For the complete documentation index, see llms.txt.The Conjunction Data Message (CDM) is a standardized format for communicating close approach (conjunction) assessment data between spacecraft operators and tracking organizations. Each CDM represents a single conjunction event between two space objects and includes critical information for collision risk assessment.
Key Components
A CDM contains several distinct sections:- Header: General message metadata including format version, creation date, and originator information
- Relative Metadata/Data: Conjunction-specific information such as Time of Closest Approach (TCA), miss distance, relative speed, and collision probability
- Object Metadata: Identification and reference frame information for both objects involved in the conjunction
- Object Data: State vectors (position and velocity) and covariance matrices for each object, providing position uncertainty information
Critical Fields
- TCA (Time of Closest Approach): The UTC timestamp when the two objects are closest
- MISS_DISTANCE: Overall separation distance between objects at TCA (meters)
- COLLISION_PROBABILITY: Statistical probability of collision (0.0 to 1.0)
- RELATIVE_SPEED: Magnitude of relative velocity between objects (m/s)
- Covariance Matrices: Uncertainty ellipsoids for each object’s position
Complete definition of the CDM standard on CCSDS 508.0-B-1 guidelines.