Who watches the sky?.

Every satellite operator faces the same basic problem: orbit is crowded, and you cannot avoid what you cannot see. Space situational awareness is the work of detecting objects in orbit with radars and telescopes, keeping a catalog of them, and calculating their future positions closely enough to tell when two of them will pass dangerously near each other. The scale of the task has grown sharply. The European Space Agency's Space Environment Report 2025 states that surveillance networks tracked roughly 39,000 to 40,000 objects, about 11,000 of them active payloads, while models estimate around 54,000 objects larger than 10 centimeters and roughly 1.2 million between 1 and 10 centimeters (ESA).

The output of all this tracking travels in a few standard formats. A two-line element set, or TLE, is a compact description of an object's orbit. An ephemeris is a table of an object's predicted positions over time. When a screening system finds that two objects will pass close, it issues a conjunction data message in a format standardized internationally by the Consultative Committee for Space Data Systems, so that warnings from different providers can be read the same way (Office of Space Commerce). The broader policy label for managing all of this traffic is space traffic management, or STM.

The key point for a non-specialist is that a collision warning is only as good as the data behind it. Registering that an object exists is not the same as continuously knowing where it is. That gap, between what is on paper and what is trackable in real time, is where much of the governance argument lives.

The oldest relevant instrument is the Convention on Registration of Objects Launched into Outer Space, which entered into force on 15 September 1976 (UNOOSA). It requires a launching state to keep a national registry and to furnish the United Nations with information such as an object's designator, launch date, general orbital parameters, and general function. It does not require sharing precise, continuously updated tracking data usable for collision avoidance, and in practice registration is often delayed or incomplete. So the treaty establishes that an object exists without establishing where, minute to minute, it is.

U.S. national policy tried to close part of that gap domestically. Space Policy Directive-3, signed on 18 June 2018, states that a civil agency, the Department of Commerce, should be responsible for the publicly releasable portion of the Defense Department catalog and administer an open architecture data repository; that basic U.S. Government-derived SSA data and basic STM services should be available free of direct user fees; and that the Secretary of Defense shall maintain the authoritative catalog of space objects (White House). The last clause matters: even in the policy that hands the civil job to Commerce, the definitive catalog stays with defense.

At the multilateral level the instruments are voluntary. The Committee on the Peaceful Uses of Outer Space adopted its Long-Term Sustainability Guidelines, a preamble plus 21 non-binding guidelines, in June 2019 (UN General Assembly, A/74/20). Several bear directly on data-sharing: they encourage enhancing the registration of space objects, exchanging updated contact information and information on orbital events, improving the accuracy and sharing of orbital data, promoting the sharing of space-debris monitoring information, and performing conjunction assessment during all controlled phases of flight (Space Generation Advisory Council). Alongside them, a UN Group of Governmental Experts established by General Assembly resolution 65/68, made up of experts from 15 countries, issued a consensus report on transparency and confidence-building measures dated 29 July 2013, recommending voluntary steps such as exchanging information on space policy and space objects and giving collision-avoidance notifications (UN General Assembly, A/68/189).

For years the practical global warning service ran out of the U.S. military. Space-track.org is hosted and maintained by the 18th Space Defense Squadron at Vandenberg Space Force Base, and it disseminates SSA data, including two-line element sets and conjunction data messages, to approved users worldwide, not only to U.S. government operators (U.S. Space Force). That made a military unit the de facto public catalog and collision-warning desk for much of the world's satellite fleet.

The civil replacement is the Traffic Coordination System for Space, or TraCSS, built by the Office of Space Commerce inside the Commerce Department to implement the open-architecture repository that Space Policy Directive-3 called for. TraCSS began delivering spaceflight-safety, meaning conjunction-screening, services on 30 September 2024, after receiving authority to operate from NOAA in August 2024; that first phase provided conjunction data messages for roughly 1,000 space objects six times daily to an initial group of about nine satellite operators (Office of Space Commerce). As of mid-2026 the Office of Space Commerce program page reported that the system had grown to dozens of pilot users and thousands of screened satellites, and had begun signing national government accounts including Australia, Brazil, Egypt, Finland, Germany, the Republic of Korea, and the United Kingdom (Office of Space Commerce).

The two systems run in parallel during the transition. According to the Office of Space Commerce's own FAQ, the intent is that the military will eventually stop routinely providing the spaceflight-safety services now available through TraCSS while continuing its national-security space operations (Office of Space Commerce). No firm cutover date has been published, so for now operators can draw on both the military desk and the civil one.

