Hong Kong (CNN) – China successfully docked a second laboratory module to its under-construction space station, the China Manned Space Agency (CMSA) said Monday, as the country takes a step closer to completing its orbital outpost by the end of the year.
The Wentian module was launched atop a Long March 5B rocket from Hainan Island at 2:22 p.m. local time on Sunday.
Wentian, China’s largest ever spacecraft weighing 23 metric tons, is equipped with four scientific cabinets to conduct ecological and biotechnological experiments under varying gravity conditions. It also features a robotic arm for external experiments and an additional airlock for spacewalks.
The docking marks the penultimate phase in the construction of China’s ambitious three-module Tiangong space station project, which is slated to finish construction by late 2022.
Construction of the space station began in April last year, with the launch of the Tianhe module — the station’s main living quarters. In October, China is expected to launch a second laboratory module, known as Mengtian. The two laboratory modules will link-up to form a T-shaped structure, with Tianhe in the center.
Monday’s docking took place with three Chinese astronauts aboard the space station, who arrived in June on the Shenzhou 14 crewed mission.
The Tiangong space station is the world’s second operational orbital outpost, alongside the International Space Station (ISS).
Chinese astronauts have long been excluded from the ISS, due to US political objections and legislative restrictions. Russia, a longtime contributor to the ISS, has also left the project.
Last year, China was heavily criticized for its handling of space debris after it launched its first module on a Long March 5B rocket.
The remnants of the rocket made an uncontrolled re-entry to Earth and plunged into the Indian Ocean near the Maldives 10 days after the launch last May.