Spy Satellites

North Korea has launched a spy satellite. The usefulness of spy satellites is probably limited. As far as permanent structures the whole world is on Google Earth and, at least the west, is on Google Street View. Traditional spying has largely been replaced by hacking and, even aside from hacking, more can probably be found out just by using the internet than in looking down from outer space.

It is a relatively simple matter to make a building that one wants to keep hidden look like a warehouse. Spy satellites are visual so that clouds provide effective cover. A military drill that is to be kept secret can be done on a cloudy day.

The place where spy satellites are useful is watching ships at sea, and I am surprised that more precautions are not taken. I don't think that radar is particularly useful for ships at sea. Radar waves are short wavelength, meaning that they are limited to the horizon and, if a ship can be picked up on radar it can probably also be seen visually.

It is not possible to completely hide a ship. But the hulls of warships are painted light gray to make them less visible, from a distance, against the sky. In the past navy ships have been painted in "Dazzle" camouflage. While this does not completely "hide" the ship it can confuse an observer as to what type of a ship it is and it's direction. With visibility at sea often being poor Dazzle might make a large ship look like two smaller ships, or vice versa. It might make a ship that is crossing the field of view appear instead to be moving directly toward or away from the observer.

But it doesn't look like anything is being done to conceal ships from spy satellites. Look at the following two images of a warship from Google Earth. It is very visible from above and could easily be seen by satellite. If the hull of the ship is painted light gray to be less visible against the sky, then why couldn't the deck of the ship be made the same color as the water? It would reduce the visibility of the ship from a satellite by at least 90%.