AST owns no spectrum. It has to have a local partner in country like Tmobile or Claro to operate. They use the partner's spectrum. If they transit without spectrum rights they'll be fined. If they receive without an MNO partner it's unlawful surveillance. They're only going to operate in places where their partner is currently permitted to operate. If there's a prohibition on transmission because of radioastronomy AST will need to observe that prohibition too. Also, GPS space segment clocks are hyperstable over long periods, they only need to be calibrated once every 10 years.

I've been in GN&C for 20 years. The best book by far for entry level astrydynamics is Bate Muller White, Fundamentals of Astrodynamics. It's a paperback and it costs about $8 used. The math is the real deal and worth taking a look at (it's not for regular people). It was written to prep Airforce Academy grads in the wake of Sputnik. but if you ignore that and read the introduction of the sections it's an extraordinary background and foundation.