ISO 26900:2024

Space data and information transfer systems - Orbit data messages

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; f) assessing mutual physical and electromagnetic interference among satellites orbiting the same celestial body (primarily Earth, Moon, and Mars at present); g) performing orbit conjunction (collision avoidance) studies; and h) developing and executing collaborative maneuvers to mitigate interference or enhance mutual operations. This document includes sets of requirements and criteria that the message formats have been designed to meet. For exchanges in which these requirements do not capture the needs of the participating agencies and satellite operators, another mechanism may be selected. This document is an international standard published under the auspices of CCSDS and International Standards Organization (ISO) Technical Committee 20, Subcommittee 13, developed jointly and in concert with the ISO TC20/SC14. As such, this CCSDS standard is also properly labeled as ISO 26900. The recommended Orbit Data Message format is ASCII (reference REF R_ISO_IEC_8859_1_1998 \h [4] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000001600000052005F00490053004F005F004900450043005F0038003800350039005F0031005F0031003900390038000000 ). This document describes both ‘Keyword = Value Notation’ (KVN) as well as Extensible Markup Language (XML) (reference REF R_505x0b3XMLSpecificationforNavigationDa \h[5] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000002800000052005F00350030003500780030006200330058004D004C00530070006500630069006600690063006100740069006F006E0066006F0072004E0061007600690067006100740069006F006E0044000000 ) formatted messages. Selection of KVN or XML format should be mutually agreed between message exchange partners. NOTE – As currently specified, an OPM, OMM, or OEM file is to represent orbit data for a single spacecraft, and the OCM is to represent orbit data for either a single spacecraft or single parent spacecraft of a parent/child spacecraft deployment scenario. It is possible that the architecture may support multiple spacecraft per file; this could be considered in the future.

Systèmes de transfert des informations et données spatiales — Messages pour données d'orbites

General Information

• Status: Published
• Publication Date: 08-Feb-2024
• ICS: 49.140 - Space systems and operations
• Technical Committee: ISO/TC 20/SC 14 - Space systems and operations
• Drafting Committee: ISO/TC 20/SC 14 - Space systems and operations
• Current Stage: 6060 - International Standard published
• Start Date: 09-Feb-2024
• Due Date: 24-Aug-2024
• Completion Date: 09-Feb-2024

Relations

• Consolidates: ISO/IEC 29121:2018 - Information technology - Digitally recorded media for information interchange and storage - Data migration method for optical disks for long-term data storage
• Effective Date: 03-Dec-2022
• Revises: ISO 26900:2012 - Space data and information transfer systems - Orbit data messages
• Effective Date: 27-Aug-2022

Overview

ISO 26900:2024 - “Space data and information transfer systems - Orbit data messages” - defines standardized message formats for exchanging spacecraft orbit information. Published jointly as a CCSDS recommended standard (CCSDS 502.0-B-3), ISO 26900:2024 specifies four orbit data message types: Orbit Parameter Message (OPM), Orbit Mean‑Elements Message (OMM), Orbit Ephemeris Message (OEM), and Orbit Comprehensive Message (OCM). The standard supports both Keyword = Value Notation (KVN) and XML encodings (recommended ASCII/ISO‑8859‑1), with format choice agreed by exchange partners.

Key topics and technical requirements

• Standard message types: OPM, OMM, OEM for single-spacecraft orbit data; OCM for single spacecraft or a parent spacecraft in deployment scenarios.
• Message content & structure: defined header, metadata and data sections; mandatory and optional keywords; units and time tags.
• Support for operational needs: orbit states (cartesian/Keplerian), ephemeris time histories, accelerations, maneuvers, covariance matrices and uncertainty representations.
• Identification & tracking: MESSAGE_ID and other metadata fields for message annotation and traceability.
• Syntax & validation: KVN rules, ODM/XML schema, and validation guidance including regular-expression (regex) patterns for ingest and conformance checking.
• Interoperability: normative keyword values registry (SANA Registry) to harmonize vocabulary and reduce ambiguity across agencies and operators.
• Encoding & file handling: recommended ASCII (ISO‑8859‑1) encoding; guidance on aggregating multiple ODMs into navigation message files.
• 2024 edition updates: addition of OCM, MESSAGE_ID field, updated EPHEMERIS_TYPE values, and parameter pairings (e.g., BSTAR/BTERM) to support SGP/SGP4 and SGP4-XP propagators.

