ISO 18423:2013

Space data and information transfer systems — Pseudo-Noise (PN) Ranging Systems

ISO 18423:2013 provides a Recommendation for Space Data System Standards in the area of transparent and regenerative Pseudo-Noise (PN) ranging systems. The PN ranging system is used to measure the round-trip light time between a ground station and a spacecraft. Regenerative ranging is primarily relevant for low Signal-to-Noise Ratio (SNR) cases like those seen in deep space missions; transparent ranging is more suitable for high SNR cases or when high accuracy ranging is not required. ISO 18423:2013 defines both transparent and regenerative PN ranging systems for non-data relay satellite users. The specification for PN code components and generation, on-board spacecraft regenerative/transparent processing, ground station processing, and uplink and downlink signal modulation are defined. ISO 18423:2013 does not specify individual implementations or products, implementation of service interfaces within real systems, or the management activities required to configure and control the protocol.

Systèmes de transfert des informations et données spatiales — Systèmes de mesure du pseudo-bruit

General Information

• Status: Withdrawn
• Publication Date: 28-May-2013
• Withdrawal Date: 28-May-2013
• 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: 11-Aug-2015

Relations

• Revised: ISO 18423:2015 - Space data and information transfer systems — Pseudo-Noise (PN) Ranging Systems
• Effective Date: 02-Aug-2014

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 18423
First edition
2013-06-01

Space data and information transfer
systems — Pseudo-Noise (PN) Ranging
Systems
Systèmes de transfert des informations et données spatiales —
Systèmes de mesure du pseudo-bruit




Reference number
ISO 18423:2013(E)
©
ISO 2013

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ISO 18423:2013(E)

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©  ISO 2013
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ISO 18423:2013(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.
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 documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2. www.iso.org/directives
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. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received. www.iso.org/patents
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
ISO 18423 was prepared by the Consultative Committee for Space Data Systems (CCSDS) (as
CCSDS 414.1-B-1, March 2009) 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.

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INTERNATIONAL STANDARD ISO 18423:2013(E)

Space data and information transfer systems — Pseudo-Noise
(PN) Ranging Systems
1 Scope
This International Standard provides a Recommendation for Space Data System Standards in the area of
transparent and regenerative Pseudo-Noise (PN) ranging systems. The PN ranging system is used to
measure the round-trip light time between a ground station and a spacecraft. Regenerative ranging is primarily
relevant for low Signal-to-Noise Ratio (SNR) cases like those seen in deep space missions; transparent
ranging is more suitable for high SNR cases or when high accuracy ranging is not required.
This International Standard defines both transparent and regenerative PN ranging systems for non–data relay
satellite users. The specification for PN code components and generation, on-board spacecraft
regenerative/transparent processing, ground station processing, and uplink and downlink signal modulation
are defined. This International Standard does not specify a) individual implementations or products, b)
implementation of service interfaces within real systems, or c) the management activities required to configure
and control the protocol.
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 414.1-B-1, March 2009, Pseudo-Noise (PN) Ranging Systems.
For the purposes of international standardization, the modifications outlined below shall apply to the specific
clauses and paragraphs of publication CCSDS 414.1-B-1.
Pages i to vi
This part is information which is relevant to the CCSDS publication only.
3 Revision of publication CCSDS 414.1-B-1
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 414.1-
B-1. To this end, NASA will act as a liaison body between CCSDS and ISO.
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ISO 18423:2013(E)












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ISO 18423:2013(E)

Recommendation for Space Data System Standards
PSEUDO-NOISE (PN)
RANGING SYSTEMS
RECOMMENDED STANDARD
CCSDS 414.1-B-1
BLUE BOOK
March 2009
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ISO 18423:2013(E)
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
AUTHORITY



Issue: Recommended Standard, Issue 1
Date: March 2009
Location: Washington, DC, USA

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 documents 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 document is published and maintained by:

