ISO 11104:2003

Space data and information transfer systems — Time code formats

ISO 11104:2003 specifies the requirements for time code formats for space data and information transfer systems for civil space applications.

Systèmes de transfert des informations et données spatiales — Formats des codes horaires

General Information

• Status: Withdrawn
• Publication Date: 09-Dec-2003
• Withdrawal Date: 09-Dec-2003
• ICS: 49.140 - Space systems and operations
• Technical Committee: ISO/TC 20/SC 13 - Space data and information transfer systems
• Drafting Committee: ISO/TC 20/SC 13 - Space data and information transfer systems
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 05-Dec-2011

Relations

• Revised: ISO 11104:2011 - Space data and information transfer systems — Time code formats
• Effective Date: 26-Feb-2011
• Revises: ISO 11104:1991 - Space data and information transfer systems — Time code formats
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 11104
Second edition
2003-12-15

Space data and information transfer
systems — Time code formats
Systèmes de transfert des informations et données spatiales —
Formats des codes horaires



Reference number
ISO 11104:2003(E)
©
ISO 2003

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ISO 11104:2003(E)
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ISO 11104:2003(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 11104 was prepared by the Consultative Committee for Space Data Systems
(CCSDS) (as CCSDS 301.0-B-3, January 2002) and was adopted (without modifications except those stated
in Clause 2 of this International Standard) by Technical Committee ISO/TC 20, Aircraft and space vehicles,
Subcommittee SC 13, Space data and information transfer systems.
This second edition cancels and replaces the first edition (ISO 11104:1991), which has been technically
revised.


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INTERNATIONAL STANDARD ISO 11104:2003(E)

Space data and information transfer systems — Time code
formats
1 Scope
This International Standard specifies the requirements for time code formats for space data and information
transfer systems for civil space applications.
The scope and field of application are furthermore detailed in subclauses 1.1 and 1.2 of the enclosed CCSDS
publication.
2 Requirements
Requirements are the technical recommendations made in the following publication (reproduced on the
following pages), which is adopted as an International Standard:
CCSDS 301.0-B-3, January 2002, Recommendations for space data system standards — Time code formats.
For the purposes of international standardization, the modifications outlined below shall apply to the specific
clauses and paragraphs of publication CCSDS 301.0-B-3.
Pages i to v
This part is information which is relevant to the CCSDS publication only.
3 Revision of publication CCSDS 301.0-B-3
It has been agreed with the Consultative Committee for Space Data Systems that Subcommittee
ISO/TC 20/SC 13 will be consulted in the event of any revision or amendment of publication CCSDS 301.0-B-3.
To this end, NASA will act as a liaison body between CCSDS and ISO.

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ISO 11104:2003(E)
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ISO 11104:2003(E)





RECOMMENDATION FOR SPACE
DATA SYSTEM STANDARDS


TIME CODE
FORMATS


CCSDS 301.0-B-3

BLUE BOOK


January 2002

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ISO 11104:2003(E)
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
AUTHORITY


Issue: Blue Book, Issue 3
Date: January 2002
Location: Not Applicable

This document has been approved for publication by the Management Council of the
Consultative Committee for Space Data Systems (CCSDS) and represents the consensus
technical agreement of the participating CCSDS Member Agencies. The procedure for
review and authorization of CCSDS Recommendations is detailed in the Procedures Manual
for the Consultative Committee for Space Data Systems, and the record of Agency
participation in the authorization of this document can be obtained from the CCSDS
Secretariat at the address below.

This Recommendation is published and maintained by:

CCSDS Secretariat
Program Integration Division (Code M-3)
National Aeronautics and Space Administration
Washington, DC 20546, USA