Applications and who uses it

ISO 26900:2024 is aimed at organizations that create, exchange or consume orbit data messages:

• Space agencies and mission operators for planning, tracking, and navigation support.
• Ground segment and tracking networks for scheduling and conducting metric predicts.
• Flight dynamics teams for orbit propagation, orbit reconstruction and maneuver planning.
• Space situational awareness (SSA) and collision-avoidance/conjunction-analysis teams performing conjunction studies and risk assessments.
• Commercial satellite operators and service providers collaborating on multi-operator operations (e.g., coordinated maneuvers, interference mitigation).

Practical uses include pre‑flight planning, scheduling tracking support, performing orbit comparisons, executing collaborative maneuvers, and exchanging ephemerides for collision avoidance.

Related standards and resources

• CCSDS Recommended Standards (this document is CCSDS 502.0-B-3).
• ODM normative keyword values published at the SANA Registry (https://sanaregistry.org/r/navigation_standard_normative_annexes/).
• Encoding reference: ISO/IEC 8859‑1 (ASCII/Latin‑1) recommended for KVN files.

ISO 26900:2024 enables reliable, interoperable orbit data exchange across international and commercial space stakeholders, reducing ambiguity and improving operational coordination.

Standards Content (Sample)

International
Standard
ISO 26900
Second edition
Space data and information transfer
2024-02
systems — Orbit data messages
Systèmes de transfert des informations et données spatiales —
Messages pour données d'orbites
Reference number
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of
(a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice
of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
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For an explanation of the voluntary nature of standards, the meaning of ISO specific terms
and expressions related to conformity assessment, as well as information about ISO's adherence
to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by the Consultative Committee for Space Data Systems (CCSDS) (as CCSDS
502.0-B-3, Apil 2023) and drafted in accordance with its editorial rules. It was assigned to Technical
Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee SC 14, Space systems and operations and
adopted under the “fast-track procedure”.
This second edition cancels and replaces the first edition (ISO 26900:2012), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Changes in the messages:
— The OCM was added to provide better support for ISO Technical Committee 20, Subcommittee 14
objectives (see section 6).
— MESSAGE_ID was added to the OPM, OMM, and OEM to provide better satisfaction of
requirement P10 (identification and annotation of messages).
— EPHEMERIS_TYPE was updated in the OMM to reflect currently used numbering scheme.
— BSTAR and MEAN_MOTION_DDOT fields are paired with BTERM and AGOM parameters to
support the SGP and SGP4 propagators as well as the new SGP4-XP propagator, respectively.

iii
— Changes in the document:
— A new CCSDS repository for normative keyword values for navigation messages has
been created at the SANA Registry, accessible on the Internet at:
https://sanaregistry.org/r/navigation_standard_normative_annexes/. (See annex B for details
on the affected keywords and links to the content.)
— Several annexes were added. Some are required by CCSDS rule changes, and some are for the
provision of supplementary material.
— Examples for OPM, OMM, and OEM that formerly appeared in sections 3, 4, and 5, respectively,
have been moved to an informative annex.
— The ‘Checklist ICD’ that was added in ODM Version 2 has been discontinued. This Checklist ICD,
intended to convey information that the OPM, OEM, and OMM did not address, such as third-
body perturbations, solar pressure model, solid tides, ocean tides, Earth albedo, and polar
motion, has now been replaced by the material that can be specified in the Orbit Comprehensive
Message.
Any feedback or questions on this document should be directed to the user’s national standards body.
A complete listing of these bodies can be found at www.iso.org/members.html.

iv
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
CONTENTS
Section Page
1 INTRODUCTION . 1-1
1.1 PURPOSE AND SCOPE . 1-1
1.2 APPLICABILITY . 1-2
1.3 RATIONALE . 1-2
1.4 DOCUMENT STRUCTURE . 1-2
1.5 CONVENTIONS AND DEFINITIONS . 1-3
1.6 REFERENCES . 1-5
2 OVERVIEW . 2-1
2.1 ORBIT PARAMETER MESSAGE . 2-1
2.2 ORBIT MEAN-ELEMENTS MESSAGE . 2-1
2.3 ORBIT EPHEMERIS MESSAGE . 2-2
2.4 ORBIT COMPREHENSIVE MESSAGE . 2-2
2.5 EXCHANGE OF MULTIPLE MESSAGES . 2-3
2.6 DEFINITIONS . 2-3
3 ORBIT PARAMETER MESSAGE . 3-1
3.1 GENERAL . 3-1
3.2 OPM CONTENT/STRUCTURE . 3-2
4 ORBIT MEAN-ELEMENTS MESSAGE . 4-1
4.1 GENERAL . 4-1
4.2 OMM CONTENT/STRUCTURE . 4-2
5 ORBIT EPHEMERIS MESSAGE . 5-1
5.1 GENERAL . 5-1
5.2 OEM CONTENT/STRUCTURE . 5-1
6 ORBIT COMPREHENSIVE MESSAGE . 6-1
6.1 GENERAL . 6-1
6.2 OCM STRUCTURE AND OVERARCHING REQUIREMENTS . 6-2
7 ORBIT DATA MESSAGE SYNTAX . 7-1
7.1 OVERVIEW . 7-1
7.2 GENERAL . 7-1
CCSDS 502.0-B-3 Page v April 2023

