CAUTION - This text file is provided for the sole purpose of allowing 
text-string searching.  It is NOT a faithful reproduction of the 
published document:  figures, equations, special characters, and 
character attributes used to convey information are not reproduced in 
this text file;  tables, which may be reproduced as text, may have lost 
crucial row or column alignment.

A Portable Document Format (PDF) version of this document is available 
in the main document listing.  The PDF file contains all elements of the 
document as published by the CCSDS.  The PDF file should be used in all 
cases where there is a need for faithful reproduction of the information 
contained in the published document.


                               CONSULTATIVE
                               COMMITTEE FOR
                            SPACE DATA SYSTEMS



                         RECOMMENDATION FOR SPACE
                          DATA SYSTEMS STANDARDS


                    +----------------------------------+
                    |                                  |
                    |       RADIO FREQUENCY AND        |
                    |        MODULATION SYSTEMS        |
                    |              PART 1              |
                    |  EARTH STATIONS AND SPACECRAFT   |
                    |                                  |
                    +----------------------------------+



                               CCSDS 401.0-B

                                 BLUE BOOK








                                 AUTHORITY



                *******************************************
                *   Issue:     Blue Book                  *
                *   Date:      September 1989             *
                *   Location:  CCSDS Plenary Meeting      *
                *              September 1989             *
                *              Ottawa, Canada             *
                *******************************************



These  Recommendations  reflect the consensus technical  agreement  of  the
following  member  agencies of the Consultative Committee  for  Space  Data
Systems (CCSDS):

o  British National Space Centre (BNSC)/United Kingdom.
o  Canadian Space Agency (CSA)/Canada.
o  Centre National D'Etudes Spatiales (CNES)/France.
o  Deutsche   Forschungsanstalt  fuer  Luft-und  Raumfahrt  e.V  (DLR)/West
   Germany.
o  European Space Agency (ESA)/Europe.
o  Indian Space Research Organization (ISRO)/India.
o  Instituto de Pesquisas Espaciais (INPE)/Brazil.
o  National Aeronautics and Space Administration (NASA)/USA.
o  National Space Development Agency of Japan (NASDA)/Japan.

The following observer agencies also concur with these Recommendations:

o  Chinese Academy of Space Technology (CAST)/People's Republic of China.
o  Department  of  Communications,  Communications  Research  Centre  (DOC-
   CRC)/Canada.
o  Institute of Space and Astronautical Science (ISAS)/Japan.


These Recommendations are published by:

   CCSDS Secretariat
   Communications and Data Systems Division (Code 0S)
   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  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.

These  RECOMMENDATIONS are issued by, and represent the consensus  of,  the
CCSDS Plenary body. Agency endorsement of these RECOMMENDATIONS 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 these RECOMMENDATIONS nor any  ensuing  STANDARDS
     are a substitute for a memorandum of agreement.

No  later  than five years from its date of issuance, these RECOMMENDATIONS
will be reviewed by the CCSDS to determine whether they 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.




                                 FOREWORD


This document, which is a set of technical Recommendations prepared by  the
Consultative Committee for Space Data Systems (CCSDS), is intended for  use
by participating space agencies in their development of radio frequency and
modulation systems for earth stations and spacecraft.

These  Recommendations allow implementing organizations within each  agency
to  proceed coherently with the development of compatible Standards for the
flight  and  ground  systems  that  are within  their  cognizance.   Agency
Standards derived from these Recommendations may implement only a subset of
the  optional  features  allowed  by the  Recommendations  herein,  or  may
incorporate features not addressed by the Recommendations.

In  order  to  establish a common framework within which the  agencies  may
develop  standardized communications services, the CCSDS advocates adoption
of  a  layered systems architecture.  These Recommendations pertain to  the
physical  layer of the data system.  Within the physical layer,  there  are
additional   layers   covering  the:  technical   characteristics,   policy
constraints,  and  procedural elements relating to communications  services
provided  by  the  radio frequency and modulation systems.  Recommendations
contained  in  this  document  have been  grouped  into  separate  sections
representing technical, policy, and procedural matters.

These  Recommendations for Radio Frequency and Modulation Systems, Part  1:
Earth  Stations and Spacecraft, were developed for conventional  near-earth
and  deep space missions having moderate communications requirements.  Part
2  will be concerned with data relay satellites and will address the  needs
of  users requiring services not provided by the earth stations covered  in
this document.

The  CCSDS  will  continue to develop Recommendations  for  Part  1:  Earth
Stations  and  Spacecraft, to ensure that new technology  and  the  present
operating environment are reflected.  New Recommendations for Part 1, which
are  developed in the future, will utilize the same format and be  designed
to  be  inserted  into  this book.  Holders of this  document  should  make
periodic  inquiry of the CCSDS Secretariat, at the address shown above,  to
make sure that their book is fully current.

Through  the  process of normal evolution, it is expected  that  expansion,
deletion,  or  modification to this document will be required.   Therefore,
these  Recommendations are subject to CCSDS document management and  change
control procedures which are defined in Reference [1].




                             DOCUMENT CONTROL


  DOCUMENT       TITLE                            DATE STATUS/REMARKS

CCSDS 401.0 B-1  Recommendations  for  Space      January   Original Issue
                 Data System Standards. Radio      1987
                 Frequency  and  Modulation
                 Systems, Part 1: Earth Stations
                 and Spacecraft, Issue-1


CCSDS 401.0 B-1  Recommendations  for  Space      September New RF and Mod.
                 Data System Standards. Radio        1989   Recommendations
                 Frequency  and  Modulation            added  to  Book  at
                 Systems, Part 1: Earth Stations       September  1989
                 and Spacecraft, Issue-1               Ottawa Plenary




                                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]  Radio Frequency and Modulation Report, CCSDS 411.0 G-1, June 1990,  or
     latest edition.

[3]  Radio  Regulations,  International  Telecommunication  Union,  Geneva,
     Switzerland, 1982.

[4]  Recommendations  and  Reports  of the  CCIR,  1986  Plenary  Assembly,
     Dubrovnik, Yugoslavia, 1986.


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




CONTENTS

SECTION   TITLE     ISSUE     PAGE
NO.                                                      DATE     NO.
 
 
       AUTHORITY                                         09-89    i

       STATEMENT OF INTENT                               09-89    ii

       FOREWORD                                          09-89    iii

       DOCUMENT CONTROL                                  09-89    iv

       REFERENCES                                        09-89    v


1.0    INTRODUCTION                                      09-89    1.0-1

  1.1    PURPOSE                                        09-89    1.0-1

  1.2    SCOPE                                          09-89    1.0-1

  1.3    APPLICABILITY                                  09-89    1.0-1

  1.4    DOCUMENT FORMAT                                09-89    1.0-1

  1.5    DEEP SPACE AND NON DEEP SPACE                  09-89    1.0-3


2.0    TECHNICAL RECOMMENDATIONS`                        09-89    2.0-1

         EARTH-TO-SPACE RF RECOMMENDATION SUMMARY       09-89    2.0-2

         TELECOMMAND RECOMMENDATION SUMMARY             09-89    2.0-3

         SPACE-TO-EARTH RF RECOMMENDATION SUMMARY       09-89    2.0-4

         TELEMETRY RECOMMENDATION SUMMARY               09-89    2.0-5

         RADIO METRIC RECOMMENDATION SUMMARY            09-89    2.0-6

         SPACECRAFT RECOMMENDATION SUMMARY              09-89    2.0-7


2.1    EARTH-TO-SPACE RF RECOMMENDATIONS

  2.1.1  RF CARRIER MODULATION OF THE EARTH-TO-SPACE
          LINK                                           01-87    2.1.1-1

  2.1.2  POLARIZATION OF EARTH-TO-SPACE LINKS           01-87    2.1.2-1

  2.1.3A TRANSMITTER FREQUENCY SWEEP RANGE ON
          EARTH-TO-SPACE LINK, CATEGORY A                01-87    2.1.3A-1

  2.1.3B TRANSMITTER FREQUENCY SWEEP RANGE ON
          EARTH-TO-SPACE LINK, CATEGORY B                01-87    2.1.3B-1

  2.1.4A TRANSMITTER FREQUENCY SWEEP RATE ON
          EARTH-TO-SPACE LINK, CATEGORY A                01-87     2.1.4A

  2.1.4.BTRANSMITTER FREQUENCY SWEEP RATE ON
          EARTH-TO-SPACE LINK, CATEGORY B                01-87     2.1.4B

  2.1.5  RELATIONSHIP OF MODULATOR INPUT VOLTAGE
          TO RESULTANT RF CARRIER PHASE SHIFT            01-87     2.1.5-1

  2.1.6  RF CARRIER SUPPRESSION ON EARTH-TO-SPACE
          LINKS FOR RESIDUAL CARRIER SYSTEMS             01-87     2.1.6-1

  2.1.7B OPERATIONAL AND EQUIPMENT CONSTRAINTS
          RESULTING FROM SIMULTANEOUS TELECOMMAND,
          TELEMETRY, AND RANGING IN RESIDUAL CARRIER
          SYSTEMS, CATEGORY B                            09-89    2.1.7B-1

  2.1.8A MINIMUM EARTH STATION TRANSMITTER
          FREQUENCY RESOLUTION FOR SPACECRAFT
          RECEIVER ACQUISITION, CATEGORY A               09-89    2.1.8A-1

  2.1.8B MINIMUM EARTH STATION TRANSMITTER
          FREQUENCY RESOLUTION FOR SPACECRAFT
          RECEIVER ACQUISITION, CATEGORY B               09-89    2.1.8B-1


2.2    TELECOMMAND RECOMMENDATIONS

  2.2.2  SUBCARRIERS IN TELECOMMAND SYSTEMS             01-87     2.2.2-1

  2.2.3  CHOICE OF WAVEFORMS IN TELECOMMAND LINKS       01-87     2.2.3-1

  2.2.4  RANGE OF TELECOMMAND BIT RATES                 01-87     2.2.4-1

  2.2.5  TELECOMMAND SUBCARRIER FREQUENCY STABILITY     01-87     2.2.5-1

  2.2.6  SYMMETRY OF BASEBAND MODULATING WAVEFORMS      09-89     2.2.6-1

 
2.3    SPACE-TO-EARTH RF RECOMMENDATIONS

  2.3.1  RESIDUAL CARRIERS FOR LOW RATE TELEMETRY,
          SPACE-TO-EARTH LINKS                           01-87     2.3.1-1

  2.3.2  SUPPRESSED CARRIER FOR HIGH RATE TELEMETRY,
          SPACE-TO-EARTH LINKS                           01-87     2.3.2-1

  2.3.3A EARTH STATION RECEIVER ACQUISITION
          FREQUENCY SWEEP RANGE, CATEGORY A              01-87    2.3.3A-1

  2.3.3B EARTH STATION RECEIVER ACQUISITION
          FREQUENCY SWEEP RANGE, CATEGORY B              01-87    2.3.3B-1

  2.3.4A EARTH STATION RECEIVER ACQUISITION
          FREQUENCY SWEEP RATE, CATEGORY A               09-89    2.3.4A-1

  2.3.4B EARTH STATION RECEIVER ACQUISITION
          FREQUENCY SWEEP RATE, CATEGORY B               01-87    2.3.4B-1

  2.3.5  POLARIZATION OF SPACE-TO-EARTH LINKS           01-87    2.3.5-1

  2.3.6  RELATIONSHIP OF MODULATOR INPUT VOLTAGE
          TO RESULTANT RF CARRIER PHASE SHIFT            01-87     2.3.6-1

  2.3.7  EARTH STATION OSCILLATOR REFERENCE
          FREQUENCY STABILITY                            01-87     2.3.7-1

  2.3.8  RF CARRIER SUPPRESSION ON SPACE-TO-EARTH
          LINKS FOR RESIDUAL CARRIER SYSTEMS             01-87     2.3.8-1


2.4  TELEMETRY RECOMMENDATIONS

  2.4.2  MODULATING PCM WAVEFORMS FOR SUPPRESSED
          CARRIER SYSTEMS                                01-87     2.4.2-1

  2.4.3  SUBCARRIERS IN LOW BIT RATE RESIDUAL
          CARRIER TELEMETRY SYSTEMS                      01-87     2.4.3-1

  2.4.4  PSK MODULATION FOR TELEMETRY SUBCARRIERS       01-87     2.4.4-1

  2.4.5  TELEMETRY SUBCARRIER WAVEFORMS                 01-87     2.4.5-1

  2.4.6  TELEMETRY SUBCARRIER FREQUENCY STABILITY       01-87     2.4.6-1

  2.4.7  CHOICE OF PCM WAVEFORMS IN RESIDUAL
          CARRIER TELEMETRY SYSTEMS                      01-87     2.4.7-1

  2.4.8  SYMMETRY OF BASEBAND MODULATING WAVEFORMS      09-90     2.4.8-1

  2.4.9  MINIMUM MODULATED SYMBOL TRANSITION
          DENSITY ON THE SPACE-TO-EARTH LINK             09-89     2.4.9-1

  2.4.10 CHANNEL INPUT AND CODING CONVENTIONS
          FOR QPSK SYSTEMS                               09-89     2.4.10-1


2.5    RADIO METRIC RECOMMENDATIONS

  2.5.1A MINIMUM EARTH STATION GROUP DELAY
          CALIBRATION ACCURACY, CATEGORY A               09-89    2.5.1A-1

  2.5.2A MINIMUM EARTH STATION RANGING GROUP
          DELAY STABILITY, CATEGORY A                    09-89    2.5.2A-1

  2.5.2B MINIMUM EARTH STATION RANGING GROUP
          DELAY STABILITY, CATEGORY B                    09-89    2.5.2B-1

  2.5.3A MINIMUM SPACECRAFT RANGING CHANNEL
          GROUP DELAY STABILITY, CATEGORY A              09-89    2.5.3A-1

  2.5.3B MINIMUM SPACECRAFT RANGING CHANNEL
          GROUP DELAY STABILITY, CATEGORY B              09-89    2.5.3B-1

  2.5.4A RANGING TRANSPONDER BANDWIDTH FOR
          RESIDUAL CARRIER SYSTEMS, CATEGORY A                  09-89    2.5.4A-1

  2.5.4B RANGING TRANSPONDER BANDWIDTH FOR
          RESIDUAL CARRIER SYSTEMS, CATEGORY B           09-89    2.5.4B-1

  2.5.5A PN CODE PHASE SHIFT STABILITY REQUIRED
          IN SPREAD SPECTRUM REGENERATIVE
          RANGING TRANSPONDERS, CATEGORY A               09-89    2.5.5A-1


2.6    SPACECRAFT RECOMMENDATIONS

  2.6.1  TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE
          2025 - 2120 MHz AND 2200 - 2300 MHz BANDS      01-87    2.6.1-1

  2.6.2  TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE
          7145 - 7235 MHz AND 8400 - 8500 MHz BANDS      01-87    2.6.2-1

  2.6.3A TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE
          2025 - 2110 MHz AND 8450 - 8500 MHz BANDS,
          CATEGORY A                                     01-87    2.6.3A-1

  2.6.4A TRANSPONDER TURNAROUND FREQUENCY RATIOS
          FOR THE 7190 - 7235 MHz AND 2200 - 2290 MHz
          BANDS, CATEGORY A                              01-87    2.6.4A-1

  2.6.5B TRANSPONDER TURNAROUND FREQUENCY RATIOS
          FOR THE 2110 - 2120 MHz AND 8400 - 8450 MHz
          BANDS, CATEGORY B                              01-87    2.6.5B-1

  2.6.6B TRANSPONDER TURNAROUND FREQUENCY RATIOS
          FOR THE 7145 - 7190 MHz AND 2290 - 2300 MHz
          BANDS, CATEGORY B                              01-87    2.6.6B-1

  2.6.12 SPACECRAFT TRANSPONDER IF AND AGC AMPLIFIER
          BANDWIDTHS FOR COHERENT OPERATION              09-89    2.6.12-1


3.0    POLICY RECOMMENDATIONS                            09-89    3.0-1

         FREQUENCY UTILIZATION RECOMMENDATION
          SUMMARY                                        09-89    3.0-2

         POWER LIMITATIONS RECOMMENDATION SUMMARY       09-89    3.0-3

         MODULATION METHODS RECOMMENDATION
          SUMMARY                                        09-89    3.0-4

         OPERATIONAL PROCEDURES RECOMMENDATION
          SUMMARY                                        09-89    3.0-5

         TESTING RECOMMENDATION SUMMARY                 09-89    3.0-6

         SPACECRAFT SYSTEMS RECOMMENDATION
          SUMMARY                                        09-89    3.0-7


3.1    FREQUENCY UTILIZATION

  3.1.1  EFFICIENT UTILIZATION OF THE 2 GHz BANDS BY
          SATELLITE MISSIONS                             01-87    3.1.1-1

  3.1.2A USE OF THE 8450 - 8500 MHz BAND FOR SPACE
          RESEARCH, CATEGORY A                           01-87    3.1.2A-1

  3.1.3A USE OF THE 13.25 - 15.35 GHz BANDS FOR SPACE
          RESEARCH, CATEGORY A                           01-87    3.1.3A-1

  3.1.4A CONSTRAINTS ON THE USE OF THE 13.25 - 15.35 GHz
          BAND FOR SPACE RESEARCH, CATEGORY A            09-89    3.1.4A-1

  3.1.5B USE OF THE 31.8 - 34.7 GHz BAND FOR SPACE
          RESEARCH, CATEGORY B                           01-87    3.1.5B-1

  3.1.6B CHANNEL FREQUENCY PLAN FOR 2, 7, AND 8 GHz,
          CATEGORY B                                     01-87    3.1.6B-1


3.2    POWER LIMITATIONS

  3.2.1  LIMITATIONS ON EARTH-TO-SPACE LINK POWER
          LEVELS                                         01-87    3.2.1-1


3.3    MODULATION METHODS

  3.3.1  OPTIMAL RANGING MODULATION WAVEFORMS FOR
          SIMULTANEOUS RANGING, TELECOMMANDING AND
          TELEMETRY OPERATIONS                           09-89    3.3.1-1

  3.3.2A CRITERIA FOR USE OF DIRECT SEQUENCE SPREAD
          SPECTRUM MODULATION, CATEGORY A                09-89    3.3.2A-1

  3.3.3A CRITERIA FOR USE OF QPSK MODULATION IN
          SUPPRESSED CARRIER SYSTEMS, CATEGORY A         09-89    3.3.3A-1


3.4    OPERATIONAL PROCEDURES

  3.4.1  SIMULTANEOUS TELECOMMAND, TELEMETRY,
          AND RANGING OPERATIONS                         09-89    3.4.1-1

  3.4.2  CHARGED PARTICLE MEASUREMENTS IN THE
          TELECOMMUNICATIONS PROPAGATION PATH            09-89    3.4.2-1


3.5    TESTING RECOMMENDATIONS

  3.5.1  MINIMUM SET OF SPACECRAFT - EARTH STATION
          TESTS REQUIRED TO ENSURE COMPATIBILITY         09-89    3.5.1-1


3.6    SPACECRAFT SYSTEMS

  3.6.1A REDUCTION IN INTERFERENCE FROM SPACE-TO-SPACE
          LINKS TO OTHER SPACE SERVICES IN THE 2025 -
          2110 AND 2200 - 2290 MHz BANDS, CATEGORY A     09-89    3.6.1A-1


4.0    PROCEDURAL RECOMMENDATIONS                        09-89    4.0-1

         DESIGN TOOLS RECOMMENDATION SUMMARY             09-89    4.0-2


4.1    DESIGN TOOLS

  4.1.1  SELECTION OF OPTIMUM MODULATION INDICES FOR
          SIMULTANEOUS RANGING, TELECOMMAND, AND
          TELEMETRY OPERATIONS                           09-89    4.1.1-1

  4.1.2  TELECOMMUNICATIONS LINK DESIGN CONTROL
          TABLE                                          09-89    4.1.2-1

  4.1.3  STANDARD TERMINOLOGY FOR
          TELECOMMUNICATIONS LINK PERFORMANCE
          CALCULATIONS                                   09-89    4.1.3-1


5.0    TERMINOLOGY AND GLOSSARY                          09-89    5.0-1

  5.1    TERMINOLOGY                                     09-89    5.1-1

  5.2    GLOSSARY                                        09-89    5.2-1




1.0  INTRODUCTION


1.1   PURPOSE

This  document  recommends  standards for radio  frequency  and  modulation
systems  operated  by  the Consultative Committee for  Space  Data  Systems
(CCSDS) member and observer agencies.

