how far can satellites see?

Answer 1

It depends on where it's pointing, how well it's made, what it was designed to do, and what it has to look through. They can see up to a few hundred meters into the ground or up to 13 billion lightyears into space.

An artificial satellite is a robot in space. It's ability to "see" is determined by the types, sizes and capacities of sensors, optics and control systems its builders decide to use.

One consideration is sensitivity. If your optics are too small or otherwise not able to collect enough light, the sensor elements won't trigger reliably and the satellite will see very little. If a sensor element is too sensitive for the light it collects, it will trigger all the time and all it will see is glare.

Another consideration is resolution. There is a practical limit to the size of any image. If you are taking pictures of the entire Earth, you will not be able to include details like smaller rivers, islands and cities. If you are focusing on small buildings and cars, you may not be able to capture the entire block. There are just too many pixels in an image that wide at that level of detail.

The "satellite" images you find on MapQuest or GoogleMaps are really aerial images, taken from airplanes, not satellites. A satellite would have to look through a hundred miles of wind, water vapor and temperature gradients to the ground. You've probably seen stars twinkle at night? Well, the surface of the Earth twinkles too when you're looking hard enough from up there.

From space, one meter resolution is very good. That means an object one meter wide will be one pixel wide to your satellite. One meter objects halfway between pixels or smaller than a half pixel will not show at all. The best spy satellites with the highest resolution and farthest zoom might be able to detect down to a few dozen centimeters, but with normal air turbulence, they will require sophisticated computer analysis to resolve details out of the fuzzy, grainy images they get. You might be able to read a billboard from orbit with computer help, but not a large-print book.

Looking the other way, a satellite can see much farther than a human can. Space telescopes are designed to see extremely far, from hundreds to billions of light years. But the farther you look, the narrowerr your field of view has to be. So a hundred million LY view might by only 50 LY wide. You need to be sure you're looking in the right direction or you'll miss your target.

Another problem with long distanc viewing is dimness. Just as your view narrows to a fraction of a degree as you zoom in on a distant star, the number of photons you capture gets smaller. A star radiates in all directions, but if your collector is only a meter or two wide, there are only a few photons from that star hitting it in a reasonable time. Either you need a bigger target or a longer exposure.

The Hubble did a "Narrow Field, Deep Space Survey" a few years back that photographed a tiny patch of black space. Every orbit, for about a month, it took a photo from the exact same position, in the exact same direction, for the same amount of time. When the exposures were all combined, the astronomers saw an image of hundreds of tiny galaxies up to about 13 billion lightyears away. There's no other way that image could be captured. It had to wait for enough photons to arrive to paint the images. That's why Hubble doesn't take photos of the Moon. For one, it's too bright. For another, it moves too fast. Even if Hubble could track it, it would be a blur.

One other consideration is light frequency. The Hubble takes some amazing photos in the visible light spectrum. It even does some infrared and ultraviolet. But the best X-ray images are taken by the Spicer Space Telescope. It's designed for the high-energy, ultra-short wavelengths that novas, pulsars, quasars and black holes give off. It takes a very different type of picture of the same things other telescopes look at, seeing more (and less) than they do.

Turning groundward again, there are other ways of looking at things. Radio waves at different frequencies bounce off a surface. Some bounce below the surface. So we can get radar images of the ground and sub-surface features like water tables, oil deposits, old caravan routes and such. These are more like listening than "seeing" but 3D maps can be very visual.

Answer 2

Satellites, and people too, can basically see infinitely far. For example, when you look at the stars you are seeing trillions of miles because that is how far away the stars are. The Hubble Space Telescope can't see any farther than your eye, but it can see dimmer light and smaller things. So it can see things that are not bright enough or big enough for your eye to see, but you eye alone could see that far if there was some really big and bright thing that far away to be seen.

Answer 3

satellite you probably meant space telescopes can see upto 12 billion light years. They are in space to avoid the haze of earth's atmosphere and can see fainter objects. Hubble has seen stars forming in nebulas. Stars exploding near the edge of the universe.

Answer 4

When I was in the military I learned alot about our satelite links. What I have seen is that a satelite can not only zoom in on a specific target but they can also zoom in on specific people. For example I have seen where we can zoom in on Bin Laden's terrorist groups in the desert. They can tell the difference between our troops and terrorists.

We are able to watch certain training facilities and track the vehicles and troops that come in and out of the facility. We also can do this with other countries that may be hiding weapons of mass destruction.

The galaxy itself is about 100,000 light-years wide. We see most of its contents only with powerful telescopes working at various wavelengths of light not visible to humans.

As for what we can see in space with the use of satelites, it is up for debate. We can see the milky way and many planets. A light-year is the distance light travels in one year, racing at a speed of 186,000 miles per second. It's equal to about 5.88 trillion miles, or 9.46 trillion kilometers.

Answer 5

The Hubble Space Telescope can see stars that are at the edge of the known universe, i.e., >13 billion lightyears away

Answer 6

2 meters (6 feet) looking down and looking out ward, far, really far.

Answer 7

a long way if they turn the lights on...