v
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
CONTENTS (continued)
Section Page
7.3 ODM LINES . 7-1
7.4 ORBIT DATA MESSAGES IN ‘KEYWORD = VALUE NOTATION’
(I.E., NON-XML) AND ORDER OF ASSIGNMENT STATEMENTS . 7-2
7.5 VALUES . 7-3
7.6 OCM VECTOR DATA TYPE. 7-4
7.7 UNITS IN THE ORBIT DATA MESSAGES . 7-5
7.8 COMMENTS IN THE ORBIT DATA MESSAGES . 7-6
7.9 ORBIT DATA MESSAGE KEYWORDS . 7-8
7.10 VALIDATION AND INGEST OF KVN CONTENT VIA REGULAR
EXPRESSIONS (OR ‘REGEX’) . 7-9
8 CONSTRUCTING AN ODM/XML INSTANCE. 8-1
8.1 OVERVIEW . 8-1
8.2 XML VERSION. 8-2
8.3 BEGINNING THE INSTANTIATION: ROOT ELEMENT TAG . 8-2
8.4 THE STANDARD ODM/XML HEADER SECTION . 8-3
8.5 THE ODM/XML BODY SECTION . 8-4
8.6 THE ODM/XML METADATA SECTION . 8-4
8.7 THE ODM/XML DATA SECTION . 8-4
8.8 CREATING AN OPM INSTANTIATION . 8-5
8.9 CREATING AN OMM INSTANTIATION . 8-6
8.10 CREATING AN OEM INSTANTIATION . 8-8
8.11 CREATING AN OCM INSTANTIATION . 8-10
8.12 CREATING A COMBINED INSTANTIATION . 8-13
8.13 SPECIAL SYNTAX RULES FOR ODM/XML. 8-16
ANNEX A IMPLEMENTATION CONFORMANCE STATEMENT
PROFORMA (NORMATIVE) . A-1
ANNEX B VALUES FOR SELECTED KEYWORDS (NORMATIVE) . B-1
ANNEX C SECURITY, SANA, AND PATENT CONSIDERATIONS
(INFORMATIVE) . C-1
ANNEX D ABBREVIATIONS AND ACRONYMS (INFORMATIVE) . D-1
ANNEX E RATIONALE FOR THIS STANDARD (INFORMATIVE) . E-1
ANNEX F TECHNICAL MATERIAL AND CONVENTIONS FOR
ODM DATA (INFORMATIVE) . F-1
ANNEX G ODM EXAMPLES (INFORMATIVE) . G-1
ANNEX H INFORMATIVE REFERENCES (INFORMATIVE). H-1
ANNEX I ITEMS FOR AN INTERFACE CONTROL DOCUMENT
(INFORMATIVE) . I-1
ANNEX J CHANGES VERSUS PREVIOUS VERSION (INFORMATIVE) . J-1
CCSDS 502.0-B-3 Page vi April 2023

