Chinese first robotic cargo spacecraft which docked to Tiangong-2 space station on April 22, 2017, performed recently another test rendezvous.
Spacecraft was launched from Wenchang Space Center LC-2 launch site on the top of the Long March 7 rocket over seven months after delivering Tiangong-2 to orbit on September 15, 2016.
After docking performed two days after launch, Tianzhou-1 performed series of tests covering connecting fueling and oxygen lines between vehicle and station and on June 20, 2017 it performed undocking, rendezvous and docking. Whole experiment lasted around 90 minutes. On the next day Tianzhou-1 undocked again and begun lasting 12 weeks mission on orbit to show its capabilities for prolonged tasks requiring independent flight control without any intervention from ground control centers. Mission also covered deploying nanosatellite from outer adapter - first in the history of Chinese space program release of the satellite in outer space by a host spacecraft.
After settling on 395 km orbit vehicle performed series of scientific experiments mainly from fluid physics in microgravity, non Newton gravitation and medicine. On August 1 at 07:03 UTC nanosatellite Silky Road was deployed. Spacecraft weighing 4.5 kg (10 cm x 10 cm x 30 cm) is first from the constellation of 30 remote sensing satellites prepared by Xi’an Institute of Surveying and Mapping in cooperation with the Chinese Academy of Sciences. This also marked closing end of solo mission of Tianzhou-1.
On September 12, 2017, Tianzhou begun rendezvous with Tiangong-2 remaining on 369.65 km x 369.65 km orbit at 09:24 UTC. Maneuver was similar to approaches of Shenzhou manned spacecraft planned for future short time missions (previous missions of Shenzhou finished with docking to Tiangong lasted two days). After series of engine burns Tianzhou reached distance of 52 km from station and initialize onboard guidance system. Automatic approach begun and after reaching distance of 5 km radar guidance system switched to optical, laser based mode. After reaching 400 m, 120 m and 30 m vehicle automatically paused approach to verify its position. From 30 m point Tianzhou-1 fired thrusters and begun to move slowly to docking port of Tiangong-2 to touch port with speed of 0.2 m/s at 15:58 UTC.
Last undocking and rendezvous is planned after another refuelling session. Tianzhou-1 emptied from propellant will be released from docking port to burn in atmosphere over Pacific later this year.