Just occurred to me that this will be an important development step for SpaceX to do. By developing and getting expertise in their own satellite system around Earth, SpaceX will have the experience to launch and establish a comparable satellite network above Mars. IMHO, this will be an important first step in establishing sustainable colonies/manned exploration of Mars.
Your comment got me thinking about satellites for Mars. You could do something like we do on Earth and park a satellite in areostationary position in an areosynchronous orbit (ASO). It seems to be 11,000 miles out from the planet. That is less than half of what it is for Earth at 22,236 miles because of the lesser gravity of Mars.
Areosynchronous orbit - Wikipedia
I expect an entire constellation won't be needed for quite a while. Park one satellite to start with above your landing region and a few others for transfer data to Earth when the landing site is facing away from Earth. I'm sure someone has already figured out what would work best.