vi
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
CONTENTS (continued)
Figure Page
6-1 LTM Covariance Element Ordering following Time Tag . 6-28
6-2 UTM Covariance Element Ordering following Time Tag . 6-28
6-3 Full Covariance Element Ordering following Time Tag . 6-28
6-4 LTM Covariance/Correlation Element Ordering following Time Tag . 6-29
6-5 UTM Covariance/Correlation Element Ordering following Time Tag . 6-29
8-1 ODM/XML Basic Structure . 8-1
8-2 Comparison of Single Message OPM with NDM Combined Instantiation . 8-14
8-3 NDM Combined Instantiation Showing Mix of ODMs and Use of Attributes . 8-15
F-1 Depiction of Optimally Enclosing Box and Definitions of MAX, INT,
and MIN Orientation Vectors Relative to OEB Parent Frame . F-2
F-2 Depiction of Optical Viewing CATS Angle Geometry . F-6
F-3 Diagram of Time-based Duty Cycle (DC_TYPE = ‘TIME’) . F-7
F-4 Diagram of a Rotating Spacecraft Body’s Progression through an Inertial
Clock Angle-based Duty Cycle (DC_TYPE = ‘TIME_AND_ANGLE’) . F-7
F-5 Regex Pattern for CCSDS Timecode . F-10
F-6 Regex Pattern Matching Sequence for CCSDS Timecode . F-11
F-7 Regex for a Non-Decimal String . F-12
F-8 Regex for Free-Text String . F-12
F-9 Regex for String Containing Numerical Value with Optional Units . F-12
F-10 Regex for String Containing Numerical Value with Optional Units . F-13
G-1 Simple OPM File Example . G-1
G-2 OPM File Example with Optional Keplerian Elements and Two Maneuvers . G-2
G-3 File Example with Covariance Matrix . G-3
G-4 OPM File Example with Optional Keplerian Elements, Covariance Matrix,
and a User-defined Parameter . G-4
G-5 OPM File Example in XML Format . G-5
G-6 Example Two Line Element Set . G-6
G-7 OMM File Example without Covariance Matrix . G-6
G-8 OMM File Example with Covariance Matrix . G-7
G-9 OMM with Units and a User-defined Parameter . G-8
G-10 OMM File Example in XML Format . G-9
G-11 OEM Example with No Acceleration, No Covariance . G-10
G-12 OEM Example with Optional Accelerations . G-11
G-13 OEM Example with Optional Covariance Matrices . G-12
G-14 OEM File Example in XML Format . G-14
G-15 Simple/Succinct OCM Example with Only Cartesian PVA Ephemeris . G-15
G-16 OCM Example with Space Object Characteristics and Perturbations . G-17
G-17 OCM Example with Deployed Objects and Low-level Thrusting Maneuver
during Deployment to Make ‘String-of-Pearls’ Deployment . G-17
G-18 OCM Example with Multiple Orbit Time Histories, a Maneuver, OD,
Cartesian, and Keplerian Ephemeris . G-19
G-19 OCM Example with Covariance Matrix Time Histories in Two Element Set Types . G-20
CCSDS 502.0-B-3 Page vii April 2023

vii
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
CONTENTS (continued)
Figure Page
G-20 OCM Example in XML Format . G-21
G-21 Aggregating Multiple ODMs into a Single NDM File . G-22
G-22 Aggregating OPM, OMM, OEM, and OCM in a Single Navigation Data
Message XML . G-25
Table
3-1 OPM Header . 3-3
3-2 OPM Metadata . 3-4
3-3 OPM Data. 3-6
4-1 OMM Header . 4-3
4-2 OMM Metadata . 4-4
4-3 OMM Data . 4-5
5-1 OEM File Layout Specifications . 5-2
5-2 OEM Header . 5-3
5-3 OEM Metadata . 5-4
5-4 OEM Covariance Keywords . 5-8
6-1 OCM File Layout and Ordering Specification . 6-3
6-2 OCM Header . 6-5
6-3 OCM Metadata . 6-6
6-4 OCM Data: Trajectory State Time History . 6-14
6-5 OCM Data: Space Object Physical Characteristics . 6-21
6-6 OCM Data: Covariance Time History . 6-31
6-7 OCM Data: Maneuver Specification . 6-37
6-8 OCM Data: Selectable Propulsive (i.e., Non-Deployment) Maneuver Fields
in the Maneuver Time History Data . 6-45
6-9 OCM Data: Selectable Deployment Fields in the Maneuver Time History Data . 6-46
6-10 OCM Data: Perturbations Specification. 6-48
6-11 OCM Data: Orbit Determination Data . 6-53
6-12 OCM Data: User-Defined Parameters . 6-56
8-1 ODM/XML Root Element Tags . 8-2
8-2 Examples of Units in OPM/XML . 8-5
8-3 OPM/XML Tag Delimiters . 8-6
8-4 Examples of Units in OMM/XML . 8-7
8-5 OMM/XML Tag Delimiters . 8-8
8-6 Examples of Units in OEM/XML . 8-9
8-7 OEM/XML Tag Delimiters . 8-10
8-8 Examples of Units in OCM/XML . 8-11
8-9 OCM/XML Tag Delimiters. 8-12
E-1 Services Available with Orbit Data Messages . E-5
F-1 Space Surveillance Observation Product Description . F-16
CCSDS 502.0-B-3 Page viii April 2023

