QINGDAO - Jiaolong, China's first manned deep-sea submersible, is scheduled to leave for a voyage in the northwest Pacific Ocean on June 25, according to oceanic authorities.

Its carrier, Xiangyanghong 09, left the eastern port city of Qingdao on Saturday. It will pick up Jiaolong from the city of Jiangyin, Jiangsu Province, according to the State Oceanic Administration (SOA)'s North China Sea Branch.

During the 40-day voyage, Jiaolong will conduct research on cobalt-rich crusts in the ocean and is expected to return in August, according to the SOA branch.

The branch has sent 45 members of staff on the mission. Most of them have been on previous Jiaolong missions.

Xiangyanghong 09, which has been service for more than 30 years, underwent thorough testing and maintenance before it set off.

In late November, the sub will leave for the southwest Indian Ocean to carry out scientific research on polymetallic sulfides. It is expected to return to China in March.

Jiaolong reached 7,062 meters in the Pacific's Mariana Trench in a dive in June 2012.

During a trial and exploration voyage from June to September 2013, it explored the South China Sea and the northeast and northwest of the Pacific, accomplishing 21 dives.

Scientists brought back 390 creatures from the seabed representing 71 species, including coral, sea cucumbers and sea anemones, as well as a number of samples including 161 polymetallic nodules, 32 rocks and 180 kg of sediment.