1.2   SCOPE

Recommendations contained in this document, Radio Frequency and  Modulation
Systems,  Part  1,  focus upon the standardization  of  RF  and  modulation
systems  for  earth stations and spacecraft.  Part 2, when completed,  will
comprise Recommendations relating to data relay satellite systems.   Unlike
the  CCSDS  Radio  Frequency and Modulation Report,  Reference  [2],  these
Recommendations  describe the capabilities, policies, and  procedures  that
the  CCSDS  agencies believe will be needed in future years.  By  proposing
specific  characteristics and attributes for subjects in these  categories,
the CCSDS hopes that the ensuing designs will be sufficiently similar so as
to  permit  cross-support of one agency's spacecraft  by  another  agency's
network.

These Recommendations are complementary to the information contained in the
RF  and  Modulation  Report.   To  obtain a complete  understanding  of  an
agency's  tracking facilities, readers should consult both documents.   The
Report  describes  the  RF  and  modulation characteristics  of  spacecraft
tracking  systems that the CCSDS member and observer agencies are  planning
for  the  post-1990  time  period.  It comprises a multiplicity  of  tables
summarizing the technical characteristics of those systems.

These  Recommendations  do  not  provide  specific  designs.   Rather  they
describe  certain  capabilities and provide  technical  characteristics  in
sufficient  detail  so  that  an  agency may design  compatible  equipment.
Guidelines  are  also provided for the use of agencies' RF  and  modulation
systems, as well as, their use of the RF spectrum.   Because an ability  to
provide   cross-support  implies  some  standardization   of   design   and
operations, certain procedural Recommendations have been included to assist
in  these  areas.  Recommendations are assigned to one  of  three  sections
depending  upon  whether  their  primary focus  is  technical,  policy,  or
procedural in nature.

These  Recommendations are intended to promote an orderly transition to  RF
and  modulation  systems that are internationally  compatible.   The  CCSDS
believes that this course will not only assure better engineering practices
but, also, that it will facilitate international cross-support agreements.

1.3   APPLICABILITY

These  Recommendations apply to future implementation of RF and  modulation
systems.   In combination with the RF and Modulation Report, Reference [2],
this document describes the physical transport system used to carry data to
and from spacecraft and earth stations.

1.4   DOCUMENT FORMAT

These  introductory  remarks  are followed  by  three  sections  containing
technical, policy and procedural Recommendations, respectively.  Often,  it
is  not obvious to which section a Recommendation belongs because it may be
concerned with more than one area.  The decision usually turns upon whether
the primary focus is quantitative, directive, or instructive.

Section  2  contains  Technical  Recommendations.   Following  the   format
established   in   the   CCSDS   RF   and  Modulation   Report,   technical
Recommendations  are  subdivided  into  groups  representing  the   various
subsystems.  These are:

     2.1  Earth-to-Space Radio Frequency     2.4   Telemetry
     2.2  Telecommand                        2.5   Radio Metric
     2.3  Space-to-Earth Radio Frequency     2.6   Spacecraft

Recommendations  pertaining to each of these subjects are grouped  together
for  easy accessibility.  This approach facilitates cross referencing  with
the  Report.  If a reader wishes to determine whether an agency  follows  a
specific  CCSDS  Recommendation, he need only  turn  to  the  corresponding
section in the Report to determine that agency's capabilities.

Section 3 comprises Policy Recommendations.  Because of the requirement for
sharing  the  radio  frequency  spectrum,  it  is  desirable  to  establish
guidelines   to   promote   its   efficient   use.    Accordingly,    these
Recommendations are directive in nature and are principally concerned  with
operational aspects.  Specific sections are:

     3.1  Frequency Utilization              3.4   Operational Procedures
     3.2  Power Limitations                  3.5   Testing Recommendations
     3.3  Modulation Methods                 3.6   Spacecraft Systems

Section   4   holds  Procedural  Recommendations.   Here  will   be   found
Recommendations intended to assist agencies with procedures  or  processes.
At this juncture, only one subsection has been identified.  This is:

     4.1  Design Tools

As  additional  procedural  topics are identified,  this  section  will  be
expanded with appropriate subsections.

Section 5 defines Terms and provides a Glossary for acronyms used in  these
Recommendations.   This  section is intended  as  an  aid  for  readers  to
facilitate a uniform interpretation of the Recommendations. Two subsections
are required:

     5.1  Terminology                        5.2   Glossary

Because  the Recommendations are designed to be easily removable from  this
book  to  facilitate  copying,  a unique page  numbering  system  has  been
employed.   Recommendation  page  numbers  contain  information  about  the
section,  subsection, position, mission category, and page  number.   Thus,
Page  2.5.3A-1  tells  the  reader, in order, that  this  is:  a  Technical
Recommendation  (2),  for  Radio Metric systems  (5),  the  third  in  that
subsection (3), concerned with Category A missions (A), the first  page  of
that  Recommendation  (1).  This numbering system,  is  intended  to  avoid
confusion  and  errors  when  returning  pages  to  the  book  by  uniquely
describing the position of each page in the document.

Unlike other CCSDS Recommendations which focus upon specific topics such as
channel coding or SFDUs, this document contains several subjects related to
radio  frequency and modulation systems.  To promote brevity, clarity,  and
expandability,  the authors have adopted a recommendation format  which  is
similar  to  the  one used by the International Telecommunications  Union's
(ITU) International Radio Consultative Committee (CCIR).

Each  Recommendation  consists of brief statements and  generally  requires
only  one  or  two pages.  Reasons justifying each Recommendation  are  set
forth  in clear, crisp sentences.  When appropriate, additional information
providing  the rationale for a Recommendation is included as  an  annex  to
this  document.   This  modular  format  permits  inclusion  of  additional
Recommendations as the CCSDS agencies' RF and modulation systems  grow  and
as technology matures.


1.5   DEEP SPACE AND NON-DEEP SPACE

Much  of  the radio frequency standardization has already been accomplished
by  the  International Telecommunications Union (ITU) and will be found  in
the   Radio  Regulations.   The  provisions  contained  in  the  ITU  Radio
Regulations,  as  well  as  applicable  CCIR  documents,  are  adopted  and
incorporated here by reference.

Four  radiocommunication  services are  of  interest  to  the  CCSDS.    In
accordance with the ITU definitions these are: the Space Research  Service,
the  Space Operation Service, the Earth Exploration Satellite Service,  and
the Meteorological Satellite Service.

Within the Space Research Service, a distinction is made between Deep Space
and   non-Deep   Space   spacecraft.   Those  bands  allocated   to   Space
Research/Deep   Space  shall  only  be  used  by  spacecraft   engaged   in
interplanetary research, whose range exceeds a specified distance.

Earth  station - spacecraft distance is important for two reasons.   First,
certain  frequencies are reserved for spacecraft operating in  Deep  Space.
Second, the RF and modulation characteristics may be different for the  two
categories.

Formerly,  the  Radio  Regulations set the Deep  Space  boundary  at  lunar
distance.   However,  the advent of spacecraft in highly  elliptical  earth
orbits that go beyond lunar distance, or which may be in orbits around  the
sun-earth  libration points, resulted in non-optimum use of the Deep  Space
bands  when  frequency assignments for these missions were based  upon  the
former definition.

In  October  1988, the World Administrative Radio Conference (WARC)  ORB-88
revised the boundary for Deep Space contained in Article 1 of the ITU Radio
Regulations.  The new boundary for Deep Space, which became effective on 16
March  1990, has been established to be at a distance equal to, or  greater
than, 2.0 x 106 km.

While  the Radio Regulations contain a definition for Deep Space,  they  do
not specifically name that zone lying closer to the earth.  Thus, there  is
no internationally recognized term for non-Deep Space missions.

Several  years  ago, the CCSDS recognized the deficiencies with  the  ITU's
lunar  distance  Deep  Space boundary.  Accordingly, CCSDS  members  agreed
among  themselves to establish the Deep Space boundary at 2.0  x  10**6  km
whenever  that was possible under the then existing Radio Regulations.   To
avoid  confusion with the ITU's definition for Deep Space, as  well  as  to
simplify  the nomenclature for missions at any distance, the CCSDS  defined
the following mission categories:

     Category A          Those  missions having an altitude above the earth
                         of less than, 2.0 x 10**6km.

     Category B          Those  missions having an altitude above the earth
                         of greater than, or equal to, 2.0  x 10**6 km.

Figure 1.5-1 pictorially depicts the Category A and B mission regions.

Because  this terminology has become well established over the  years,  and
because  the  ITU  has still failed to define that region lying  closer  to
earth  than  2.0  x  10**6  km, the CCSDS will  continue  to  use  the  two
Categories to represent the applicability of a Recommendation to a specific
class of mission.

Therefore, the letter A or B following the Recommendation number means that
the  Recommendation  applies solely to Category A or  Category  B  missions
respectively.  If the Recommendation number stands alone, with neither an A
or B following, then that Recommendation applies equally to both Category A
and Category B missions.

                                  [IMAGE]

FIGURE 1.5-1.  MISSION CATEGORIES




2.0  TECHNICAL RECOMMENDATIONS

Section  2  focuses upon the technical characteristics of RF and modulation
systems  for  earth  stations and spacecraft.   Each  recommended  standard
delineates a specific capability which the CCSDS agencies believe  will  be
needed  in  future  years.  Some suggested standards  argue  for  retaining
existing  facilities, while others propose developing systems not presently
used  by  any agency.  The goal is to set forth recommended standards  with
which the agencies can create a group of uniform capabilities.

To facilitate the document's use, this section has been subdivided into six
modules, each containing an individual subject:

     2.1  Earth-to-Space Radio Frequency          2.4  Telemetry
     2.2  Telecommand                             2.5  RadioMetric
     2.3  Space-to-Earth Radio Frequency          2.6  Spacecraft

Note that these subsections are identical to, and have been arranged in the
same  order  as,  those found in the CCSDS Radio Frequency  and  Modulation
Report.   However,  an  additional  subsection  for  spacecraft  has   been
included.    Here,  one  can  find  those  characteristics  pertaining   to
spacecraft radio frequency and modulation systems.

Six   summary  tables  corresponding  to  the  six  modules  follow   these
introductory  remarks.   These tables contain the subject  matter  of  each
recommendation, its number, and a summary description.  Using these tables,
the  reader  can  quickly  locate  specific  recommendations  contained  in
Section 2.



                 EARTH-TO-SPACE RF RECOMMENDATION SUMMARY

REC.       RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
2.1.1   Phase Modulation                   Use with residual carriers.
2.1.2   Circular Polarization              Use on earth-to-space RF links.
2.1.3A  +/- (1-150) kHz; +/- (1-500) kHz   Min Cat A acquisition sweep
                                           range at 2 and 7 GHz.
2.1.3B  +/- (1-300) kHz; +/- (1-1000) kHz  Min Cat B acquisition sweep
                                           range at 2 and 7 GHz.
2.1.4A  500 Hz/s <= 50 kHz/s               Min Cat A acquisition sweep
                                           rate range.
2.1.4B  1 Hz/s <= 10 kHz/s                 Min Cat B acquisition sweep
                                           rate range.
2.1.5   Pos Voltage  -> Pos Phase Shift    Modulator input voltage to
                                           carrier phase shift.
2.1.6   10 dB Carrier Suppression          Max carrier suppression
                                           resulting from all signals.
2.1.7B  Mod Indices; Data Rates Codes      Constraints from simultaneous
                                           service operations.
2.1.8A  Uplink Freq Steps <= 100 Hz        Min Cat A earth station
                                           transmitter freq resolution.
2.1.8B  Uplink Freq Steps 0.01 <= 5 Hz     Min Cat B earth station
                                           transmitter freq resolution.



                    TELECOMMAND RECOMMENDATION SUMMARY

REC.       RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
2.2.1   Reserved
2.2.2   8 or 16 kHz, PSK, Sine Wave        Subcarrier frequencies,
                                           modulation, and waveform.
2.2.3   NRZ-L, M                           Choice of telecommand data
                                           waveforms.
2.2.4   4000/2**n;  n = 0, 1, 2 ... 9      Range of telecommand bit rates.
2.2.5   +/- 2 x 10**-4f[sub]sc; +/- 1 x    Subcarrier frequency offset and
        10**-5; +/- 5 x 10**-5             stabilities.
2.2.6   0.98 <= 1.02                       Symmetry of baseband modulating
                                           waveforms.



                 SPACE-TO-EARTH RF RECOMMENDATION SUMMARY

REC.       RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
2.3.1   Residual Carriers                  Use with low bit rate telemetry
                                           systems.
2.3.2   Suppressed Carriers                Use where residual carriers
                                           exceed PFD limits.
2.3.3A  +/- 150 kHz; +/- 600 kHz           Min Cat A acquisition sweep
                                           range at 2 and 8 GHz.
2.2.3B  +/- 300 kHz; +/- 1 MHz             Min Cat B acquisition sweep
                                           range at 2 and 8 GHz.
2.2.4A  100 Hz/s <= 420 kHz/s              Min Cat A acquisition sweep
                                           rate at 2 and 8 GHz.
2.2.4B  1 Hz/s <= 10 kHz/s                 Min Cat B acquisition sweep
                                           rate at 2 and 8 GHz.
2.3.5   RCP or LCP                         Polarization of space-to-earth
                                           links.
2.3.6   Pos Voltage -> Pos Phase Shift     Modulator input voltage to
                                           carrier phase shift.
2.3.7   +/- 5 x 10**-13 (0.2 <= s <= 100)  Min earth station reference
                                           frequency stability.
2.3.8   10 dB Carrier Suppression          Max carrier suppression
                                           resulting from all signals.



                     TELEMETRY RECOMMENDATION SUMMARY

REC.       RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
2.4.1   Reserved
2.4.2   NRZ-M (DNRZ) Modulation            Use with suppressed carrier
                                           systems.
2.4.3   Subcarriers                        Use with very low rate residual
                                           carrier subsystems.
2.4.4   PSK Modulation                     Use with telemetry subcarriers.
2.4.5   Sine Wave; Square Wave             Cat A; Cat B subcarrier
                                           waveforms.
2.4.6   +/- 1 x 10**-4f[sub]sc; +/- 1 x    Subcarrier frequency offset and
        10**-6; +/- 1 x 10**-5             stabilities.
2.4.7   NRZ-L; SP-L                        Choice of PCM waveforms in
                                           resid. carrier systems.
2.4.8   0.98 <= 1.02                       Symmetry of baseband modulating
                                           waveforms.
2.4.9   64; 125/1000; 275/1000             Min Cat A:  Cat B symbol
                                           transition densities.
2.4.10  00=0 deg; 01=90 deg; 11=180 deg;   Channel coding conventions for
         10=270 deg                        QPSK systems.



                    RADIO METRIC RECOMMENDATION SUMMARY

REC.       RECOMMENDED CHARACTERISTICS     RECOMMENDATION
 NO.                                                   SUMMARY
2.5.1A  10 ns                              Min Cat A group delay
                                           calibration accuracy.
2.5.2A  20 ns                              Min Cat A earth station group
                                           delay stability in 12h.
2.5.2B  2 ns                               Min Cat B earth station group
                                           delay stability in 12h.
2.5.3A  +/- 50 ns                          Min Cat A spacecraft group
                                           delay stability.
2.5.3B  +/- 30 ns                          Min Cat B spacecraft group
                                           delay stability.
2.5.4A  +/- 0.5 dB (3 kHz <= 110 kHz)      Min Cat A ranging transponder
                                           bandwidth.
2.5.4B  +/- 0.5 dB (3 kHz <= 1.1 MHz)      Min Cat B ranging transponder
                                           bandwidth.
2.5.5A  20 ns                              Max Cat A regen. transponder PN
                                           code delay change.


