1. Some comments on the TLE problemetic Main point: the TLE are self consistent and need no other informations The only extrapolation program usable is SGP4 or SDP4 To include the TLE in the “CCSDS world “ there are two faces: the <form < = syntaxe ==  no problem The <physical content < = semantic  difficult (or impossible) to achieve In fact it depends on the accuracy needed and the extrapolation horizon. In any case the SGP4 and SDP4 models are mandatory so they must be well and ‘uniquely ‘ define in my opinion,the following pictures give the possible interfaces between ‘TLE world’ and ‘CCSDS world’

2. Mean orbital elements in TLE format Extrapolation only with SGP4 for low earth orbit SDP4 for deep earh orbit similar but in an other semantic to the keplerian elements only of OPM but in mean elements need only SGP4 or SDP4 results osculating elements in Thrue Of Date Position Velocity IDENTICAL to the osculating elements only of OPM FOR OPM WITH AND WITHOUT CHANGES need to Assume Concsistency with B* parameter and DRAG_AREA SOLAR_RAD_AREA DRAG_COEFF SOLAR_RAD_COEFF INPUT problem of propagation accuracy CCSDS WORLD

3. Mean orbital elements in TLE format Extrapolation only with SGP4 for low earth orbit SDP4 for deep earh orbit results osculating elements in Thrue Of Date Position Velocity identical to the osculating elements only of OEM FOR OEM without change Need to assume Concsistency with B* parameter and DRAG_AREA SOLAR_RAD_AREA DRAG_COEFF SOLAR_RAD_COEFF CCSDS WORLD

4. NEW OPM IN Mean orbital elements in TLE format OD using ephemeris as measurements only with SGP4 for low earth orbit OR SDP4 for deep earh orbit results Kind of mean elements in Thrue Of Date Position Velocity ( parameter B*…?) FOR A TLE LIKE OPM OR OEM Assume Concsistency with B* parameter and DRAG_AREA SOLAR_RAD_AREA DRAG_COEFF SOLAR_RAD_COEFF INPUT OSCULATING ELEMENTS EPHEMERIS GENERATION NEW OEM IN Mean orbital elements in TLE format