a10/a11

a10.md

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+# PNT Carrier Wave
+The UHF frequencies around 1.6 GHz were chosen for GPS and related applications
+because they provide a sensible tradeoff between
+- antenna size (bigger for lower frequencies),
+- ionospheric refraction (higher for lower frequencies),
+- absorption (higher for higher frequencies).

a11.md

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+# GNSS attacks
+Spoofing refers to identifying as another identity, in this case the GNSS satellite,
+broadcasting false signals with the goal of manipulating the course of aircraft or naval vessels.
+Jamming refers to making the service unavailable by decreasing the signal-to-noise ratio.
+Jamming is a lower effort attack as it does not require knowledge of the protocols in use.
+Both make the original service unavailable, however because spoofing provides false information
+instead, it is harder to detect and poses a greater threat.