viii
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
1 INTRODUCTION
1.1 PURPOSE AND SCOPE
This Orbit Data Messages (ODM) Recommended Standard 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;
f) assessing mutual physical and electromagnetic interference among satellites orbiting
the same celestial body (primarily Earth, Moon, and Mars at present);
g) performing orbit conjunction (collision avoidance) studies; and
h) developing and executing collaborative maneuvers to mitigate interference or enhance
mutual operations.
This Recommended Standard includes sets of requirements and criteria that the message
formats have been designed to meet. For exchanges in which these requirements do not
capture the needs of the participating agencies and satellite operators, another mechanism
may be selected.
The ODM Recommended Standard is an international standard published under the auspices
of CCSDS and International Standards Organization (ISO) Technical Committee 20,
Subcommittee 13, developed jointly and in concert with the ISO TC20/SC14. As such, this
CCSDS standard is also properly labeled as ISO 26900.
The recommended Orbit Data Message format is ASCII (reference [4]).
This ODM document describes both ‘Keyword = Value Notation’ (KVN) as well as
Extensible Markup Language (XML) (reference [5]) formatted messages. Selection of KVN
or XML format should be mutually agreed between message exchange partners.
NOTE – As currently specified, an OPM, OMM, or OEM file is to represent orbit data for
a single spacecraft, and the OCM is to represent orbit data for either a single
spacecraft or single parent spacecraft of a parent/child spacecraft deployment
scenario. It is possible that the architecture may support multiple spacecraft per
file; this could be considered in the future.
CCSDS 502.0-B-3 Page 1-1 April 2023
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
1.2 APPLICABILITY
The Orbit Data Message family of standardized orbit messages is applicable to all phases of
the spacecraft and launch vehicle life cycle. The rationale behind the design of each orbit
data message is described in annex E and may help the application engineer to select a
suitable message. Definition of the orbit accuracy underlying a particular orbit message is
outside of the scope of this Recommended Standard and should be mutually agreed upon
between message exchange partners (or specified via COMMENT sections in the message
itself). Applicability information specific to each orbit data message format appears in
sections 3, 4, 5, and 6, as well as in annex subsections E2.4 and E2.5.
This Recommended Standard is applicable only to the message format and content, but not to
its transmission. The transmission of the message between agencies and operators is outside
the scope of this document and should be mutually agreed between message exchange
partners.
Description of the message formats based on the use of XML is detailed in section 8.
1.3 RATIONALE
This update to version 2 of the Orbit Data Messages adds a fourth message type, the OCM,
based on collaboration of the CCSDS Navigation Working Group and the ISO Technical
Committee 20, Subcommittee 14, Working Group 3 (ISO TC20/SC14/WG3). A full list of
the changes in this document is in annex J.
1.4 DOCUMENT STRUCTURE
Section 2 provides a brief overview of the CCSDS-recommended Orbit Data Message types,
the OPM, OMM, OEM, and OCM.
Section 3 provides details about the structure and content of the OPM.
Section 4 provides details about the structure and content of the OMM.
Section 5 provides details about the structure and content of the OEM.
Section 6 provides details about the structure and content of the OCM.
Section 7 discusses the syntax considerations of the set of Orbit Data Messages (OPM,
OMM, OEM, and OCM).
Section 8 provides details on the XML instantiations of the OPM, OMM, OEM, and OCM.
Following the principal content of the document, there are several annexes, both normative
and informative, to guide the ODM user.
CCSDS 502.0-B-3 Page 1-2 April 2023
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
1.5 CONVENTIONS AND DEFINITIONS
1.5.1 NOTATION
1.5.1.1 Unit Notations
The following conventions for unit notations apply throughout this Recommended Standard,
with message-specific guidance provided in 7.7. Units are drawn from the International
System of Units (SI); units are either SI base units, SI derived units, or units outside the SI
that are accepted for use with the SI (reference [1]). Except as noted, the units used within
this document are as follows:
– d: days, 86400 SI seconds;
– kg: kilograms;
– km: kilometers;
– m: meters;
– n/a: (units are not applicable);
– %: percent;
– s: SI seconds;
-22
– SFU: Solar Flux Units, equivalent to 10 W/(m**2*Hz);
– W: watts.
1.5.1.2 General
The following notational conventions are used in this document:
a) multiplication of units is denoted with a single asterisk ‘*’ (e.g., ‘kg*s’);
b) exponents of units are denoted with a double asterisk ‘**’ (e.g., m = m**2);
