secure form of communication for the military. down the hall, extremely high frequency communications. also secure coms for the military, a favorite of u.s. special forces. and down here you have what they call the neighborhood watch satellites. those are the satellites that are looking out for all the other satellites in the u.s. military's arsenal to guff them early warning of potential threats in space. >> free pass 52. >> 1-8-4, go. >> 52. >> this is the team at schriever responsible for the global positioning system or gps constellation. >> you're good to execute 52. >> copy that. >> now approaching their 38th anniversary of the launch of its first satellite -- >> 3180 continues to perform well. >> the gps constellation is the biggest and arguably the most important network of satellites in space today. >> and we have indication of spacecraft separation.