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If we assume that humans will eventually visit (if not colonize) Mars, and we consider the benefits to terrestrial navigation and communication of the GPS and Iridium systems...

Would a precursor to human travel to Mars logically be the establishment of a GPS-style constellation of navigation satellites and/or an Iridium-style constellation of communication satellites in Martian orbit?

Is that something Mars mission planners have written into their plans, have considered, or have dismissed as unnecessary?

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2 Answers 2

Each orbiter at Mars has a secondary mission as a data relay satellite for other Mars missions. Mars Reconnaissance Orbiter (NASA), Mars Express (ESA), Mars Odyssey (I think) are all used to relay data from the smaller landers back to Earth.

So a small network of communication satellites is already in orbit with a few more coming.

None of them have clocks of the accuracy needed for GPS style navigation, but some similar system seems likely, even if just for search and rescue, once serious manned exploration/habitation of Mars occurs.

But that is probably several decades away still, Elon Musk notwithstanding.

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A Mars GPS system cannot be a high priority considering the challenges of life support. GPS is a hit on Earth because it has billions of users. If you divide the multi billion dollar cost on say 12 astronauts on Mars, you need extremely productive use to motivate the investment.

Without global magnetic field, a compass is useless on Mars, so there is a need for navigational aid. But radio beacons on the ground at landing sites would be much more cost effective.

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The last sentence is what makes this the right answer, at least for the foreseeable future. Beacons would be orders of magnitude cheaper than a Mars GPS system. Beacons help solve the dead reckoning problem for precision landing at a predetermined site. They are not a global solution (now you need lots of beacons), but that isn't the concern for the foreseeable future. –  David Hammen Jun 11 at 12:29
    
Would beg to disagree: pinpoint landing at an unexplored location requires satellite-based navaids. A GPS system is too expensive, but getting range and range-rate updates from satellites with known orbits will be of much help during early trajectory correction maneuvers. –  Deer Hunter Jun 11 at 13:21
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@Deer Hunter A (visual) Terrain Relative Navigation system is considered for NASAs 2020 Mars rover. It certainly sounds like a feasible concept. Unless there is a sand storm, like when the Soviet Mars 3 landed in 1971... planetary.org/blogs/guest-blogs/van-kane/… –  LocalFluff Jun 11 at 13:57
    
Optical navigation is necessary for the descent phase, to compensate for the winds and atmosphere discrepancies. Satnav complements it by allowing corrections long before entry. –  Deer Hunter Jun 11 at 14:34
    
But 4+ GPS satellites in Mars orbit could cost more than the entire MER program. Landing with better precision than MSL Curiosity isn't worth that much, until there's a substantial human colony there. –  LocalFluff Jun 11 at 15:15

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