CCSDS 508.0-R-1, Conjunction Data Message (Red Book, Issue 1 ...

DRAFT CCSDS RECOMMENDED STANDARD FOR CONJUNCTION DATA MESSAGESANNEX CCONJUNCTION INFORMATION DESCRIPTION(INFORMATIVE)C1RELATIVE DATATCA (Time of Closest Approach): The date and time of the predicted conjunction. Thistime tag is also the epoch of the relative state vector, Object1 and Object2 state vectors, aswell as the effective time of the covariance matrices for both Object1 and Object2.COLLISION_PROBABILITY: The probability that Object1 and Object2 will collide.COLLISION_PROBABILITY_METHOD: The method used to compute the valueassociated with the COLLISION_PROBABILITY keyword. Options are ‘FOSTER-1992’(see reference [D4]), ‘CHAN-1997’ (see reference [D8]), ‘PATERA-2001’ (see reference[D6]), ‘ALFANO-2005’ (see reference [D7]), or ‘OTHER’. If ‘OTHER’ is specified, a fullreference should be provided in CDM comments.MISS_DISTANCE: How close the two objects are going to be based upon the conjunctionassessment screening results.RELATIVE_SPEED: How fast the two objects are moving relative to each other at thetime of the predicted encounter.RELATIVE_POSITION/RELATIVE_VELOCITY: Object2’s position/velocity relativeto Object1’s position/velocity, calculated by taking the difference of the position and velocityvectors relative to the frame in which they are defined, with components expressed in theObject1-centered RTN coordinate frame at the time of closest approach.RTN Coordinate Frame: Object-centered coordinate system. The Object1-centered RTNcoordinate frame: R (Radial) is the unit vector in the radial direction, N (Normal) is the unitvector normal to the satellite’s inertial orbit plane (in the direction of the satellite’s angularmomentum), and T (Transverse) is the unit vector that completes the right-hand coordinateframe (see figure C-1).TVN Coordinate Frame: Object-centered coordinate system. The Object1-centered TVNcoordinate frame is defined as: V (Velocity) is the unit vector in the velocity direction, N(Normal) is the unit vector normal to the satellite’s inertial orbit plane (in the direction of thesatellite’s angular momentum), and T (Transverse) is the unit vector that completes the righthandcoordinate frame (see figure C-1).CCSDS 508.0-R-1 Page C-1 March 2012