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REFLECTIONS Ed Chenevey

I found an interesting article in the June 9 issue of Aviation Week which has extensive coverage of the air over Iraq. What immediately caught my eye was an accounting of "tweeking " GPS. A group in Colorado had been able to optimize GPS satellite performance several times a day over a designated area. But the windows were short. They needed 4 hours to configure the system, identify the applicable satellites and drive down the errors associated with a 1 hour window at that particular location. They managed to get 6 meter accuracy accross the theater.

In mid March they were asked for improvements. They were able to update the satellite navigation systems by concentrating only on the spacecraft that would be visible from Iraq, essentially updating each as it entered the Theater. The average GPS position accuracy over Baghdad was 3 meters between Mar 19 and Apr 18. Think, that means that you could target either the front or rear of your car. There is a by the minute histogram of GPS performance over Baghdad for Mar 28 showing that the best performance was 1.2 meters; i.e. the difference between the front and back seat in your car. I haven't a clue as how they determine that the satellite is accurately positioned.

There are several other articles describing other aspects of our tecnology driven war which allowed target changes while in the air.

The July issue of Popular Science has a cover article on Burt Rutan's SpaceShip One.