Navigation in the Asteroid Belt

Navigation requires time and position data and the ability to calculate and plot a course. Historically, we have used “fixed” points like stars and buoys and beacons and landmarks and we plotted courses to fixed destinations. More recently we have learned to use a network of Global Positioning System (GPS) satellites. The satellites move constantly relative to any ground position, but broadcast time and position data that allows a ground position to pinpoint it’s own position. From the users viewpoint, the ground features stay in fixed positions and the navigation grid overhead moves.

In the asteroid belt, a similar network of navigational “satellites” will be needed. They will move in a variety of orbital trajectories around the Sun, designed like the current GPS grid to provide constant coverage at all points in the Solar System. But in addition to broadcasting their own time and position, they will also collect observational data of nearby objects and make it available on demand. This will provide an early warning system about small fast moving objects that may become threats.

Habitat cities in the asteroid belt will all be in different orbital trajectories. A city that is nearby at one time will be on the other side of the Solar System a few years later and then will eventually come back by again. This is not going to have a significant impact on navigation, but will change cultural factors because of time delays.

The standard measuring unit has been designated as 1 AU or Astronomical Unit, after the distance of the orbit of Earth from the Sun. 1 AU is just over 149 million kilometers or 93 million miles. Mars is found at 1.5 AUs. The asteroid belt spans from just under 2 AUs to just over 4 AUs and Jupiter is just beyond 5 AUs.

Light and radio waves take 8 minutes to travel that 1 AU distance from the Sun to the Earth. If a habitat city in the asteroid belt orbits at 3.5 AUs, light from the Sun will take 28 minutes to reach it and 56 minutes to go from one side of the asteroid belt to the other at that orbital radius. This means most communications from one city to another will incur time delays of from a few minutes to an hour.

It makes sense to utilize the same network of navigational satellites for communications relays. These NAV/COMM stations will combine the functions of GPS satellites, radar stations, and network routers.

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