With Aegis destroyers and Patriot Advanced Capability-3 missiles deployed and standing by, Japan’s military appears ready to shoot down any debris from North Korea’s rocket — or even the rocket itself — should it threaten the country this week.

But some experts say that the probability of rocket parts falling on Japanese territory is extremely low, and the chance of the missile batteries detecting and destroying them is even lower.

“The rocket’s proposed trajectory does not pose any risk to Japan if all goes as planned,” and no interception will probably be necessary, Motoaki Kamiura, a military analyst and author of several books on the Self-Defense Forces, told The Japan Times in a recent interview.

“Even if something does go wrong and pieces of the rocket start plunging toward the country, we are talking about debris that will fall from the sky randomly,” he said. “No country in the world has a defense system capable of intercepting such debris.”

According to data submitted by North Korea to the International Maritime Organization, the launch will take place between 7 a.m. and noon from Thursday to April 16. Pyongyang claims the purpose of the launch is to put a satellite into orbit, but most Western nations consider it a disguised ballistic missile test.

The rocket will briefly fly over Okinawa Prefecture, but its first booster is expected to drop into the East China Sea west of South Korea and the second into waters east of the Philippines.

Nevertheless, “a number of countries are potentially affected” by the North’s rocket, Peter Lavoy, principal deputy assistant to the U.S. defense secretary, told the House Armed Services Committee earlier this month in Washington.

Lavoy said some debris could potentially cause damage in areas from Japan and South Korea to the Philippines. The comments immediately set off alarm bells in Tokyo.

Following Japan’s decision to use its state-of-the-art ¥1 trillion missile defense system, the Defense Ministry has deployed seven PAC-3 land-to-air interceptor missiles in Okinawa and Tokyo. In addition, three Maritime Self-Defense Force destroyers equipped with Aegis combat systems and Standard Missile-3 interceptors will be stationed in the Sea of Japan and in waters around Okinawa.

Adding to the show, hundreds of troops have been positioned around Okinawa in case of “an emergency,” however unlikely.

The PAC-3 and SM-3 systems depend on data from the high-tech radars on the Aegis vessels and from U.S. military satellites that can detect the rocket’s heat signature.

The U.S., meanwhile, is deploying its own Aegis destroyers to the East China Sea to collaborate with the Japanese vessels, while surrounding nations are also on high alert.

The Philippine government has imposed a no-fly zone over the area where debris could fall from Thursday to April 16, while Seoul has said it will use its missile defense system to shoot down the rocket if it poses a threat.

According to reports, Taiwan also plans to position PAC-3 and other missile systems on the east side of the island, although it has not disclosed specific details.

When ordering the SDF to ready the missile shield in late March, Defense Minister Naoki Tanaka said he “would make solid preparations to protect people’s lives and property and take all possible measures.”

But just a few days later, Tanaka acknowledged in a Diet hearing that the defense system can’t cover all corners of Japan. Even if it could, analyst Kamiura said the ground-based PAC-3s and SM-3s aboard the Aegis destroyers aren’t sophisticated enough to provide much of a defense.

SM-3s are designed to intercept a target at an altitude of approximately 300 km, while the North Korean rocket will likely be traveling at an altitude of 370 km, like the one that flew over Japan in 2009.

The PAC-3 missiles, meanwhile, will be ineffective unless an object flies directly within their 20-km range and in a straight trajectory.

Setting up the missile shield is more about “giving local residents some sense of safety” than actually shooting down any debris, Kamiura said.

Tetsuo Maeda, a former professor at Tokyo International University and an expert on military and national security, agrees.

Maeda noted that when North Korea launched an alleged satellite in April 2009, the first booster fragmented into more than 50 pieces of different shapes and sizes that scattered randomly across the Pacific Ocean.

In the improbable event that parts of the rocket fall onto Japanese territory, the SM-3 and PAC-3 systems are not advanced enough to counter such a dispersal pattern.

“The defense system isn’t being positioned to shoot down the debris, because technically it is not capable of doing that,” Maeda said. “Positioning troops and the defense system is only an act to show that they are doing their job, and that it is necessary for Japan’s defense.”

Given the likelihood that all will be quiet in Okinawa, there appear to be few reasons to put the defense shield on standby.

Its deployment, Maeda said, will serve as a rehearsal for the SDF to position troops, prepare for an enemy strike and detect the missile’s path to prepare for future threats. Another reason is to test Japan’s early warning system, which failed miserably and caused considerable embarrassment in 2009 by sending out inaccurate information that triggered nationwide panic — not once, but twice — before North Korea’s rocket actually blasted off.

This time around, the Defense Ministry will again receive launch information from U.S. spy satellites and instantly pass it on to the prime minister’s office.

But the government will also try out the new J-Alert emergency warning system that is designed to swiftly transmit information to local municipalities, especially in Okinawa. It will be the first time the system is used for missile launch warnings.

So far, however, J-Alert has gotten off to a rocky start. During a test April 5, the emergency signal was not sent correctly to seven of Okinawa’s 26 municipalities and authorities were not able to relay the warning to residents. The glitch forced the internal affairs ministry to conduct a second test prior to North Korea’s launch.

Another difference from the North’s 2009 rocket concerns Japan’s ability to collect any debris. The government failed to collect any rocket pieces after that launch, but the radar systems on the Aegis destroyers this time will be able to project the boosters’ landing spots within 15 to 20 minutes after takeoff, Kamiura said.

And unlike the 2009 booster that dropped into the Pacific about 280 km west of Akita Prefecture, parts from this week’s launch are projected to fall over the East China Sea, which is far shallower than the Pacific and whose seabed could potentially be searched for debris.

“Retrieving rocket components will allow us to learn about the North’s military technology, welding techniques and metalworking abilities. There’s some hope this time around,” Kamiura said.

But security expert Maeda said that despite the government’s explanations and justifications for preparing the missile defense system, the deployment may be an overreaction.

“A panicked reaction and full-scale interceptor deployment by Japan to counter the launch only serves North Korea’s purposes” and boosts Pyongyang’s diplomatic leverage, he warned.