Time for the "brass" to wake up and small the manure. The good news is that a proven and robust terrestrial back up can be up and running fairly quickly when and if it is funded. In fact, it was running until 2008 when the administration cut all funding to save $40M a year. Unfortunately, they also cut funding for preservation and security, so we'll have to start over equipment wise in most places. However the companies like Ursa Nav that make the equipment are still in business, still making the equipment, albeit for other countries. I speak of e-LORAN. An augmentation of the decades old LORAN C program that was the gold standard for navigation before GPS, and actively used worldwide until funding was cut. Ironically, the USCG who ran 90% of the system had just completed upgrading equipment preparatory to implementing eLORAN which uses ground differential stations to provide GPS standard accuracy where needed. All we need to do is get the decision makers off their collective butt.