Some Shijian-series satellites have drawn significant concerns from the United States government and space observers who cite unannounced launches, undisclosed sub-satellites deployed in orbit, unusual orbital maneuvers, and demonstrated rendezvous proximity operations (RPO) including the close inspection and towing of other satellites.

Observers question the robotic arm's dual-purposes for space debris cleanup and kinetic attacks against adversary satellites.

These varied positions have ranged from 37.7°E over Africa to 180°E over the Marshall Islands, uncharacteristic of other satellites designed for communications.

[11][12][13] Shijian-17's robotic arm also earned mentions in the U.S. Office of the Secretary of Defense's congressionally-mandated Annual Report to Congress: Military and Security Developments involving the People's Republic of China.

The satellite incorporated a high-thrust ion propulsion system, a large trussed structure and a higher payload capacity.

The satellite would operate at the Ka band with 70 Gb/s capacity, capable of providing broadband internet to whole mainland China.

SJ-21 drew further suspicion in January 2022 when, according to commercial space monitoring firm ExoAnalytic Solutions, SJ-21 went "missing" from its orbital slot to dock with defunct Beidou G2 (Compass G2) navigation satellite capitalizing on the inability of optical satellites to track space-objects during the day.

[28][29][30] Many observers suspect the spacecraft, like many of China's Yaogan and Gaofen satellites, serve primarily military purposes under the cover of more mundane missions.

[31][32] With SJ-21's demonstrate capability to tug satellites from their orbit and China's increasing interest in space power, the spacecraft likely also offers the Chinese government a tool for counterspace operations.

[25][26][33][29] Victoria Samson, the Washington Office director for the Secure World Foundation said "You could look at China working to develop the capability to remove inactive satellites on orbit as a way in which it is being a responsible space actor and cleaning up debris that it caused.

"[29][34] Samson also praised commercial space situational awareness (SSA) providers for presenting the public and academia with satellite tracking capabilities previously exclusive to government.