A Japanese daily says the U.S. has deployed ballistic missile monitors in Japan to guard against North Korea’s launch of a long-range missile.

The Sankei Shimbun said two RC-135S Air Force airborne intelligence platforms were deployed to Japan. Known as Cobra Ball, the devices carry infrared telescopes for tracking ballistic-missile tests at long range.

The deployment aims to discourage the North from test-firing its Taepodong-2 missile.

The report said Japan’s Self-Defense Force is employing electronic reconnaissance planes and strengthening intelligence gathering on the North’s missile launch.

In 2006, the U.S. deployed missile monitors in its military base in Okinawa a month before North Korea launched seven ballistic missiles.