[fsmv]

Presumably the missile needs GPS to hit the target so if you jam right when the missile is coming in the missile will miss so you can't really jam the warning

Also if you broadcast noise when your missile is about to hit then your own jamming signal acts as an early warning as well, although I guess it wouldn't provide location.

[jandrewrogers]

US weapon systems have never relied on GPS for guidance. Some will accept GPS corrections to the primary inertial guidance system but those corrections will be rejected if they deviate more than a few meters from the inertial guidance. US missiles in particular use precision terminal guidance which doesn't involve GPS at all; in these systems GPS would only be used to correct mid-course guidance.

There has been anecdotal evidence for years suggesting that the latest US inertial guidance technology is sufficiently precise and accurate that GPS correction no longer adds value.

[karp773]

I do not think that is correct. For example, Excalibur [1] relies on GPS and proved to be quite inefficient in Ukraine. Russia figured out how to jam them in a few months.

[1] https://en.wikipedia.org/wiki/M982_Excalibur

[stouset]

ICBMs don’t rely on GPS. They are typically self-guided and use a blend of their known launch location, inertial navigation using gyroscopes, celestial navigation (yes, looking at stars), and a few other techniques.

[sidewndr46]

This isn't true for US made weapons. They explicitly do not use GPS because it is the first thing to go in a war