mounts.

Fun project.

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#22
post #16

KH-11 had a theoretical resolution in the inches. "Not quite good enough to identify faces." Those were first launched in the seventies, so I assume they are doing much better now. I think it's safe to assume 5cm or better resolution on a minutely refresh.

makes you wonder why the imagery floating around with reporting on war zones and incidents are of such bullshit quality. even the supposedly recorded-with-mobile footage is always so bad. as if the person is stumbling around not knowing their phone's cammera is rolling.

I assume militaries don't provide news outlets with their highest resolution spy imagery as to not disclose the extent of their capabilities.

I'd also suspect anyone recording a news-worthy "incident" on their mobile phone in a war zone has other priorities than maintaining a stable image.

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#23
Some links for you:

https://space.stackexchange.com/questions/3868/is-photograph...

http://boards.straightdope.com/sdmb/showthread.php?t=627617

https://everything2.com/title/Spy+satellites+can%2527t+read+...

A perfect 2.4-meter mirror observing in the visual (500 nm) would have a diffraction limited resolution of around 0.05 arcsec, which from an orbital altitude of 250 km would correspond to a ground sample distance of 0.05 m. Operational resolution should be worse due to effects of the atmospheric turbulence.

https://en.wikipedia.org/wiki/KH-11_Kennen

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#24
post #16

KH-11 had a theoretical resolution in the inches. "Not quite good enough to identify faces." Those were first launched in the seventies, so I assume they are doing much better now. I think it's safe to assume 5cm or better resolution on a minutely refresh.

makes you wonder why the imagery floating around with reporting on war zones and incidents are of such bullshit quality. even the supposedly recorded-with-mobile footage is always so bad. as if the person is stumbling around not knowing their phone's cammera is rolling.

> makes you wonder why the imagery floating around with reporting on war zones and incidents are of such bullshit quality.

Hard to say what you're talking about without examples, but stuff like military targeting cameras are frequently 1970s tech, and looking via infrared to boot. There's plenty of high-res footage from war zones available.

> even the supposedly recorded-with-mobile footage is always so bad. as if the person is stumbling around not knowing their phone's cammera is rolling.

Being shot at has that sort of effect. That said, there's some pretty remarkable 4k drone footage coming out of ISIS these days, along with lots of GoPro footage.

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#25
post #19

I'm assuming this is all pretty well classified, but I would be shocked if the US government hasn't had the ability to do that for a long time. Consider that back in 2012, the National Reconnaissance Office donated two surplus telescopes to NASA that were substantially better than the Hubble telescope. If those are the sort of telescopes that the government has no need of anymore, imagine what the state-of-the-art is…

Hubble was launched in 1990, is it surprising that 22 years later, NRO telescopes are substantially better ?

The satellites would've been near contemporaries of Hubble, not 22 years junior. NRO didn't need them anymore.

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#26

I'm assuming this is all pretty well classified, but I would be shocked if the US government hasn't had the ability to do that for a long time. Consider that back in 2012, the National Reconnaissance Office donated two surplus telescopes to NASA that were substantially better than the Hubble telescope. If those are the sort of telescopes that the government has no need of anymore, imagine what the state-of-the-art is…

Not sure why you're being downvoted for this. https://en.wikipedia.org/wiki/2012_National_Reconnaissance_O...

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#27
High-rez satellite cameras don’t film videos.

Satellite cameras don’t have a 2D sensor you can find in a traditional camera. Instead, they feature a long narrow sensor. As the satellite flies over the earth, the sensor records a single row below the satellite. That row is oriented perpendicular to the satellite’s velocity. As the satellite flies, it scans a long strip of land underneath.

It works similar to a flatbed scanner. Can you film a video with the scanner? I don’t think so.

https://en.wikipedia.org/wiki/Push_broom_scanner

About Bin Laden, the live satellite feed was not filmed from space. The feed was recorded by an on-body camera of an American soldier, transferred to a telecom satellite, then back to Earth, at Obama’s place.

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#28

I worked a earth imaging system (EIS) back in the 1990s. I didn't have security clearance (almost got it and realized it had no benefit to me but a bunch of crap I'd have to do, or not do/say, so I passed). I'm pretty sure that the satellites at the time could read 3 inch newspaper print under the right conditions which happened rarely. I've got a tack sharp 600mm Canon lens and it's sort of useless for a lot of stuf…

I remeber flipping through some spy tech book a while ago and one photo, allegedly quite famous, stuck with me - it was of a wrist watch on a hand of someone lying on a beach and while it was on a blurry side you could still tell what the time was. From the context it was taken in the 70s and from what I gathered it was a satellite snap.

Now thinking about it, it might've been a high-altitude plane (U2) photo instead, but I'm not sure.

Has anyone else seen this photo?

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#29

I expect drones are now more relevant than satellites for localised imaging. For example http://www.cropcopter.co/uav-imagery-vs-satellite/

Yes. There was a piece on 60 Minutes a few years back where they had a big (~20 ft. wingspan maybe), loud drone circling overhead a few thousand feet up. It was inaudible and invisible. What's the point in solving a hard problem like hi-res imagery from space when you can just fly one of these over the target practically at will? (With a Hellfire missile attached, no less.) Range and airspace issues notwithstanding, the drone future is a scary place.

Re: Ask HN: Which is the most powerful satellite camera directed towards earth?

#30
post #28

I worked a earth imaging system (EIS) back in the 1990s. I didn't have security clearance (almost got it and realized it had no benefit to me but a bunch of crap I'd have to do, or not do/say, so I passed). I'm pretty sure that the satellites at the time could read 3 inch newspaper print under the right conditions which happened rarely. I've got a tack sharp 600mm Canon lens and it's sort of useless for a lot of stuf…

I remeber flipping through some spy tech book a while ago and one photo, allegedly quite famous, stuck with me - it was of a wrist watch on a hand of someone lying on a beach and while it was on a blurry side you could still tell what the time was. From the context it was taken in the 70s and from what I gathered it was a satellite snap. Now thinking about it, it might've been a high-altitude plane (U2) photo instead…

That really rather sounds like from within the atmosphere - heat shimmer alone should make this sort of resolution very difficult indeed from space.
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