Special Ship Retires in Yokosuka

25 January 2026, Yokosuka 

— Research ship 'Mirai' holds its final public viewing; formerly 'Mutsu', active in the Arctic and other regions

The research vessel 'Mirai' (about 8,700 tons) of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Yokosuka, Kanagawa Prefecture, which had been in operation for 28 years for observing the Arctic Ocean and deploying large observation buoys in tropical seas, was retired, and its final public viewing was held on the 25th at Yokosuka New Port Pier in the city.

Its predecessor was Japan's first nuclear-powered ship, the 'Mutsu,' which was launched in 1969. In 1974, there was a radiation leak accident off the eastern coast of Aomori Prefecture. After repairs and test voyages, the ship was divided into three sections. The central part, which contained the nuclear reactor, was removed, and the bow and stern were reused and fitted with diesel engines, transforming it into the 'Mirai.' The nuclear reactor is on display at the Mutsu Science and Technology Museum in Mutsu City, Aomori Prefecture.

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From the Nuclear-Powered Ship to "Mirai" 

The journey of "Mirai" was itself a testament to the culmination of Japanese science and technology. Its predecessor was Japan's first nuclear-powered ship, "Mutsu." In 1997, it was reborn as a state-of-the-art research vessel powered primarily by a diesel engine, enabling observations in previously challenging conditions, such as extremely cold seas and rough weather. With a length of 128.5 meters and a weight of 8,706 tons, its size was also a weapon for ensuring stable data collection even in turbulent waves. 

Over 28 years, it traveled approximately 2.3 million kilometers (equivalent to 58 trips around the Earth). It made over 20 Arctic voyages, alerting the world to the severe reality of declining sea ice. In research that forecasts humanity's future—such as studies on climate change phenomena and global warming—it was recognized by scientists worldwide as a "floating ocean laboratory." 

Currently, construction is underway on "Mirai II," which is scheduled to take over the duties of Mirai, with completion aimed for around November this year.

New Development at YRP

https://corp.mobile.rakuten.co.jp/english/news/press/2023/0731_01/

Rakuten Mobile, Inc. and Yokosuka Telecom Research Park Co., Ltd. today opened a new RIC (RAN Intelligent Controller)*¹ research facility at the Yokosuka Research Park in Kanagawa Prefecture, Japan, with the aim of contributing to the further advancement of Open RAN (Radio Access Network) development.

Rakuten Mobile will conduct research and development (R&D) on RIC at the research facility, while Yokosuka Telecom Research Park will provide the research location, as the two companies aim to accelerate the advancement of Open RAN technologies. The research facility will be used to verify improvements in network efficiency, power saving and security enhancements by deploying emulators for RIC development, and using RICs to manage Rakuten Mobile's test RAN environment according to network usage conditions.

The research facility is equipped with a verification environment that uses Rakuten Mobile's fully virtualized cloud-native mobile network, allowing domestic and international telecommunications and communication service provider equipment manufacturers and other Rakuten Mobile partners to access the research facility remotely to verify Open RAN integration and conduct RIC proof-of-concept (PoC) testing*³. 

Yokosuka Telecom Research Park provides the infrastructure necessary for conducting demonstration experiments of next-generation telco technology at the Yokosuka Research Park. The RIC research facility will utilize this location for RIC research and development.

Soleil No Oka Park

There is a very nice and large park located on a bluff along the west coast of Yokosuka City.  It is called "Soleil no Oka", which can be translated as "Sunshine Hill".  The park has wide open green areas, fields of flowers, amusement facilities, restaurants, etc., and also a large (pay) parking lot. 

Its location is a bit off the beaten track, so to speak, but once you learn the way to get there, it is a quick and convenient drive. 

Of interest, one of the reasons why such an expansive park like Soliel No Oka exists in the otherwise-crowded Yokosuka & Miura Peninsula area, is due to the site's unique history.

Towards the end of World War II, in 1945, Japan's Imperial Navy decided to build an air base on top of the Nagai bluff, which was a strategic location overlooking the Pacific Ocean approaches to Sagami Bay.  So, a long runway, hangars, and other airfield buildings and facilities were built at Nagai Air Base.  Its mission was to launch aircraft (including "Kamikaze" bombers) defend Japan from U.S. & Allied forces trying to land on Japanese soil.  

But, as things turned out, Japan surrendered before that happened, so Nagai Air Base was never actually used for combat operations.  Instead, after being taken over by U.S. Occupation authorities, many wooden-frame, Western-style, dwellings were built there, as the Japanese naval air base was converted into the U.S. Navy's "Nagai Family Housing Area". 

Nagai was used by American military-associated families until 1983, when it was finally closed and returned to the government of Japan.  In the years that followed, it was eventually decided that the area would be converted into a park, and Soleil No Oka was built and then opened for business in April 2005.

