[MOIMS-NAV-EXEC] CCSDS 502.0-B-3: OMM Standard Clarifications

[Daniel Oltrogge]

Irene –

Thank you sincerely for your questions. The OMM is of special importance and criticality right now due to the exceedance of the “5 digit SSC numbers”, so many are switching to the OMM.

Responses below in BLUE.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Dan Oltrogge ▪ CSSI Director and Chief Scientist ▪ COMSPOC Corporation ▪ 719-482-4552<mailto:719-482-4552> ▪ dan at comspoc.com<mailto:dan at comspoc.com>


From: MOIMS-NAV-EXEC <moims-nav-exec-bounces at mailman.ccsds.org> On Behalf Of irene.caracciolo--- via MOIMS-NAV-EXEC
Sent: Wednesday, April 29, 2026 2:48 AM
To: moims-nav-exec at mailman.ccsds.org
Cc: Frederic.Schoutetens at dlr.de
Subject: [MOIMS-NAV-EXEC] CCSDS 502.0-B-3: OMM Standard Clarifications

Dear Navigation Working Group,
With the following email I would like to raise some questions regarding Chapter 4, sections 4.2.3 and 4.2.4 of the CCSDS 502.0-B-3 document.
Specifically, in Table 4-2 the MEAN_ELEMENT_THEORY keyword has the following examples: SGP, SGP4, SGP4-XP, DSST and USM, but in Table 4-3 the section dedicated to TLE Related Parameters is only required if MEAN_ELEMENT_THEORY = SGP/SGP4, which is not included as example in Table 4-2.
As noted in Table 4-2, the third column contains examples of theory, but this list is not exhaustive, meaning that someone else is free to create their own satellite theory. The intent of the “SGP/SGP4” reference was to signify “SGP or SGP4”. But furthermore, even that clarification would not be sufficient, because these TLE parameters are also relevant to SGP4-XP and PPT3, for example. So this has now been clarified in the attached proposed new versions of the documents as “SGP, SGP4, SGP4-XP, or PPT3”.

Moreover, this condition seems to be misleading when considering the BSTAR/BTERM and the MEAN_MOTION_DDOT/AGOM keywords, for which different conditions are defined in terms of MEAN_ELEMENT_THEORY. For instance:


  *   BSTAR or BTERM are required for MEAN_ELEMENT_THEORY =SGP4 and MEAN_ELEMENT_THEORY = SGP4-XP respectively (which are not considered in the main condition);

  *   MEAN_MOTION_DDOT or AGOM are requested only if MEAN_ELEMENT_THEORY=SGP or PPT3 and MEAN_ELEMENT_THEORY=SGP4-XP (which are not considered in the main condition).

This is not seen to be conflicting, as “This section is only required if MEAN_ELEMENT_THEORY is set to SGP, SGP4, SGP4-XP, or PPT3).” Is still correct; one needs to include this section, even if the parameters you list above are conditional on the theory selected.

These two cases raise the following doubts:

  1.  Should the TLE Related Parameters section be considered also if MEAN_ELEMENT_THEORY= SGP, SGP4, SGP4-XP, PPT3 ?

Yes, you are correct; the new amended text addresses this.


  1.  A) If not, should the BSTAR/BTERM and the MEAN_MOTION_DDOT/AGOM keywords be excluded from the section?

N/A


B) If yes, if MEAN_ELEMENT_THEORY=SGP or PPT3 should the BSTAR/BTERM be excluded? Same question goes for MEAN_MOTION_DDOT/AGOM if MEAN_ELEMENT_THEORY= SGP4.



These elements of information do not need to be excluded; they are simply ignored in any case. Added statements for all relevant terms to clarify, e.g., “NOTE: This keyword is unnecessary and shall be ignored if MEAN_ELEMENT_THEORY is set to SGP, SGP4, or PPT3.”

Thank you in advance for your assistance.

Kind regards,
Irene Caracciolo


——————————————————————————
Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)
German Aerospace Center
Space Operations and Astronaut Training | Spaceflight Technology | Münchener Str. 20 | 82234 Weßling | Germany

Irene Caracciolo | Flight Dynamics Services
Phone +49 8153 28 3017 | Mobile +39 392 6160389 | irene.caracciolo at dlr.de<mailto:irene.caracciolo at dlr.de>
DLR.de<http://www.dlr.de/>

DLR is represented by the Executive Board and employees authorised by it.
Head of DLR's legal department, Linder Hoehe, 51147 Cologne, can provide information (DLR.de/imprint<https://dlr.de/imprint>).

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