                     SPACECRAFT RECOMMENDATION SUMMARY

REC.       RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
2.6.1   221/240 Transponder Radio          Freq ratio 2025-2120 MHz to
                                           2200-2300 MHz.
2.6.2   749/880 Transponder Ratio          Freq ratio 7145-7235 MHz to
                                           8400-8500 MHz.
2.6.3A  221/900 Transponder Ratio          Cat A Freq ratio 2025-2110 MHz
                                           to 8450-8500 MHz.
2.6.4A  765/240 Transponder Ratio          Cat A Freq ratio 7190-7235 MHz
                                           to 2200-2290 MHz.
2.6.5B  221/880 Transponder Ratio          Cat B Freq ratio 2110-2120 MHz
                                           to 8400-8450 MHz.
2.6.6B  749/240 Transponder Ratio          Cat B Freq ratio 7145-7190 MHz
                                           to 2290-2300 MHz.
2.6.7   Reserved for 13-15 GHz and
to
2.6.11  32-34 GHz Transponder Ratios
2.6.12  15 <= 45 Hz; 1 <= 3 Hz             Min Cat A; Cat B transponder
                                           AGC amplifier BW.


2.1.1     RF CARRIER MODULATION OF THE EARTH-TO-SPACE LINK

The CCSDS,

considering

(a)    that most space agencies currently utilize spacecraft receivers
       employing phase-locked loops;

(b)    that conventional phase-locked loop receivers require a residual
       carrier to operate efficiently;

(c)    that phase modulation results in efficient demodulation;

recommends

     that  CCSDS  agencies provide a capability to support phase modulation
     with a residual carrier for their earth-to-space links.

2.12      POLARIZATION OF EARTH-TO-SPACE LINKS

The CCSDS,

considering

(a)    that a linear electric field polarization on links to spacecraft,
       having nearly omnidirectional antenna patterns, may vary
       considerably with aspect angle;

(b)    that the aspect angle of a near-earth orbiting satellite varies
       greatly during a pass;

(c)    that for satellites having a stable linear polarization in the
       direction of the earth station (e.g., geostationary satellites with
       suitable attitude stabilization or satellites using tracking
       antennas) the propagation effects such as Faraday rotation may
       cause substantial rotation in the received polarization at lower
       carrier frequencies;

(d)    that automatic correction of rotation in the earth station's
       polarization adds undesirable complexity to the system;

(e)    that most existing earth stations are equipped for RCP and LCP
       polarization;

recommends

(1)    that CCSDS agencies use circular polarization on their earth-to-
       space RF links for telecommand and ranging;

(2)    that payload service links use circular polarization in those cases
       where TTC is carried out in the payload service band or where on-
       board antennas are shared with payload functions;

(3)    that the earth station be designed to switch between LCP and RCP
       polarization without causing an interruption of the transmitted
       carrier exceeding 5 seconds in those cases where changes of
       polarization are desired.


2.13A     TRANSMITTER FREQUENCY SWEEP RANGE ON EARTH-TO-SPACE LINKS,
          CATEGORY A

The CCSDS,

considering

(a)  that the doppler frequency shift on the earth-to-space link, resulting
     from relative motion between earth stations and Category A spacecraft,
     can achieve values up to:

          +/-   80 kHz at 2 GHz
          +/- 300 kHz at 7 GHz;

(b)  that  the rest frequency uncertainties in spacecraft receivers are  in
     the order of:

          +/-   50 kHz at 2 GHz
          +/- 200 kHz at 7 GHz;

(c)  that  the  lock-in  frequency range of spacecraft  receivers  is  much
     smaller than the frequency deviations given in (a) and (b);

(d)  that  the  doppler  frequency shift can usually  be  predicted  to  an
     accuracy of better than +/- 1 kHz;

(e)  that most of the spacecraft receivers have a tracking range up to:

          +/- 150 kHz at 2 GHz
          +/- 500 kHz at 7 GHz;

(f)  that the acquisition time should be kept to a minimum;

recommends

     that the earth station's transmitter should have a minimum sweep range
     capability of at least:

          +/- 1 kHz

     and a maximum sweep range capability of:

          +/- 150 kHz at 2 GHz
          +/- 500 kHz at 7 GHz.

2.1.3B    TRANSMITTER FREQUENCY SWEEP RANGE ON EARTH-TO-SPACE LINKS,
          CATEGORY B

The CCSDS,

considering

(a)  that the doppler frequency shift on the earth-to-space link, resulting
     from relative motion between earth stations and category B spacecraft,
     can achieve values up to:

          +/- 250 kHz at 2 GHz
          +/- 900 kHz at 7 GHz;

(b)    that the rest frequency uncertainties in spacecraft receivers are on
the order of:

          +/- 1 kHz at 2 GHz
          +/- 4 kHz at 7 GHz;

(c)  that  the  doppler  frequency shift can usually  be  predicted  to  an
     accuracy of +/- 1 kHz;

(d)  that  most of the spacecraft receivers have tracking ranges less  than
     or equal to:

          +/- 300 kHz at 2 GHz
          +/-    1 MHz at 7 GHz;

(e)  that  the  lock-in  frequency range of spacecraft  receivers  is  much
     smaller than the frequency deviations given in (a) and (b) above;

(f)  that  the  effect on the radio link, resulting from variation  in  the
     columnar charged-particle content, is generally negligible;

(g)  that the acquisition time should be kept to a minimum;

recommends

     that the earth station's transmitter should have a minimum sweep range
     capability of:

          +/- 1 kHz at 2 and 7 GHz

     and a maximum sweep range capability of at least:

          +/- 300 kHz at 2 GHz
          +/-    1 MHz at 7 GHz.

2.1.4A    TRANSMITTER FREQUENCY SWEEP RATE ON EARTH-TO-SPACE LINKS,
          CATEGORY A

The CCSDS,

considering

(a)  that the rate of change of the doppler frequency shift on the earth-to-
     space link, resulting from relative motion between earth stations  and
     Category A spacecraft, is smaller than:

    3 kHz/s at 2 GHz
   10 kHz/s at 7 GHz;

(b)  that most of the spacecraft receivers have a phase-locked loop with  a
     bandwidth  (2  B[sub]LO)  in the range 200  Hz  to  800  Hz  at  their
     threshold;

(c)  that  the  maximum permissible rate of input frequency  variation  for
     most types of spacecraft receivers is between 2 kHz/s and 30 kHz/s  at
     their threshold;

(d)  that  the  frequency sweep rate on the earth-to-space link  should  be
     chosen such that the total rate of frequency variation, resulting from
     both  the transmitter's sweep rate and the orbital doppler rate,  does
     not unlock the spacecraft's phase-locked loop;

(e)  that the acquisition time should be kept to a minimum for each mission
     phase;

recommends

     that  the  earth station's transmitter should have a minimum frequency
     sweep rate capability of:

          500 Hz/s

     and a maximum frequency sweep rate capability of at least:

          50 kHz/s.

2.1.4B    TRANSMITTER FREQUENCY SWEEP RATE ON EARTH-TO-SPACE LINKS,
          CATEGORY B

The CCSDS,

considering

(a)  that the rate of change of the doppler frequency shift on the earth-to-
     space link, resulting from relative motion between earth stations  and
     category B spacecraft, is smaller than:

            60 Hz/s at 2 GHz
          200 Hz/s at 7 GHz;

(b)  that most of the spacecraft receivers have a phase-locked loop with  a
     bandwidth  (2  B[sub]LO)  in the range  10  Hz  to  100  Hz  at  their
     threshold;

(c)  that  the  maximum permissible rate of input frequency  variation  for
     this type of spacecraft receiver is between 6 Hz/s and 1 kHz/s at  its
     threshold;

(d)  that  the  maximum permissible rate of input frequency  variation  for
     signals above the receiver's threshold can be as much as 10 kHz/s;

(e)  that  the  frequency sweep rate on the earth-to-space link  should  be
     chosen such that the total rate of frequency variation, resulting from
     both  the transmitter's sweep rate and the orbital doppler rate,  does
     not unlock the spacecraft's phase-locked loop;

(f)  that the acquisition time should be kept to a minimum for each mission
     phase;

recommends

     that  the  earth station's transmitter should have a minimum frequency
     sweep rate capability of:

          1 Hz/s

     and a maximum frequency sweep rate capability of at least:

          10 kHz/s.


2.1.5     RELATIONSHIP OF MODULATOR INPUT VOLTAGE TO RESULTANT RF CARRIER
          PHASE SHIFT

The CCSDS,

considering

     that  a  clear relationship between the modulating signal and  the  RF
     carrier's phase is desirable to avoid unnecessary ambiguity problems;

recommends

     that a positive-going voltage at the modulator input should result  in
     an advance of the phase of the radio frequency signal.




__________________
NOTE:

l.   This Recommendation is also filed as Rec. 401 (2.3.6) B-1.


2.1.6     RF CARRIER SUPPRESSION ON EARTH-TO-SPACE LINKS FOR RESIDUAL
          CARRIER SYSTEMS

The CCSDS,

considering

     that  high  modulation indices may make the residual carrier difficult
     to detect with a conventional phase-locked loop receiver;

recommends


     that  CCSDS agencies select modulation indices such that the reduction
     in carrier power, with respect to the total unmodulated carrier power,
     does not exceed 10 dB.




__________________
NOTE:

1.   This Recommendation is also filed as Rec. 401 (2.3.8) B-1.


2.1.7B    OPERATIONAL AND EQUIPMENT CONSTRAINTS RESULTING FROM SIMULTANEOUS
          TELECOMMAND AND RANGING IN RESIDUAL CARRIER SYSTEMS, CATEGORY B

The CCSDS,

considering

(a)    that coherent transmissions are generally employed for making range
       measurements to a Category B mission spacecraft;

(b)    that conventional phase locked loop receivers require a residual
       carrier component to operate properly;

(c)    that sufficient power must be reserved to the residual carrier so
       that the spacecraft receiver can track with an acceptable phase
       jitter;

(d)    that sufficient power must be allocated to the command data channel
       to obtain the required bit error rate;

(e)    that in two-way operation, the noise contained in the transponder's
       ranging channel bandwidth will be retransmitted to the earth
       station along with the ranging signal;

(f)    that sufficient power must be allocated to the ranging signal to
       obtain the required accuracy and probability of error;

(g)    that some ranging systems permit the simultaneous transmission of
       several tone frequencies from the earth station and that a proper
       choice of these frequencies will minimize the cross-modulation and
       interference to the telecommand signal by the ranging signal;

(h)    that transmission of a single, low frequency ranging tone by the
       earth station may result in interference in the telecommand channel
       on the spacecraft;

recommends

(1)    that the telecommand modulation index shall not be less than 0.2
       radians peak;

(2)    that the telecommand data bit rate shall not exceed 2000 b/s when
       simultaneous telecommand and ranging operations are required;

(3)    that the earth station's ranging modulation index shall not exceed
       1.4 radians peak;

(4)    that the telecommand subcarrier's period should be an integer
       subdivision of the data bits's period;

(5)    that for those ranging systems which do not conform with
       "recommends" (6) below, the telecommand subcarrier's period should
       be a coherent multiple of the ranging tone's period;

(6)    that, where necessary, each and every lower frequency ranging tone
       be chopped (modulo-2 added) with the highest frequency ranging
       tone;

2.1.8A    MINIMUM EARTH STATION TRANSMITTER FREQUENCY RESOLUTION FOR
          SPACECRAFT RECEIVER ACQUISITION, CATEGORY A

The CCSDS,

considering

(a)    that Category A spacecraft receivers typically have phase-locked
       loop bandwidths (2 B[sub]LO) in the range of 200 to 800 Hz at their
       thresholds;

(b)    that, for spacecraft receivers having a second order phase-locked-
       loop with the threshold bandwidths shown in (a), the frequency lock-
       in range is typically 267 to 1067 Hz;

(c)    that steps in earth station's transmitter frequency which exceed the
       spacecraft receiver's lock-in range can result in long acquisition
       times or complete failure of the spacecraft to acquire the signal;

(d)    that some margin should be included to ensure proper acquisition of
       the earth station's signal by the spacecraft receiver's phase-
       locked loop;

(e)    that the spacecraft's receiver may fail to acquire or remain locked
       to the earth station's transmitted signal if abrupt phase
       discontinuities in that signal occur during the acquisition of that
       signal;

recommends

(1)    that the earth station transmitter's frequency be adjustable over
       its specified operating range in increments (step size) of 100 Hz
       or less;

(2)    that the earth station transmitter's RF phase continuity be
       maintained at all times during tuning operations, using frequency
       sweep rates that are in accordance with Recommendation 401 (2.1.4A)
       B-1, which will ensure that the spacecraft's receiver remains
       locked following acquisition.


2.1.8B    MINIMUM EARTH STATION TRANSMITTER FREQUENCY RESOLUTION FOR
          SPACECRAFT RECEIVER ACQUISITION, CATEGORY B

The CCSDS,

considering

(a)  that  Category B spacecraft receivers typically have phase-locked loop
     bandwidths  (2  B[sub]LO)  in the range of  10  to  100  Hz  at  their
     thresholds;

(b)  that  for spacecraft receivers having a second order phase-locked-loop
     with  the  threshold  bandwidths shown in (a), the  frequency  lock-in
     range is typically 13 to 133 Hz;

(c)  that  steps in earth station's transmitter frequency which exceed  the
     spacecraft  receiver's lock-in range can result  in  long  acquisition
     times or complete failure of the spacecraft to acquire the signal;

(d)  that  some  margin should be included to ensure proper acquisition  of
     the  earth  station's signal by the spacecraft receiver's phase-locked
     loop;

(e)  that,   with   certain  Category  B  missions,  it  is  desirable   to
     continuously  tune the earth-to-space link's transmitter frequency  to
     maintain its value, at the spacecraft, at a single, optimal frequency;

(f)  that the spacecraft's receiver may fail to acquire or remain locked to
     the earth station's transmitted signal if abrupt phase discontinuities
     in that signal occur during the acquisition of that signal;

recommends

(1)  that  the  earth station's transmitter frequency be variable over  its
     specified  operating  range in increments (step  size)  which  can  be
     adjusted from 0.01 Hz to 5 Hz;

(2)    that the earth station transmitter's RF phase continuity be
       maintained at all times during tuning operations, using frequency
       sweep rates that are in accordance with Recommendation 401 (2.1.4B)
       B-1, which will ensure that the spacecraft's receiver remains
       locked following acquisition.

2.2.2     SUBCARRIERS IN TELECOMMAND SYSTEMS

The CCSDS,

considering

(a)    that most space agencies presently utilize either 8 kHz or 16 kHz
       subcarriers for telecommand transmissions where data rates are less
       than or equal to 4 kb/s;

(b)    that modulation schemes employing subcarriers reduce the
       interference to the RF carrier loop resulting from data sidebands;

(c)    that PSK modulation is the most efficient type of digital modulation
       because of its bit error performance;

(d)    that it is important to limit the occupied bandwidth;

recommends

     that CCSDS agencies use a sine wave subcarrier for telecommand, with a
     frequency of either 8 kHz or 16 kHz, which has been PSK modulated.

2.2.3     CHOICE OF WAVEFORMS IN TELECOMMAND LINKS

The CCSDS,

considering

(a)    that NRZ-L, -M waveforms result in efficient spectrum utilization;

(b)    that present telecommand bit rates are generally less than or equal
       to 4 kb/s;

(c)    that telecommand data sidebands are separated from the carrier by
       employing a PSK subcarrier;

(d)    that NRZ-L waveforms result in very good signal-to-noise
       performance;

(e)    that NRZ-M waveforms avoid ambiguity errors;

recommends

(1)    that CCSDS agencies use NRZ-L, -M waveforms with PSK subcarriers for
       telecommand data;

(2)    that due consideration be given to the bit transition density of the
       telecommand modulation to ensure proper operation of the
       spacecraft's receiving equipment.

2.2.4     RANGE OF TELECOMMAND BIT RATES

The CCSDS,

considering

(a)    that many space agencies utilize PCM-PSK modulation for the
       telecommand links;

(b)    that phase coherency between the PCM signal and the subcarrier
       facilitates system implementation;

(c)    that subcarrier frequencies of either 8 kHz or 16 kHz are commonly
       used;

(d)    that many space agencies have developed, or will develop, equipment
       using telecommand data rates in the range 8-4000 b/s;

recommends

(1)    that CCSDS agencies provide telecommand bit rates in the range
       4000/2**n b/s, where n = 0, 1, 2, ..., 9;

(2)    that data bit and subcarrier transitions should coincide.




_______________________
NOTE:

1.     A 4000 b/s rate should only be used with a 16 kHz subcarrier and
       care should be taken to ensure that harmful interactions with other
       signals do not occur.


2.2.5     TELECOMMAND SUBCARRIER FREQUENCY STABILITY

The CCSDS,

considering

(a)    that the present use of subcarriers for modulating the earth-to-
       space RF links represents a mature technique for both Categories A
       and B missions and, therefore, is a well settled standard;

(b)    that modifications of this standard imply costly changes to space
       agencies' networks;

recommends

     that CCSDS agencies' earth stations be designed to provide telecommand
     subcarriers with characteristics which are equal to or better than:

          Maximum Subcarrier Frequency Offset     +/- (2 x 10**-4)f[sub]sc;

          Minimum Subcarrier Frequency Stability  +/- 1 x 10**-5
          (1 second);

          Minimum Subcarrier Frequency Stability  +/- 5 x 10**-5
          (24 hours).




_______________________
NOTE:

1.   f[sub]sc = frequency of telecommand subcarrier.


2.2.6     SYMMETRY OF BASEBAND DATA MODULATING WAVEFORMS

The CCSDS,

considering

(a)    that the earth station's transmitter power should be used as
       efficiently as possible;

(b)    that undesired spectral components in the earth station's
       transmitted signal should be minimized;

(c)    that time-asymmetry in the modulating waveform results in a DC-
       component;

(d)    that such a DC-component in the modulating waveform results in a
       data power loss because of AC-coupling in the modulator;

(e)    that, in addition to the power loss, time-asymmetry results in
       matched filter losses;

(f)    that the above losses should not exceed 0.1 dB;

(g)    that the out-of-band emissions resulting from the time-asymmetry in
       the modulating waveform can be reduced by additional filtering;

recommends

     that,  the  symmetry of all baseband square wave modulating  waveforms
     should be such that the mark-to-space ratio will lie between 0.98  and
     1.02.



_______________________
NOTE:

1.     This Recommendation is also filed as Rec. 401 (2.4.8) B-1 for the
       space-to-earth link.

2.     Where Bi-Phase modulation is utilized, larger baseband signal
       losses, than are permitted by considering (f), may result.


