Space traffic management: Who has the right of way in space?

The number of satellites in orbit is growing rapidly, bringing with it an increased risk of collisions between operators that do not always share common rules or procedures. This essay explores why space traffic management will be essential to ensuring the safe and sustainable use of space in the decades ahead.

Monday morning. You head down to the garage to drive to the office. As you come up the ramp, you meet one of your neighbors. No problem—you’ve already agreed that he’ll yield. As you pull out of the structure, you come across a car from the building next door, where a similar arrangement is in place.

A little farther down the road, the situation changes. An unfamiliar car is coming straight toward you in your lane. You don’t know each other, there’s no agreement, and no traffic authority to tell you who should give way. Both of you stop, roll down your windows, and decide who will move aside.

Now imagine the same situation, except neither car can stop. While you’re figuring out what to do, both vehicles keep moving toward each other. And to make matters worse, you’re both blindfolded, relying entirely on guidance from traffic controllers who know where every other vehicle is and where it’s heading.

Something similar is happening in space today. Thousands of satellites orbit Earth without a clear and internationally accepted set of rules to coordinate space traffic efficiently and predictably. Addressing this challenge is precisely the goal of what is known as space traffic management (STM).

Operational satellites must also share orbital space with vast amounts of debris: defunct satellites, remnants of launch vehicles, and fragments generated by explosions or collisions. Altogether, more than 16,000 tons of human-made objects are currently orbiting Earth.

The eyes of space traffic

For this coordination to be possible, satellite operators need to know what objects surround them and how their trajectories will shift over time. That’s precisely the role of space surveillance and tracking (SST) systems. In Europe, this responsibility falls to EU Space Surveillance and Tracking (EU SST), which operates, among other capabilities, two collision-warning centers: one in Spain and one in France. Working in coordination, these centers provide services to hundreds of operational satellites around the world.

Under contract with the Spanish Space Agency and with funding from EU SST, GMV operates and maintains the Spanish Space Surveillance and Tracking Operations Center (S3TOC).

When debris was the problem

Until little more than a decade ago, between 2,000 and 3,000 operational satellites shared orbit with space debris. The situation was far from ideal, particularly because of the countless fragments too small to be routinely tracked yet large enough to destroy a satellite on impact.

Much of the concern centered on the well-known Kessler effect: a chain reaction in which each collision generates new debris, which in turn leads to further collisions.

While the Kessler effect remains a threat, coordinating traffic was relatively straightforward. Most risks came from non-maneuverable objects, and collision alerts involving two maneuverable satellites were rare. Returning to our morning commute: if there’s a rock in the middle of the road, it’s not going to move, so it’s obvious who needs to steer around it.

The rise of satellite constellations

The deployment of large constellations for communications and Earth observation has driven exponential growth in the number of satellites, particularly in low Earth orbit (LEO). Today, there are around 16,000 satellites in orbit, more than 12,000 of them operating in LEO.

For those of us who work in this field every day, the changes of the past few years have been impossible to miss. Encounters involving two maneuverable satellites have gone from rarity to everyday occurrence.

In some cases, the situation is simple. The operators know each other, communication channels are well established, or prior agreements are already in place regarding who should maneuver. Coordination can then be handled quickly and efficiently.

But there are also far more complex situations. The operator of a satellite may be unknown, there may be no operational point of contact, or there may be no information available about the satellite’s ability to maneuver. Who should move? What happens if both satellites maneuver? What if neither does?

This lack of transparency increases uncertainty and heightens the perception of risk in an environment of growing economic and strategic importance.

Current projections suggest that this trend will continue throughout the coming decade. Various estimates place the number of satellites in orbit in the tens of thousands within the next few years, while international efforts to curb the generation of new debris could help stabilize its growth.

From traffic surveillance to traffic management

If that happens, the dominant challenge will no longer be satellites avoiding space debris, but tens of thousands of satellites coordinating their movements with one another.

All of this reinforces the need to move toward a true STM framework: a set of rules, procedures, and coordination mechanisms that enable safe and sustainable operations in an increasingly congested environment.

Let’s return to the driver in our story. On a crowded road, no one questions the need for traffic signs, rules, and coordination mechanisms. Road safety would be impossible without them.

The good news is that there is growing international recognition of the urgency of addressing this challenge. The United Nations, standards bodies such as ISO, and a range of initiatives promoted by the European Union, including the EU Space Act, are already working to build common frameworks. At the same time, strides are being made on the technical front through comparison exercises involving different service providers, such as those conducted between EU SST and its U.S. counterpart, the Traffic Coordination System for Space (TraCSS).

STM is following the same path already taken by road, maritime, and air traffic. The difference is that in space there are no sovereign boundaries, vehicles travel at nearly 28,000 kilometers per hour, and a single wrong decision can create fragments that remain in orbit for decades. Reaching international agreements on how to manage space traffic is no longer a challenge for the future. It’s a necessity if space is to remain a safe, sustainable, and accessible environment for all.

Author: María Antonia Ramos