Recommendation for Space

RECOMMENDATION FOR SPACE

DATA SYSTEMS STANDARDS

ORBIT DATA
MESSAGES

CCSDS 301.0-B-2

RED BOOK

ISSUE 1

April 2001

CCSDS RECOMMENDATION FOR ORBIT DATA MESSAGES

AUTHORITY

* * * * * * * * * * * * * * * * * * * * * * * * *

* Issue: Red Book, Issue 1 *

* Date: April 2001 *

* Location: CCSDS Panel-1 Meeting *

* April 2001 *

* Darmstadt, Germany *

* * * * * * * * * * * * * * * * * * * * * * * * *

This Recommendation reflects the consensus technical agreement of the following member Agencies of the Consultative Committee for Space Data Systems (CCSDS):

·  Centre National D'Etudes Spatiales (CNES)/France.

·  Deutsche Forschungsanstalt für Luft und Raumfahrt e.V. (DLR)/West Germany.

·  European Space Agency (ESA)/Europe.

·  National Aeronautics and Space Administration (NASA)/USA.

·  National Space Development Agency of Japan (NASDA)/Japan.

The following observer Agency also concurs with this Recommendation:

·  Institute of Space and Astronautical Science (ISAS)/Japan.

This Recommendation is published and maintained by:

CCSDS Secretariat

Communications and Data Systems Division (Code-OS)

National Aeronautics and Space Administration

Washington, DC 20546, USA

STATEMENT OF INTENT

The Consultative Committee for Space Data Systems (CCSDS) is an organization officially established by the management of eight member space Agencies. The Committee meets periodically to address data systems problems that are common to all participants, and to formulate sound technical solutions to these problems. Inasmuch as participation in the CCSDS is completely voluntary, the results of Committee actions are termed RECOMMENDATIONS and are not considered binding on any Agency.

This RECOMMENDATION is issued by, and represents the consensus of, the CCSDS Plenary body. Agency endorsement of this RECOMMENDATION is entirely voluntary. Endorsement, however, indicates the following understandings:

·  Whenever an Agency establishes a CCSDS-related STANDARD, this STANDARD will be in accord with the relevant RECOMMENDATION. Establishing such a STANDARD does not preclude other provisions that an Agency may develop.

·  Whenever an Agency establishes a CCSDS-related STANDARD, the Agency will provide other CCSDS member Agencies with the following information:

-- The STANDARD itself.

-- The anticipated date of initial operational capability.

-- The anticipated duration of operational service.

·  Specific service arrangements shall be made via memoranda of agreement. Neither this RECOMMENDATION nor any ensuing STANDARD is a substitute for a memorandum of agreement.

No later than five years from its date of issuance, this Recommendation will be reviewed by the CCSDS to determine whether it should: (1) remain in effect without change, (2) be changed to reflect the impact of new technologies, new requirements, or new directions, or (3) be retired or cancelled.

FOREWORD

This document is a technical Recommendation for orbit data formats and has been prepared by the Consultative Committee for Space Data Systems (CCSDS). The set of orbit data formats described in this Recommendation is the baseline concept for trajectory representation in data interchange applications that are cross-supported between Agencies of the CCSDS.

This Recommendation establishes a common framework and provides a common basis for the formats of orbit data. It allows implementing organizations within each agency to proceed coherently with the development of compatible derived Standards for the flight and ground systems that are within their cognizance. Derived Agency Standards may implement only a subset of the optional features allowed by the Recommendation and may incorporate features not addressed by this Recommendation.

Through the process of normal evolution, it is expected that expansion, deletion or modification to this document may occur. This Recommendation is therefore subject to CCSDS document management and change control procedures that are defined in Reference[1].

