Satellite surveillance?

Question

Please help me with these questions:
Describe the stationary orbit of the surveillance satellites and give a general outline of how the satellite maintains a fixed position relative to an observer on Earth.
Make a list of advantages and disadvantages of satellite surveillance, explain why each is an advantage/disadvantage, and relate the advantages/disadvantages to individual rights and social issues.

Answer 1

A stationary orbit is a geosynchronous earth orbit (GEO). There are very few surveillance satellites that use that orbit because of the disadvantages (discussed below).

How can you achieve a GEO? If your orbital period is exactly the same as the rotation of the earth (~24 hours/day), then your satellite is in a GEO. Your satellite may be located 'above' any longitude on the earth (above the equator), but you would be stuck looking down on that longitude (and that range of longitudes at + or - 60 degrees from where you were "parked" in orbit).

Physics dictates that if your orbital velocity is 24 hours/day, that you will be at an altitude of 22,236 statute miles above sea level. 22,000 miles is a LOOONNNGGG way to be doing any type of decent spying, even with the best of optics. This is the biggest disadvantage to surveillance from GEO. One advantage of surveillance from GEO is that your field-of-view is much wider (about a 60 degree radius cone-base on the surface of the earth) than normal spy satellites which orbit on the order of 100 miles up (near earth orbit NEO). Spy satellites at 100 miles up only have a field of view on the order of 100 miles on the surface, not 1000s of miles from GEO.

Another advantage GEO satellites have is they can 'see' the target all the time. NEO satellites pass over the target for only moments at-a-time and may not be able to see the same target for days until their orbit takes them around again to the same spot on the ground. A disadvantage to GEO spy satellites is, that the spyee knows the spy-er is always up there and can hide things underground or wait for cloud cover to "do stuff".

As for the social implications -- they are up there, they are watching, have been for decades, and there is little we as ordinary citizens can do to stop it. On the other hand -- what have you got to hide?

BTW, GPS satellites use a mid-earth orbit (MEO), not a GEO.

.

Answer 2

There's a mix of right & wrong information in these answers.

It's true that satellites which maintain a fixed position relative to an observer on earth, are probably too far away to do any surveillance. They're about 22,000 miles high--almost 3 earth diameters. This can't be helped--if you tried to move them any closer, the laws of physics would prevent them from "hovering" over the same spot.

Such satellites exist, but they're used for communication (i.e. satellite TV and satellite radio); not for surveillance.

The responder who said that GPS satellites behave in this way, is incorrect. GPS satellites are in 12-hour orbits, which means they're much closer to the earth than geosynchronous satellites.

Answer 3

Surveillance satellites do not maintain a fixed position over the Earth because if they did they could only look down on the Equator and they would be much too high up to see fine detail.

Surveillance satellites are in low Earth orbits and pass over their targets, so can only see them intermittently.

Answer 4

Sounds like you need to review your general orbit knowledge. Its called GEO-SYNCHRONOUS ORBIT. Weather satellites use such orbits. If it's stationary it moves in-sync with the earth. 1 rev every 24 hours. There is only 1 altitude it can be for this to occur and one position; above the equator. Use your imagination about advantages and disadvantages: terrorists vs. snooping ; weather prediction, environmental changes; movement of armies, navies; come on think!

Answer 5

The guy before me is sadly wrong. It is called a geosynchronous orbit. I don't know much about it but wiki does :)

http://en.wikipedia.org/wiki/Geosynchronous_orbit

have fun