CCSDS 301.0-B-3 Page i January 2002
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
STATEMENT OF INTENT
The Consultative Committee for Space Data Systems (CCSDS) is an organization officially
established by the management of 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:
o 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 which an Agency may develop.
o 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.
o 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 canceled.
In those instances when a new version of a Recommendation is issued, existing CCSDS-
related Agency standards and implementations are not negated or deemed to be non-CCSDS
compatible. It is the responsibility of each Agency to determine when such standards or
implementations are to be modified. Each Agency is, however, strongly encouraged to direct
planning for its new standards and implementations towards the later version of the
Recommendation.
CCSDS 301.0-B-3 Page ii January 2002
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
FOREWORD
This document is a technical Recommendation for time code formats and has been prepared
by the Consultative Committee for Space Data Systems (CCSDS). The set of time code
formats described in this Recommendation is the baseline concept for time 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 time code 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 which are defined in
Reference [1]. Current versions of CCSDS documents are maintained at the CCSDS Web
site:
http://www.ccsds.org/
Questions relating to the contents or status of this document should be addressed to the
CCSDS Secretariat at the address indicated on page i.
CCSDS 301.0-B-3 Page iii January 2002
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
At time of publication, the active Member and Observer Agencies of the CCSDS were:

Member Agencies

– Agenzia Spaziale Italiana (ASI)/Italy.
– British National Space Centre (BNSC)/United Kingdom.
– Canadian Space Agency (CSA)/Canada.
– Centre National d’Etudes Spatiales (CNES)/France.
– Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)/Germany.
– European Space Agency (ESA)/Europe.
– Instituto Nacional de Pesquisas Espaciais (INPE)/Brazil.
– National Aeronautics and Space Administration (NASA)/USA.
– National Space Development Agency of Japan (NASDA)/Japan.
– Russian Space Agency (RSA)/Russian Federation.

Observer Agencies

– Austrian Space Agency (ASA)/Austria.
– Central Research Institute of Machine Building (TsNIIMash)/Russian Federation.
– Centro Tecnico Aeroespacial (CTA)/Brazil.
– Chinese Academy of Space Technology (CAST)/China.
– Commonwealth Scientific and Industrial Research Organization (CSIRO)/Australia.
– Communications Research Centre (CRC)/Canada.
– Communications Research Laboratory (CRL)/Japan.
– Danish Space Research Institute (DSRI)/Denmark.
– European Organization for the Exploitation of Meteorological Satellites
(EUMETSAT)/Europe.
– European Telecommunications Satellite Organization (EUTELSAT)/Europe.
– Federal Service of Scientific, Technical & Cultural Affairs (FSST&CA)/Belgium.
– Hellenic National Space Committee (HNSC)/Greece.
– Indian Space Research Organization (ISRO)/India.
– Institute of Space and Astronautical Science (ISAS)/Japan.
– Institute of Space Research (IKI)/Russian Federation.
– KFKI Research Institute for Particle & Nuclear Physics (KFKI)/Hungary.
– MIKOMTEK: CSIR (CSIR)/Republic of South Africa.
– Korea Aerospace Research Institute (KARI)/Korea.
– Ministry of Communications (MOC)/Israel.
– National Oceanic & Atmospheric Administration (NOAA)/USA.
– National Space Program Office (NSPO)/Taipei.
– Swedish Space Corporation (SSC)/Sweden.
– United States Geological Survey (USGS)/USA.
CCSDS 301.0-B-3 Page iv January 2002
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
DOCUMENT CONTROL

Document Date Status and Substantive Changes
Original Issue (superseded).
CCSDS Time Code January
301.0-B-1 Formats, Issue 1 1987
Issue 2 (superseded).
CCSDS Time Code April
301.0-B-2 Formats, Issue 2 1990
Current issue (supersedes Issue 2)
CCSDS Time Code January
301.0-B-3 Formats, Issue 3 2002
CCSDS 301.0-B-3 Page v January 2002
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
CONTENTS

Section Page
1 INTRODUCTION.1-1
1.1 PURPOSE.1-1
1.2 SCOPE.1-1
1.3 CATEGORIZING OF CCSDS TIME CODE FORMATS.1-1
1.4 APPLICABILITY.1-2
1.5 BIT NUMBERING CONVENTION AND NOMENCLATURE.1-2
2 TIME CODE FORMATS.2-1
2.1 TIME CODE FIELDS.2-1
2.2 CCSDS UNSEGMENTED TIME CODE (CUC).2-2
2.3 CCSDS DAY SEGMENTED TIME CODE (CDS) .2-3
2.4 CCSDS CALENDAR SEGMENTED TIME CODE (CCS) .2-4
2.5 CCSDS ASCII CALENDAR SEGMENTED TIME CODE (ASCII) .2-6
2.6 AGENCY-DEFINED CODES.2-9