2.3.1     RESIDUAL CARRIERS FOR LOW RATE TELEMETRY, SPACE-TO-EARTH LINKS

The CCSDS,

considering

(a)    that many space agencies own and/or operate earth stations for
       communication with spacecraft in which they have substantial
       investments;

(b)    that these earth stations contain receiving equipment employing
       phase-locked loops;

(c)    that conventional phase-locked loop receivers require a residual
       carrier component to operate properly;

(d)    that most space agencies use autotrack systems for Category A
       missions, which need a residual carrier;

recommends

     that CCSDS agencies retain residual carrier receiving systems in their
     earth  stations  for  use  with missions  having  low  rate  telemetry
     requirements.


2.3.2     SUPPRESSED CARRIERS FOR HIGH RATE TELEMETRY, SPACE-TO-EARTH LINKS

The CCSDS,

considering

(a)    that present technology makes the implementation of suppressed
       carrier systems practicable;

(b)    that a comparison of carrier signal-to-noise ratios in a
       conventional residual carrier phase-locked loop with those in a
       suppressed carrier loop shows that the latter provides a
       substantial advantage over the former, frequently exceeding 10 dB;

(c)    that a comparison of data symbol errors occurring in a conventional
       residual carrier phase-locked loop system with those occurring in a
       suppressed carrier loop System shows that the latter's performance
       is no worse, and frequently is better, than that of the former;

(d)    that suppressed carrier systems lend themselves to compliance with
       PFD limits on the earth's surface more readily than do residual
       carrier systems;

(e)    that some space agencies still use autotrack systems for their
       Category A missions, which need a residual carrier;

recommends

(1)    that CCSDS agencies utilize suppressed carrier systems for space-to-
       earth communications when a residual carrier system would exceed
       the PFD limits on the earth's surface;

(2)    that CCSDS agencies may provide a beacon for autotracking their
       Category A missions using suppressed carrier modulation.

2.3.3A    EARTH STATION RECEIVER ACQUISITION FREQUENCY SWEEP RANGE,
          CATEGORY A

The CCSDS,

considering

(a)    that the space-to-earth link may be operated in either a coherent
       turnaround mode, or in a one-way mode;

(b)    that for the coherent turnaround mode, the doppler frequency shift
       induced on both the earth-to-space and the space-to-earth links is
       the major factor to be considered in selecting the frequency sweep
       range;

(c)    that for the one-way mode, both the doppler frequency shift induced
       on the space-to-earth link and the frequency stability of the
       spacecraft's oscillator are the major factors to be considered in
       selecting the frequency sweep range;

(d)    that the maximum rate of change of distance between the earth
       station and Category B spacecraft can reach values of up to 10
       km/s;

(e)    that the minimum frequency stability found in Category A spacecraft
       reference frequency oscillators is about +/- 2 x 10**-5;

recommends

(1)    that CCSDS agencies' earth station receivers be capable of frequency
       Sweep ranges of at least:

          +/- 150 kHz at 2 GHz
          +/- 600 kHz at 8 GHz

(2)    that CCSDS agencies provide a minimum sweep range that is consistent
       with their ability to predict the doppler frequency shift.

2.3.3B    EARTH STATION RECEIVER ACQUISITION FREQUENCY SWEEP RANGE,
          CATEGORY B

The CCSDS,

considering

(a)    that the space-to-earth link may be operated in either a coherent
       turnaround mode, or in a one-way mode;

(b)    that in the coherent turnaround mode, the doppler frequency shift
       induced on both the earth-to-space and the space-to-earth links is
       the major factor to be considered in selecting the frequency sweep
       range;

(c)    that the effect on the radio link, resulting from variation in the
       columnar charged-particle content, is generally negligible;

(d)    that the maximum rate of change of distance between the earth
       station and Category B spacecraft can reach values of up to 35
       km/s;

(e)    that the minimum frequency stability found in Category B spacecraft
       reference frequency oscillators is about 1 x 10**-6;

recommends

     that  CCSDS agencies' earth station receivers be capable of  frequency
     sweep ranges of at least:

          +/- 300 kHz at 2 GHz
          +/-     1 MHz at 8 GHz.


2.3.4A    EARTH STATION RECEIVER ACQUISITION FREQUENCY SWEEP RATE, CATEGORY
          A

The CCSDS,

considering

(a)    that the space-to-earth link may be operated in either a coherent
       turn-around mode or in a one-way mode;

(b)    that in the coherent turn-around mode, the doppler frequency rates
       induced on both the earth-to-space and the space-to-earth links are
       the major factors to be considered in selecting the earth station
       receiver's frequency sweep rate;

(c)    that in the one-way mode, the doppler frequency rate on the space-to-
       earth link and the earth station receiver's phase locked loop
       bandwidth (2 B[sub]LO), with its resulting maximum permissible
       input frequency variation, are the major factors to be considered
       in selecting the sweep rate;

(d)    that the rate-of-change of velocity between the earth station and
       Category A spacecraft can reach values up to 380 m/s**2 at orbital
       altitudes of 300 km, which results in frequency variation rates of
       approximately 3 kHz/s at 2 GHz and 10 kHz/s at 8 GHz in the one-way
       mode (or 6 kHz/s and 20 kHz/s respectively in the coherent turn-
       around mode);

(e)    that the earth station's receivers generally have phase locked loop
       bandwidths (2 B[sub]LO) in the range of 30 Hz to 2 kHz at their
       threshold;

(f)    that, for an acquisition probability of 0.9, the maximum permissible
       rate of input frequency variation for this type of earth station
       receiver is between 100 Hz/s and 400 kHz/s at its threshold;

(g)    that the earth station receiver's frequency sweep rate plus the
       spacecraft's doppler frequency rate must not exceed the receiver's
       ability to achieve phase-locked operation;

(h)    that the acquisition time should be kept to a minimum for each
       mission phase;

recommends

     that CCSDS agencies' earth station receivers operating in the 2 and  8
     GHz bands should have a minimum frequency sweep rate not exceeding 100
     Hz/s and a maximum frequency sweep rate of at least 420 kHz/s.


2.3.4B    EARTH STATION RECEIVER ACQUISITION FREQUENCY SWEEP RATE, CATEGORY
          B

The CCSDS,

considering

(a)    that the space-to-earth link may be operated in either a coherent
       turnaround mode, or in a one-way mode;

(b)    that in the coherent turnaround mode, the doppler frequency rates
       induced on both the earth-to-space and the space-to-earth links are
       the major factors to be considered in selecting the earth station
       receiver's frequency sweep rate;

(c)    that in the one-way mode, the doppler rate on the space-to-earth
       link and the earth station receiver's phase-locked loop bandwidth
       (2 B[sub]LO), with its resulting maximum permissible input
       frequency variation, are the major factors to be considered in
       selecting the sweep rate;

(d)    that the rate of change of velocity between the earth station and
       category B spacecraft can reach values up to 10 m/s**2;

(e)    that the earth station's receivers have phase-locked loop bandwidths
       (2 B[sub]LO) in the range of 1 Hz to 1 kHz at their thresholds;

(f)    that typical earth station receivers, operating in the 2 and 8 GHz
       bands, allow a maximum permissible rate of input frequency
       variation of between 1 Hz/s and 10 kHz/s;

(g)    that the receiver's frequency sweep rate, plus the orbital doppler
       frequency rate, must not exceed the earth station receiver's
       ability to achieve phase-locked operation;

(h)    that the acquisition time should be kept to a minimum for each
       mission phase;

(i)    that a lower limit for the signal-to-noise ratio in the earth
       station receiver's phase-locked loop is approximately 8.5 dB;

recommends

     that CCSDS agencies' earth station receivers, operating in the 2 and 8
     GHz bands, should have a minimum sweep rate not exceeding 1 Hz/s and a
     maximum sweep rate of at least 10 kHz/s.


2.3.5     POLARIZATION OF SPACE-TO-EARTH LINKS

The CCSDS,

considering

(a)    that a linear electric field polarization on links from spacecraft,
       having nearly omnidirectional antenna patterns, may vary
       considerably with aspect angle;

(b)    that the aspect angle of a near-earth orbiting satellite varies
       greatly during a pass;

(c)    that for satellites having a stable linear polarization in the
       direction of the earth station (e.g., geostationary satellites with
       suitable attitude stabilization or satellites using tracking
       antennas), the propagation effects such as Faraday rotation may
       cause changes in the received polarization at lower carrier
       frequencies;

(d)    that many earth stations are equipped with polarization diversity
       receivers;

(e)    that many existing spacecraft TTC antenna designs provide circular
       polarization;

recommends

(1)    that CCSDS agencies utilize LCP or RCP polarization for satellite
       TTC space-to-earth links unless sharing of equipment with payload
       functions requires a different approach;

(2)    that automatic polarization tracking should be used for reception of
       satellite signals wherever possible;

(3)    that polarization diversity reception should be used to meet the
       required system time constants at earth stations used for Category
       A missions.

2.3.6     RELATIONSHIP OF MODULATOR INPUT VOLTAGE TO RESULTANT RF CARRIER
          PHASE SHIFT

The CCSDS,

considering

     that  a  clear relationship between the modulating signal and  the  RF
     carrier's phase is desirable to avoid unnecessary ambiguity problems;

recommends

     that a positive-going voltage at the modulator input should result  in
     an advance of the phase of the radio frequency signal.





________________________
NOTE:

1.     This Recommendation is also filed as Rec. 401 (2.1.5) B-1.

2.3.7     EARTH STATION OSCILLATOR REFERENCE FREQUENCY STABILITY

The CCSDS,

considering

(a)    that most of the space agencies use a reference frequency standard
       to which the earth station's receiver and transmitter local
       oscillators are locked;

(b)    that the short term frequency stability of the local oscillator
       substantially determines the range rate measurement's accuracy for
       Category A missions;

(c)    that the long term frequency stability of the local oscillator
       substantially determines the range rate measurement's accuracy for
       Category B missions;

(d)    that it is desirable for many missions to determine range rate with
       an accuracy of 1 mm/s or better;

(e)    that the oscillator's frequency shall be sufficiently stable such
       that its effect upon the range rate measurement's error shall be
       significantly less than 1 mm/s;

(f)    that, in addition to the foregoing, the long term stability of the
       local oscillator is also determined by the drift permitted in the
       earth station's clock which should not exceed 10 microseconds per
       month;

recommends

(1)    that the short term frequency stability (Allan Variance) shall be
       better than +/- 5 x 10**-13 for time intervals between 0.2 s and
       100 s;

(2)    that for Category B missions and for timekeeping, the long term
       frequency stability shall be better than +/- 2 x 10**-12 for any
       time interval greater than 100 s.


2.3.8     RF CARRIER SUPPRESSION ON SPACE-TO-EARTH LINKS FOR RESIDUAL
          CARRIER SYSTEMS

The CCSDS,

considering

     that  high  modulation indices may make the residual carrier difficult
     to detect with a conventional phase-locked loop receiver;

recommends

     that  CCSDS agencies select modulation indices such that the reduction
     in carrier power, with respect to the total unmodulated carrier power,
     does not exceed 10 dB.




________________________
NOTE:

1.     This Recommendation is also filed as Rec. 401 (2.1.6) B-1.

2.4.2     MODULATING PCM WAVEFORMS FOR SUPPRESSED CARRIER SYSTEMS

The CCSDS,

considering

(a)    that interaction between data sidebands and their RF carrier causes
       undesirable performance degradation;

(b)    that suppressed carrier modulation schemes eliminate interaction
       between data sidebands and the RF carrier;

(c)    that the necessary bandwidth for a suppressed carrier system with
       NRZ modulation is less than for a residual carrier system using
       Manchester or subcarrier modulation schemes;

(d)    that the lack of a carrier reference at the demodulator results in a
       phase ambiguity of 180 degrees in the data;

(e)    that this phase ambiguity is unacceptable and must be removed either
       by providing periodic, recognizable bit patterns for polarity
       determination, or by using a modulation that is insensitive to
       polarity;

(f)    that DNRZ modulation is insensitive to polarity;

(g)    that DNRZ inherently produces doublet errors, but bit pattern
       polarity determination schemes can result in the loss of entire
       frames;

(h)    that some CCSDS member agencies use DNRZ suppressed carrier
       modulation in their relay satellites to reduce the necessary
       bandwidth while preventing data-carrier interaction;

(i)    that either NRZ-M or NRZ-S is an acceptable DNRZ modulation scheme;

(j)    that NRZ-M is currently in use;

recommends

(1)    that suppressed carrier modulation schemes use NRZ-M waveforms;

(2)    that in convolutionally encoded systems requiring conversion between
       NRZ-L and NRZ-M, the conversion from NRZ-L take place before the
       input to the Viterbi encoder, and the conversion from NRZ-M to NRZ-
       L take place after the output from the Viterbi decoder in order to
       maximize performance.


2.4.3     SUBCARRIERS IN LOW BIT RATE RESIDUAL CARRIER TELEMETRY SYSTEMS

The CCSDS,

considering

(a)    that at low bit rates, interaction between data sidebands and the
       residual RF carrier causes a performance degradation;

(b)    that subcarrier modulation schemes eliminate interaction between
       data sidebands and the residual RF carrier;

(c)    that some space agencies presently utilize ranging systems whose
       minor tones are below 20 kHz and whose major tone is 100 kHz, while
       others are planning to do so in the near future;

(d)    that simultaneous ranging and telemetry operation should be
       possible;

recommends

(l)    that CCSDS agencies use subcarriers with their residual carrier
       systems when transmitting low bit rates;

(2)    that the subcarrier be placed between the 20 kHz and 100 kHz ranging
       tones, or above the 100 kHz tone.

2.4.4     PSK MODULATION FOR TELEMETRY SUBCARRIERS

The CCSDS,

considering

(a)    that PSK modulation is a very efficient type of digital modulation
       because of its bit error performance;

(b)    that many space agencies presently utilize PSK subcarrier modulation
       techniques, while others are planning to do so in the near future;

recommends

     that  CCSDS  agencies  use PSK subcarrier modulation  if  a  telemetry
     subcarrier is employed.


2.4.5     TELEMETRY SUBCARRIER WAVEFORMS

The CCSDS,

considering

(a)    that space agencies frequently employ subcarriers to separate data
       sidebands from the RF carriers;

(b)    that for Category A missions, it is more important to limit the
       occupied bandwidth while for Category B missions, it is more
       important to minimize the susceptibility to in-band interference;

(c)    that it is easier to generate square wave subcarriers;

recommends

(1)    that for Category A mission telemetry transmissions, CCSDS agencies
       use sine wave subcarriers when they are modulated in the PSK mode;

(2)    that for Category B mission telemetry transmissions, CCSDS agencies
       use square wave subcarriers when they are modulated in the PSK
       mode.


2.4.6     TELEMETRY SUBCARRIER FREQUENCY STABILITY

The CCSDS,

considering

(a)    that the present use of subcarriers for modulating the space-to-
       earth RF links represents a mature technique for both Categories A
       and B missions and, therefore, is a well settled standard;

(b)    that modifications of this standard imply costly changes to space
       agencies' networks;

recommends

     that   spacecraft  radio  frequency  subsystems  generating  telemetry
     subcarriers be designed with characteristics equal to or better than:

          Maximum Subcarrier Frequency Offset     +/- (1 x 10**-4)f[sub]sc

          Minimum Subcarrier Frequency Stability  +/- 1 x 10**-6
          (short term)

          Minimum Subcarrier Frequency Stability  +/- 1 x 10**-5
          (long term)




_________________________
NOTES:

1.     f[sub]sc = frequency of telemetry subcarrier.

2.     Short term time intervals are less than or equal, 100 times the
       subcarrier's waveform period.


2.4.7     CHOICE OF PCM WAVEFORMS IN RESIDUAL CARRIER TELEMETRY SYSTEMS

The CCSDS,

considering

(a)    that NRZ waveforms rely entirely on data transitions for symbol
       clock recovery, and this recovery becomes problematical unless an
       adequate transition density can be guaranteed;

(b)    that due to the presence of the mid-bit transitions, Split Phase
       (SP) waveforms provide better properties for bridging extended
       periods of identical symbols after initial acquisition;

(c)    that convolutionally encoded data have sufficient data transitions
       to ensure symbol clock recovery in accordance with the CCSDS
       recommended standards;

(d)    that with coherent PSK subcarrier modulation, it is possible by
       adequate hardware implementation to bridge extended periods of
       identical symbols even when NRZ waveforms are used;

(e)    that NRZ waveforms without a subcarrier have a non-zero spectral
       density at the RF carrier;

(f)    that coherent PSK subcarrier modulated by NRZ data and using an
       integer subcarrier frequency to symbol rate ratio, as well as SP
       waveforms, have zero spectral density at the RF carrier;

(g)    that the ambiguity which is peculiar to NRZ-L and SP-L waveforms can
       be removed by adequate steps;

(h)    that use of NRZ-M and NRZ-S waveforms results in errors occurring in
       pairs;

(i)    that it is desirable to prevent unnecessary decoder node switching
       by frame synchronization prior to convolutional decoding
       (particularly true for concatenated convolutional Reed-Solomon
       coding);

(j)    that to promote standardization, it is undesirable to increase the
       number of options unnecessarily, and that for any proposed scheme,
       those already implemented by space agencies should be considered
       first;

recommends

(1)    that for modulation schemes which use a subcarrier, the subcarrier
       to bit rate ratio should be an integer;

(2)    that in cases where a subcarrier is employed, NRZ-L should be used;

(3)    that for direct modulation schemes having a residual carrier, only
       Split Phase - Level (SP-L) waveforms should be used;

(4)    that ambiguity resolution should be provided.

2.4.8     SYMMETRY OF BASEBAND DATA MODULATING WAVEFORMS

The CCSDS,

considering

(a)   that the spacecraft's transmitter power should be used as efficiently
as possible;

(b)   that  undesired  spectral components in the spacecraft's  transmitted
signal should be minimized;

(c)   that  time-asymmetry  in the modulating waveform  results  in  a  DC-
component;

(d)   that such a DC-component in the modulating waveform results in a data
power loss because of AC-coupling in the modulator;

(e)  that, in addition to the power loss, time-asymmetry results in matched
filter losses;

(f)  that the above losses should not exceed 0.1 dB;

(g)   that  the out-of-band emissions resulting from the time-asymmetry  in
the modulating waveform can be reduced by additional filtering;

recommends

that,  the symmetry of all baseband square wave modulating waveforms should
be such that the mark-to-space ratio will lie between 0.98 and 1.02.




