The image above comes courtesy of this article at Defense Industry Daily.
It illustrates the workings of Cooperative Engagement Capability (CEC), a system of pooling radar and sensor data among warships and other platforms to provide a more complete image of the battlespace:
The Cooperative Engagement Transmission Processing Set (CETPS) AN/USG-2 coordinates all task force Anti-Air Warfare (AAW) sensors into a single real time, fire control quality composite track picture which significantly improves battle force AAW defense. The CETPS distributes sensor data from each Cooperating Unit (CU) to all other CUs utilizing a real time, high data rate, line of sight (LOS), fire control quality sensor and engagement data distribution network. This CETPS is extremely jam resistant and provides very accurate gridlocking between units. The data is then combined into a common track picture by employing high capacity, parallel processing and advanced algorithms.Of course, the first thing I thought of when reading this article was the prospective impact of such a system on the US-Japan alliance. Perhaps not profound in and of itself -- Japan has already struggled with the question of whether its Aegis cruisers operating in the Indian Ocean can participate in "collective defense" if a threat against coalition warships was detected, not to mention its ongoing struggle with the collective defense implications of missile defense -- CEC would be another element pushing Japan to interact with allies on a reciprocal basis.
At this point, every little bit helps.