c) square roots of units are denoted by the same exponent notation of a double asterisk
‘**’ (e.g., √𝑘𝑚 = km**0.5);
d) division of units is denoted with a single forward slash ‘/’ (e.g., m/s);
e) the usual order of operations ordering applies (e.g., exponents before multiplication).
CCSDS 502.0-B-3 Page 1-3 April 2023
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
1.5.2 NOMENCLATURE
1.5.2.1 Normative Text
The following conventions apply for the normative specifications in this Recommended
Standard:
a) the words ‘shall’ and ‘must’ imply a binding and verifiable specification;
b) the word ‘should’ implies an optional, but desirable, specification;
c) the word ‘may’ implies an optional specification;
d) the words ‘is’, ‘are’, and ‘will’ imply statements of fact.
NOTE – These conventions do not imply constraints on diction in text that is clearly
informative in nature.
1.5.2.2 Informative Text
In the normative sections of this document, informative text is set off from the normative
specifications either in notes or under one of the following subsection headings:
– Overview;
– Background;
– Rationale;
– Discussion.
1.5.3 DEFINITIONS
For the purposes of this document, the following definitions apply:
a) the word ‘agencies’ may also be construed as meaning ‘satellite operators’ or
‘satellite service providers’;
b) the word ‘participant’ denotes an entity that can acquire or broadcast navigation
messages and/or radio frequencies, for example, a spacecraft, a tracking station, a
tracking instrument, or an agency/operator;
c) the notation ‘n/a’ signifies ‘not applicable’;
d) depending on context, the term ‘ODM’ may be used to refer to this document or may
be used to refer collectively to the OPM, OMM, OEM, and OCM messages;
e) an ‘observation’ is a unique measurement set of a satellite’s state from a single sensor
configuration at a single time (e.g., azimuth from a single sensor at a single time);
CCSDS 502.0-B-3 Page 1-4 April 2023
CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES
f) a ‘sensor track’ is a set of observations within a specified number of minutes for the
same object, observed by the same sensor configuration, where each observation is
within a specified number of minutes (which is dependent on the orbit regime of the
object) of the other observations in the track (e.g., a set of 10 two-way transponder
range measurements from the same sensor using the same transponder on the
satellite), and where the number of minutes could alternately be defined as the time
between start and stop of the measurement ‘session’ or signal modulation that enables
metric tracking.
1.6 REFERENCES
The following publications contain provisions which, through reference in this text,
constitute provisions of this document. At the time of publication, the editions indicated
were valid. All publications are subject to revision, and users of this document are
encouraged to investigate the possibility of applying the most recent editions of the
publications indicated below. The CCSDS Secretariat maintains a register of currently valid
CCSDS publications.
[1] The International System of Units (SI). 8th ed., 2006; updated in 2014. Sèvres, France:
BIPM, 2006.
[2] Time Code Formats. Issue 4. Recommendation for Space Data System Standards (Blue
Book), CCSDS 301.0-B-4. Washington, D.C.: CCSDS, November 2010.
[3] “Online Index of Objects Launched into Outer Space.” United Nations Office for Outer
Space Affairs (UNOOSA). https://www.unoosa.org/oosa/osoindex/.
[4] Information Technology—8-Bit Single-Byte Coded Graphic Character Sets—Part 1:
Latin Alphabet No. 1. International Standard, ISO/IEC 8859-1:1998. Geneva: ISO,
1998.
[5] XML Specification for Navigation Data Messages. Issue 3. Recommendation for Space
Data System Standards (Blue Book), CCSDS 505.0-B-3. Washington, D.C.: CCSDS,
May 2023.
[6] Paul V. Biron and Ashok Malhotra, eds. XML Schema Part 2: Datatypes. 2nd ed. W3C
Recommendation.
[7] IEEE Standard for Floating-Point Arithmetic. 3rd ed. IEEE Std 754-2019. New York:
IEEE, 2019.
[8] Henry S. Thompson, et al., eds. XML Schema Part 1: Structures. 2nd ed. W3C
Recommendation.
[9] Tracking Data Message. Issue 2. Recommendation for Space Data System Standards
(Blue Book), CCSDS 503.0-B-2. Washington, D.C.: CCSDS, June 2020.
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[10] Attitude Data Messages. Issue 1. Recommendation for Space Data System Standards
(Blue Book), CCSDS 504.0-B-1. Washington, D.C.: CCSDS, May 2008.
[11] “CCSDS Navigation Standards Normative Annexes.” Space Assigned Numbers
Authority. https://sanaregistry.org/r/navigation_standard_normative_annexes.
[12] Re-entry Data Message. Issue 1. Recommendation for (Blue Book), CCSDS 508.1-B-1.
Washington, D.C.: CCSDS, November 2019.
[13] Pointing Request Message. Issue 1. Recommendation for (Blue Book), CCSDS 509.0-
B-1. Washington, D.C.: CCSDS, February 2018.
[14] Conjunction Data Message. Issue 1. Recommendation for Space Data System
Standards (Blue Book), CCSDS 508.0-B-1. Washington, D.C.: CCSDS, June 2013.

