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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Space situational awareness (SSA) is the information and analysis used to understand activity in orbit and protect spacecraft. To prevent collisions, operators use conjunction assessment: they compare a spacecraft’s predicted path with tracked objects, evaluate predicted close approaches, and decide whether to maneuver or take another mitigating action. A screening alert is a reason to assess risk—not proof that a collision will occur—and the spacecraft owner or operator retains the maneuver decision.
SSA and conjunction assessment are related, but not the same
SSA is the broader picture of the orbital environment. Conjunction assessment is the collision-risk workflow applied to a particular spacecraft: it looks for predicted close approaches between that asset and tracked objects. A conjunction means two predicted paths will pass near each other; it does not mean a collision is certain.
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Screening identifies potential encounters. Further risk analysis helps operators decide whether an encounter warrants action. NASA’s Conjunction Assessment Risk Analysis (CARA) describes automated trend information and analyst review for conjunctions considered high risk.
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- Prepare trajectory and operational information. NASA CARA describes using an owner/operator trajectory that includes planned maneuvers, alongside a separate trajectory based on non-cooperative tracking data that does not know about upcoming maneuvers. Timely trajectory and maneuver updates help make a predicted encounter meaningful: if the spacecraft’s planned path changes, the assessment needs to reflect that.
- Screen the spacecraft against tracked objects. A conjunction assessment compares the protected asset’s predicted trajectory with a catalog of tracked objects. The result is a set of potential close approaches for further consideration, not a list of certain collisions.
- Evaluate the encounter. Operators and supporting analysts assess whether a predicted approach presents enough risk to merit action. NASA CARA describes automated trend information and analyst review for high-risk cases. The sources cited here do not establish a universal probability threshold that every mission uses.
- Coordinate a response. The owner/operator weighs the assessment against mission constraints and decides whether to maneuver or take another mitigating action. U.S. Space Force doctrine, from November 2023, assigns maneuver decisions to spacecraft owners/operators; it describes USSPACECOM as supporting collision-avoidance efforts through predictive-ephemeris screening. NASA CARA describes its role as assisting with risk-mitigation planning and execution.
- Continue assessing. Collision avoidance is an operational process, not a one-time warning. Repeated screening and updated operational information help operators reassess an encounter as predicted trajectories and plans change.
Screening cadence depends on the service and orbit
The cited NASA materials describe different screening schedules in specific service contexts. They are not evidence that every operator worldwide receives the same coverage or cadence.
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| Service description | Screening cadence stated | Context |
|---|---|---|
| NASA overview of on-orbit conjunction assessment | Three times daily | The overview says the 18th Space Defense Squadron conducts the screenings. |
| NASA CARA service description | Three times daily for LEO spacecraft; twice daily for other spacecraft | These are the results-delivery frequencies CARA describes for its service. |
The cadence is only one part of a workflow. A service may screen trajectories, while risk assessment and analyst support are separate parts of the decision process. Operators should understand what a given service provides and what information it needs from them.
What operators should take from an alert
- A close-approach alert is not a collision prediction. It identifies a predicted encounter that needs interpretation.
- Operational data matters. Planned maneuvers and current trajectories affect how an encounter should be assessed.
- Screening supports, but does not make, the maneuver decision. Government screening and NASA support can inform the operator, who weighs mission constraints and chooses a response.
- There is no universal action threshold established here. Mission-specific procedures govern how an operator evaluates risk and decides when to act.
What the historical CDM dataset does—and does not—show
NASA CARA reports using more than 450,000 Conjunction Data Messages (CDMs) from 2015–2018 to evaluate whether machine-learning capabilities could enhance or augment collision-avoidance decision-making. That is a historical research dataset. It is not a current count of active conjunctions or tracked objects, nor a measure of how many collision warnings occur each year.
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Where commercial SSA services fit
In a NASA release dated December 15, 2020, then-NASA Administrator Jim Bridenstine said, “Now is the time for space operators to leverage innovative commercially available space situational awareness data, information, and analysis to mitigate the potential for in-orbit collisions and sustain key orbital regimes.” The statement identifies commercial SSA data and analysis as a possible resource; it does not replace the operator’s responsibility to assess mission needs and decide on mitigation.
For a deeper operational reference, NASA publishes a best-practices handbook on spacecraft conjunction assessment and collision avoidance. Its existence makes it a relevant technical reference for operators, but the cited material does not establish a specific retail edition or listing.
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