Zombie satellites: wandering threats in orbit

In recent years, increasing attention has been paid to satellites orbiting Earth—not only to their active operations, but also to their defunct yet still “wandering” presence. These objects are often referred to as “zombie satellites.” But what exactly does this term mean, and why do they pose a real threat to functioning communication, military, or scientific satellites? In this article, we thoroughly examine the phenomenon, its causes, consequences, and potential future solutions. Additionally, we highlight a particularly fascinating historical case: an amateur Oscar satellite used by the Polish resistance during martial law.

What is a zombie satellite?

The term “zombie satellite” refers to spacecraft that are formally inactive or uncontrollable but continue to orbit the Earth, sometimes even emitting radio signals. These objects have lost their original functions due to technical faults, power supply failures, or software malfunctions. Most of these satellites were never decommissioned or deliberately converted into space debris and thus simply “remain in orbit.”

In some cases, zombie satellites reactivate, emit signals, or even interfere with specific frequencies. This can be critical if they affect communication or navigation bands.

Origin and history of the phenomenon

Since the launch of the first artificial satellite, Sputnik-1 (1957), the number of satellites in orbit has steadily increased. Over the decades, thousands of satellites have been launched, many of which are now inactive. The concept of zombie satellites gained attention in the 2000s when several satellites “resurrected,” meaning they began transmitting signals or interfering with frequencies after years of silence.

During the Cold War era, many abandoned or silent satellites remained in orbit and later began emitting various signals. These are often difficult to identify, and radio amateurs and space surveillance systems continuously work to map them.

How does a satellite become a zombie?

1. Power supply failures: If the satellite’s solar panels are damaged or obstructed by space debris, it may lose power, shutting down communication and onboard systems.

2. Software errors: Freezing, firmware bugs, or other software issues may render satellites uncontrollable. These faults are typically impossible to repair remotely.

3. Communication loss: If ground control loses contact with a satellite, it may become functionally dead, even if partially operational.

4. Orbital drift: Space gravitational effects, solar flares, and other anomalies can unpredictably alter orbits, posing collision risks.

What threats do zombie satellites pose?

• Physical collisions: Uncontrolled satellites can collide with active ones, causing catastrophic space accidents. A single collision may produce thousands of debris fragments, further increasing risks.

• Frequency interference: Active but uncontrolled satellites may interfere with military, navigation, or scientific communication channels.

• Navigation errors: Faulty or misleading signals can affect GPS and other systems, posing risks to aviation and maritime operations.

• False alarms: Military systems may misinterpret signals, perceiving them as threats and escalating diplomatic tensions.

Notable zombie satellite cases

• LES-5 (1967): Reactivated in 2020 after decades of silence, partially regaining functionality.

• Galaxy 15 (2010): Became uncontrollable yet continued transmitting signals, disrupting other satellites.

• NOAA-17: Caught fire before disintegrating, posing a significant hazard.

• Oscar satellite and the Polish resistance (1980s): During martial law, the Polish Solidarity movement and other resistance groups used an amateur Oscar satellite for clandestine communication. Though officially out of use, the satellite still relayed signals, helping to bypass the regime’s information blockade. This case illustrates how zombie satellites can occasionally serve positive roles under exceptional circumstances.

How are zombie satellites managed?

• International surveillance systems: Such as the Space Surveillance Network (SSN), which tracks space objects and reports anomalies.

• Automatic decommissioning: Some modern satellites feature pre-installed systems that terminate operations at end-of-life.

• Laser or robotic arm removal: These developing technologies aim to actively remove or neutralize defunct satellites.

• International collaboration: Transparency and shared data systems are increasingly important in managing space traffic.

Future trends and potential solutions

• Active debris removal missions: Initiatives like ClearSpace-1 and Astroscale aim to collect and remove defunct satellites from orbit.

• Autonomous self-destruct systems: Intelligent satellites capable of identifying malfunctions and initiating controlled deorbiting.

• International agreements: Standardized procedures and legal frameworks may help with long-term prevention and management.

Tips for radio amateurs

• Monitor unusual signals: Zombie satellites often display intermittent activity, offering unique observation opportunities.

• Use spectrum analyzers: Helpful in identifying anomalous frequencies.

• Report detections: Platforms like SatNOGS or Heavens-Above gather valuable global data.

Frequently asked questions

• How common are zombie satellites? – Increasingly frequent due to satellite constellations and mass launches.

• Do they re-enter the atmosphere? – Some do, but most remain in high or geostationary orbits.

• Can they be repaired? – In theory, yes, but only via costly and rare missions.

Zombie satellites represent a growing issue in the era of booming space activity. Humanity must maintain order not just on Earth, but in orbit as well. Science, technology, and international cooperation are key to mitigating these risks. The Polish Oscar satellite story also highlights the unpredictable legacy of space technology—what once seemed obsolete may find new purpose.