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2 OVERVIEW
2.1 ORBIT PARAMETER MESSAGE
An OPM specifies the position and velocity of a single object at a specified epoch.
Optionally, osculating Keplerian elements may be provided. It should be noted that a
sequence of OPMs for either a single object or for multiple objects can be aggregated into a
single Navigation Data Message (NDM) XML file as described in 8.12 and shown in
annex G. This message is suited to exchanges that (1) involve automated interaction and/or
human interaction, and (2) do not require high-fidelity dynamic modeling.
The OPM requires the use of a propagation technique to determine the position and velocity
at times different from the specified epoch, leading to a higher level of effort for software
implementation than for the OEM.
The OPM also contains an optional 6x6 position/velocity covariance matrix that reflects the
uncertainty of the orbit state and may be used in the propagation process to estimate future
uncertainties.
The OPM allows for modeling of any number of maneuvers (as both finite and instantaneous
events) and simple modeling of solar radiation pressure and atmospheric drag.
Though primarily intended for use by computers, the attributes of the OPM also make it
suitable for applications such as exchanges by email, FAX, or voice, or applications in which
the message is to be frequently interpreted by humans.
2.2 ORBIT MEAN-ELEMENTS MESSAGE
The OMM contains the orbital characteristics of a single object at a specified epoch,
expressed in mean Keplerian elements: mean motion, eccentricity, inclination, right
ascension of ascending node, argument of perigee, and mean anomaly. These are adequate
for providing the initial mean state of analytical and semi-analytical orbit models. In
addition, the OMM contains values for parameters that facilitate the modeling of non-
conservative forces for various mean element theories.
It may be noted that a sequence of OMMs for either a single object or for multiple objects
can be aggregated into a single NDM XML file as described in 8.12 and shown in annex G.
The OMM is suited to exchanges that (1) involve automated interaction and/or human
interaction, and (2) do not require high-fidelity dynamic modeling. Such exchanges may be
inter-agency exchanges, or ad hoc exchanges among satellite operators when interface
control documents have not been negotiated. Ad hoc interactions usually involve more than
one satellite, each satellite controlled and operated by a different operating authority.
The OMM includes keywords and values that may be used to generate canonical NORAD Two
Line Element (TLE) sets to accommodate the needs of heritage users (see annex H,
reference [H3]).
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The OMM also contains an optional covariance matrix that reflects the uncertainty of the
mean Keplerian elements. This information may be used to determine contact parameters
that encompass uncertainties in predicted future states of orbiting objects of interest.
This message is suited for directing antennas and planning contacts with satellites. It is not
recommended for assessing mutual physical or electromagnetic interference among Earth-
orbiting spacecraft, developing collaborative maneuvers, or propagating precisely the orbits
of active satellites, inactive man-made objects, and near-Earth debris fragments. It is not
suitable for numerical integration of the governing equations.
Though primarily intended for use by computers, the attributes of the OMM also make it
suitable for applications such as exchanges by email, FAX, or voice, or applications in which
the message is to be frequently interpreted by humans.
2.3 ORBIT EPHEMERIS MESSAGE
An OEM specifies the position and velocity of a single object at multiple epochs contained
within a specified time range. It should be noted that a sequence of OEMs for either a single
object or for multiple objects can be aggregated into a single NDM XML file as described
in 8.12 and shown in annex G. The OEM is suited to exchanges that (1) involve automated
interaction (e.g., computer-to-computer communication when frequent, fast automated time
interpretation and processing is required), and (2) require higher fidelity or higher precision
dynamic modeling than is possible with the OPM.
The OEM allows for dynamic modeling of any number of gravitational and non-gravitational
accelerations. The OEM requires the use of an interpolation technique to interpret the
position and velocity at times different from the tabular epochs.
The OEM also contains an optional covariance matrix that reflects the uncertainty of the orbit
solution used to generate states in the ephemeris.
2.4 ORBIT COMPREHENSIVE MESSAGE
An OCM specifies position and velocity of either a single object or an en masse parent/child
deployment scenario stemming from a single object. It should be noted that a sequence of
OCMs for either a single object or for multiple objects can be aggregated into a single NDM
XML file as described in 8.12 and shown in annex G.
The OCM aggregates and extends OPM, OEM, and OMM content in a single comprehensive
