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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →Satellite operators share orbit information with conjunction-assessment services, which screen predicted trajectories and send results—often as a Conjunction Data Message (CDM)—for the operator to evaluate. The message reports an assessed close approach; it does not order or execute a maneuver. The operator and mission team decide whether and how to respond.
The data chain: from orbit information to an operator’s decision
- Orbit data is exchanged. An operator, tracking service, or other authorized source provides information describing an object’s orbit. The data may be sent in a standardized Orbit Data Message (ODM) format.
- A service screens predicted trajectories. An assessment provider uses available orbit information to look for predicted close approaches. Some services also screen an operator’s predictive ephemeris—the operator’s predicted positions over time.
- The provider issues conjunction information. For an event, the provider can send a CDM containing assessment information associated with the predicted closest approach. The message gives the operator information to assess collision risk and, if needed, consider an avoidance maneuver.
- The operator evaluates the event and coordinates a response. The mission team reviews the event as new observations and orbit data arrive, and may share updated ephemerides or maneuver plans with the relevant service. The team—not the CDM—decides what action to take.
This separation matters: orbit data describes motion, a conjunction assessment characterizes a predicted event, and an operational decision determines whether to maneuver. A close-approach alert alone is not a maneuver instruction.
What the standard messages carry
The Consultative Committee for Space Data Systems (CCSDS) publishes the CDM as a standard format for exchanging spacecraft conjunction information among assessment originators, satellite owner/operators, and other authorized parties. CCSDS lists CDM Issue 1 as June 2013, with technical corrigenda through October 2021.
Orbit information can be exchanged through the ODM family. The Office of Space Commerce’s 2023 standards recommendations identify four message types:
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| Message | Expanded name | Role described in the Office of Space Commerce standards recommendations |
|---|---|---|
| OPM | Orbit Parameter Message | One of four ODM formats identified for orbit-data exchange supporting conjunction studies and other operational needs. |
| OMM | Orbit Mean-Elements Message | One of four ODM formats identified for orbit-data exchange supporting conjunction studies and other operational needs. |
| OEM | Orbit Ephemeris Message | One of four ODM formats identified for orbit-data exchange supporting conjunction studies and other operational needs. |
| OCM | Orbit Comprehensive Message | One of four ODM formats identified for orbit-data exchange supporting conjunction studies and other operational needs. |
The standards recommendations describe these exchanges as useful not only for conjunction studies, but also for tracking, navigation, orbit comparison, and other operational needs. A CDM, by contrast, carries conjunction-assessment information; it is not a substitute for the orbit data used to perform screening.
Format details can change by implementation. TraCSS CDM Specification version 2.1, published in 2025, described KVN, XML, and JSON encodings with the same information across formats. The NOAA Office of Space Commerce announced updated CDM, OMM, OCM, and catalog-format specifications on January 22, 2026. For current TraCSS implementation details, use that newer versioned specification rather than assuming the 2025 description is still the latest.
Who exchanges data with whom
There is no single global orbit-data source or conjunction provider. Services differ in their inputs, access policies, update cadence, supported formats, and operational arrangements; the examples below describe documented U.S. and European services, not a universal workflow.
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Space-Track and the 18th Space Defense Squadron
Space-Track documentation describes 18th Space Defense Squadron (18 SDS) services that screen operator-provided predictive ephemerides and return results in CDM format. Space-Track also provides operator resources including close-approach notifications, CDMs, example message formats, and maneuver-notification information. Its documentation says collision avoidance is the responsibility of the satellite owner/operator, while 18 SDS supports those efforts by screening predictive ephemerides and providing CDMs. This is the service’s description of its support, not a claim about a universal legal rule in every jurisdiction.
ESA’s conjunction assessment service
The European Space Agency (ESA) says it combines CDMs provided under a data-sharing agreement with U.S. Strategic Command and ESA’s own orbit data to analyze close approaches. Its service supports ESA missions and missions flown by other agencies. ESA describes a web interface through which flight-control teams, flight-dynamics teams, and mission managers can review event information and assessment history.
TraCSS and its pilot participants
TraCSS—the U.S. Department of Commerce’s Traffic Coordination System for Space—began accepting satellite owner/operator registrations directly through its webpage in early 2026. The NOAA Office of Space Commerce reported in August 2026 that 82 pilot user organizations representing more than 11,370 satellites and 10 national government accounts had onboarded. Those are dated program figures, not a permanent total or a measure of global coverage.
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How operators assess a changing close-approach risk
A predicted miss distance is only one part of collision-risk assessment. ESA says risk also depends on the sizes of the objects, flyby geometry, and orbit uncertainties for both objects. Its service updates predictions several times a day and provides event assessment history, so an event’s calculated risk can change as observations and orbit information are updated.
In practice, operators review the event’s time and geometry, miss distance, uncertainty information, and how the assessment has evolved. If a team is considering a maneuver, updated operator ephemerides or the proposed maneuver information may need to be shared with the assessment service so the predicted outcome can be evaluated. The precise workflow and data-sharing rules depend on the service and mission.
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1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsESA’s page “Automating collision avoidance” offers a historical, fleet-specific illustration of why assessment workload can be substantial: it described hundreds of alerts per week for a typical satellite in low Earth orbit, with about two alerts per week per satellite requiring detailed follow-up for ESA’s then-current fleet in those low-altitude orbits. The same page described a probability greater than typically 1 in 10,000 as a point at which ESA’s process called for teams to prepare a maneuver. These figures describe ESA’s context on that page, not a current universal alert rate or a threshold that operators everywhere should apply.
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How the assessment becomes an operational response
A CDM informs the mission team; it does not choose a maneuver. The operator may need to evaluate the evolving event with flight-dynamics specialists, flight controllers, and mission managers, then coordinate internally and with the relevant assessment provider. A planned maneuver can itself change the predicted encounter, which is why sharing updated orbit information and reviewing subsequent assessments can be part of the coordination process.
Services do not establish one common decision threshold or automatic maneuver rule. Operators should follow their responsible SSA provider’s procedures, current service policy, mission rules, and the applicable current message specification. The cited U.S. and ESA descriptions do not establish that every operator worldwide uses the same provider, agreement, access rules, formats, or coordination protocol.
What this means for satellite operators
- Know which service is assessing the event. Confirm its data inputs, update cadence, access policy, accepted formats, and support arrangements.
- Keep orbit information current. An assessment depends on available orbit data, and later observations can alter the predicted event.
- Read the assessment, not just the alert. Consider uncertainty, geometry, event timing, and assessment history alongside miss distance.
- Coordinate proposed actions through the mission process. Share updated ephemerides or maneuver information with the service when its workflow calls for it, and evaluate the resulting assessment with the mission team.
NOAA’s Office of Space Commerce also describes commercial conjunction-assessment screening services as a service category, alongside government programs. The available descriptions do not establish a universal ranking or imply that any one service is suitable for every mission; operators need to compare the service characteristics that matter to their own data and operating requirements.
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