ISO 22644:2006 specifies two standard message formats for use in transferring spacecraft orbit information between space Agencies: the Orbit Parameter Message (OPM) and the Orbit Ephemeris Message (OEM). Such exchanges are used for
pre-flight planning for tracking or navigation support;
scheduling tracking support;
carrying out tracking operations (sometimes called metric predicts);
performing orbit comparisons;
carrying out navigation operations such as orbit propagation.
ISO 22644:2006 includes sets of requirements and criteria that the message formats have been designed to meet. For exchanges where these requirements do not capture the needs of the participating Agencies, another mechanism may be selected.