_______________________
NOTE:

1.     This Recommendation is also filed as Rec. 401 (2.2.6) B-1 for the
       earth-to-space link.

2.    Where Bi-Phase modulation is utilized, larger baseband signal losses,
than are permitted by considering (f), may result.

2.4.9     MINIMUM MODULATED SYMBOL TRANSITION DENSITY ON THE SPACE-TO-EARTH
LINK

The CCSDS,

considering

(a)   that  symbol  clock  recovery systems  usually  extract  the  clock's
frequency from the received symbol transitions;

(b)  that a large imbalance between ones and zeros in the data stream could
result in a bit-error-rate degradation in the symbol detection process;

(c)  that NRZ waveforms are widely used in standard modulation systems;

(d)   that  NRZ waveforms require sufficient symbol transitions for  symbol
clock recovery;

(e)  that the tracking system loop bandwidth is usually less than, or equal
to, one percent of the symbol rate;

(f)  that, for Category A, the specified degradation in bit error rate, due
to symbol sync error, is usually less than 0.3 dB;

(g)  that, for Category B, the specified degradation in bit error rate, due
to symbol sync error, is usually less than 0.1 dB;

recommends

(1)  that the maximum string of either ones or zeros be limited to 64 bits;

(2)   that,  for  Category  A, a minimum of 125 transitions  occur  in  any
sequence of 1000 consecutive symbols;(1)

(3)   that,  for  Category  B, a minimum of 275 transitions  occur  in  any
sequence of 1000 consecutive symbols;(1)




________________________
NOTE:

(1)   See:   CCSDS  Recommendation  for Packet  Telemetry,  CCSDS  102-B-2,
January 1987, or later issue and CCSDS Recommendation for Telemetry Channel
Coding,  CCSDS  101.0-B-2, January 1987, or later issue  to  determine  the
recommended method(s) for ensuring adequate symbol transition density.


2.4.10    CHANNEL INPUT AND CODING CONVENTIONS FOR QPSK SYSTEMS

The CCSDS,

considering

(a)    that a clear relation between digital information and the resulting
       RF carrier phase is necessary to reconstruct the digital data
       stream following reception and demodulation;

(b)    that the digital data format will conform to the CCSDS
       Recommendation for Packet Telemetry;

(c)    that some communications systems with high data rate transmission
       requirements use QPSK modulation;

(d)    that the phase states representing each of the possible debit values
       should be judiciously chosen so that a phase error of 90 degrees
       can cause an error in no more than one bit;

(e)    that it should be possible to have two logically independent
       channels;

(f)    that in the case of a single data stream the odd and even bits
       should be forwarded to two independent channels;

recommends

(1)    that the serial input digital data stream to QPSK systems be divided
       so that odd bits are modulated on the I-channel and even bits are
       modulated on the Q-channel.

(2)    that carrier phase states have the following meanings:

          -    0 degrees represents a "00" bit pair,
          -    90 degrees represents a "01" bit pair,
          -    180 degrees represents a "11" bit pair,
          -    270 degrees represents a "10" bit pair.

2.5.1A    MINIMUM EARTH STATION GROUP DELAY CALIBRATION ACCURACY, CATEGORY
          A

The CCSDS,

considering

(a)    that earth station group delay calibrations must include all
       equipment used for ranging measurements;

(b)    that the path used for earth station group delay calibration is not
       always identical with the path used for ranging measurements;

(c)    that earth station group delay calibrations require frequency
       translation to close the loop between the earth station's
       transmitting and receiving equipment;

(d)    that frequency translation requires the use of a transponder or
       frequency translator which will not be in the path during ranging
       measurements;

(e)    that the group delay measurement error, exclusive of frequency
       translation, can reasonably be kept as low as 2 nanoseconds;

(f)    that the group delay measurement error of the frequency translation
       equipment can also be kept as low as 2 nanoseconds;

(g)    that, where a frequency translator is employed to close the loop
       between the earth station's transmitting and receiving equipment,
       the ranging tone modulation indices used for up- and/or down-link
       during calibrations are generally not the same as those used during
       ranging measurements;

(h)    that the group delay variation of the earth station receiver
       resulting from the use of different modulation indices does not
       exceed 4 nanoseconds;

(i)    that the calibration error due to spurious modulation in the earth
       station's equipment does not exceed 2 nanoseconds;

recommends

     that  the  earth station's group delay be calibrated with an  accuracy
     better than, or equal to, 10 nanoseconds for Category A missions.


2.5.2A    MINIMUM EARTH STATION RANGING GROUP DELAY STABILITY, CATEGORY A

The CCSDS,

considering


(a)    that most space agencies use ranging measurements for spacecraft
       orbit or trajectory determination;

(b)    that a ranging accuracy of 10 meters is generally adequate to meet
       the orbit or trajectory determination accuracy required by Category
       A missions;

(c)    that the accuracy of the ranging measurement is dependent upon the
       following factors:
     -     the  accuracy  with  which the station has  been  located  on  a
     geodetic grid;
     -    the accuracy with which the medium can be modeled;
     -    the accuracy of the frequency and timing system;
     -     the  accuracy with which the ranging channel's group  delay  has
     been calibrated;
     -    the ranging data noise;
     -    the group delay variations between calibrations;

(d)    that the ground system's contribution to the total 10 meter ranging
       error can be limited to 30 percent of the total;

(e)    that the elapsed time between the ranging calibration and the actual
       measurement can be limited to 12 hours or less;

recommends

     that  the  total  group delay variation in the ground station  ranging
     equipment, over any 12 hour period, shall not exceed 20 nanoseconds.


2.5.2B    MINIMUM EARTH STATION RANGING GROUP DELAY STABILITY, CATEGORY B

The CCSDS,

considering

(a)    that most space agencies use ranging measurements for spacecraft
       orbit or trajectory determination;

(b)    that precision range measurements are frequently required to meet
       the scientific objectives of Category B missions;

(c)    that the ranging data can yield scientific information about the
       medium and other physical phenomena;

(d)    that the value of the information obtained from the ranging
       measurement for scientific purposes is directly related to its
       accuracy;

(e)    that to satisfy the needs of all users, the ranging system should be
       capable of measurement accuracies of three meters or better;

(f)    that the accuracy of the ranging measurement is dependent upon the
       following factors:
     -     the  accuracy  with  which the station has  been  located  on  a
     geodetic grid;
     -    the accuracy with which the medium can be modeled;
     -    the accuracy of the frequency and timing system;
     -     the  accuracy with which the ranging channel's group  delay  has
     been calibrated;
     -    the ranging data noise;
     -    the group delay variations between calibrations;

(g)    that, in order to meet the measurement accuracies set forth in (e)
       above, it is important to control the magnitude of the error
       sources listed in (f) above;

(h)    that group delay variations in the ground station ranging equipment,
       which occur between calibrations of that delay, should not exceed
       ten percent of the total error budget;

(i)    that the elapsed time between the ranging calibration and the actual
       measurement can be limited to 12 hours or less;

(j)    that short term variations in group delay affect range rate
       measurements which are sometimes required for range measurement;

recommends

(1)    that the total group delay variation in the ground station ranging
       equipment, over any 12 hour period, shall not exceed 2 nanoseconds.

(2)    that the derivative of the group delay (in a mean square sense) with
       time is within +/- 0.1 mm/s.

2.5.3A    MINIMUM SPACECRAFT RANGING CHANNEL GROUP DELAY STABILITY,
          CATEGORY A

The CCSDS,

considering

(a)    that most space agencies use ranging measurements for spacecraft
       orbit or trajectory determination;

(b)    that a distance measurement accuracy of 10 meters is generally
       adequate to meet the orbit or trajectory determination accuracies
       required by Category A missions;

(c)    that the highest frequency ranging signal determines the precision
       of the range measurement;

(d)    that the principal delay encountered by the highest frequency
       ranging signal results from the narrow band filter in the
       transponder's ranging channel;

(e)    that, in the absence of thermal noise, the spacecraft transponder's
       contribution to the total 10 meter ranging error should not exceed
       15 percent of the total;

(f)    that transponder ranging channel phase linearity is desirable since
       it facilitates removing the range ambiguities;

(g)    that a linear phase response of transponder's ranging channel can be
       achieved with a four-pole Bessel bandpass filter having a one-sided
       bandwidth of 200 kHz and a group delay of 10 microseconds;

(h)    that a group delay stability of a few percent is easily achievable
       for such a filter;

recommends

(1)    that the delay variation of the highest frequency ranging signal,
       which occurs in the spacecraft's transponder, shall not exceed +/-
       50 nanoseconds;

(2)    that pre-launch calibrations, together with telemetered data
       (voltage, temperature, static phase error, etc.) be sufficient to
       permit calculation of the transponder's ranging channel group delay
       with an accuracy of +/- 5 nanoseconds at any time;

(3)    that recommendations (1) and (2) are applicable over the full range
       of doppler frequencies, input signal level, temperatures, and
       voltages encountered during the mission's lifetime;



________________________
NOTE:

1.     For ranging transponder bandwidth, refer to Recommendation 401
       (2.5.4A).

2.5.3B    MINIMUM SPACECRAFT RANGING CHANNEL GROUP DELAY STABILITY,
          CATEGORY B

The CCSDS,

considering

(a)    that most space agencies use ranging measurements for spacecraft
       orbit or trajectory determination;

(b)    that a distance measurement accuracy of 3 meters is generally
       adequate to meet the orbit or trajectory determination accuracies
       required by Category B missions;

(c)    that the highest frequency ranging signal determines the precision
       of the range measurement;

(d)    that the principal delay encountered by the highest frequency
       ranging signal results from the narrow band filter in the
       transponder's ranging channel;

(e)    that, in the absence of thermal noise, the spacecraft transponder's
       contribution to the total 3 meter ranging error should not exceed
       25 percent of the total;

(f)    that transponder ranging channel phase linearity is desirable since
       it facilitates removing the range ambiguities;

(g)    that a linear phase response of transponder's ranging channel can be
       achieved with a four-pole Bessel bandpass filter having a one-sided
       bandwidth of 3.5 MHz and a group delay of 600 nanoseconds;

(h)    that a filter group delay stability of a few percent is easily
       achievable;

(i)    that transponders with two or more space-to-earth links having
       frequency diversity provide a means for determining range
       measurement errors induced by charged particles if the group delay
       difference(s) between the transponder's ranging channels is known
       with great accuracy;

recommends

(1)    that the delay variation of the highest frequency ranging signal,
       which occurs in the spacecraft's transponder, shall not exceed +/-
       30 nanoseconds;

(2)    that pre-launch calibrations, together with telemetered data
       (voltage, temperature, static phase error, etc.) be sufficient to
       permit calculation of the transponder's ranging channel group delay
       with an accuracy of +/- 2.5 nanoseconds at any time;

(3)    that the variation in differential delay between any two channels in
       a single transponder be less than +/- 2 nanoseconds;

(4)    that the above recommendations are applicable over the full range of
       doppler frequencies, input signal level, temperatures, and voltages
       encountered during the mission's lifetime;


_________________________
NOTE:

1.     For ranging transponder bandwidth, refer to Recommendation 401
       (2.5.4B).

2.5.4A    RANGING TRANSPONDER BANDWIDTH FOR RESIDUAL CARRIER SYSTEMS,
          CATEGORY A

The CCSDS,

considering

(a)    that, for most missions, the ranging signals occupy a larger
       bandwidth than telecommand or housekeeping telemetry signals;

(b)    that it is important to limit the occupied bandwidth in the Category
       A mission frequency bands;

(c)    that sine-wave ranging modulation is used for limiting the occupied
       bandwidth;

(d)    that range measurement precision increases with the frequency of the
       highest frequency (major) ranging tone;

(e)    that most space agencies presently utilize a 100 kHz major tone as a
       compromise between range measurement precision and bandwidth
       occupancy;

(f)    that most space agencies currently employ tones at or above 4 kHz;

(g)    that the spacecraft transponder's ranging filter must reject d.c.
       and very low frequencies so that the residual carrier energy is not
       re-modulated on the return link;

(h)    that it is important to minimize earth-to-space link noise which is
       re-modulated on the space-to-earth link;

(i)    that high phase linearity of the spacecraft transponder's ranging
       channel filter over its bandwidth facilitates removing range
       ambiguities when multiple range tones are used;

(j)    that the ranging transponder's bandwidth can be adequately
       controlled using a 4-pole Bessel linear-phase bandpass filter which
       properly defines the attenuation roll-off characteristics;

recommends

(1)    that spacecraft transponders incorporate a bandpass filter in their
       ranging channel;

(2)    that the transponder ranging channel's baseband frequency response
       be uniform within +/- 0.5 dB within the frequency range 3 kHz to
       110 kHz;

(3)    that the transponder's ranging channel be designed to not deviate
       more than +/- 6 degrees from a linear phase-frequency relationship
       within the bandwidth stated in recommends (2).

2.5.4B    RANGING TRANSPONDER BANDWIDTH FOR RESIDUAL CARRIER SYSTEMS,
          CATEGORY B

The CCSDS,

considering

(a)    that range measurement precision increases with the frequency of the
       highest frequency (major) range code component;

(b)    that some space tracking systems for Category B missions employ
       square-wave ranging modulation having range code component
       frequencies from 1 Hz to 1 MHz;

(c)    that other spacecraft tracking systems for Category B missions
       employ sine wave tones, which can be selected in frequency from 100
       kHz to 1 MHz, which may be phase modulated by a square wave code;

(d)    that these systems are designed to bi-phase modulate the high
       frequency code component with the low frequency code components to
       reduce interference with the telecommand and telemetry signals;

(e)    that the ranging transponder's bandwidth required to accommodate the
       ranging codes described in (b) permit flexibility in the selection
       of the types of ranging codes and modulation techniques;

(f)    that the ranging transponder's bandwidth can be adequately
       controlled using a 4-pole Bessel linear-phase bandpass filter which
       properly defines the attenuation roll-off characteristics;

(g)    that some margin should be included in the transponder filter's
       bandwidth to ensure proper operation with the commonly used 1 MHz
       tone or code;

recommends

(1)    that spacecraft transponders incorporate a bandpass filter in their
       ranging channel;

(2)    that the transponder ranging channel's baseband frequency response
       be uniform within +/- 0.5 dB within the frequency range 3 kHz to
       1.1 MHz;

(3)    that the one-half power (-3 dB) bandpass frequencies of the
       transponder's ranging channel be greater than 3 MHz and less than 1
       kHz;

(4)    that the transponder's ranging channel be designed to not deviate
       more than +/- 6 degrees from a linear phase-frequency relationship
       within the bandwidth stated in recommends (3);

(5)    that the one-sided equivalent noise bandwidth be limited to 3.5 MHz.


2.5.5A    PN CODE PHASE SHIFT STABILITY REQUIRED IN SPACECRAFT SPREAD
          SPECTRUM REGENERATIVE RANGING TRANSPONDERS, CATEGORY A

The CCSDS,

considering

(a)    that most agencies use ranging measurements for spacecraft orbit or
       trajectory determination;

(b)    that Pseudo-Noise (PN) code sequences are used by some spacecraft
       transponders to make ranging measurements;

(c)    that, in the ranging mode, these transponders must synchronize an on-
       board PN code generator to the received PN code;

(d)    that, usually, the earth-to-space link's signal-to-noise ratio in
       the ranging code's tracking loop is sufficiently large so that the
       phase error in the spacecraft's code tracking loop is an
       insignificant part of the ranging measurement error;

(e)    that a 1-sigma distance measurement accuracy of 10 meters is
       generally sufficient to meet the orbit or trajectory determination
       requirements of Category A missions;

(f)    that the spacecraft transponder's contribution to the total 10 meter
       distance measurement error should not exceed 30 percent of the
       total;

(g)    that the variation of transponder's temperature is the principal
       cause of instability in the time delay and is normally measured and
       recorded prior to launch;

recommends

     that  the  time  delay of PN codes through a spacecraft's  transponder
     should not vary from its calibrated, pre-launch value by more than  20
     nanoseconds.

2.6.1     TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE
          2025-2120 MHz AND 2200-2300 MHz BANDS

The CCSDS,

considering

(a)    that a great number of space missions, which require coherency
       between the earth-to-space and space-to-earth links for development
       of navigational data, operate in the above frequency bands;

(b)    that for space missions which require coherency, a turnaround
       frequency ratio must be defined;

(c)    that many CCSDS agencies have used the 221/240 turnaround ratio in
       their space missions for many years;

(d)    that many CCSDS agencies have developed equipment using this ratio
       for their spacecraft and earth stations which represent a large
       financial investment;

(e)    that the 221/240 turnaround frequency ratio adequately translates
       the 2025 - 2120 MHz band to the 2200 - 2300 MHz band;

recommends

(1)    that CCSDS agencies continue to use the 221/240 turnaround frequency
       ratio for Category A and Category B space missions which are
       operating in the above bands;

(2)    that this turnaround frequency ratio is only necessary for those
       space missions which require both cross support from other
       agencies' earth stations and coherency between the earth-to-space
       and space-to-earth links.

2.6.2     TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE
          7145-7235 MHz AND 8400-8500 MHz BANDS

The CCSDS,

considering

(a)    that a great number of space missions which require coherency
       between the earth-to-space and space-to-earth links for development
       of navigational data operate in the above frequency bands;

(b)    that for space missions which require coherency, a turnaround
       frequency ratio must be defined;

(c)    that some CCSDS agencies have used the 749/880 turnaround ratio for
       several years and others are planning its use for the near future;

(d)    that some CCSDS agencies have developed equipment using this ratio
       for their spacecraft and earth stations and others are planning to
       do so in the near future, representing a large financial
       investment;

(e)    that the 749/880 turnaround frequency ratio adequately translates
       the 7145 - 7235 MHz band to the 8400 - 8500 MHz band;

recommends

(1)    that CCSDS agencies use the 749/880 turnaround frequency ratio for
       their Category A and Category B space missions operating in the
       7145 - 7235 and 8400 - 8500 MHz bands;

(2)    that this turnaround frequency ratio is only necessary for those
       space missions which require both cross support from other
       agencies' earth stations and coherency between the earth-to-space
       and space-to-earth links.

