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

DRAFT CCSDS RECOMMENDED STANDARD FOR CONJUNCTION DATA MESSAGESCommonality Between RTN and TVNThe primary difference between the RTN and the TVN frames is that the RTN frame isanchored on the unit radial vector R, and the TVN frame is anchored on the unit velocityvector V. The unit normal vector N is the same vector for both the RTN and TVN frames.The unit transverse vector T completes the right-hand coordinate frame for both the RTN andTVN frames, but is not in the same direction for both frames. The TVN frame can beparticularly useful for analyzing elliptical orbits where the user would like one coordinateaxis to align with the velocity direction of motion. The RTN and TVN frames are the samewhen Object1 is at apoapsis, periapsis, or when its orbit is perfectly circular. Transformationsfrom EME2000, GCRF or ITRF to RTN or TVN should always use inertial velocities in thetransformation.NGeocentricRadius Vectorof VehicleDirection ofMotionNTObject1OrbitalPlaneVRTFigure C-1: Definition of the RTN and TVN Coordinate FramesSCREEN_VOLUME_SHAPE/SCREEN_VOLUME: Shape (ellipsoid or box) of thescreening volume used to screen the satellite catalog for possible conjunctors with Object1.The screening volume is the component size of the screening volume shape (in the Object1centered RTN or TVN reference frame).C2METADATAADDITIONAL_TRACKING: Information concerning whether additional sensor trackinghas been applied to the orbit determination of the object. Once a potential conjunction hasbeen determined, it is common practice to then use additional sensor resources wherepossible, beyond what is normally used, to better define the object’s orbit.CCSDS 508.0-R-1 Page C-2 March 2012