CCSDS Secretariat
Space Communications and Navigation Office, 7L70
Space Operations Mission Directorate
NASA Headquarters
Washington, DC 20546-0001, USA
CCSDS 414.1-B-1 Page i March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
STATEMENT OF INTENT
The Consultative Committee for Space Data Systems (CCSDS) is an organization officially
established by the management of its members. 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 Recommended Standards and are not
considered binding on any Agency.
This Recommended Standard is issued by, and represents the consensus of, the CCSDS
members. Endorsement of this Recommendation is entirely voluntary. Endorsement,
however, indicates the following understandings:
o Whenever a member establishes a CCSDS-related standard, this standard will be in
accord with the relevant Recommended Standard. Establishing such a standard
does not preclude other provisions which a member may develop.
o Whenever a member establishes a CCSDS-related standard, that member will
provide other CCSDS members 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 Recommended Standard nor any ensuing standard is a substitute for a
memorandum of agreement.
No later than five years from its date of issuance, this Recommended Standard 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 Recommended Standard is issued, existing
CCSDS-related member standards and implementations are not negated or deemed to be non-
CCSDS compatible. It is the responsibility of each member to determine when such
standards or implementations are to be modified. Each member is, however, strongly
encouraged to direct planning for its new standards and implementations towards the later
version of the Recommended Standard.
CCSDS 414.1-B-1 Page ii March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
FOREWORD
Through the process of normal evolution, it is expected that expansion, deletion, or
modification of this document may occur. This Recommended Standard is therefore subject
to CCSDS document management and change control procedures, which are defined in the
Procedures Manual for the Consultative Committee for Space Data Systems. 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 414.1-B-1 Page iii March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
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.
– China National Space Administration (CNSA)/People’s Republic of China.
– Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)/Germany.
– European Space Agency (ESA)/Europe.
– Russian Federal Space Agency (RFSA)/Russian Federation.
– Instituto Nacional de Pesquisas Espaciais (INPE)/Brazil.
– Japan Aerospace Exploration Agency (JAXA)/Japan.
– National Aeronautics and Space Administration (NASA)/USA.

Observer Agencies

– Austrian Space Agency (ASA)/Austria.
– Belgian Federal Science Policy Office (BFSPO)/Belgium.
– Central Research Institute of Machine Building (TsNIIMash)/Russian Federation.
– Centro Tecnico Aeroespacial (CTA)/Brazil.
– Chinese Academy of Sciences (CAS)/China.
– Chinese Academy of Space Technology (CAST)/China.
– Commonwealth Scientific and Industrial Research Organization (CSIRO)/Australia.
– CSIR Satellite Applications Centre (CSIR)/Republic of South Africa.
– Danish National Space Center (DNSC)/Denmark.
– European Organization for the Exploitation of Meteorological Satellites
(EUMETSAT)/Europe.
– European Telecommunications Satellite Organization (EUTELSAT)/Europe.
– Geo-Informatics and Space Technology Development Agency (GISTDA)/Thailand.
– Hellenic National Space Committee (HNSC)/Greece.
– Indian Space Research Organization (ISRO)/India.
– Institute of Space Research (IKI)/Russian Federation.
– KFKI Research Institute for Particle & Nuclear Physics (KFKI)/Hungary.
– Korea Aerospace Research Institute (KARI)/Korea.
– Ministry of Communications (MOC)/Israel.
– National Institute of Information and Communications Technology (NICT)/Japan.
– National Oceanic and Atmospheric Administration (NOAA)/USA.
– National Space Organization (NSPO)/Chinese Taipei.
– Naval Center for Space Technology (NCST)/USA.
– Scientific and Technological Research Council of Turkey (TUBITAK)/Turkey.
– Space and Upper Atmosphere Research Commission (SUPARCO)/Pakistan.
– Swedish Space Corporation (SSC)/Sweden.
CCSDS 414.1-B-1 Page iv March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
– United States Geological Survey (USGS)/USA.
CCSDS 414.1-B-1 Page v March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
DOCUMENT CONTROL

Document Title Date Status
CCSDS Pseudo-Noise (PN) Ranging March 2009 Current issue
414.1-B-1 Systems, Recommended Standard,
Issue 1




CCSDS 414.1-B-1 Page vi March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
CONTENTS
Section Page
1 INTRODUCTION. 1-1

1.1 PURPOSE . 1-1
1.2 SCOPE . 1-1
1.3 APPLICABILITY . 1-1
1.4 RATIONALE . 1-1
1.5 CONVENTIONS AND DEFINITIONS . 1-2
1.6 REFERENCES . 1-3