2.6.3A    TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE
          2025-2110 MHz AND 8450-8500 MHz BANDS, CATEGORY A

The CCSDS,

considering

(a)    that future Category A space missions will use earth-to-space links
       in the 2025 - 2110 MHz band in conjunction with space-to-earth
       links in the 8450 - 8500 MHz band;

(b)    that these space missions may require coherency between the earth-to-
       space and space-to-earth links for the development of navigational
       data;

(c)    that for space missions which require coherency, a turnaround
       frequency ratio must be defined;

(d)    that the two frequency bands under consideration differ regarding
       the available bandwidth;

(e)    that the lower and upper parts of the 2025-2110 MHz band are already
       rather densely occupied by long term missions and, consequently,
       they should be avoided;

(f)    that for reasons of standardization of the on-board receiver design,
       a ratio between the two bands under consideration should be chosen
       in such a way as to conserve the number "221" of the "221/240"
       ratio for 2 GHz downlink/uplink systems;

(g)    that for reasons of simplicity of on-board transmitter design, a
       ratio which can be divided down to small integers should be
       selected;

recommends

(1)    that CCSDS agencies use a turnaround frequency ratio of 221/900 for
       systems operating in the 2075 - 2087 MHz and 8450 - 8500 MHz bands;

(2)    that this turnaround frequency ratio is only necessary for those
       space missions which require both cross support from other
       agencies' earth stations and coherency between the earth-to-space
       and space-to-earth links.

2.6.4A    TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE
          7190-7235 MHz AND 2200-2290 MHz BANDS, CATEGORY A

The CCSDS,

considering

(a)    that future Category A space missions will use earth-to-space links
       in the 7190 - 7235 MHz band in conjunction with space-to-earth
       links in the 2200 - 2290 MHz band;

(b)    that these space missions may require coherency between earth-to-
       space and space-to-earth links for the development of navigational
       data;

(c)    that for space missions which require coherency, a turnaround
       frequency ratio must be defined;

(d)    that the two frequency bands under consideration differ regarding
       the available bandwidth;

(e)    that the lower and upper parts of the 2200 - 2290 MHz band are
       already rather densely occupied by long term missions and,
       consequently, they should be avoided;

(f)    that in many cases, the 2 GHz transponder will not be modified, and
       the 7 GHz earth-to-space link can be considered as optional;

(g)    that a design goal of the 2/8 GHz transponder should be a simplicity
       of interfaces and system flexibility;

(h)    that similarity of the circuit layout with the transponders
       developed for the deep space frequency bands may make hardware
       reuse possible;

recommends

(1)    that CCSDS agencies use a turnaround frequency ratio of 765/240 for
       systems operating in the 7190 - 7235 MHz and 2256 - 2270 MHz bands;

(2)    that this turnaround frequency ratio is only necessary for those
       space missions which require both cross support from other
       agencies' earth stations and coherency between the earth-to-space
       and space-to-earth links.

2.6.5B    TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE
          2110-2120 MHz AND 8400-8450 MHz BANDS, CATEGORY B

The CCSDS,

considering

(a)    that Category B space missions use earth-to-space links in the 2110
       - 2120 MHz band in conjunction with space-to-earth links in the
       8400 - 8500 MHz band;

(b)    that many of these space missions require coherency between the
       earth-to-space and space-to-earth links for the development of
       navigational data;

(c)    that for space missions which require coherency, a turnaround
       frequency ratio must be defined;

(d)    that for reasons of standardization of the on-board receiver design,
       a ratio between the two bands under consideration should be chosen
       in such a way as to conserve the number "221" of the "221/240"
       ratio for 2 GHz uplink/downlink systems;

(e)    that for reasons of simplicity of on-board transmitter design, a
       ratio which can be divided down to small integers should be
       selected;

(f)    that some CCSDS agencies utilize a turnaround frequency ratio of
       221/880 and others are planning to do so in the near future;

recommends

(1)    that CCSDS agencies use a turnaround frequency ratio of 221/880 for
       their Category B missions operating in the 2110 - 2120 MHz and 8400
       - 8450 MHz bands;

(2)    that this turnaround frequency ratio is only necessary for those
       space missions which require both cross support from other
       agencies' earth stations and coherency between the earth-to-space
       and space-to-earth links.

2.6.6B    TRANSPONDER TURNAROUND FREQUENCY RATIOS FOR THE 7145 - 7190 MHz
          AND 2290 - 2300 MHz BANDS, CATEGORY B

The CCSDS,

considering

(a)    that Category B space missions will use earth-to-space links in the
       7145 - 7190 MHz band in conjunction with space-to-earth links in
       the 2290 - 2300 MHz band;

(b)    that many of these space missions require coherency between the
       earth-to-space and space-to-earth links for the generation of
       navigational data;

(c)    that for space missions which require coherency, a turnaround
       frequency ratio must be defined;

(d)    that for reasons of standardization of on-board receiver design, a
       turnaround frequency ratio containing the number "749" of the
       "749/880" ratio for the 7 GHz uplink/8 GHz downlink systems should
       be selected;

(e)    that for reasons of standardization of on-board transmitter design,
       a turnaround frequency ratio containing the number "240" of the
       "221/240" ratio for 2 GHz uplink/downlink systems should be
       selected;

recommends

(1)    that CCSDS agencies use a turnaround frequency ratio of 749/240 for
       Category B missions operating in the 7145 - 7190 MHz and 2290 -
       2300 MHz bands;

(2)    that this turnaround frequency ratio is only necessary for those
       space missions which require both cross support from other
       agencies' earth stations and coherency between the earth-to-space
       and space-to-earth links.
















                              RECOMMENDATIONS
                                   2.6.7
                                  THROUGH
                                  2.6.11

                       RESERVED FOR 13 - 15 GHz AND
                          32 - 34 GHz TRANSPONDER
                        TURNAROUND FREQUENCY RATIO

2.6.12    SPACECRAFT TRANSPONDER IF AND AGC AMPLIFIER BANDWIDTHS
          FOR COHERENT OPERATION

The CCSDS,

considering

(a)    that most space agencies utilize spacecraft receivers employing
       phase-locked loops;

(b)    that most of these receivers are implemented as double conversion
       superheterodyne radios with two stage i.f. bandpass filters, and
       automatic gain controls (AGC);

(c)    that a spacecraft's transponder is said to be operating coherently
       if its receiver is phase-locked to a signal, f[sub]r , an earth
       station and the spacecraft's transmitted signal, f[sub]t , is a
       rational multiple of f[sub]r, such that: f[sub]t = (m/n)f[sub]r,
       where m and n are integer numbers and the ratio (m/n) is called the
       transponder turnaround frequency ratio;

(d)    that the predetection i.f. bandpass filters' bandwidths and the
       carrier AGC loop's bandwidth are very important in determining the
       spacecraft receiver's phase-locked loop operation;

(e)    that the predetection bandwidths must be neither too large nor too
       small because the former can result in a degraded signal-to-noise
       ratio while the latter produces false locks during acquisition of
       the earth-to-space link;

(f)    that for Category A missions, where the earth-to-space signal
       strength can vary both rapidly and substantially, it is the
       practice to design AGC loops with a fast response;

(g)    that for Category B missions, where the earth-to-space signal
       strength generally changes slowly and slightly, it is the practice
       to design AGC loops with a slow response;

(h)    that, when the spacecraft's receiver is operating in an unlocked
       mode, the AGC amplifier's gain is determined by the total received
       signal plus noise power while, when it is operating in a phase-
       locked mode, the AGC amplifier's gain is determined solely by the
       received carrier's signal power;

recommends

(1)    that the spacecraft transponder's turnaround frequency ratios be
       selected from those contained in Section 2.6 of this book;

(2)    that the spacecraft's transponder have two-sided predetection filter
       bandwidths of not less than 250 kHz followed by a second filter of
       not less than 3 kHz;

(3)    that, for Category A missions, spacecraft transponders be designed
       to permit selection of the two-sided carrier AGC loop bandwidth
       over a range of at least 15 Hz to 45 Hz depending upon mission
       conditions;

(4)    that, for Category B missions, spacecraft transponders be designed
       to permit selection of the two-sided carrier AGC loop bandwidth
       over a range of at least 1 Hz to 3 Hz depending upon mission
       conditions;

(5)    that the spacecraft transponder's AGC include coherent and non-
       coherent detectors.

3.0   POLICY RECOMMENDATIONS


Section  2  concerns  itself  with  Recommendations  pertaining  to   Radio
Frequency  and Modulation systems' technical characteristics.  By contrast,
this chapter focuses upon radio frequency spectrum usage.

Rules governing a user's operations in the frequency bands are as important
as  the  equipment's  technical specifications.   As  crowding  of  the  RF
spectrum  increases, standards become an imperative to order.  In  a  broad
sense,  the  International Telecommunication Union (ITU) establishes  high-
level  spectrum  policy with its Radio Regulations.   Here,  the  principal
concern is with establishing lower-level Recommendations promoting the most
efficient use of the ITU's frequency allocations.

These  policies are intended to supplement, not supplant, those promulgated
by  the  ITU. This goal is reached by increasing the relevance of  specific
ITU  regulations to spacecraft communications.  Each Recommendation  begins
with  applicable provisions of the ITU's Radio Regulations as a  foundation
and provides additional guidelines for that particular application.

By  establishing  the  following agreements, the  CCSDS  agencies  hope  to
significantly reduce spectrum congestion.  Then, the potential  for  mutual
interference in spacecraft communications should decrease accordingly.

A  significant  number  of new Recommendations are concerned  with  Policy.
Filing all such Recommendations in a single section makes them difficult to
locate  and promotes disorder.  Accordingly, there are now six Policy  sub-
sections:

     3.1 Frequency Utilization   3.4   Operational Procedures
     3.2 Power Limitations       3.5 Testing Recommendations
     3.3 Modulation Methods      3.6 Spacecraft Systems

These  sub-sections are intended to be general categories into which Policy
Recommendations  can be filed and which will simplify  a  readers  task  in
locating specific items.

               FREQUENCY UTILIZATION RECOMMENDATION SUMMARY

 REC.      RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
3.1.1   2 GHz System Parameters            Efficient use of 2 GHz band by
                                           satellite missions.
3.1.2.  10 MHz Occupied BW                 Max Cat A telemetry bandwidth
A                                          in 8 GHz band.
3.1.3A  > 10 MHz Occupied BW               Cat A missions should use 13-15
                                           GHz band.
3.1.4A  Constraints                        Cat A constraints on use of 13-
                                           15 GHz band.
3.1.5B  31.8-32.3 ; 34.2-34.7 GHz          Reserved for Cat B missions.
3.1.6B  Channel Frequencies                Cat B channel frequency plan
                                           for 2, 7, and 8 GHz.


                 POWER LIMITATIONS RECOMMENDATION SUMMARY

 REC.      RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
3.2.1   EIRP Levels                        Limitations on earth-to-space
                                           link.


                 MODULATION METHODS RECOMMENDATION SUMMARY

 REC.      RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
  NO.
3.3.1   Sine Wave ; Square Wave            Cat A; Cat B  ranging
                                           modulation waveforms.
3.3.2A  Spread Spectrum                    Cat A criteria for use of
                                           spread spectrum modulation.
3.3.3A  OQPSK ; QPSK                       Cat A criteria for use.


               OPERATIONAL PROCEDURES RECOMMENDATION SUMMARY

REC.    RECOMMENDED CHARACTERISTICS        RECOMMENDATION SUMMARY
NO.
3.4.1   Simultaneous Rng, Cmd, Tlm         Design spacecraft for
                                           simultaneous operations.
3.4.2   Measurement Methods                Charged particle measurement
                                           methods.


                      TESTING RECOMMENDATION SUMMARY

 REC.      RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
3.5.1   Test Names                         Min spacecraft-earth station
                                           compatibility tests.


                 SPACECRAFT SYSTEMS RECOMMENDATION SUMMARY

REC.       RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
3.6.1A  Power Spectral Density             Constraints on space-to-space
                                           links.


3.1.1     EFFICIENT UTILIZATION OF THE 2 GHz BANDS BY SATELLITE MISSIONS

The CCSDS,

considering

(a)    that frequency bands 2025 - 2110 and 2200 - 2290 MHz are shared co-
       equally by the following space services:  Space Research, Space
       Operation, and Earth Exploration Satellite (EES);

(b)    that these bands constitute mission bands for the Space Research and
       EES services and tracking, telemetry, and telecommand (TTC) bands
       for other space services making use of the Space Operation service
       allocations;

(c)    that these bands are of prime importance for the satellite missions
       of CCSDS agencies and will remain so for many years to come as no
       comparable alternative frequency allocations are available;

recommends

     that,  in  order  to  make maximum use of these  bands  for  satellite
     missions   of   all  kinds,  appropriate  technical  and   operational
     constraints be observed, particularly:

  i       The TTC systems for geostationary satellites should be designed and
          constructed to the general characteristics contained in CCIR
          Report 678, Dubrovnik, 1986, as set forth in Table 3.1.1-1.
          Given the state-of-the-art in satellite receiver technology as
          demonstrated by numerous existing 2 GHz TTC systems, higher earth
          station EIRPs are not desired and will be detrimental to the
          effective use of the RF spectrum as well as the geostationary
          orbit.

  ii      Space systems, which are designed to operate in mission bands other
          than 2025 - 2110 MHz and 2200 - 2290 MHz, but which utilize TTC
          systems within these bands, should limit the use of such TTC
          systems to launch, orbit insertion, and emergency operations in
          accordance with the definition of the Space Operation service
          (ITU/RR/25).  By limiting the use of such TTC systems, the
          possibility of interference between spacecraft operating in the
          Space Operation, Space Research, and Earth Exploration Satellite
          (EES) services will be greatly reduced.

  iii     With a view to facilitating sharing of the 2 GHz bands, TTC and data
          transmission systems on spacecraft operating in the Space
          Research and Earth Exploration Satellite services should also be
          designed in such a way that the occupied bandwidths in the earth-
          to-space and space-to-earth links, as well as earth stations'
          EIRPs, are kept to a minimum.

3.1.1     EFFICIENT UTILIZATION OF THE 2 GHz BANDS BY SATELLITE MISSIONS
          (Continued)


                               TABLE 3.1.1-1

                    TYPICAL SYSTEM PARAMETERS AT 2 GHz

          MODE            SYSTEM PARAMETERS        SPACE
                                                   OPERATIONS
                                                   (up to
                                                   geostationary
                                                   altitude)


          Reception at    Telemetry bandwidth      100 kHz
          earth station   Tracking bandwidth       400 kHz
                          G/T, earth stations      Approx. 20
                                                   dB/K


          Transmission    Telecommand bandwidth    100 kHz
          from earth      Tracking bandwidth       400 kHz
          stations        EIRP, earth station      Approx. 65
                                                   dBW



3.1.2A    USE OF THE 8450-8500 MHz BAND FOR SPACE RESEARCH, CATEGORY A

The CCSDS,

considering

(a)    that the 8450 - 8500 MHz band contains the only primary worldwide
       allocation to the Space Research service below 40 GHz, affording it
       particularly good protection from interference;

(b)    that the total allocated bandwidth is limited to 50 MHz;

(c)    that CCIR Recommendation 610 sets the limit for Category A missions
       at 2,000,000 km instead of lunar distance as currently defined in
       the ITU Radio Regulations (cf. ITU/RR/169);

(d)    that space missions to the region between lunar distance and
       2,000,000 km will need spectrum accommodation outside the deep
       space bands, in accordance with (c);

(e)    that space missions mentioned under (d) may have technical
       requirements, which can only be satisfied in the 8450 - 8500 MHz
       bands;

(f)    that certain space missions have a 2/8 GHz coherency requirement,
       determined by mission objectives;

recommends

(1)    that space missions requiring an occupied bandwidth, as defined in
       ITU/RR/147, of more than 20% of the available bandwidth (i.e., in
       excess of 10 MHz) should not be approved for a frequency assignment
       in the 8450 - 8500 MHz band without detailed consideration of their
       requirements;

(2)    that space missions mentioned in (d), (e), and (f) above should be
       given priority for use of the 8450 - 8500 MHz band;

(3)    that CCSDS agencies approve space missions with bandwidth
       requirements in excess of 10 MHz in the 8450 - 8500 MHz band only
       on a case-by-case basis and impose, where necessary, operational
       limitations on their use of this band.

3.1.3A    USE OF THE 13.25-15.35 GHz BANDS FOR SPACE RESEARCH,
          CATEGORY A

The CCSDS,

considering

(a)    that frequency bands are allocated to the Space Research service
       between 13.25 and 15.35 GHz, i.e.,

                    13.25 - 13.40 GHz (earth-to-space)
                    13.40 - 14.30 GHz (no direction indicated)
                    14.40 - 14.47 GHz (space-to-earth)
                    14.50 - 15.35 GHz (no direction indicated)

(b)    that these bands are allocated with a secondary status and
       consequently may not enjoy full protection from interference at all
       sites and all times;

(c)    that these bands were found feasible for use with near-earth
       satellites in CCIR Recommendation 364;

(d)    that a link near 15 GHz may provide about 1.5-2.5 dB improvement in
       the space-to-earth link compared to the current 8 GHz band, while a
       link near 33 GHz may provide 5.0-7.7 dB improvement compared to 8
       GHz;

(e)    that the limits of power flux density on the earth's surface for the
       13.4 - 15.35 GHz bands are specified by CCIR Recommendation 510-1
       to be:

          -148  dB (W/m**2) in any 4 kHz band for angles of arrival between
          0 and 5 degrees above the horizontal plane;

          -148  +  0.5 (delta - 5) dB (W/m**2) in any 4 kHz band for angles
          of  arrival, delta  (degrees) between 5 and 25 degrees above  the
          horizontal plane;

          -138  dB (W/m**2) in any 4 kHz band for angles of arrival between
          25 and 90 degrees above the horizontal plane;

(f)    that these PFD limits allow operation of earth stations with G/Ts of
       typically 35-40 dB/K;


3.1.3A    USE OF THE 13.25-15.35 GHz BANDS FOR SPACE RESEARCH,
          CATEGORY A (continued)

recommends

     that  the  13.25  -  15.35 GHz frequency bands of the  Space  Research
     service  be  used for Category A satellites, particularly  with  those
     missions  having  requirements for large bandwidths, which  cannot  be
     accommodated in other frequency bands of this service (such as in  the
     2 and 8 GHz bands).




