Watch on Pyongyang heightened

The U.S., Japanese and South Korean militaries are cooperating to closely monitor North Korea’s movements, taking advantage of their tactical reconnaissance assets in preparation for a possible missile launch by Pyongyang.

South Korean and U.S. intelligence authorities have been on alert since Jan. 6, when North Korea conducted its fourth nuclear test and have been keeping a particularly close eye on activity at the country’s Sohae Satellite Launching Station, also known as Tongchang-ri, in Cholsan County, North Pyongan Province.

Tongchang-ri along with the Punggye-ri Nuclear Test Site in Kilju County, North Hamgyong Province, are considered areas of special interest.

“Looking at past examples, North Korea has conducted nuclear tests and long-range rocket launches as a set,” a South Korean government official said Wednesday. “After the Jan. 6 nuclear test, we have bolstered surveillance for the whole Tongchang-ri area, and heavy movement was detected.”

Since North Korea alerted international agencies Tuesday of its plan to launch an Earth observation satellite, interpreted as a pretense for a long-range missile launch, intelligence authorities have leveled up their monitoring systems, using terrestrial and naval radars to potentially trace North Korea’s missile launch when it happens.

In a move to counter North Korea’s missile threat, Japan last week dispatched its Aegis destroyer, equipped with radars that can track long-range ballistic missiles and mounted with Standard Missile-3 (SM-3) interceptors.

North Korea notified international agencies, including the International Maritime Organization, on Tuesday to say that it would conduct a satellite launch sometime between 7 a.m. and noon between Feb. 8 and 25.

Japanese Defense Minister Gen Nakatani on Wednesday ordered the deployment of its Aegis destroyers and Patriot missile batteries, which can shoot down North Korean rockets.

The South Korean Navy also bolstered defenses in the Yellow Sea deploying two Aegis destroyers.

“In the past, only one Aegis destroyer was dispatched in the West Sea [Yellow Sea], but an additional destroyer was dispatched toward Jeju Island,” a South Korean military official said. “Depending on the situation, the remaining Aegis destroyer may join them.”

The Aegis destroyers are equipped with a multi-function SPY-1D radar system that is capable of detecting ballistic missiles as far as 1,000 kilometers.

In December 2012, it took Korea’s Aegis destroyer Sejong the Great just 54 seconds to detect the launch of North Korea’s long-range missile in the Yellow Sea, quicker than the U.S. or Japanese Aegis destroyers. Sejong also detected North Korea’s missile launch in 2009.

On land, the South Korean anti-ballistic radar Green Pine and early warning and control aircraft Peace Eye are closely monitoring the situation.

The Green Pine system has a range of 500 kilometers and detected North Korea’s long-range rocket launch in December 2012 in 120 seconds; Peace Eye took 97 seconds.

The United States is also using its reconnaissance satellite systems, including the Defense Support Program (DSP) and the Space-Based Infrared System (SBIRS), to monitor North Korea.

BY SARAH KIM, JEONG YONG-SOO [kim.sarah@joongang.co.kr]