2 OVERVIEW . 2-1

REGENERATIVE PSEUDO-NOISE RANGING . 3-1
3

3.1 OVERVIEW . 3-1
3.2 PN CODE STRUCTURE . 3-1
3.3 GROUND STATION UPLINK PROCESSING . 3-2
3.4 ON-BOARD PROCESSING . 3-4
3.5 GROUND STATION DOWNLINK PROCESSING . 3-7

4 TRANSPARENT PSEUDO-NOISE RANGING . 4-1

4.1 OVERVIEW . 4-1
4.2 PN CODE STRUCTURE . 4-1
4.3 GROUND STATION UPLINK PROCESSING . 4-1
4.4 ON-BOARD TRANSPARENT PROCESSING . 4-2
4.5 GROUND STATION DOWNLINK PROCESSING . 4-4

5 SECURITY . 5-1

5.1 INTRODUCTION . 5-1
5.2 SECURITY CONCERNS WITH RESPECT TO THE CCSDS DOCUMENT . 5-1
5.3 POTENTIAL THREATS AND ATTACK SCENARIOS . 5-1
5.4 CONSEQUENCES OF NOT APPLYING SECURITY TO THE
TECHNOLOGY . 5-2

ANNEX A SPECIFICATIONS FOR PN RANGING (NORMATIVE) . A-1
ANNEX B EXAMPLE OF AVAILABLE CHIP RATES (INFORMATIVE) .B-1
ANNEX C INFORMATIVE REFERENCES (INFORMATIVE) . C-1
ANNEX D ABBREVIATIONS AND ACRONYMS (INFORMATIVE) . D-1
CCSDS 414.1-B-1 Page vii March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
CONTENTS (contintued)
Figure Page
3-1 Regenerative T4B PN Code Generation . 3-1
3-2 Regenerative T2B PN Code Generation . 3-2
4-1 Transparent T2B PN Code Generation . 4-1

Table
3-1 Uplink Chip Rates . 3-3
3-2 Theoretical Ranging Code Phase Acquisition Time for the On-Board Receiver . 3-6
3-3 Theoretical (One-Way) Ranging Jitter for the On-Board Receiver . 3-6
3-4 Theoretical Ranging Code Phase Acquisition Time for the Station Receiver . 3-9
3-5 Theoretical (One-Way) Ranging Jitter for the Station Receiver . 3-9
4-1 Theoretical Ranging Code Phase Acquisition Time for the Station Receiver
(Transparent Ranging) . 4-5
4-2 Theoretical (One-Way) Ranging Jitter for the Station Receiver
(Transparent Ranging) . 4-5
A-1 Key Specifications for On-Board PN Regenerative Ranging . A-1
A-2 Key Specifications for PN Ranging and On-Board Transparent Channel . A-2
B-1 Example of Available Chip Rates . B-1



CCSDS 414.1-B-1 Page viii March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
1 INTRODUCTION
1.1 PURPOSE
The purpose of this document is to provide a Recommendation for Space Data System
1
Standards in the area of transparent and regenerative Pseudo-Noise (PN) ranging systems.
The PN ranging system is used to measure the round-trip light time between a ground station
and a spacecraft. Regenerative ranging is primarily relevant for low Signal-to-Noise Ratio
(SNR) cases like those seen in deep space missions; transparent ranging is more suitable for
high SNR cases or when high accuracy ranging is not required.
1.2 SCOPE
This Recommended Standard defines both transparent and regenerative PN ranging systems
for non–data relay satellite users. The specification for PN code components and generation,
on-board spacecraft regenerative/transparent processing, ground station processing, and
uplink and downlink signal modulation are defined in this document. This Recommended
Standard does not specify a) individual implementations or products, b) implementation of
service interfaces within real systems, or c) the management activities required to configure
and control the protocol.
1.3 APPLICABILITY
The Recommended Standard specified in this document is to be invoked through the normal
standards programs of each CCSDS Agency and is applicable to those missions for which
cross support based on capabilities described in this Recommended Standard is anticipated.
Where mandatory capabilities are clearly indicated in sections of the Recommended
Standard, they must be implemented when this document is used as a basis for cross support.
Where options are allowed or implied, implementation of these options is subject to specific
bilateral cross support agreements between the Agencies involved.
1.4 RATIONALE
The CCSDS believes it is important to document the rationale underlying the
recommendations chosen, so that future evaluations of proposed changes or improvements
will not lose sight of previous decisions. Concept and rationale behind the decisions that
formed the basis for this Recommended Standard are found in the CCSDS Pseudo-Noise
Ranging Systems Green Book (reference [C1]).