hybrid message (file) and includes the following additional capabilities:
– Optional Earth Orientation (UT1 and UTC) at a nearby (relevant) reference epoch;
– Optional Leap second specification;
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– Optional area cross-sections for drag, Solar Radiation Pressure (SRP) perturbations
modeling;
– Optional spacecraft dimensions and orientation information for collision probability
estimation;
– Optional orbit states (specified using one or more of Cartesian and orbit elements and
reference frames) for a single or parent object at either a single epoch or as a time
history (ephemeris);
– Optional covariance matrix of selectable/arbitrary order for a single or parent object at
either a single epoch or as a time history (ephemeris) that reflects the uncertainty of
the orbit solution or simulation used to obtain the nominal states in the orbit state(s);
– Optional covariance content options (e.g., Cartesian 3x3, 6x6, 7x7, or any
combination of order, reference frame, and orbit elements);
– Optional maneuver specification (impulsive or finite burn);
– Optional perturbations model specification;
– Optional orbit determination data and metrics.
The OCM simultaneously emphasizes flexibility and message conciseness by offering
extensive optional content while minimizing mandatory content. The OCM is well-suited for
exchanges that (1) involve automated interaction (e.g., computer-to-computer communication
when frequent, fast automated time interpretation and processing is required), and (2) involve
regular orbit data transfer for numerous objects (e.g., 200,000) using minimal network
bandwidth, disk storage, and quantity of files. The OCM allows the user, in a single
message/file, to either embed high-fidelity orbit propagation into an ephemeris time history
(akin to the OEM ephemeris) or specify orbital states that can be propagated with supplied
perturbations model parameters (akin to OPM content), or both.
2.5 EXCHANGE OF MULTIPLE MESSAGES
For a given object, multiple OPM, OMM, or OEM messages may be provided in a message
exchange session to achieve ephemeris fidelity requirements, whereas a single, self-contained
OCM may be sufficient. If ephemeris information for multiple objects is to be exchanged,
then multiple OPM, OMM, OEM, or OCM files must be used, with the exception that the
OCM supports parent/child deployment scenario specifications in a single message.
2.6 DEFINITIONS
Definitions of time systems, reference frames, planetary models, maneuvers, and other
fundamental topics related to the interpretation and processing of state vectors and spacecraft
ephemerides are provided in reference [H1].
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3 ORBIT PARAMETER MESSAGE
3.1 GENERAL
3.1.1 Orbit information may be exchanged between two participants by sending a state
vector (see reference [H1]) for a specified epoch using an OPM. The message recipient must
have an orbit propagator available that is able to propagate the OPM state vector to compute
the orbit at other desired epochs. For this propagation, additional ancillary information
(spacecraft properties such as mass, area, and maneuver planning data, if applicable) may be
included with the message.
3.1.2 Osculating Keplerian elements and the Gravitational Coefficient may be included in
the OPM in addition to the Cartesian state to aid the message recipient in performing
consistency checks. If any Keplerian element is included, the entire set of elements must be
provided.
3.1.3 If participants wish to exchange mean element information, then the OMM or OCM
should be the selected message type (see sections 4 and 6.)
3.1.4 The use of the OPM is best applicable under the following conditions:
a) an orbit propagator consistent with the models used to develop the orbit data should
be available at the receiver’s site.
b) the receiver’s modeling of gravitational forces, solar radiation pressure, atmospheric
drag, and thrust phases (see reference [H1]) should fulfill accuracy requirements
established between the exchange partners.
3.1.5 The OPM shall be a plain text file consisting of orbit data for a single object.
NOTE – A sequence of OPMs for either a single object or for multiple objects can be
aggregated into a single NDM XML file as described in 8.12 and shown in annex G.
3.1.6 The OPM file-naming scheme should be mutually agreed between message exchange
partners.
3.1.7 The method of exchanging OPMs should be mutually agreed between message
exchange partners.
NOTES
1 Detailed syntax rules for the OPM are specified in section 7.
2 Example OPMs and associated supplementary (non-normative) information are
provided in annex G.
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3.2 OPM CONTENT/STRUCTURE
3.2.1 GENERAL
The OPM shall be represented as a combination of the following:
a) a header;
b) metadata (data about data);
c) data; and
d) optional comments (explanatory information).
3.2.2 OPM HEADER
3.2.2.1 Table 3-1 specifies for each header item:
a) the keyword to be used;
b) a short description of the item;
c) examples of allowed values; and
d) whether the item is
...