ANNEX A RANGE OF SEGMENT COUNTERS FOR SEGMENTED
TIME CODES .A-1
ANNEX B RATIONALE FOR TIME CODES. B-1
ANNEX C GLOSSARY OF SELECTED TIME TERMS.C-1
ANNEX D CONVERSION BETWEEN TAI AND UTC .D-1
ANNEX E EXAMPLE OF ACCOMMODATION OF AGENCY-DEFINED
CODES (PB-5J). E-1
ANNEX F INFORMATIVE REFERENCES . F-1


Table
B-1 Applicability of the Criteria . B-2
B-2 Time Code Services . B-3
B-3 Service Categories of Time Codes. B-4

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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
1 INTRODUCTION
1.1 PURPOSE
The purpose of this Recommendation is to establish a small number of standardized
recommended time code formats for use in data interchange applications between Agencies of
the CCSDS. This Recommendation does not address timing performance issues such as
stability, precision, accuracy, etc.
1.2 SCOPE
Time codes are digital representations of time information. Four standard CCSDS-
Recommended time codes are described (one "unsegmented" and three "segmented" codes)
which use the international standard second as the fundamental unit of time.
An unsegmented time code is a pure binary count of time units and fractional time units from
a starting time called the "epoch".
A segmented time code is one in which the count of time units and fractional time units is
accumulated in two or more cascaded counters which count modulo of various bases and start
from the epoch.
The four Recommended time code formats carry both the time data (in the TIME
SPECIFICATION FIELD, or T-FIELD) and, where applicable, additional information (in the
TIME CODE PREAMBLE FIELD or P-FIELD) that uniquely identifies a specific time code
format. The P-FIELD may be either explicit or implicit (refer to paragraph 2.1.1).
1.3 CATEGORIZING OF CCSDS TIME CODE FORMATS
In this Recommendation, four Levels of time code formats can be defined based on the four
degrees of interpretability of the code.
All time code Levels provide for recognizing the boundaries of the time code field and thus
that field can be transferred, as a block, to another location.
Level 1: Complete Unambiguous Interpretation
Level 1 code formats are fully self-defined and allow absolute time interpretation for the
events tagged with the code. Time comparison with other time sources utilizing Level 1 codes
can thus be made. These codes are the CCSDS-Recommended codes and have the
Recommended epochs.
CCSDS 301.0-B-3 Page 1-1 January 2002
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
Level 2: Partial Interpretation
Level 2 code formats have a fully self-defined structure, but support only partial
interpretation because it is necessary to obtain the epoch from an external source. Relative
time interpretation for the events tagged with Level 2 formats can be made. To make
accurate time comparisons with other time sources which use other epochs (Level 1 or Level
2), additional information must be obtained from external sources.
Level 3: No Interpretation Except for Recognition of Increasing Time Value
Level 3 code formats are those for which only the code length is self-defined and a
monotonically increasing (possibly non-uniformly increasing) value is guaranteed except for
the recycling instant (i.e., counter rollover). For Level 3 codes, the epoch, the time units, and
the T-field structure are not self-defined.
Level 4: No Interpretation
Level 4 code formats are those for which only the code length is self-defined. No other
features of the code are identified.
1.4 APPLICABILITY
This Recommendation contains a number of time codes 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
B and may help the application engineer to select a suitable code. Definition of the timing
accuracy underlying a particular time code is not a function of this Recommendation but is the
responsibility of the authority cognizant of time performance for the applicable system.
1.5 BIT NUMBERING CONVENTION AND NOMENCLATURE
In this document, the following convention is used to identify each bit in an N-bit field. The
first bit in the field to be transmitted (i.e., the most left justified when drawing a figure) is
defined to be "Bit 0"; the following bit is defined to be "Bit 1" and so on up to "Bit N-1".
When the field is used to express a binary value (such as a counter), the Most Significant Bit
(MSB) shall be the first transmitted bit of the field, i.e., "Bit 0".
CCSDS 301.0-B-3 Page 1-2 January 2002
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
BIT 0 BIT N-1