1
The term ‘transparent ranging’ is used in this standard to mean non-regenerative ranging or turn-around
ranging.
CCSDS 414.1-B-1 Page 1-1 March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
1.5 CONVENTIONS AND DEFINITIONS
1.5.1 DEFINITIONS
The following definitions apply throughout this Recommended Standard:
chip rate: rate at which the PN code bits (or ‘chips’) are transmitted.
coherent transponder: transponder for which the downlink carrier is phase-coherent with
the received uplink carrier.
component sequences: family of shorter-length PN sequences used to form the ranging PN
code using logic operations.
range clock: PN component code with the highest frequency (i.e., shortest period);
determines the range resolution.
regenerative ranging: type of ranging where the spacecraft demodulates and acquires the
ranging code by correlation with a local code replica from the uplink ranging signal,
and regenerates the ranging code on the downlink.
transparent ranging: type of ranging where the spacecraft frequency-translates the uplink
ranging signal to the downlink without code acquisition (i.e., non-regenerative
ranging or turn-around ranging).
one-way jitter: ranging jitter in meters resulting from measuring the round-trip light time and
halving the measurement to compute the distance.
1.5.2 NOMENCLATURE
The following conventions apply through this Recommended Standard:
– the words ‘shall’ and ‘must’ imply a binding and verifiable specification;
– the word ‘should’ implies an optional, but desirable, specification;
– the word ‘may’ implies an optional specification;
– the words ‘is’, ‘are’, and ‘will’ imply statements of fact.
1.5.3 CONVENTIONS
In this document, the following convention is used:
– A ‘+1’ ranging chip corresponds to a binary 0 value;
– A ‘-1’ ranging chip corresponds to a binary 1 value.
CCSDS 414.1-B-1 Page 1-2 March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
1.6 REFERENCES
The following documents contain provisions which, through reference in this text, constitute
provisions of this Recommended Standard. At the time of publication, the editions indicated
were valid. All documents are subject to revision, and users of this Recommended Standard
are encouraged to investigate the possibility of applying the most recent editions of the
documents indicated below. The CCSDS Secretariat maintains a register of currently valid
CCSDS Recommended Standards.
[1] Radio Frequency and Modulation Systems—Part 1: Earth Stations and Spacecraft.
Recommendation for Space Data System Standards, CCSDS 401.0-B-19. Blue Book.
Issue 19. Washington, D.C.: CCSDS, July 2008.
NOTE – Informative references are provided in annex C.

