One of the challenges aviation faces using space-based infrastructure is the possibility of loss of the signal. The diagram below identifies the vulnerabilities to GNSS. The following page will consider the mitigations that ATM can put in place to enable safe operations to continue, albeit in some options at lower levels of service performance.
Because the signal from GPS is commonly used by a myriad of applications, ATM must comprehend that a deliberate interference of the GPS signal may not be directed at aviation; however, the by-product could be the loss of the signal-in-space (SIS) during a critical stage of flight. For this reason, contingency measures must be considered. As more satellite navigation constellations providing additional aeronautically protected signals become available, the robustness of satellite navigation will improve; however, the vulnerability to GNSS can never be eliminated.
More on GNSS mitigation can be found here.
