It was foreseen. There is a huge amount of literature on hardening of GPS from the begining of the technology. Here's so random examples: https://onlinelibrary

It was foreseen. There is a huge amount of literature on hardening of GPS from the begining of the technology. Here's so random examples: https://onlinelibrary.wiley.com/doi/abs/10.1002/j.2161-4296.1989.tb01514.x https://onlinelibrary.wiley.com/doi/abs/10.1002/j.2161-4296.... https://apps.dtic.mil/sti/html/tr/ADA057265/ https://apps.dtic.mil/sti/html/tr/ADA057265/ https://www.ion.org/publications/abstract.cfm?articleID=12012 https://www.ion.org/publications/abstract.cfm?articleID=1201... https://repository.arizona.edu/handle/10150/609916 https://repository.arizona.edu/handle/10150/609916