CCSDS 414.1-B-1 Page 1-3 March 2009
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ISO 18423:2013(E)
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
2 OVERVIEW
Several upcoming missions require higher accuracy spacecraft position determination
compared to currently supported missions. One solution to cope with these new requirements
is the use of regenerative PN ranging systems. Regenerative ranging presents several
advantages with respect to the classical non-regenerative ranging, which is the approach at
present used by CCSDS Agencies supporting deep space missions. The regenerative ranging
technique requires the use of PN codes with important impacts for on-board transponder and
Earth station design, differing from non-regenerative systems for which transparent
transponders are commonly used.
Even though the advantages of regenerative ranging are mainly relevant to the low SNR case
(e.g., deep space missions), the use of PN ranging with transparent on-board processing is
also possible. This solution is attractive in presence of good link margin or when very
accurate ranging is not needed with performance similar to non-PN ranging systems. A
transponder based on a transparent ranging channel will have reduced complexity compared
with the regenerative case. The spacecraft demodulates a large frequency range around the
carrier and re-modulates the entire bandpass including the uplink noise onto the downlink
4
carrier. With a transparent system, the ranging SNR at the station is proportional to 1/r
where r is the distance to be measured. In a regenerative PN ranging system, a PN ranging
code is phase modulated on the uplink carrier and transmitted from the ground station to the
spacecraft. This ranging signal is derived using a logical combination of a ranging clock and
several component PN codes. Received by the spacecraft, the ranging signal is demodulated
by the spacecraft transponder, and the ranging code is acquired. The spacecraft then
regenerates the ranging code coherently with the uplink code and phase modulates the
downlink carrier with the locally generated version of the ranging code. Back at the ground
station, the station receiver demodulates the downlink and correlates the received ranging
signal with a local model of the range clock and component PN codes to determine the
2
round-trip light time. The ranging SNR at the station is therefore proportional to 1/r where r
is the distance to be measured.
Selection of the ranging clock frequency determines the range precision. Likewise, the
component codes structure and combination logic affect the code acquisition time and
probability, range ambiguity, and range precision. The PN codes in this Recommended
Standard have been selected to provide high ranging accuracy while maintaining a reasonable
code acquisition time.
For transparent PN ranging, the uplink process is exactly the same as in the regenerative
ranging case. However, in transparent PN ranging the spacecraft does not attempt to acquire
the ranging code; instead, it phase modulates the uplink ranging signal as received on board
onto the downlink without further processing. The ground station receiver demodulates the
downlink and performs the PN ranging correlation in the same manner as for regenerative
ranging. Because any uplink noise is re-modulated onto the downlink, transparent ranging
accuracy will generally not be as good as with regenerative ranging; however, transparent
ranging requires less complexity in the spacecraft transponder.
CCSDS 414.1-B-1 Page 2-1 March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
This Recommended Standard is divided into two main parts covering regenerative PN
ranging and transparent PN ranging. This Recommended Standard contains sections on the
selection of PN code structure and modulation scheme, ground station uplink processing, on-
board spacecraft processing, and ground station downlink processing.

CCSDS 414.1-B-1 Page 2-2 March 2009
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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
3 REGENERATIVE PSEUDO-NOISE RANGING
3.1 OVERVIEW
This section provides recommendations for regenerative PN ranging. Specifically,
recommendations are made for the PN code structure and modulation scheme, ground station
transmit (uplink) processing, on-board regenerative processing, and ground station receive
(downlink) processing.
3.2 PN CODE STRUCTURE
3.2.1 OVERVIEW
This subsection defines the PN ranging code components and combination logic for
generating the regenerative PN ranging codes.
3.2.2 WEIGHTED-VOTING BALANCED TAUSWORTHE, ν=4
For range measurements where the ranging accuracy is of primary concern, the PN ranging
code called Weighted-voting balanced Tausworthe, ν=4 (T4B) shall be selected.
The code is made up of six binary (±1) periodic ‘component sequences’ with a combination
algorithm based on giving ν=4 votes to the clock component C1 as shown in figure 3-1.
The resulting ranging sequence C is periodic with length L = 2 × 7 × 11 × 15 × 19 × 23 =
1,009,470 chips.
C1
+1 –1
C2
+1 +1 +1 –1 –1 +1 –1
C3
+1 +1 +1 –1 –1 –1 +1 –1 +1 +1 –1
C4
+1 +1 +1 +1 –1 –1 –1 +1 –1 –1 +1 +1 –1 +1 –1
C5
+1 +1 +1 +1 –1 +1 –1 +1 –1 –1 –1 –1 +1 +1 –1 +1 +1 –1 –1
C6
+1 +1 +1 +1 +1 –1 +1 –1 +1 +1 –1 –1 +1 +1 –1 –1 +1 –1 +1 –1 –1 –1 –1

where the combined sequence is C = sign(4C1+ C2 − C3 − C4 + C5 − C6)
Figure 3-1: Regenerative T4B PN Code Generation
CCSDS 414.1-B-1 Page 3-1 March 2009
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Combining Logic

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ISO 18423:2013(E)
CCSDS RECOMMENDED STANDARD FOR PSEUDO-NOISE RANGING SYSTEMS
3.2.3 WEIGHTED-VOTING BALANCED TAUSWORTHE, ν=2
For range measurements where the acquisition time is of primary concern, such as for
missions where the ranging signal will be very weak, the PN ranging code called Weighted-
...