There is no single catalog that every state and company treats as authoritative, and there is no binding treaty that requires anyone to share the precise orbital positions a good warning needs. Commercial firms have built their own. Through the Office of Space Commerce's pathfinder projects, companies such as COMSPOC, LeoLabs, and Slingshot Aerospace maintain their own independent space-object catalogs (Office of Space Commerce). That means multiple, partly proprietary pictures of the same sky coexist, and they do not always agree about a given close approach.

The stakes are not hypothetical. On 10 February 2009 the active Iridium 33 and the derelict Russian Kosmos 2251 collided at about 789 kilometers altitude and a closing speed of roughly 11.7 kilometers per second; by July 2011 the U.S. Space Surveillance Network had catalogued more than 2,000 large debris fragments from the event (CelesTrak). Deliberate destruction adds more. On 15 November 2021 a Russian direct-ascent anti-satellite missile test destroyed the defunct Kosmos 1408, spreading debris across roughly 300 to 1,100 kilometers; the United States reported identifying about 1,500 trackable pieces, and the International Space Station crew sheltered during early debris passes (U.S. Space Command). Each such event permanently enlarges the catalog that everyone then has to screen against.

The workload scales with the catalog. As the number of tracked objects climbed into the tens of thousands, the daily volume of conjunction data messages generated by U.S. screening grew into the tens of thousands as well, according to operations descriptions from the 18th Space Defense Squadron (USU SmallSat Conference paper). More objects mean more warnings, more of which are false alarms, which raises the value of accurate, widely shared data and also the cost of getting it wrong.

One view holds that basic tracking data and collision warnings should come from a designated civilian government agency running an open, free repository, the model in Space Policy Directive-3 and TraCSS. Supporters, including many satellite operators who rely on free warnings, argue that traffic coordination is an inherently governmental safety function that should be civil-led rather than run by the military, and that a common government-anchored catalog reduces the confusion of competing proprietary ones; U.S. Senate appropriators used the 'inherently governmental' framing when they moved to restore TraCSS funding (SpacePolicyOnline). A competing view holds that commercial firms have already shown they can track objects and provide conjunction assessment, so government should minimize its role and rely on the private sector. This was the stated rationale of the U.S. FY2026 budget request to terminate most TraCSS funding, that the private sector could supply the services and the directive's intent had largely been met (Payload).

A third view starts from the fact that no single national catalog is universally trusted. On this account, transparency should be built through multilateral instruments, the voluntary Long-Term Sustainability Guidelines and confidence-building measures, and potentially an international coordination mechanism, so that no one state's data or framing dominates; advocates stress consensus soft law adopted at the Committee on the Peaceful Uses of Outer Space (UNOOSA). Cutting against all of these is a national-security caution: high-accuracy orbital data can reveal a satellite's sensor capabilities, maneuvers, and mission intent, so military and some government operators are wary of publishing precise ephemerides or maneuver plans. From that standpoint, keeping the authoritative catalog under defense control and limiting public release is a legitimate necessity, and Space Policy Directive-3 itself reserves the authoritative catalog to the Secretary of Defense (White House).

Running through the whole debate is an older split over whether transparency should be voluntary or legally binding. Some states hold that voluntary measures are the realistic, achievable path and that binding treaties are premature; others, under the long-running Prevention of an Arms Race in Outer Space agenda, argue voluntary measures are insufficient and that binding rules are needed. No consensus binding instrument on space transparency exists (UNODA). This explainer does not adjudicate among these positions; it sets them side by side.

The most immediate uncertainty is money. The U.S. FY2026 budget request proposed sharply cutting the Office of Space Commerce and terminating most TraCSS funding, reducing the office's roughly $65 million FY2025 level toward about $10 million, on the argument that the private sector could provide the services (SpacePolicyOnline). Congressional appropriators moved the other way, with the Senate mark providing about $60 million (SpaceNews). The final enacted figure is a matter for the signed appropriations law, but the direction of the fight is clear: the civil-agency model and the market model are being weighed against each other in real time.

The multilateral track continues in parallel. The Committee on the Peaceful Uses of Outer Space established a Working Group on the Long-Term Sustainability of Outer Space Activities in 2021 under a five-year mandate to help states implement the 2019 guidelines, identify emerging challenges, and consider possible additional ones (UNOOSA). Industry, for its part, has weighed in on continuity: a coalition representing more than 450 space, satellite, and defense companies petitioned Congress in July 2025 against the proposed cuts, arguing they would put commercial and government operators at risk (Via Satellite).

None of this resolves the underlying question of who should hold the coordinating role, or how much data those with the best data will actually share. The instruments encourage sharing; they do not compel it. The catalogs multiply; none is agreed to be definitive. That leaves a working system held together, for now, by a mix of a military desk, a young civil service, commercial providers, and voluntary guidelines, with no settled answer about which of them should anchor the whole.