____________________________
NOTE:

1.     The Tracking and Data Relay Satellite System (TDRSS) uses the 13.25
       to 15.35 GHz band with the 13.4 to 14.0 GHz portion being used for
       space-to-earth and TDRSS-to-user (satellite) transmissions.  This
       lower portion of the band is susceptible to interference from
       Category A missions and consequently should be used with due
       consideration to the TDRSS use.  (Sharing of this portion of the
       band may be feasible in certain circumstances, e.g., if
       transmissions of the near-earth spacecraft are pointed at the earth
       only and are restricted to those parts of the orbit where no
       interference will be carried to the White Sands, NM TDRSS earth
       station.)

3.1.4A    CONSTRAINTS ON THE USE OF THE 13.25-15.35 GHz BAND FOR SPACE
          RESEARCH, CATEGORY A

The CCSDS,

considering

(a)    that bandwidth requirements in excess of 10 MHz are increasingly
       difficult to satisfy in frequency bands allocated to the Space
       Research Service below 10 GHz;

(b)    that the 8450 - 8500 MHz band has been identified as appropriate for
       Category A missions requiring less than 10 MHz of bandwidth as
       specified in Recommendation 401 (3.1.2A) B-1;

(c)    that the sharing situation in this band, where the Space Research
       Service has only a secondary status, is difficult and does not lend
       itself to the use of classical modulation schemes which exhibit a
       high interference potential and a high susceptibility to
       interference;

(d)    that spectrum spreading types of modulation can considerably
       alleviate the sharing problems addressed in (c) above;

(e)    that some CCSDS member agencies are actively pursuing plans for
       space research missions which require very large bandwidths, e.g.,
       spaceborne VLBI, geodesy and geodynamics;

(f)    that errors in measurement precision caused by ionospheric effects
       at about 14 GHz are reduced by a factor of 2.8 as compared to those
       at 8.4 GHz, for single frequency measurement systems;

(g)    that sharing of the 13.25 - 13.40 GHz part of the band (allocated to
       Space Research, earth-to-space, Secondary, under Article 14) with
       the Radionavigation service (Primary) is currently impossible;

(h)    that the 13.40 - 14.00 GHz part of the band is allocated to the
       Radiolocation service (Primary) and active sensors on spacecraft
       (Secondary);

(i)    that any use of the 13.40 - 14.00 GHz part of the band by the Space
       Research Service should be compatible with active sensors in this
       band;

(j)    that, in the 13.40 - 14.00 GHz part of the band, sharing with the
       Radiolocation Service is difficult and does not lend itself to
       reception at earth stations, i.e., to space-to-earth transmissions;

(k)    that the 14.00 - 15.35 GHz part of the band is densely occupied by
       the Fixed Service (14.30-15.35 GHz) and earth-to-space links of the
       Fixed Satellite Service (14.00 - 14.80 GHz) and that, consequently,
       assignment of earth-to-space links of the Space Research Service
       are difficult;

(l)    that certain parts of the 13.25 - 15.35 GHz band have assignments to
       data relay satellites;

(m)    that CCSDS members should ensure compatibility between their
       operations in the 13.25 -15.35 GHz band;

3.1.4A    CONSTRAINTS ON THE USE OF THE 13.25-15.35 GHz BAND FOR SPACE
          RESEARCH, CATEGORY A (Continued)

recommends

(1)    that the 13.25 - 15.35 GHz band be used only for those Category A
       space research missions having requirements for occupied bandwidths
       in excess of 10 MHz;

(2)    that use of the 13.25 - 13.40 GHz band by Category A missions
       requiring an occupied bandwidth of less than 10 MHz be approved
       only in exceptional cases, with prior coordination by the Space
       Frequency Coordination Group (SFCG), and after appropriate
       operational constraints are determined;(1)

(3)    that the spectrum of data transmissions in the 13.25 - 15.35 GHz
       band shall be sufficiently spread so as to ensure adequate
       protection for other services operating in the band;

(4)    that the 13.40 - 14.00 GHz portion of the band be used for earth-to-
       space transmissions.  These transmissions shall not exceed the
       following EIRP density limits (see Figure 3.1.4A-1 on following
       page);

P' ([rho]) = -(20 + 8.8 [rho]**2) dBW/Hz;         for 0.0 deg <= [rho] <= 1.3 deg
P' ([rho]) = -34.4 dBW/Hz;                        for 1.3 deg <= [rho] <= 1.7 deg
P' ([rho]) = -(28.7 + 25 log[sub]10[rho]) dBW/Hz; for 1.7 deg <= [rho] <= 48 deg
P' ([rho]) = -70.7 dBW/Hz;                        for 48 deg <=  [rho] <= 180 deg

where:   ([rho])  is the off-axis angle.


(5)    that use of the 13.25 - 13.40 GHz part of the band not be considered
       for earth-to-space transmissions at this time;

(6)    that particular attention be given to compatibility problems if
       spaceborne receivers for earth-to-space transmissions and for
       active sensors, both using the 13.40 - 14.00 GHz band, are located
       on a common spacecraft;

(7)    that the 14.00 - 15.35 GHz part of the band be used for space-to-
       earth transmissions;

(8)    that detailed frequency coordination be effected with data relay
       satellite operators, particularly where frequency assignments near
       the Tracking and Data Relay Satellite System's (TDRSS's) feeder
       link frequencies are considered.




_______________________
NOTE:

(1)    The Frequency Management Office of the CCSDS Agency seeking to use
       this band is responsible for initiating this action.

3.14A     CONSTRAINTS ON THE USE OF THE 13.25-15.35 GHz BAND FOR SPACE
          RESEARCH CATEGORY (Continued)




                                  [IMAGE]


3.1.5B    USE OF THE 31.8-34.7 GHz BANDS FOR SPACE RESEARCH, CATEGORY B

The CCSDS,

considering

(a)    that as spectrum usage increases, the potential for radio frequency
       interference (RFI) becomes greater;

(b)    that telemetry links from missions in deep space, having very weak
       signals at the earth stations, are particularly susceptible to RFI;

(c)    that frequency bands above 15 GHz are currently less crowded than
       those below 15 GHz;

(d)    that allocated bands that are practicable with current or near
       future technology exist near 33 GHz, in particular:


            FREQUENCY ALLOCATIONS IN THE SPACE RESEARCH SERVICE


          FREQUENCY         DIRECTION          ALLOCATION STATUS
          BAND (GHz)

           31.8 - 32.3      space-to-earth     Secondary*
           34.2 - 34.7      earth-to-space     Secondary*


(e)    that a link near 15 GHz may provide about 1.5-2.5 dB improvement in
       the space-to-earth link compared to the current 8 GHz band, while a
       link near 33 GHz may provide 5.0-7.7 dB improvement compared to 8
       GHz;

(f)    that a link near 15 GHz may provide about 5 dB improvement in the
       earth-to-space link compared to the current 7 GHz band, while a
       link near 33 GHz may provide an improvement of 10 dB compared to 7
       GHz;

(g)    that the allocations near 15 GHz and near 33 GHz are secondary;
       however, the 33 GHz allocation is primary in the U.S., Spain, and
       Australia, providing it with more protection from interference than
       is provided to the 15 GHz band;

____________________________
      *   Primary for deep space in the U.S., Spain, and Australia.  Primary
          for space research in Bulgaria, Cuba, Hungary, Mongolia, Poland,
          the German Democratic Republic, Czechoslovakia, and the U.S.S.R.

3.1.5B    USE OF THE 31.8-34.7 GHz BANDS FOR SPACE RESEARCH, CATEGORY B
          (Continued)

(h)    that further consideration will have to be given to sharing
       considerations for either the 15 or 33 GHz bands.  However, the 33
       GHz band is somewhat better protected;

recommends

(1)    that the frequency band:

          31.8 - 32.3 GHz         be utilized for Space Research
                                  (space-to-earth, Category B only);

          34.2 - 34.7 GHz         be utilized for Space Research
                                  (earth-to-space, Category B only);

(2)    that CCSDS agencies utilize the bands near 33 GHz for communications
       with Category B missions in preference to those allocated to deep
       space near 13 and 17 GHz;

(3)    that channel plans and transponder turnaround frequency ratios be
       developed as soon as possible linking the bands near 33 GHz to the
       2, 7, and 8 GHz, Category B bands;

(4)    that further consideration be given to the allocation status and the
       study of sharing criteria for the 31.8 - 32.3 and 34.2 - 34.7 GHz
       bands.

3.1.6B    CHANNEL FREQUENCY PLAN FOR 2, 7, AND 8 GHz, CATEGORY B

The CCSDS,

considering

(a)    that channel frequency plans for Category B missions exist for the
       2, 7, and 8 GHz bands while others are being developed for the 32
       and 34 GHz bands;

(b)    that the sets of channel frequency pairs in these existing plans are
       based upon the recommended turnaround ratios;

(c)    that members of the Space Frequency Coordination Group (SFCG) have
       resolved to select frequencies for their Category B missions from
       the existing channel frequency plans;

(d)    that most past, existing, and planned Category B missions have
       assigned frequencies that were selected on the basis of these
       existing channel frequency plans;

(e)    that CCSDS agencies conducting Category B missions have coordinated
       the selection of frequencies from those embodied in the existing
       channel frequency plans in order to avoid interference between
       missions;

recommends

(1)    that CCSDS agencies select frequencies for their Category B missions
       operating in the 2, 7, and 8 GHz bands from the channel frequency
       plan contained in Table 3.1.6B-1;

(2)    that frequency selection be coordinated with an appropriate
       organization, such as the SFCG, to ensure the orderly use of the
       channel frequency plan.

3.1.6B    CHANNEL FREQUENCY PLAN FOR 2, 7, AND 8 GHZ, CATEGORY B
          (Continued)

                TABLE 3.1.6B-1:  CHANNEL CENTER FREQUENCIES

__________________________________________________________________________

      2110 - 2120 MHz    2290 - 2300 MHz   7145 - 7190 MHz   8400 -  8450 MHz
      Uplink Channel     Downlink Channel  Uplink Channel    Downlink Channel
      Center Frequency  Center Frequency   Center Frequency  Center Frequency
Channel     (MHz)            (MHz)              (MHz)              (MHz)
__________________________________________________________________________

    1                    2290.185185       7147.286265
    2                    2290.555556       7148.442131
    3                    2290.925926       7149.597994
    4                    2291.296296       7150.753857
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    5*  2110.243056      2291.666667       7151.909724      8402.777780
    6   2110.584105      2292.037037       7153.065587      8404.135803
    7   2110.925154      2292.407407       7154.221450      8405.493826
    8   2111.266204      2292.777778       7155.377316      8406.851853
    9   2111.607253      2293.148148       7156.533179      8408.209876
    10  2111.948303      2293.518519       7157.689045      8409.567903
    11  2112.289352      2293.888889       7158.844908      8410.925927
    12  2112.630401      2294.259259       7160.000771      8412.283950
    13  2112.971451      2294.629630       7161.156637      8413.641977
    14  2113.312500      2295.000000       7162.312500      8415.000000
    15  2113.653549      2295.370370       7163.468363      8416.358023
    16  2113.994599      2295.740741       7164.624229      8417.716050
    17  2114.335648      2296.111111       7165.780092      8419.074073
    18  2114.676697      2296.481481       7166.935955      8420.432097
    19  2115.017747      2296.851852       7168.091821      8421.790124
    20  2115.358796      2297.222222       7169.247684      8423.148147
    21  2115.699846      2297.592593       7170.403550      8424.506174
    22   2116.040895     2297.962963       7171.559413      8425.864197
    23  2116.381944      2298.333333       7172.715276      8427.222220
    24  2116.722994      2298.703704       7173.871143      8428.580248
    25  2117.064043      2299.074074       7175.027006      8429.938271
    26  2117.405092      2299.444444       7176.182868      8431.296294
    27  2117.746142      2299.814815       7177.338735      8432.654321
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    28  2118.087191                        7178.494597      8434.012344
    29  2118.428241                        7179.650464      8435.370371
    30  2118.769290                        7180.814838      8436.738395
    31  2119.110339                        7181.962190      8438.086418
    32  2119.451389                        7183.118056      8439.444445
    33  2119.792438                        7184.273919      8440.802468
    34**                                   7185.429783      8442.160493
    35                                     7186.585617      8443.518517
    36                                     7187.741511      8444.876542
    37                                     7188.897375      8446.234566
    38                                                      8447.592591
    39                                                      8448.950616
___________________________________________________________________________

* Channels 5-27 are fully coherent in all four bands.
** Channels 34-39 frequencies are estimates only.


3.2.1     LIMITATIONS ON EARTH-TO-SPACE LINK POWER LEVELS

The CCSDS,

considering

(a)    that spectral occupation of frequency bands used by space agencies
       is increasing rapidly;

(b)    that in many cases the same frequencies will be shared by several
       spacecraft;

(c)    that excessive EIRP levels radiated from earth stations will make
       frequency sharing increasingly difficult and result in inefficient
       use of the radio frequency spectrum;

(d)    that Pc/No, Eb/No, and the minimum signal level required due to the
       limitations of the receiver's dynamic range determine the required
       EIRP from the earth station;

(e)    that the required signal level at the spacecraft's receiver input is
       frequently the dominant parameter determining the EIRP required
       from the earth station;

recommends

(1)    that CCSDS agencies limit the EIRP levels on the earth-to-space
       links to those realistically required for safe spacecraft operation
       which can be achieved in the following ways:

     -      CCSDS agencies avoid using high power transmitters having a fixed
            output and adjust their transmitted power level to the minimum
            needed to meet project requirements;

     -      CCSDS agencies obtain the required EIRP by using reasonable
            antenna diameters in order to reduce both sidelobe radiation
            and transmitter power levels (Guideline: antenna diameter/RF
            wavelength equal to or greater than 70);

     -      CCSDS agencies place CCIR Recommendation 465-1 as a
            requirement in antenna specifications;

(2)    that spacecraft equipment designers should endeavor to provide equal
       margins for Pc/No, Eb/No and the minimum signal required to fall
       within the receiver's dynamic range.

3.3.1     OPTIMAL RANGING MODULATION WAVEFORMS FOR SIMULTANEOUS RANGING,
          TELECOMMANDING, AND TELEMETRY OPERATIONS

The CCSDS,

considering

(a)    that two-way transmissions are employed for making range
       measurements to a distant spacecraft;

(b)    that telecommand and telemetry signals are phase shift-keyed onto
       the subcarriers and then phase-modulated onto a sinusoidal residual
       RF carrier [see Recommendations 401 (2.1.1) B-1, 401 (2.4.3) B-1,
       401 (2.4.4) B-1];

(c)    that telemetry signals may also be directly modulated on the RF
       carrier in conformance with Recommendation 401 (2.4.7) B-1;

(d)    that sine-wave subcarriers are recommended for the telecommand
       channel [see Recommendation 401 (2.2.2) B-1];

(e)    that sine-wave subcarriers are recommended for Category A mission's
       telemetry channels, and square-wave subcarriers are recommended for
       Category B mission's telemetry channels [see Recommendation 401
       (2.4.5) B-1];

(f)    that, for simultaneous telecommand and ranging on the earth-to-space
       link, the telecommand performance suffers some degradation due to
       command-ranging cross-modulation components;

(g)    that, for simultaneous telemetry and ranging on the space-to-earth
       link, the telemetry performance may be degraded due to interference
       from the filtered versions of the uplink ranging, feed-through
       telecommand, cross-modulation components and noise;

(h)    that the timing offset due to different clocks between the
       telecommand and telemetry may cause serious telemetry bit error
       rate (BER) degradation;

(i)    that the telecommand BER performance is virtually identical for
       either sine wave or square wave ranging modulation;

(j)    that, for Category B missions, the telemetry BER performance is
       insensitive to the type of ranging waveforms used when operated
       simultaneously with the ranging on the space-to-earth link;

(k)    that the use of a square-wave ranging signal makes the telemetry BER
       performance more susceptible to data-to-data interference
       (resulting from the timing offset due to different clocks between
       the telecommand and telemetry) than the sine-wave ranging;

(l)    that, for Category A missions, the telemetry BER performance is
       sensitive to the timing offset when operated simultaneously with
       either a square-wave or sine-wave ranging signal;

(m)    that for Category B missions, it is important to minimize the
       required transmitted power level on the space-to-earth link;

3.3.1     OPTIMAL RANGING MODULATION WAVEFORMS FOR SIMULTANEOUS RANGING,
          COMMANDING, AND TELEMETRY OPERATIONS (Continued)

(n)    that for Category A missions, it is necessary to minimize the
       adjacent channels interference;

(o)    that the use of a sine-wave ranging signal will minimize the
       occupied bandwidth;

recommends

(1)    that, for Category B mission's earth-to-space links, either a sine
       wave or a square wave ranging signal may be used when operated
       simultaneously with the telecommand;

(2)    that, for Category A mission's earth-to-space links, sine wave
       ranging shall be used when operated simultaneously with the
       telecommand;

(3)    that, for Categories A and B mission's space-to-earth links, sine
       wave ranging should be used when operated simultaneously with the
       telemetry;


3.3.2A    CRITERIA FOR USE OF DIRECT SEQUENCE SPREAD SPECTRUM MODULATION,
          CATEGORY A

The CCSDS,

considering

(a)    that frequency bands must often be shared between several users
       which can result in mutual interference;

(b)    that such mutual interference can result in significant link
       degradation or even unusable links for certain periods of time;

(c)    that spread spectrum systems can be designed to tolerate a high
       level of interference from other communications systems.

(d)    that, in some cases, spread spectrum modulation can assist in
       meeting the PFD limits set forth in the International
       Telecommunication Union's (ITU) Radio Regulations;

(e)    that direct sequence spread spectrum systems can be designed to
       provide ranging measurements by using the spreading code which
       eliminates the need for a separate ranging signal;

recommends

(1)    that direct sequence spread spectrum modulation be used in any of
       the following cases:

  -       where the intra-service sharing conditions are such that other
          modulation methods will not provide the required performance or
          mutual compatibility with other transmissions assigned to the
          same frequency band;

  -       where the inter-service sharing conditions are such that the
          susceptibility to actual or potential interference from
          transmissions in other services assigned to the same frequency
          band cannot be kept within acceptable limits by other modulation
          methods;

  -       where the power flux density limits, as set forth in the ITU Radio
          Regulations, Article 28, cannot be met using other methods;

(2)    that spread spectrum systems shall be designed to minimize unwanted
       emissions in the same allocated frequency band;

(3)    that unwanted emissions generated by spread spectrum systems shall
       conform with applicable protection criteria of radio communications
       services in other frequency bands.

