Martian Wireless Networks

In 2005, we ran a curated virtual space mission for Georgia Tech’s graduate-level ECE 6390, Satellite Communications. The project was entitled “Martian Wireless Networks” and involved a hypothetical wireless network to link radios across the surface of Mars. The project page archive can be found here and an extended description below.  We should acknowledge a big assist from Prof. Paul Steffes for this one as well.

Over the next 20 years, NASA expects to have a host of landers, rovers, aerobots (self-controlled airplanes), and even astronauts on the surface, or in the tenuous atmosphere, of the planet Mars. Your engineering firm is to design a system allowing uninterrupted inter-communications between all of the Mars-based assets (landers, astronauts, aerobots, etc.), as well as communication between all Mars-based assets with NASA facilities on earth. Since the Martian day is about 24.5 hours long (similar to Earth), ground-based landers and astronauts will not be in the line-of-sight to earth for periods of over 12 hours, so relay satellites will be required. Since the ground-based terminals will be at all locations on the Martian surface, 100% surface coverage must be provided.

You may assume there will be up to 50 terminals on the Martian surface, and they must be reasonably compact so as to be transportable to Mars (i.e. no aperture sizes larger than 1 meter diameter on the surface). Relay spacecraft may be much larger, determined by the practical limits of launcher size (e.g. the space shuttle payload bay). Each ground terminal must be able to uplink data at rates up to 1.5 Mbps and have it received both at Earth or by any other terminal on Mars. Each ground terminal must be able to receive its own targeted data stream from the Earth at 1.5 Mbps, and one additional 1.5 Mbps data stream from one of the other Martian surface assets, which should be fully selectable from the other 49 data streams being transmitted. Since frequency allocations on the surface of Mars are not (yet) a big problem, you may select any frequencies you like for communication between the surface terminals and the relay spacecraft (except 1.40-1.43 GHz, 4.9- 5.0 GHz, 10.6-10.7 GHz, and 15.3-15.4 GHz, which would interfere with radio telescopes on the Earth.) However, communication with the earth will be conducted by communicating with stations of the NASA Deep Space Network (DSN, http://deepspace.jpl.nasa.gov) which can communicate in the following bands: Earth-to-Mars: 7190-7250 MHz and 34.2-34.7 GHz, Mars-to-Earth: 8400-8460 MHz and 31.8-32.3 GHz.

In addition to your design of the overall system (spacecraft orbits, transponder designs, modu- lation type, multiple access, etc.) you must design the terminals to be used on the Martian surface and the orbiting relay satellites (block diagrams and appropriate solar power system). You may as- sume the NASA DSN Stations are already built and available for use. 34-meter diameter parabolic antennas are used at the DSN, with TSY S = 20 K, and aperture efficiency equalling 0.94. The DSN transmitters are capable of transmitting up to 500,000 watts and at least one station is always able to view Mars. The bit error rates on the overall links from the Mars stations back to earth and the earth to Mars must not exceed 10−6.

Show that your design is most cost-effective (total cost, including spacecraft and Mars surface terminals) by justifying all cost estimates or assumptions. You may estimate the cost of Mars orbiters as being $200 M (including launch) plus 1$ M per transmitted watt of power (not EIRP).