DOCUMENT CONTROL

Document Title Date Status/Remarks

CCSDS 301.0-B-1 Recommendation for Space April Original

Data System Standards: 2001 Issue

Orbit Data Formats, Issue 1

CONTENTS

Sections Page

REFERENCES vii

1 INTRODUCTION 1-1

1.1 PURPOSE 1-1

1.2 SCOPE 1-1

1.3 CATEGORIZING OF CCSDS ORBIT DATA MESSAGES 1-1

1.4 APPLICABILITY 1-2

2 ORBIT PARAMETER MESSAGE (OPM) 2-1

2.1 APPLICABILITY 2-1

2.2 REQUIREMENTS FOR THE OPM FORMAT 2-1

2.2.1 OPM FILE 2-1

2.2.2 LINES 2-1

2.2.3 KEYWORDS 2-1

2.2.4 VALUES 2-2

2.2.5 UNITS 2-2

2.3 HEADER FIELD 2-2

2.4 OPM KEYWORD SET 2-2

2.5 SPECIFICATION OF OPM KEYWORD VALUES 2-4

2.5.1 GENERAL INFORMATION KEYWORDS 2-4

2.5.2 STATE VECTOR KEYWORDS 2-5

2.5.3 KEPLERIAN ELEMENT & GRAVITATIONAL COEFFICIENT KEYWORDS 2-5

2.5.4 SPACECRAFT PARAMETER KEYWORDS 2-5

2.5.5 MANEUVER KEYWORDS 2-5

2.6 CCSDS ORBIT PARAMETER MESSAGE (OPM) EXAMPLES 2-6

3 EPHEMERIS MESSAGE (EPH) 3-1

3.1 REQUIREMENTS FOR THE EPH MESSAGE FORMAT 3-1

3.1.1 EPH FILE 3-1

3.1.2 LINES 3-1

3.1.3 EPH MESSAGE FIELDS 3-1

3.1.4 KEYWORDS 3-2

3.1.5 VALUES 3-2

3.1.6 UNITS 3-2

3.2 HEADER FIELD 3-2

3.3 EPH MESSAGE METADATA 3-2

3.4 COMMENTS 3-4

3.5 EPHEMERIS DATA 3-4

3.6 CCSDS EPHEMERIS (EPH) MESSAGE EXAMPLES 3-4

Annexes

A RATIONALE FOR ORBIT DATA CODES A-1

B GLOSSARY OF SELECTED ORBIT DATA TERMS B-1

REFERENCES

[1] "Procedures Manual for the Consultative Committee for Space Data Systems", Issue 1, Consultative Committee for Space Data Systems, August 1985 or later issue.

[2] Navigation Data: Definition and Conventions. Recommendations for Space Data Systems, CCSDS 501.0-GB-1, Draft – Green Book, Washington, D.C.: CCSDS, October 2000 or later issue.

[3] SPACEWARN Bulletin, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA, Internet: http://nssdc.gsfc.nasa.gov/spacewarn.

[4] Recommendations and Reports of the CCIR, XVth Plenary Assembly, Geneva 1982, Vol. VII: Standard Frequencies and Time, as modified in 1983 and 1985, or later issue.

[5] "Information Processing--8-bit Single-byte Coded Graphic Character Sets--Part 1: Latin Alphabet No. 1," first edition, International Standard ISO 8859-1, International Organization for Standardization, 1987.

The latest issue of CCSDS documents may be obtained from the CCSDS Secretariat at the address indicated on page i.

Issue 2 Page 11 April 2001

CCSDS RECOMMENDATION FOR ORBIT DATA MESSAGES

1 INTRODUCTION

1.1 PURPOSE

CCSDS Panel 1J is charged with specifying and recommending a modern spacecraft ephemeris (trajectory) data standard for use in transferring spacecraft orbit information between member agencies. Such exchanges are required for (1) pre-flight planning for tracking or navigation support, (2) officially scheduling tracking support, (3) carrying out tracking operations (sometimes called metric predicts), and (4) orbit comparisons.

The purpose of this Recommendation is to establish two standardized recommended orbit data formats for use in ground-to-ground data interchange applications between Agencies of the CCSDS. This Recommendation does not address precision and accuracy of the derived spacecraft state.

1.2 SCOPE

Orbit data are digital representations of orbit information. Two standard CCSDS-recommended orbit data codes are described (the “Orbit Parameter Message” and “Ephemeris” codes) which use the international standards of kilometers and kilometers per second as the fundamental units of distance and velocity, respectively. The two Recommended orbit data formats carry the object identification (in the OBJECT_NAME field), the coordinate frame center (in the CENTER_NAME field), the coordinate frame identification (in the REF_FRAME field), and the time system (in the TIME_SYSTEM field). Additional information required for each data format is listed in chapters 2 and 3.

