HELSINKI — China’s Tianzhou-4 cargo spacecraft released a small satellite after its departure from the Tiangong space station and ahead of its controlled deorbiting.

The release of the Zhixing-3A satellite was not announced by the Tianzhou spacecraft operators, but was revealed by the satellite developers and its service providers and later tracked in orbit by the U.S. Space Force’s 18th Space Defense Squadron, which focuses on space domain awareness.

Tianzhou-4 launched May 9 on a Long March 7 rocket from China’s coastal Wenchang spaceport and docked with the orbiting Tianhe core module seven hours later. The mission delivered around 6 tons of supplies to support the scheduled Shenzhou-14 crewed mission which followed in early June.

After completing its primary mission the freighter undocked from the completed, three-module Tiangong at 1:55 a.m Eastern Nov. 9, making way for the subsequent Tianzhou-5 cargo mission to dock at the station. Tianzhou-4 was then deorbited over the South Pacific at 6:21 p.m. Eastern, Nov. 15, according to China’s human spaceflight agency, CMSA.

Zhixing-3A, which CMSA had stated in April was to fly aboard Tianzhou-5, was deployed into orbit from Tianzhou-4 at 5:02 a.m. Eastern Nov. 13, after 188 days in storage and a day ahead of Tianzhou-4’s deorbiting. 

The satellite was released from a cubesat deployer developed by the China Academy of Space Technology (CAST), the main spacecraft maker under the China Aerospace Science and Technology Corporation (CASC) and manufacturer of Tianzhou spacecraft.

The deployment was initially revealed by a commercial space firm Emposat (Hangtian Yuxing), which provides commercial satellite telemetry, tracking, and control services, with a network including facilities in China, Argentina, France, Kenya, South Africa, Samoa and more.

Emposat reported a first uplink from its station in Azerbaijan shortly after deployment, with a first downlink in Xinjiang, west China, minutes later.

Days later, 18th SDS cataloged Zhixing-3A as NORAD 54245, tracking the satellite in a 375 x 396-kilometer orbit with an inclination of 41.5 degrees.

The satellite was developed by commercial firm Beijing Smart Satellite Space Technology Co., Ltd. The firm announced the remote sensing and radio software satellite was operational on Nov. 25 after completing on-orbit testing. 

Smart Satellite is planning a constellation of X-band synthetic aperture radar satellites. In July last year it signed a related agreement with 12th Institute of the China Electronics Technology Group (CETC), a domestic leader in microwave electron vacuum devices. 

Emposat also provides on-orbit collision warning and space situational awareness services. The requirement for such commercial services was effectively codified in a “notice on promoting the orderly development of small satellites” (Chinese) issued in May 2021, stating that small satellites developed in China should be capable of collision avoidance maneuvers and end-of-lifetime deorbiting. Chinese satellite propulsion startups have also emerged as plans for commercial constellations grow.

Tianzhou-5, launched earlier this month to supply the newly-arrived Shenzhou-15 crewed mission, also carried a number of cubesats to orbit. 

The Tiangong space station’s new Mengtian experiment module has a payload airlock which will allow the small, 5.2-meter-long robotic arm launched with the Wentian module to grasp science experiments and install them on payload adapters on the outside of the module. The on-orbit release mechanism can deploy small spacecraft or CubeSats of up to 100 kilograms into orbit.

Andrew Jones covers China's space industry for SpaceNews. Andrew has previously lived in China and reported from major space conferences there. Based in Helsinki, Finland, he has written for National Geographic, New Scientist, Smithsonian Magazine, Sky...