Wouldn't the smart thing be to give the projectile a light and radar absorption coating? It isn't very big, and that way you'll only spot it when it gets very close, unless it cast a shadow (light or radar) against something.
Getting luck enough to spot it with infra-red is good.
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"It is the business of the future to be dangerous" - Hawkwind
Getting luck enough to spot it with infra-red is good.
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"It is the business of the future to be dangerous" - Hawkwind