Of note, here's a previous blog post about the park's history:

https://deepyokosuka.blogspot.com/search?q=nagai

Some Oppama History

The northernmost district of Yokosuka City, which borders Yokohama City is called "Oppama" (追浜).  It is place with an interesting history.  During the early 20th Century, the coastal area of Oppama was developed into a large air base for the Imperial Navy -- it became the birthplace of Japanese naval aviation.  Its official name was: "Yokosuka Naval Air Technical Arsenal".  After World War II, the airfield and facilities were taken over by U.S. Occupation Forces, and it was renamed Naval Air Station Oppama.  Following the Korean War, in the late-1950s, NAS Oppama was closed down and returned to the Government of Japan.  A few years later, in 1961, Nissan Automobile Corporation built a large factory on former air base land -- "Nissan Oppama" became a large part of Yokosuka's economy, with several thousand employees, and many other smaller supporting businesses & subcontractors.  Oppama train station is on the Keihin Kyuko line, just a few stops from Yokosuka Chuo station.  Nearby and stretching away from Oppama station is a large & vibrant traditional shopping street ("shoten-gai" 商店街) filled with small businesses, retailers, restaurants, etc.  Oppama also is the site of a popular summer festival and occasional night bazaars.

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追浜の歴史１ - すまい造りの佐野工務店 | 横須賀市追浜の工務店すまい造りの佐野工務店 | 横須賀市追浜の工務店

We spoke with Takeshi Aoki, who published 'A Tour of Oppama’s History' and served as the director of the Oppama Administrative Center in Yokosuka City. He is currently active as the head of the 'Aoki Juku,' organized by the Kanagawa Shimbun, to learn about the changes in the town of Oppama.

Tracing its history, Oppama is a treasure trove. Long ago, the coastline of Kanazawa and Oppama, with Nojima, Natsushima, and Eboshijima islands, was said to have been very scenic. Natsushima was inhabited by ancient Jomon people around 9,500 years ago, and the Natsushima Shell Mound, now a nationally designated historic site, still exists there. 

The beaches around Natsushima are where, a century ago, an Imperial Navy captain flew a French-made seaplane. Less known, but just before the Nissan Oppama Factory, the oldest ritual site called the 'Natagiri Ruins,' featuring a rare ox skull used for rain-making ceremonies during the Kofun period, has been discovered intact.

In the Muromachi period, the construction of temples began, and Nōei-ji Temple was founded in the first year of Ōei (1394). Behind Nōei-ji Temple is the Enokido Yokoana group from the Nara period, and the artifacts excavated there are displayed at the temple. Additionally, Jitoku-ji Temple was founded in the 14th year of Ōei (1406), and Hōfuku-ji Temple was also established around the time of the Ōnin War in the 2nd year of Bunmei (1470).

In the late Edo period, in the 6th year of Kaei (1853), the U.S. Perry Expedition anchored off Natsushima and even landed on the island to collect flora and fauna. At this time, Commodore Perry surveyed Yokosuka Bay and named Sasukehana Bay and Natsushima as Webster Island. 

Upon returning to America, having observed the skillfulness of the Japanese, he predicted that if the country ended its isolation and opened up, introducing technical expertise, Japan would become a nation capable of competing with Western countries in manufacturing in the future. With the advent of the Meiji era and the advancement of modernization, Perry's prediction was precisely realized, symbolized by the old Yokosuka Naval Air Corps and the Naval Aviation Arsenal in Oppama.

Yokosuka's "Mascot Character"

 Japan is famous around the world for its "soft power" and producing lots of comics (manga -- 漫画) and cartoons (anime -- アニメ).  In keeping with its imaginative & visual artistic culture, some Japanese agencies, groups, or businesses produce what are called "mascot characters" (マスコットキャラクター) as cute and approachable representatives of their organizations.  Like the masked & costumed actors at Disneyland, a mascot character is a cute, quirky figure created to represent a place, event, organization, or company -- usually to promote local pride, tourism, or branding. They are designed with simple, endearing features and often embody regional culture, history, or products.  The mascots embody the spirit of their region, acting as approachable ambassadors that connect people emotionally to a place or brand.  Of note, Yokosuka City Government has its own mascot character called: "SUKARIN" (スカリン -- see image below).  SUKARIN was created back in 2007 to commemorate the 100th anniversary of the city.  The design was chosen through a public contest.  It is said to be a fairy that came from the sea and its gender is unknown.  The name comes from a combination of Yokosuka (SUKA) and marine/sea (RIN).  SUKARIN's blue color is inspired by the sea of Yokosuka harbor -- and it wears a small sailboat as a hat.  SUKARIN is used and displayed in support of many activities, publications, and events in Yokosuka.