How do satellites communicate with a GPS system? (2018)

The title is very confusing.<p>Satellites don&#x27;t generally communicate &#x27;with&#x27; a GPS system.<p>I think they meant, &quot;How do GPS satellites communicate with the GPS system?&quot;

For those interested in GPS, check out this article which discusses in detail how each step of the GPS process works, including acquisition, tracking, and decoding. I was thoroughly fascinated and flash-card-ified it so I will remember the facts long-term.<p><a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=40041198">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=40041198</a>

Makes you wonder if there is encryption on the uplinks for the first batch and how quickly they will be hacked.<p>Remember how they didn&#x27;t have encryption for years on the UAVs during the Iraq War and Afghanistan?<p><a href="https:&#x2F;&#x2F;www.wired.com&#x2F;2012&#x2F;10&#x2F;hack-proof-drone&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.wired.com&#x2F;2012&#x2F;10&#x2F;hack-proof-drone&#x2F;</a>

The title actually means &quot;How do GPS receivers receive signals from the GPS satellites?&quot; It&#x27;s not about other satellites communicating with GPS satellites.<p>TL;DR: They use special-purpose antennas.

GPS system = Global positioning system system

I mean the GPS satellites are in medium earth orbit so most LEO satellites receive the signal more or less the same way as people a few hundred km further down, no?<p>The comms between the GPS satellites and the ground stations is pretty interesting, see figure A4-1 in this for what happens to accuracy over time if the satellites stop getting corrections from the ground:<p><a href="https:&#x2F;&#x2F;navcen.uscg.gov&#x2F;sites&#x2F;default&#x2F;files&#x2F;pdf&#x2F;gps&#x2F;geninfo&#x2F;2020SPSPerformanceStandardFINAL.pdf" rel="nofollow">https:&#x2F;&#x2F;navcen.uscg.gov&#x2F;sites&#x2F;default&#x2F;files&#x2F;pdf&#x2F;gps&#x2F;geninfo&#x2F;...</a>