Jiaolong,?China's first deep-sea submersible,?has undergone a series of upgrades and will head to the South China Sea and the Pacific Ocean in June for a series of dives.

Fu Wentao (left) is at the controls of China's deep-sea submersible Jiaolong last year. Fu took part in Jiaolong's dive to a record depth of 7,062 meters in June in the Mariana Trench. [Photo/Xinhua]

"Jiaolong is entering a trial period ahead of a busy schedule," said Liu Feng, director of the China National Deep Sea Center.

Liu said the first dive will be in the South China Sea in June, for scientific research, while the rest will likely be conducted in two areas in the western Pacific in July, pending approval by the International Seabed Authority for China's application to explore for cobalt-rich ferromanganese crusts.

A specialist team will monitor the performance of Jiaolong, or River Dragon, and carry out any upgrades as required, he added.

Jiaolong reached its record depth of 7,062 meters in the Mariana Trench in June, proving China's capacity to explore 99.8 percent of the world's ocean floor.

Liu, from the China National Deep Sea Center, said Jiaolong will play an important role in exploring the depths and enhancing our knowledge of what lies beneath.

After the submersible's missions last year, technicians made a series of changes, including adjusting the lighting for photography and ensuring sharper video images.

"These will all be tested out in our June dive in the South China Sea," Liu said.

That mission, he said, will also see scientists dive with oceanauts.

Jiaolong is about 8.2 meters long, 3 meters wide and 3.4 meters high, weighing nearly 22 metric tons and can hold three people.

After the South China Sea dive, the submersible will go to the Pacific to conduct a geological survey. It will also collect biological and mineral samples, conduct environmental studies and prepare for mining operations.

The China Ocean Mineral Resources Research and Development Association obtained sole exploration rights to prospect for pollymetallic nodules, rocks with iron deposits, in the east Pacific in 2001.

In February, the association got an initial green light to explore for cobalt-rich ferromanganese crusts in the west Pacific from the Legal and Technical Commission under the International Seabed Authority.

"These areas will be a long-term target zone for Jiaolong to study biological diversity and geological features," Liu said.

According to the country's 12th Five-Year Plan (2011-15), China will construct a 4,000-ton mothership for deep-sea submersibles and a vessel for ocean scientific research.

To speed up exploration, another submersible with a designed depth of 4,000 meters is also under construction.

Liu said China should research and develop a series of deep-sea submersibles that can operate at various depths.

He also called for international cooperation. "We are open to the world and welcome international scientists to join our operations.

"What we do is not cheap, no single person, institution, or even a country can bear the whole burden. Sharing experiences and facilities is the solution," he said.