You can have passive radar: https://en.wikipedia.org/wiki/Passive_radar https://en.wikipedia.org/wiki/Passive_radar But yes, it needs to be doing more than re

You can have passive radar: https://en.wikipedia.org/wiki/Passive_radar https://en.wikipedia.org/wiki/Passive_radar But yes, it needs to be doing more than receiving telemetry to qualify, and there has to be something transmitting.