The military satellite network in both navigation & communication breaks down e.g. due to a virus, backdoor or worm created years before by a potential enemy state.
If you were to go into the future now, and Turkey is at war with countries, for example, and the USA/EU interrupts all US GPS, Galileo systems.
If Turkey had only its own Turkish satellite network, it would suddenly be dead or unreachable because years earlier a virus was uploaded unnoticed from some African state by a double agent, and that unnoticed into Turkey's satellite network.
We don't need to explain the end result, no matter how secure a system is declared to be, it is always crackable and the danger is great if foreigners access it because you have signed a leasing contract for satellite time to Burkina Faso. These people can't even protect a supermarket, how can they guarantee Turkey that others won't access it in this case?