An Orbit Parameter Message (OPM) is an ASCII description of the position and velocity of an object at a starting time called the “epoch.” This message is particularly suited to inter-agency exchanges which (1) involve human interaction and (2) where high-fidelity non-gravitational acceleration modeling is not required.

An Ephemeris Message (EPH) is an ASCII table representation of the position and velocity history of an object over a specified time range. The Ephemeris Message code is particularly suited to inter-agency exchanges that involve (1) automated interaction and (2) where high-fidelity non-gravitational acceleration modeling is required.

This Recommendation includes sets of requirements and criteria that the message formats have been designed to meet. For exchanges where the existing requirements do not capture the needs of the participating agencies, the participating agencies may agree to use another mechanism for that particular exchange.

1.3 CATEGORIZING OF CCSDS ORBIT DATA MESSAGES

In this Recommendation, two orbit data codes are defined based on the two forms of interpretability of the code:

Interpretability Form 1: Orbit Parameter Propagation

The Orbit Parameter Message format is fully self-defined and allows for the use of a propagation technique (analytical or numerical) to interpret the position and velocity at times different from the specified epoch; no additional information is required.

Interpretability Form 2: Tabular Interpolation

The Ephemeris Message format is fully self-defined and allows for the use of interpolation techniques to interpret the position and velocity at times different from the tabular epochs; no additional information is required.

1.4 APPLICABILITY

This Recommendation contains two orbit data messages designed for applications involving data interchange in space data systems. It does not attempt to prescribe which code to use for any particular application. The rationale behind the design of each code is described in Annex A and may help the application engineer to select a suitable code. Definition of the orbit accuracy underlying a particular orbit code is not a function of the Recommendation, but is the responsibility of the authority cognizant of navigation performance for the applicable system. Applicability information specific to each orbit data message format appears in Chapters 2 and 3.

Issue 2 Page 11 April 2001

CCSDS RECOMMENDATION FOR ORBIT DATA MESSAGES

2 ORBIT PARAMETER MESSAGE (OPM)

2.1 APPLICABILITY

Orbit information may be exchanged between two participants by sending a state vector (Ref. [2]) for a specified epoch within an Orbit Parameter Message (OPM).

In this case, the message receiver site must have an orbit propagator available which is able to propagate from the OPM state vector compute the orbit at desired epochs. For this propagation, additional ancillary information (spacecraft properties such as mass, area, and maneuver planning data, if applicable) is to be included with the message.

Thus, the use of the Orbit Parameter Message (OPM) is applicable under the following conditions:

¾  An orbit propagator is run on the receiver’s site.

¾  The modeling of solar radiation pressure, atmospheric drag and thrust phases (Ref. [2]) fulfill accuracy requirements established between the agencies.

2.2 REQUIRMENTS FOR THE OPM FORMAT

This section describes the requirements for the Orbit Parameter Message (OPM) file. The design follows the general requirement that the message shall be easily readable for both human beings and computers.

2.2.1 OPM File

¾  Each file has to contain all obligatory fields.

¾  Only those keywords shown in Table 2-2 are allowed.

¾  The order of the occurrence of obligatory and optional items is fixed as shown in Table 2-2. Exceptions are blank or comment lines.

2.2.2 Lines

¾  Line lengths in the OPM file are restricted to 80 characters.

¾  Only printable ASCII characters and blanks may be used. Control characters (such as TAB, etc.) are not allowed.

¾  The first non-blank line in the file must contain the CCSDS version specification.

¾  All data lines are provided using a syntax “keyword = value {unit}” with the exception of comment or blank lines.

¾  Blank lines may occur at any position of the file (blank lines are ignored).

¾  Comment lines may occur at any position of the file after the header.

¾  The keyword for the comment line must be given at the beginning of all comment lines.

2.2.3 Keywords

¾  Only those keywords shown in Table 2-2 are allowed.

¾  Keywords are all uppercase and do not contain blanks.

¾  At least one blank is required after each keyword.

