Defense Ministry officials suspect China has been floating balloons over Japan to spy on military radio communication to monitor the movements of the U.S. military and Japan's Self-Defense Forces.

The ministry had revealed in a Feb. 14 announcement that it "strongly suspects" several flying objects spotted over Japan over the past four years were Chinese surveillance balloons.

Defense officials said further analysis shows the objects closely resemble the one shot down by the United States 10 days prior, which gives some clues about the kind of information they were collecting.

NOT FROM PRIVATE SECTOR

A Self-Defense Forces source who compared a photo of the balloon downed by the U.S. military with the ones spotted in Japan pointed out that the antennae looked very similar.

The flying objects spotted over Japan appeared to have a cross-shaped part hanging beneath them, equipped with several antennae, just like the antennae on the balloon shot down by the United States.

China claims that the balloons were used for meteorological research. But an SDF source with experience handling weather balloons said the difference between spy and weather balloons is clear.

"It is hard to imagine them being mistaken for one another because they are completely different in size."

Weather balloons carry an instrument called a radiosonde hanging underneath them. But these balloons are two meters long at most, including the telemetry device.

The Chinese balloon shot down by the U.S. military was estimated to be about 60 meters long.

"It is unlikely a private company single-handedly launched an object this large," the source said.

China extensively promoted a military balloon of this size at a recent weapons fair and stated it intended to use them in the future.

A photo taken at the fair showed that it looked strikingly similar to the one shot down by the United States, including the shape of the antenna, the source added.

But since ground information can easily be collected from satellites orbiting in space, that would seem an unlikely reason to dispatch balloons.

"It appears that (China) collected information about radio waves traveling near the ground, which is difficult to be obtained by satellites," the ministry source said.

SPOTTED OVER KEY AREAS

The government has revealed there have been three sightings of balloon-like objects spotted in Japan's territorial airspace over the past several years: one in Kagoshima Prefecture in November 2019, another in Miyagi Prefecture in June 2020 and the third in Aomori Prefecture in September 2021.

At the time, then Defense Minister Taro Kono said the objects posed "no security threat" and the government decided not to scramble fighter jets and instead continued to closely monitor them.

Then, in January 2022, another flying object was spotted over the sea west of the Kyushu region by a Maritime SDF patrol plane, the government announced on Feb. 10.

The Defense Ministry released a one-page statement late in the evening on Feb. 14 to say that it conducted "further analysis" and concluded it "strongly suspected" that the flying objects were "unmanned surveillance balloons" flown by China.

A ministry source divulged they “made the announcement quickly because (the balloons) became a major public concern after the U.S. military shot down the balloon on Feb. 4."

According to another SDF source, it is possible that the balloon-like object flying over Aomori Prefecture was gathering information about radio waves transmitted by the U.S. military and the Air SDF's Misawa Air Base, while another spotted over Miyagi Prefecture was collecting information about those emitted by the Matsushima Air Base.

"They stay still and continue collecting radio waves during a time of peace without being noticed," the source said. "They must have always been monitoring the movements of the U.S. military and the SDF by repeatedly analyzing changes in radio waves."

Officials believe the balloons were likely operated via a satellite link and that they used onboard cameras to check their surroundings.

Some speculate the one spotted over Kagoshima Prefecture was spying on radio emissions in an area surrounding the Sendai nuclear power plant, key energy infrastructure that would be a weak point in a conflict.

Russia, for instance, has attacked Ukrainian nuclear plants during the war over the past year.

The use of balloons for military purposes is not that unusual, though, and even has a history in Japan. According to a source close to the ASDF, the government considers it a "pre-modern method" used by the Imperial Japanese Army in World War II, when it used balloons as intercontinental weapons systems to send bombs over great distances.

"It appears to be a rudimentary practice, but it means that China has always been monitoring us while no one was paying attention and no legal system (for how to respond) was in place," one source said. "It shows just how hawk-eyed China is and how artful it can be."