Our city's communication system is divided into two subsystems. The internal subsystem is made up of a matrix wiring grid that matches the SimCity grid of 200' x 200' with an antenna at each grid intersection to pick up low watt digital messages from personal devices which are transferred by wire to another antenna and then transmitted to another device within the city. These text, sound, video, picture and 3-D hologram messages can also be sent to or from the Earth, the Moon, Mars, Jupiter's moons, other space stations, or space vehicles anywhere in the solar system. For this, the message uses the external subsystem which has 12 parabolic antennas outside the space station. One problem of our communication system is to always keep these antennas aimed at their distant targets. Engineers were asked to design a system to solve this aiming problem. The first step was to define the problem. The targets orbit along a flat plane and our spherical city also rides the same flat plane and rotates on its axis at one revolution per minute. The city's rotation was set so its axis of rotation was perpendicular to the flat plane and its equator was in line with the flat plane. Our team of engineers gathered to brainstorm possible solutions, writing them down without evaluating them at first. Later we listed plus and minus tradeoffs for each idea. Engineer Steve suggested a groove around the outside equator. An antenna would ride along the groove as the target and space station moved so it always pointed at the target. It would be guided by computer. Engineer Rachel suggested putting antennas on poles at the center axis of rotation. They would each slowly rotate so as to aim at their target. Engineer Pat suggested putting a row of antennas all the way around the space station equator. Antennas would be turned on and off as the targets move. Homing devices on each planet or target would transmit a "ping." Each of the highly directional antennas would measure the ping. The closest antenna that received the most powerful ping would be turned on.

    After this brainstorming, each idea was evaluated and the tradeoffs of each idea were listed. Steve's plan had few pluses; antennas would point along the same flat plane as the targets. The idea also had minuses; each antenna would need about 10 miles of track. More than 100 miles of track would be needed. Another minus was getting the signals to the antennas as they moved along the track. Rachel's plan would be less costly to build but the antennas at the poles would still need a way to be aimed. Pat's plan sounded simple but required thousands of antennas. Also, the homing device would correctly tell which antennas should receive a signal but the long lead-off of a transmitted signal would still need to be determined. They decided on Rachel's plan and to load the orbits of each target into the guidance computer that would steer each antenna.