A passive satellite is a spacecraft designed to operate without onboard power, electronics, propulsion, or active control. It does not compute, transmit, or maneuver; instead, it performs its mission by reflecting signals or serving as a stable physical reference. In the case of laser-ranging missions, ground stations illuminate the object and measure the return signal with high precision.
For cybersecurity, passive satellites are important because they sharply reduce the spacecraft-side attack surface. With no mission software, embedded processors, or remote command interfaces, there is little onboard logic to exploit. But the risk does not disappear; it shifts to the ground segment. Timing systems, prediction files, station access, data pipelines, and analysis tools become the main targets for tampering, spoofing, or misconfiguration. Defenders use strong authentication, integrity checks, redundancy, and tightly controlled operational workflows to protect the measurement chain.