A civilian GPS broadcast was being used as part of a military key-management control plane. That breaks the assumption that GPS is only navigation traffic, and it shows a public signal can carry operational cryptographic commands at fleet scale.
Murdoch tied a sentinel seen on all 31 operational satellites in May 2011 to the rollout of OTAD and OTAR by cross-checking the transmission timing with declassified documents. The result is a covert rekeying channel riding on public space-based infrastructure, so the control message is visible in the air even when its meaning is not.
The operational lesson is about trust boundaries, not a gadget in orbit. Any system that assumes private control traffic stays private just because it rides a public broadcast now has the same exposure.