2.2.4 Values

¾  In the values associated with keywords, individual blanks are retained (are significant) but multiple blanks are equivalent to a single blank.

¾  Numbers shall be given in fixed-point notation.

¾  Values in text format are all uppercase.

¾  There are no default values assumed for keyword items.

¾  A valid value for each item must be specified in each occurrence of a keyword.

¾  The value field is a character string, limited to 32 characters (including any embedded white space); the string may include numbers.

2.2.5 Units

¾  Only units specified in Table 2-2 are allowed.

¾  For readability, units can be included as ASCII text after the value, but they do not supercede the units specified in Table 2-2.

2.3 HEADER FIELD

The orbit code header uniquely defines the options, parameters, and encoding structure of the metadata and must be included. In addition, the header provides a CCSDS Orbit Data Standard version number that identifies the format version; this is included to anticipate future changes. The explicit representation of the header is limited to only the first non-blank line whose format is described in Table 2-1.

Header String / Description / Present Value / Obligatory
CCSDS_OPM_VERS / Orbit Parameter Message version number / 1.0 / yes

Table 2-1. OPM Header Description

2.4 OPM KEYWORD SET

Table 2-2 specifies for each item (1) its required sequence of occurrence in the OPM file, (2) the keyword to be used, (3) a short description, (4) the required unit, if applicable, and (5) whether or not the item is required or optional.

Keyword / Description / Units / Obligatory
General information
SOURCE / Originator of the message. / N/A / Yes
OBJECT_NAME / Name of object / N/A / Yes
OBJECT_ID / International spacecraft designation number in format yyyy-nnn-p{pp} / N/A / Yes
CENTER_NAME / Center of coordinate system / N/A / Yes
REF_FRAME / Coordinate system / N/A / Yes
TIME_SYSTEM / Time system representation / N/A / Yes
EPOCH / Epoch of elements in format
YYYY/MM/DD hh:mm:ss.s{ssssssss} / N/A / Yes
State vector components in the specified coordinate system
X / X-component of the position vector / KM / Yes
Y / Y-component of the position vector / KM / Yes
Z / Z-component of the position vector / KM / Yes
X_DOT / X-component of the velocity vector / KM/S / Yes
Y_DOT / Y-component of the velocity vector / KM/S / Yes
Z_DOT / Z-component of the velocity vector / KM/S / Yes
Keplerian elements in the specified coordinate system (none or all parameters of this block are to be given)
SEMI_MAJOR_AXIS / Semi-major axis / KM / No
ECCENTRICITY / Eccentricity / N/A / No
INCLINATION / Inclination / DEG / No
RA_OF_ASC_NODE / Right Ascension of ascending node / DEG / No
ARG_OF_PERICENTER / Argument of pericenter / DEG / No
TRUE_ANOMALY / True anomaly / DEG / No
GM / Gravitational Coefficient / KM3/S2 / No
Spacecraft parameters
MASS / S/C Mass / KG / Yes
SOLAR_RAD_AREA / Area for solar radiation press (AR). / M2 / Yes
SOLAR_RAD_COEFF / Coefficient for solar radiation pressure (CR). / N/A / Yes
DRAG_AREA / Area for drag (AD). / M2 / Yes
DRAG_COEFF / Coefficient for drag (CD). / N/A / Yes
Following is repeated for each maneuver (none or all parameters of this block are to be given)
MAN_EPOCH_IGNITION / Epoch of ignition in format
YYYY/MM/DD hh:mm:ss.s{ssssssss} / N/A / No
MAN_DURATION / Maneuver duration / S / No
MAN_MASS_FLOW_RATE / Mass flow rate / KG/S / No
MAN_REF_FRAME / Coordinate system for velocity increment vector / N/A / No
MAN_DV_1 / 1st component of the velocity increment / KM/S / No
MAN_DV_2 / 2nd component of the velocity increment / KM/S / No
MAN_DV_3 / 3rd component of the velocity increment / KM/S / No
Comments (allowed everywhere in the message after the OPM version no.)
COMMENT / Each comment line has to begin with this keyword. / N/A / No

Table 2-2. Keyword Descriptions