This document specifies four standard message formats for use in transferring spacecraft orbit information between space agencies and commercial or governmental spacecraft operators :  The Orbit Parameter Message (OPM), the Orbit Mean-Elements Message (OMM), the Orbit Ephemeris Message (OEM), and the Orbit Comprehensive Message (OCM).  Such exchanges are used for:


a)     pre-flight planning for tracking or navigation support;


b)    scheduling tracking support;


c)     carrying out tracking operations (sometimes called metric predicts);


d)    performing orbit comparisons;


e)     carrying out navigation operations such as orbit propagation and orbit reconstruction;