N-BIT DATA FIELD
FIRST BIT TRANSMITTED = MSB

In accordance with modern data communications practice, spacecraft data fields are often
grouped into 8-bit "words" which conform to the above convention. Throughout this
Recommendation, the following nomenclature is used to describe this grouping:

8-BIT WORD = "OCTET"


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ISO 11104:2003(E)
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
2 TIME CODE FORMATS
The time code formats can be represented as a combination of a preamble field (P) and a time
specification field (T). The P-field uniquely defines the options, parameters, and encoding
structure of the T-field and should be included whenever the recipient of the time code may
be uncertain as to the selected code. The T-field and the P-field shall each be an integral
number of octets in length.
2.1 TIME CODE FIELDS
2.1.1 PREAMBLE FIELD (P-FIELD)
The time code preamble field (P-field) may be either explicitly or implicitly conveyed. If it is
implicitly conveyed (not present with T-field), the code is not self-identified, and
identification must be obtained by other means.
As presently defined, the explicit representation of the P-field is limited to one octet whose
format is described as follows:
Bit Interpretation
0 Extension flag
1 - 3 Time code identification
4 - 7 Detail bits for information on the code
The first bit (Bit 0) of the P-field is the extension flag, used to indicate that a second octet is
included in the P-field for time code identification. Such an expansion may be required to
accommodate new time codes or to provide more information (for example, on the clock
used). Presently, the value of this bit is "0", indicating that there is not a second octet present.
If a second octet is present, its first bit shall be an extension flag with the same definition: "0"
implies it is the last octet of the P-field, "1" implies another octet follows.
The detailed specifications of bits 1 to 7 are given in the following paragraphs with the
description of each code. The time code identifications (bit 1 - 3) = 000, 011 and 111 are
reserved for future application.
The preamble field does not apply in the case of the ASCII time code.
2.1.2 TIME FIELD (T-FIELD)
For each code the T-field has a basic structure and optional extensions which allow increases
in resolution or ambiguity period.
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
2.2 CCSDS UNSEGMENTED TIME CODE (CUC)
2.2.1 T-FIELD
For the unsegmented binary time codes described herein, the T-field consists of a selected
number of contiguous time elements, each element being one octet in length. An element
represents the state of 8 consecutive bits of a binary counter, cascaded with the adjacent
counters, which rolls over at a modulo of 256.
The basic time unit is the second. The T-field consists of 1 to 4 octets of coarse time
(seconds) and 0 to 3 octets of fine time (subseconds). The coarse time code elements are a
count of the number of seconds elapsed from the epoch. Four octets of coarse time results in
a maximum ambiguity period of approximately 136 years. This allows a time code
representation of time through the year 2094 for those which are referenced to the TAI epoch
of 1958 January 1.
Zero to three octets of fine code elements result in a resolution of, respectively: 1 second;
-8 -16 -24
2 second (about 4 ms); 2 second (about 15 µs); or 2 second (about 60 ns).
The CCSDS-Recommended epoch is that of 1958 January 1 (TAI), but other Agency-defined
epochs may be accommodated as a Level 2 code.
This time code is not UTC-based and leap second corrections do not apply.
2.2.2 P-FIELD
Bit 1 - 3 = Time code identification
001 — 1958 January 1 epoch (Level 1)
010 — Agency-defined epoch (Level 2)
*
Bit 4 - 5 = (number of octets of coarse time) – minus one
Bit 6 - 7 = (number of octets of fine time)

*
For the 1958 epoch, bits 4-5 must be "11" to ensure a long enough ambiguity period. The value
in this field may be variable and shall be in the range of 0 to 3, corresponding to 1 to 4 octets.

