rbital mechanics deal with two parts in MPS: the MPS satellites' orbits about Mars and how to get MPS satellites from the Earth to Mars. MPS satellites' orbits about Mars are important to the availability of the MPS location system. The coverage must be sufficient for the user's device to do the trilateration. Getting MPS satellites from the Earth to Mars is also of important to the system and more complicated; the travel duration and cost to launch the satellites are much larger than the GPS system. These two parts must be seriously considered to ensure both the system operational and to reduce the maintenance cost.