Get a Satellite Over There… Now!

The Shuttle flies pretty low by satellite standards. It takes 90 minutes for it to circle the Earth (the lower you go, the quicker you cover the surface). The Moon (which is also a satellite of the Earth) flies pretty high! As a result it takes around a month to circle the Earth. A third example would be a communications satellite, like the one your satellite dish is pointed at — it flies at about 22,000 miles altitude and takes exactly a day to circle the Earth; as a result it matches the Earth’s rotation, and appears stationary in the sky.

Now, in order for a spy satellite to cover the whole of the Earth’s surface, it flies what’s called a polar orbit — crossing both the North and South poles while the Earth spins beneath. It flies quite low in order to get a good look at the surface, and to cover a lot of ground in a short time.

Once any satellite is placed in orbit, it may fire tiny engines from time to time to change its attitude, or to minutely finesse its orbit — but 99.99999999999999 percent of the time it’s just coasting along under its own momentum.



So, if you have a spy satellite and you want to peer into someone’s car-park, or whatever, you have to wait until the next time it’s due to pass more or less directly overhead. That may be seven minutes from now — it could just as likely be seven HOURS from now.

When it does arrive at the scene, it’s not going to stop to take the pictures. There’s probably about two minutes of shooting time as it speeds past.

When on TV shows like “24” they say, “Give me a couple of minutes to position a satellite overhead… OK, we’re in! Now, let’s zoom in on the license plate…” Well, that’s fiction — what they call in the trade: Poetic License. It moves the story along.

So no, you can’t have the pictures while you wait.

Ironically, it was on Star Trek (one of the first and biggest science cheats in TV history) where Scottie more than once said, “You cannie change the laws of physics, Captain!”

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