 Over-the-horizon radars cannot pinpoint their exact locations, and would have to be used in conjunction with Chinese recon satellites; recon aircraft and submarines could also look for them, but they are vulnerable to the carrier's defenses.Finally, although the DF-21D has radar and optical sensors for tracking, it has not yet been tested against a ship target moving at-sea at up to , let alone ones using clutter and countermeasures.The "kill chain" of the missile requires processing and constantly updating data of a carrier's location, preparing the launch, programming information, and then firing, a chain the U.S. military's AirSea Battle concept involves disrupting.