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Communication and Software

Satellite Network

Overview

For our mission, constant connection must be maintained between the main base on Earth and the base on Mars, mainly because there will be people working on Mars and a constant monitoring of their progress and health conditions is an essential part of mission success. The worst-case scenario will be injury or death of one or more crew members, and therefore the more we monitor them, the less chance of failing there is.

Issues Addressed

One of the most difficult problems associated with the maintenance of Earth-Mars communications is a time delay of up to about 20 minutes using currently available technology. There is little chance that this situation will improve significanty over the timescale of our mission preparation period. We feel more confident that a constant connection between the two bases could be maintained with some delay on both ends. This will be a bit more expensive, but the safety of the astronauts is considered to be of paramount importance.

Options

We explored several options for minimizing communications delays on Mars:

Three nodes would be used: one would be a satellite in a polar orbit, another would be a satellite above the main base on Mars, and the third would be the interplanetary transportation spacecraft. In this scenario, the transportation spacecraft would maintain an orbital position appropriate to provide an open channel for a transmission to the Earth.
One satellite would be positioned to provide direct contact to the Earth and all communications from and on the Martian surface would rely on the AM band.
One satellite would be positioned above the main base as a backup, and two others would be positioned 65 degree on both sides, all in geosynchronous orbit.

After long discussions and continuous evaluation of all the advantages and disadvantages, the third option was chosen as the most appropriate for our purposes. Even though the first two are a bit cheaper, because they use less equipment, their support on Mars would be much more difficult. They would be using fuel constantly and therefore their life would be much shorter, making our already difficult mission even more difficult. If we have to overcome this problem, we would have to attach extra fuel tanks to the satellites and make them much more expensive.

Solution

The graphic below shows the basic schematics of how satellites array around Mars:

Satellite Network

The satellite, in the middle on the picture will be the one right above the landing site and the main base. The other two will be 65 degrees to either side. All the satellites will be in geosynchronous orbit, which is roughly 1.69*10⁷m above the surface of Mars. From this orbit, each satellite will be able to cover about 95% of its side of Mars (from 80.4 degrees South to 80.4 degrees North). The overall area being covered this way is about 60% of the planet and includes all the places our people and equipment could ever reach.

For the actual data transmissions, only the two outside satellites will be used. They are positioned in such way that one of them will always be in contact with Earth. The third one will be basically used as a backup; if one of the others fail it will be able to move to the failed satellite's position and replace it.

Authors: Jordan Brayanov (jordan12@mit.edu) and Artem Gleyzer (agleyzer@mit.edu)