Checking out this telescope site again:
http://www.geocities.com/telescope1999/14-5inch.html
It got me wondering. If this telescope could be placed in orbit and aimed back at the earth. Just what could one see at 1,500 power?
Do the spy satellites the US gov’t uses have optics this big or larger.
Jack
The Ofeq 5 spy satellite orbits at 480 km. The 15000x means something will appear 15000 times closer. Assuming resolution is not an issue (HAH!) you would see an object 480000 meters away like it was 32 meters (or 100 feet) away with the naked eye. From here. Now please someone smarter come in a correct this.
Sorry, 1500 power, not 15,000. See same as 1000 meters. people like me crash Mars Landers.
320 meters, 1000 feet. I’m gonna crash my damned CAR at this rate. More coffee.
Satellites can’t yet do Mammograms 
Actually, the telescopes on spy satellites are rated in resolving power, typically in terms of the smallest area that a digital camera would resolve as a pixel. The typical non-military satellite would go down to 1 square meter per pixel.
At the HowStuffWorks resolving power is covered nicely.
The US recently launched the KH-11, aka (since ‘spy’ is such an ugly word) the “anti-terror” satellite which has at least the resolving power of 10cm^2 or about the size of a softball. Beyond whatever the instrument’s power is, image processing “tricks” like oversampling would allow even higher resolution.
Actually, resolving power is an angle, not a distance. Resolving power expressed as a distance is a function of the angular resolving power of the system and of the distance to the target.
Saw something on Discovery talking about spy sattelites in the 60’s that could resolve down to a few feet. The interviewer asked him if they had improved on that any and the guy had a great line…
<smile> "What do you think? " </smile?
I think they can read the sunkist sticker on an orange from outer space.
The 10 meter Keck telescope employs modern adaptive optics and reportedly has a resolution of 0.04 arcseconds, through the atmosphere. That’s comparable to Hubble’s atmospherically unimpeded ~0.045 arcseconds. 0.04 arcseconds is equivalent to 58 mm at a distance of 300 km.
The spy satellites are roughly the same size as Hubble, so they’re not going to beat Keck by much in raw resolving power. Looking down through the atmosphere can only serve to degrade their performance from that ~2" ideal.
In other words, there’s no way a satelite can read a label or recognise a face
Resolution (probably in the two to six inch range, as far as useable resolution) is not the last word in how you get information out of satellite imagery. You can boost that, effectively on anything but mobile targets with multiple observations (oversampling) and simultaneous observations from multiple angles. It isn’t something that you can see in a single photo, but the information can be obtained by computer analysis of the target compared to known targets observed from both space and ground observers. If you keep your database updated well, you can tell which edition of the paper is lying on your porch, even if you can’t read the actual headline from a single picture.
Visual light is only one set of frequencies. It is mostly for getting pretty pictures to put in the paper to show how your enemies are “at it again.” Infrared is the stuff you want. It can tell you how often, and how long your enemies are using the motors on their tanks, planes, and heavy equipment. It can tell you the relative production load at factories, and offices. It can tell you how long ago artillery pieces were last fired.
You have to give up a little on the resolution, when you start to use infrared, though. But it doesn’t matter, if it can tell you the color and make of the car that was parked in front of a particular house two hours ago.
Now, no one has any reason to believe that NSA, or the NRO ever uses the gamma and X-ray instruments in orbit for spying. We wouldn’t do that with scientific instruments designed for peaceful and cooperative examination of the universe, would we?
Tris
You can’t do that anyway. X-rays and gamma rays do not penetrate the atmosphere. That’s why all astronomical X-ray and gamma ray observations are done from satellites and high altitude (> 100,000 ft) balloons.
It is my understanding the Hubble Space Telescope is a commercialized version of the KH-11.
The Hubble points up; KH-11s point down.
You can do truly amazing things in infra-red. For instance, by looking at the parking lot in a factory you can tell which cars arrived when by the residual heat their engines throw off. This can tell you how many shifts there are, and the nature of the workers. By analyzing vehicle types you can tell who is management and who is staff, and how shifts overlap.
And you can even ‘see’ vehicles that aren’t even there any more, because they heat up the concrete underneath them when they are parked. Pretty cool stuff.
People, the “spy” satellites have bigger reflectors/more of them than the hubble space telescope.
Face it, the Hubble Telescope was built by grant money for the purpose of observing the universe.
“Spy” satellites are made with government spending for the purpose of national security.
Which one of these takes a bigger priority?
I can guarantee you , that the latest and greatest spy satellites have resolutions greater than 10^2 cm, because think about how the military works. They don’t release classified information, until it is far out-dated. It’s probably very likely that they can see someone’s face…
Ficer, the spy satellites are at best INCHES bigger than Hubble, not multiples of Hubble, as is the Keck telescope. The size of the mirror will limit resolution until such time as someone figures out how to record and combine multiple images efficiently. That’s still very much a cutting edge problem, rather than a technology that’s been snuck onto an 80’s vintage satellite design and hidden from the astronomical community for all these years.
Alien2022, the number Corbomite gave was 10cm square, not 10^2 cm. 10cm square is about 4X4 inches.
I still maintain that the governement has satellites that far exceed the capabilities of the Hubble.
I just clicked on the link that you provided, and it brings new concepts to bear, for instance the Hubble is only one telescope in space. The government has numerous spy satellites, and every reason to solve the inferometry issues that you mentioned along with much better funding. Hence it would not surprise me that some government agency has solved the inferometry issues.
A much more formidable problem is the one of my spelling, ugh.
It might have been a Clancy novel made into a movie - whatever. I’ve seen Hollywood show a Hubble-class spy satellite point itself at whatever the baddie was and practically get his fingerprints.
One of the main hurdles in spy-telescopes are the optics themselves. It’s minor deformities in the surface of a large mirror (due to gravity and dust and such) that limit the clarity.
If a mirror (or lens) were made in space, its clarity would rival mirrors of far larger aperture.
The Pentagon certainly (or they ought to!) can make pictures with amazing clarity. As if Rumsfield were standing next to you clarity.
I’ve already said too much.
If we could take face photos from space, why would we keep deploying predators and photo planes at lower altitudes where they can get shot down? If you can see anything much smaller than an inch, without even coming down into the atmosphere, it just wouldn’t make sense to get down and dangerous, with even a unmanned craft. (Predators can’t carry a camera able to do much better than that from their best operational altitude!)
However, in the most general case, you are talking about taking multiple shots of the same twenty meter square, if you need to, under various lighting, timing, and angles, and you can extrapolate a lot of details that just a pixel doesn’t seem to have. So, if you have some essential detail you really need to photograph, that is less than ten centimeters in size, you send in a predator, other than that, most of what you want to see is bigger than a bread box. Actually, it’s mostly about the size of a car.
Another thing, having an inch by inch inventory of the entire world would be a fairly large database. Since the most effective of all photo interpretation instruments is the human being, that means multiplying the detail by a factor of a hundred is a limited return investment. Going from one meter pixels to one centimeter pixels means having 10,000 times more pixels to deal with. One centimeter pixels would make face recognition a pretty hit or miss thing. “Is that Osama bin Laden, or Abe Lincoln? No, wait, that’s Jerry Garcia!”
Tris