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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
2.3 CCSDS DAY SEGMENTED TIME CODE (CDS)
2.3.1 T-FIELD
For the segmented binary time code described herein, the T-field consists of a selected
number of contiguous time segments. Each segment represents the state of a binary counter,
cascaded with the adjacent counters, which rolls over at a modulo specified for each counter.
The segmented binary day count code Recommendation, designated CDS (CCSDS Day
Segmented), is as follows:

Submilliseconds
DAY
ms of day
of ms
SEGMENT WIDTH
See bits 6-7
16 or 24
32
(bits)
of P-Field

Each segment above is a right-adjusted binary counter. The CCSDS recommended day
segment is a continuous counter of days from 1958 January 1 starting with 0, but other
Agency-defined epochs may be accommodated as a level 2 code.
The submilliseconds segment is optional depending upon the resolution desired (see bits 6-7
of the P-Field). Since this code is UTC-based, the leap second correction must be made.
2.3.2 P-FIELD
Bits 1 - 3 = time code identification = ‘100’
Bit 4 = epoch identification:
‘0’ — 1958 January 1 epoch  (Level 1)
‘1’ — Agency-defined epoch  (Level 2)
Bit 5 = length of day segment:
‘0’ — 16-bit day segment
‘1’ — 24-bit day segments
Bits 6 - 7 = length of submillisecond segment (i.e., resolution):
‘00’ — submillisecond segment is absent (millisecond)
‘01’ — 16-bit (microsecond)
‘10’ — 32-bit (picosecond)
‘11’ — reserved for future use
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
2.4 CCSDS CALENDAR SEGMENTED TIME CODE (CCS)
2.4.1 T-FIELD
For the segmented Binary Coded Decimal (BCD) time code described herein, the T-field
consists of a variable number of contiguous time segments. Each 8-bit segment represents
two decimal digits.
Both CCS time code variations are UTC-based. The leap second correction must be made.
The calendar segmented code Recommendations, designated CCS (CCSDS Calendar
Segmented time code), are Level 1 time code formats and are as follows:
2.4.1.1 Month of Year/Day of Month Calendar Variation

OPTIONAL
-4 -6 -8 -10 -12
-2
10 s 10 s 10 s 10 s 10 s
YR MO DOM m s 10 s
h
SEGMENT
16 8 8 8 8 8 8 8 8 8 8 8
WIDTH (bits)

The year A.D. segment (YR) requires 16 bits for proper representation of the decimal year.
All other segments require 8 bits for proper representation. The month (MO) and day of
month (DOM) segments are present when the calendar variation flag (bit 4 of the P-field) is
set to zero.
2.4.1.2 Day of Year Calendar Variation

OPTIONAL
-2 -4 -6 -8 -10 -12
YR DOY h m s 10 s 10 s 10 s 10 s 10 s 10 s
SEGMENT
16 16 8 8 8 8 8 8 8 8 8
WIDTH (bits)

This variation of the CCS time code substitutes day of year (DOY) in place of the month
(MO) and day of month (DOM) segments. The day of year segment must be 16 bits long (all
segments must be multiples of 8 bits). The four most significant bits of this segment are not
used and are set to zero. The day of year segment is present when the calendar variation flag
(bit 4 of the P-field) is set to a value of one. The year A.D. segment is 16 bits in length.
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
2.4.2 P-FIELD
Bits 1 - 3 = time code identification = 101
Bit 4 = calendar variation flag:
0 — month of year/day of month variation
1 — day of year variation
Bits 5 - 7 = resolution (number of optional subsecond segments):
000 — 1 s
–2
001 — 10 s
–4
010 — 10 s
–6
011 — 10 s
–8
100 — 10 s
–10
101 — 10 s
–12
110 — 10 s
111 — not used
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ISO 11104:2003(E)
CCSDS RECOMMENDATION FOR TIME CODE FORMATS
2.5 CCSDS ASCII CALENDAR SEGMENTED TIME CODE (ASCII)
2.5.1 T-FIELD
The CCSDS ASCII segmented time code is composed of a variable number of ASCII
characters forming the T-field.
Both ASCII time code variations are UTC-based and leap second corrections must be made.
The time represented is intended to match civil time usage. Therefore, the epoch is taken to
be the usual Gregorian calendar epoch of 1 AD, and the time is that of the prime meridian.
The ASCII time code Recommendations are Level 1 time code formats.
2.5.1.1 ASCII TIME CODE A, Month/Day of Month Calendar Variation:
The format for ASCII Time Code A is as follows:
YYYY-MM-DDThh:mm:ss.d→dZ
where each character is an ASCII character using one octet with the following meanings:
YYYY = Year in four-cha
...