Space Force's 18th Space Defense Squadron maintains the US catalog of more than 47,000 tracked objects in orbit — active satellites, spent rocket bodies, and debris large enough for the Space Surveillance Network to see — and issues collision warnings to satellite operators, a mission that has grown from a back-office function into the military's busiest orbital service as commercial constellations added thousands of satellites.
This explainer covers how orbital traffic tracking actually works, who does what between the military, civil, and commercial sectors, and why the coordination model is under strain. It draws on Space Force and Office of Space Commerce documentation, Federal Communications Commission rules, and congressional research through 2025.
Why did orbital traffic become a problem?
Numbers explain it. Low Earth orbit held a few hundred active satellites for decades; by 2025, more than 11,000 active satellites were operating, the majority belonging to a single company's broadband constellation, which alone exceeded 7,000 spacecraft. Every new satellite adds conjunction risk — the possibility that two objects pass close enough to collide — and every collision adds debris, which adds risk permanently. The 2009 Iridium-Cosmos collision created more than 2,000 tracked fragments in one event, and Chinese and Russian antisatellite tests in 2007 and 2021 added thousands more, some still cataloged decades later. Analysts have long warned of a cascading debris scenario — where collisions generate debris that generates collisions — and while that cascade remains a warning rather than a documented trend, the growth curve that motivates it is on the public catalogs.
How does the tracking actually work?
The Space Surveillance Network — a mix of dedicated military radars and optical telescopes, the Space Fence radar in Kwajalein operational since 2020, and sensors contributed by other agencies and contractors — feeds observations to the 18th Space Defense Squadron at Vandenberg Space Force Base. The squadron maintains the catalog, screens every tracked object against every other, and sends conjunction assessment messages to operators when a close approach warrants it. The service is free and global: commercial and foreign operators alike receive warnings through Space-Track. What the military does not do is maneuver anyone's satellites; operators decide and execute their own avoidance moves, and file post-maneuver data back into the system. SpaceX's regulatory filings have documented tens of thousands of avoidance maneuvers by its constellation in six-month periods — automation at a scale the manual screening model was never designed for.
Who is supposed to coordinate traffic — military or civil?
Policy has bounced. Presidential policy since 2018 assigned civil space traffic coordination to the Commerce Department, whose Office of Space Commerce began building the Traffic Coordination System for Space — TraCSS — to take over civil conjunction warnings from the military, with initial releases to operators starting in 2024. The logic: the military should focus on defense, while a civil agency coordinates traffic without defense sensitivities limiting data sharing. The Trump administration in 2025 announced plans to shift TraCSS functions toward the Transportation Department, a move critics in Congress questioned and supporters framed as fitting traffic management with other transportation regulators. Through the transition, the Pentagon remains the operator of the only complete catalog, which means every civil and commercial scheme still runs on Space Force data.
| Actor | Role on the record | Constraint |
|---|---|---|
| Space Force (18 SDS) | Catalog, conjunction warnings via Space-Track | Defense mission limits data sharing |
| Office of Space Commerce | TraCSS civil coordination pilot | Transition announced 2025 |
| FCC | Five-year post-mission disposal rule (2022) | Licenses US operators only |
| Commercial SSA firms | Independent tracking, data sales to DoD | No regulatory authority |
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Are there rules of the road in orbit?
No binding traffic law exists, and the gap shapes everything else. Maneuver responsibility in a close approach is settled bilaterally — usually by operator-to-operator communication, since both parties can see the conjunction data — but there is no equivalent of maritime right-of-way, no license to operate withdrawn for reckless maneuvering, and no international body empowered to direct avoidance. What exists instead is a patchwork: the FCC's 2022 order requiring US-licensed satellites in low Earth orbit to deorbit within five years of mission end; the United Nations' non-binding long-term sustainability guidelines; national debris-mitigation standards that most launch regulators enforce through licensing; and the growing practice of commercial tracking firms publishing independent conjunction data. For constellations, the practical rules are internal: each large operator writes its own avoidance logic and coordination agreements with neighbors, which regulators have scrutinized in licensing rounds. The absence of binding rules is precisely why catalog ownership matters so much — whoever maintains the authoritative tracking data holds the only shared reference every operator accepts, and that is the position the US catalog has occupied for most of the space age.
How big is the debris problem now?
The European Space Agency's periodic environment reports supply the standard figures: roughly 40,000 objects tracked by surveillance networks worldwide, around 1.1 million fragments larger than one centimeter estimated in orbit — each capable of disabling a satellite on impact at orbital speeds — and on the order of 130 million particles above one millimeter that shields can absorb but optics cannot tolerate. Most of the mass sits in low Earth orbit between 700 and 1,000 kilometers, an altitude where drag takes centuries to clean up and where the largest constellations operate just below. The documented removal record is thin: no large derelict rocket body has been removed by a commercial mission at scale, and the first dedicated debris-removal demonstrations — national and commercial — reached orbit in the mid-2020s as technology demonstrations rather than services. Modeling by NASA's orbital debris program has long shown that even with zero new launches, existing collisions would generate new debris in certain altitude bands, the mechanism behind the cascade scenario analysts cite. That is why disposal rules and catalog screening, unglamorous as they are, carry the preventive load while removal capability matures.
What does this change?
The traffic mission is quietly reshaping Space Force acquisitions: budget documents since 2023 shift money toward commercial SSA data purchases, proliferated sensing, and automation of conjunction screening — an acknowledgment that human analysts cannot scale with the catalog. The markers to watch: whether TraCSS completes its transition and actually relieves the military of civil coordination, whether international norms on maneuver coordination and disposal harden beyond the FCC's five-year rule, and whether the catalog's growth curve forces automation faster than it can be fielded. The documented trend line points one direction — more objects, more maneuvers, more reliance on machine-speed decisions — and every institution named here is still built for a slower sky.