Air defense

Swiss eye stealth-nixing radar to protect Alpine valleys

Swiss defense officials say they are monitoring progress in the field of passive radar, a technology with the potential to track stealthy aircraft, as the country plans a multibillion-dollar upgrade of its air defenses.

Some European vendors are looking to the Alpine nation, hoping its “Air 2030” program, which is slated to include a combination of new aircraft and ground-based sensors, could finally offer a breakthrough for the still-dormant radar technique.

Unlike traditional radar sets, which emit radar waves and then track their path, passive radar equipment computes an aerial picture by reading how civilian communications signals bounce off of airborne objects. The technique works with any type of signal that’s already present in a given airspace, including radio or television broadcasts as well as emissions from mobile phone stations.

Passive radar technology promises the advantage that it cannot be detected, meaning pilots entering a monitored area may be unaware they are being tracked. That could even be the case for pilots flying stealthy aircraft like the F-35, experts say, though there appears to be no publicly available data pitting passive radar against low-observable aircraft designs and their radiation-absorbing coatings.