3.3.3A    CRITERIA FOR USE OF QPSK MODULATION IN SUPPRESSED CARRIER
          SYSTEMS, CATEGORY A

The CCSDS,

considering

(a)    that efficient use of RF spectrum resources is becoming increasingly
       important;

(b)    that suppressed carrier systems are more bandwidth and power
       efficient than are residual carrier systems;

(c)    that OQPSK systems are less sensitive to non-linear channel effects
       than are standard QPSK systems;

(d)    that sync word detection hardware for phase ambiguity resolution is
       simpler in a OQPSK system than is the case with a standard QPSK
       system;

(e)    that standard QPSK and OQPSK systems are widely used modulation
       techniques in bandwidth limited systems;

recommends

     that  OQPSK  or  standard  QPSK modulation be used  in  communications
     systems  operating  at  frequencies where the available  bandwidth  is
     limited (e.g., in the 2 and 8 GHz bands);

3.4.1     SIMULTANEOUS TELECOMMAND, TELEMETRY, AND RANGING OPERATIONS

The CCSDS,

considering

(a)    that most space agencies use ranging measurements for spacecraft
       orbit or trajectory determination;

(b)    that precision range measurements are frequently required to meet
       the scientific objectives of the mission;

(c)    that the ranging data can yield scientific information about the
       medium and other physical phenomena;

(d)    that the value of the information obtained from the ranging
       measurement for scientific purposes is directly related to its
       accuracy;

(e)    that the earth stations tend to be large, complex, and expensive to
       construct and to operate;

(f)    that it is desirable to minimize the amount of earth station time
       required for the support of missions;

(g)    that the quantity of telecommands transmitted to a spacecraft may be
       sufficiently large that it is desirable to have simultaneous
       telecommand and ranging operations;

(h)    that telemetry transmissions are generally continuous and an
       interruption for ranging operations may result in the loss of
       valuable data;

(i)    that the amount and accuracy of ranging required for missions makes
       it desirable to preserve an ability for simultaneous telecommand,
       telemetry, and ranging operations;

recommends

     that all CCSDS agencies design their spacecraft to permit simultaneous
     telecommand, telemetry, and ranging operations.


3.4.2     CHARGED PARTICLE MEASUREMENTS IN THE TELECOMMUNICATIONS
          PROPAGATION PATH

The CCSDS,

considering

(a)    that the telecommunication system's performance can be affected by
       the columnar content of charged particles in the propagation path;

(b)    that charged particles in the propagation path can result in errors
       in the range and range rate measurements reducing navigation
       accuracy;

(c)    that navigation accuracy requirements can be very high for some
       Category B missions;

(d)    that the four regions through which a telecommunications signal may
       pass which contain charged particles are:  the Earth's ionosphere,
       the interplanetary medium, the planetary ionosphere, and the solar
       corona;

(e)    that the Sun-Earth-Probe (SEP) angle is important in selecting a
       means for measuring charged particles;

(f)    that geostationary satellites are not useful for measuring charged
       particle content for regions beyond the Earth's ionosphere;

(g)    that Differenced Range vs. Integrated Doppler (DRVID) only measures
       variations in the total columnar electron content;

(h)    that method(s) utilized for measuring the charged particle content
       in the propagation path depends upon the region involved;

(i)    that Figure 3.4.2-1 shows alternative spacecraft tracking methods
       which provide information about charged particles in the
       propagation path;

recommends

(1)    that CCSDS agencies utilize the appropriate methods in Table 3.4.2-1
       to measure charged particles in the propagation path for the
       specified operating modes.

(2)    that CCSDS agencies utilize the methods and signal sources in Table
       3.4.2-2 to measure charged particles in the named regions and to
       correct the specified data.

3.4.2     CHARGED PARTICLE MEASUREMENTS IN THE TELECOMMUNICATIONS
          PROPAGATION PATH (Continued)

                                  [IMAGE]

3.4.2     CHARGED PARTICLE MEASUREMENTS IN THE TELECOMMUNICATIONS
          PROPAGATION PATH (Continued)


     Table 3.4.2-1:  RECOMMENDED CHARGED PARTICLE CALIBRATION METHODS

 TRACKING MODE       FARADAY ROT   DRVID         DUAL FREQ
 (see        Figure  user    geo    user    user   geo     slic
 3.4.2A-1)           s/c     sat    s/c     s/c    sat     (b)
 I.1a        (1-way   X       X              X      X       X range)
 I.1b        (1-way   X       X      X       X      X       X Doppler)
 I.2.1a (2-way  coh   X       X              X      X       X Rng)
 I.2.1b (2-way  coh   X       X      X       X      X       X Dop)
 I.2.2a (2-way non-                                           coh Rng)
 I.2.2b (2-way non-                  X                        coh Dop)
 II.1     Alternate   X       X              X      X       X Rng
 II.2  Simultaneous   X       X              X      X       X Rng
 II.3 S/C VLBI        X       X             (a)             X
 II4a  (2-way;   3-   X       X              X      X       X way Rng)
 II.4b  (2-way;  3-   X       X      X       X      X       X way Dop)
 NOTES:    (a)  is applicable to 2/8 GHz downlink only.
                 (b)  slic is satellite L-band Ionospheric
                          Calibration.


           Table 3.4.2-2:  APPLICABILITY OF CALIBRATION METHODS

                             EARTH's  Beyond             RANGE
    CALIBRATION      SOURCE   IONO-    IONO-    RANGE    RATE
       METHOD         USED    SPHERE  SPHERE    ERROR    ERROR
      FARADAY          S/C      X               X(1)     X(1)
      ROTATION       Geo Sat    X               X(2)     X(2)
                       S/C      X        X      X(3)     X(3)
        DUAL         Geo Sat    X               X(2)     X(2)
     FREQUENCY        slic      X               X(2)     X(2)
 DIFFERENCED RANGE     S/C      X        X
   vs. INTEGRATED    Geo Sat
        DOP
NOTES: (1)  should not be used for SEPs below 5 degrees.
       (2)  must translate ray path to user S/C line of sight.
         (3)  2/8 GHz downlink only, inaccurate below SEP = 20
                              deg.



3.5.1     MINIMUM SET OF SPACECRAFT - EARTH STATION TESTS REQUIRED TO
          ENSURE COMPATIBILITY

The CCSDS,

considering

(a)    that cross support will frequently be required for Telemetry,
       Tracking, and/or Command operation;

(b)    that it is desirable to assure compatibility of the spacecraft with
       the ground network before the launch of a spacecraft;

(c)    that this compatibility is usually verified by compatibility tests;

(d)    that all parties have a common understanding of the tests;

recommends

     that,  in  accordance  with the required cross support,  all  relevant
     tests set forth in Table 3.5.1-1 shall be performed.

3.5.1     MINIMUM SET OF SPACECRAFT - EARTH STATION TESTS REQUIRED TO
          ENSURE COMPATIBILITY (Continued)


                               Table 3.5.1-1



                          TEST TYPES

                  SPACECRAFT RADIO FREQUENCY
 
      Transmitter frequency and frequency stability
      Transmitter residual carrier phase jitter
      Transmitter RF spectrum measurement
      Receiver rest frequency determination
      Receiver acquisition frequency range and rate
      Receiver tracking frequency range and rate

                           TELEMETRY
 
      Telemetry modulation index
      Telemetry receiver carrier threshold
      Telemetry bit error rate
      Telemetry spectrum

                          TELECOMMAND
 
      S/C receiver command and carrier threshold
      S/C   receiver   telecommand  phase   modulation   index
      variation
      Telecommand receiver spurious carrier immunity
      Telecommand receiver spurious modulation immunity

                            RANGING
 
      Transponder ranging delay
      Ranging  downlink modulation index vs. uplink modulation
      index
      Ranging downlink spectrum
      Ranging  downlink modulation index vs. uplink signal-to-
      noise power

             EARTH STATION ANTENNA TRACKING SYSTEM
 
      Receiver carrier signal level threshold



3.6.1A    REDUCTION IN INTERFACE FROM SPACE-TO-SPACE LINKS TO OTHER SPACE
          SERVICES IN THE 2025 - 2110 AND 2200 - 2290 MHz BANDS, CATEGORY A

The CCSDS,

considering

(a)    that, in accordance with provisions 747 and 750 of the ITU Radio
       Regulations, space-to-space links shall not cause harmful
       interference to other space systems;

(b)    that the planned increase in the number of space-to-space links will
       nevertheless raise the likelihood of harmful interference;

(c)    that channel coding techniques, such as concatenated codes, can
       reduce the power spectral density by more than 10 dB;

(d)    that spectrum spreading techniques can also be used to reduce the
       power spectral density;

recommends

     that the power spectral density of space-to-space links be reduced  by
     using  appropriate techniques, such as concatenated codes  (see  CCSDS
     Recommendation  101.0  B-2) and/or spectrum  spreading,  in  order  to
     reduce  the  potential for harmful interference to space-to-earth  and
     earth-to-space links.

4.0   PROCEDURAL RECOMMENDATIONS

As  telecommunications systems become more sophisticated, it is  imperative
that aids be developed to assist in the design, performance evaluation, and
perhaps  even  validation of these systems.  Early on, the CCSDS  was  only
concerned  with  technical Recommendations which promoted a  uniformity  in
data  systems.  However, Subpanel 1E soon discovered that efficient use  of
the radio frequency spectrum was an imperative.  Such efficient use implies
constraints and the first Blue Book included a Policy section. This section
contained  many  Recommendations  limiting  CCSDS  Agencies  use  of  radio
frequencies beyond those already imposed by the ITU's Radio Regulations.

However,  efficient use also implies optimal designs.  The more efficiently
a  communications  link  can be made to operate,  the  more  the  frequency
spectrum can be shared with other users.  Use of the radio frequency  bands
is increasing so rapidly that sharing has become essential.

This section contains Recommendations intended to assist the CCSDS Agencies
to  efficiently design and operate their telecommunications  links.   These
Recommendations  are,  in  effect,  tools  to  optimize  the   design   and
performance of those links.  At this juncture, all Recommendations  are  in
the   category  of  design  aids.   Accordingly,  there  is  but  a  single
subsection:

     4.1  Design Tools

However,  it  is  likely that future Recommendations will also  cover  such
areas as performance evaluation and validation.

Many of these tools can be most efficiently applied if they are in the form
of computer programs. Work is underway to develop such programs for several
Recommendations.   These  programs are  being  designed  to  run  on  small
personal computers of the IBM AT class.  Periodically, readers may wish  to
inquire  of  either  the  CCSDS Secretariat, or of CCSDS  Subpanel  1E,  to
ascertain what programs are available.

                    DESIGN TOOLS RECOMMENDATION SUMMARY

 REC.     RECOMMENDED CHARACTERISTICS         RECOMMENDATION SUMMARY
 NO.
4.1.1   Mod Index Determination         Procedure for optimizing.
4.1.2   Link Design Control Table       Standard form for information
                                        exchange.
4.1.3   Terminology                     Definitions of terms found in
                                        DCT.
4.1.4   Reserved                        DCT probability density
                                        functions.


4.1.1     SELECTION OF OPTIMUM MODULATION INDICES FOR SIMULTANEOUS RANGING,
          TELECOMMAND, AND TELEMETRY OPERATIONS

The CCSDS,

considering

(a)    that two-way transmissions are generally employed for making range
       measurements to a distant spacecraft;

(b)    that, for simultaneous telecommand and ranging on the earth-to-space
       link, the telecommand performance may suffer some degradation due
       to telecommand-ranging cross-modulation components;

(c)    that, for simultaneous telemetry and ranging on the space-to-earth
       link, the telemetry performance may be degraded due to interference
       from the filtered versions of the uplink ranging, feed-through
       telecommand, cross-modulation components and noise;

(d)    that the timing offset due to synchronous clocks between the
       telecommand and telemetry may cause serious telemetry bit error
       rate (BER) degradation when the two subcarriers are not separated
       in frequency sufficiently;

(e)    that the performance degradation in the telecommand and telemetry
       due to the factors named in considerations in (b), (c) and (d) can
       be minimized if the modulation indices for telecommand, range,
       telemetry are chosen properly;

(f)    that the ranging receiver is usually not susceptible to interference
       from unwanted emissions which fall outside the receiver's
       bandwidth;

(g)    that the selected modulation indices will provide the optimum power
       division between the data (telecommand/telemetry) and the ranging
       channels for a required ranging accuracy, and a specified bit error
       rate degradation in the data channel;

(h)    that the selected modulation indices will result in adequate power
       for carrier tracking without degrading the specified data channel
       performance;

(i)    that the selected modulation indices will provide the required link
       performance margins for the carrier, range and data signals;

recommends

     that  the CCSDS agencies utilize the technique illustrated in Annex  1
     and Figure 4.1.1-1 to select the optimum set of modulation indices for
     simultaneous ranging, telecommand, and telemetry operations;



4.1.1     SELECTION OF OPTIMUM MODULATION INDICES FOR SIMULTANEOUS RANGING,
          TELECOMMAND, AND TELEMETRY OPERATIONS (Continued)

                                  ANNEX 1

The  constants A[sub]1, A[sub]2, A[sub]3, A[sub]4, A[sub]5, and the  design
factor K shown in Figure 4.1.1-1 are defined as follows:


                                  [IMAGE]

4.1.1     SELECTION OF OPTIMUM MODULATION INDICES FOR SIMULTANEOUS RANGING,
          TELECOMMAND, AND TELEMETRY OPERATIONS (Continued)

                                  [IMAGE]

FIGURE 4.1.1-1:  MT's  ALGORITHM:   AN ALGORITHM TO SEARCH  FOR  A  SET  OF
                 OPTIMUM     MODULATION    INDICES     FOR     SIMULTANEOUS
                 COMMAND/RANGE/ TELEMETRY OPERATIONS

4.1.1     SELECTION OF OPTIMUM MODULATION INDICES FOR SIMULTANEOUS RANGING,
          TELECOMMAND, AND TELEMETRY OPERATIONS (Continued)

                                  [IMAGE]



FIGURE 4.1.1-1:  MT's ALGORITHM:  AN ALGORITHM TO SEARCH FOR A SET OF
                 OPTIMUM MODULATION INDICES FOR SIMULTANEOUS
                 COMMAND/RANGE/TELEMETRY OPERATIONS

4.1.1     SELECTION OF OPTIMUM MODULATION INDICES FOR SIMULTANEOUS RANGING,
          TELECOMMAND, AND TELEMETRY OPERATIONS (Continued)


                                  [IMAGE]





FIGURE 4.1.1-1:  MT's ALGORITHM:  AN ALGORITHM TO SEARCH FOR A SET OF
                 OPTIMUM MODULATION INDICES FOR SIMULTANEOUS
                 COMMAND/RANGE/TELEMETRY OPERATIONS

4.1.1     SELECTION OF OPTIMUM MODULATION INDICES FOR SIMULTANEOUS RANGING,
          TELECOMMAND, AND TELEMETRY OPERATIONS (Continued)




                                  [IMAGE]
























FIGURE 4.1.1-1:  MT's ALGORITHM:  AN ALGORITHM TO SEARCH FOR A SET OF
                 OPTIMUM MODULATION INDICES FOR SIMULTANEOUS
                 COMMAND/RANGE/TELEMETRY OPERATIONS


4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE
          (Link and Weather Not Combined)

The CCSDS,

considering

(a)    that an ability to exchange telecommunications link performance
       information is necessary for agencies to engage in cooperative
       space missions, conduct joint space ventures, and provide ground
       station cross support to another agency's spacecraft;

(b)    that a uniform method for presenting link parameters and calculating
       link performance will facilitate the exchange of information;

(c)    that a uniform Design Control Table (DCT) is a convenient method for
       displaying telecommunications link performance information;

(d)    that the order in which the parameters are arranged in the Design
       Control Table can affect its clarity and the ease with which a
       signal can be traced through a telecommunications system;

(e)    that nominal link parameter values, representing the expected
       performance by the link, are important to an understanding of the
       telecommunications system;

(f)    that favorable and adverse tolerances on the nominal link parameter
       values are required to provide confidence in the link's
       performance;

recommends

(1)    that the uniform Design Control Table, consisting of the general
       information and link performance pages contained in the Annex, be
       used as a means for comparing telecommunications link performance
       calculations between agencies;

(2)    that in computing favorable and adverse tolerances on the nominal
       performance values, agencies should use 3-sigma values for the
       telecommand system and use 2-sigma values for all other systems.





















                     [Page intentionally left blank.]
          4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE

                      CCSDS LINK DESIGN CONTROL TABLE
                            GENERAL INFORMATION
                      (Link and Weather Not Combined)
                                                                     Page 1

                                  [IMAGE]

4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE (Continued)

                      CCSDS LINK DESIGN CONTROL TABLE
                COMMUNICATIONS SYSTEM OPERATING CONDITIONS
                      (Link and Weather Not Combined)

                                                                     Page 2

                                  [IMAGE]



4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE (Continued)

                      CCSDS LINK DESIGN CONTROL TABLE
                           EARTH - SPACE - LINK
                             INPUT DATA SHEET
                                                                     Page 3

                                  [IMAGE]


4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE (Continued)

                      CCSDS LINK DESIGN CONTROL TABLE
                           SPACE - EARTH - LINK
                             INPUT DATA SHEET
                                                                     Page 4

                                  [IMAGE]


4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE (Continued)

                      CCSDS LINK DESIGN CONTROL TABLE
                          EARTH - TO - SPACE LINK
                             LINK COMPUTATIONS
                      (Link and Weather Not Combined)
                                                                     Page 5

                                  [IMAGE]


4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE (Continued)

                      CCSDS LINK DESIGN CONTROL TABLE
                          SPACE - TO - EARTH LINK
                             LINK COMPUTATIONS
                      (Link and Weather Not Combined)
                                                                     Page 6

                                  [IMAGE]


4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE (Continued)

EXPLANATION OF THE REMARKS   :::


 1    DESIGN  TRANSMITTED CARRIER POWER (dBW) IS COMPUTED BY USING  DESIGN
      VALUE  OF Pc/Pt AND THE EIRP.  THE DESIGN VALUE OF Pc/Pt IS COMPUTED
      BY USING THE DESIGN VALUES OF MOD INDICES.
 2    MEAN  TRANSMITTED CARRIER POWER (dBW) IS COMPUTED BY USING  FAV  AND
      ADV  TOLERANCE OF Pc/Pt AND THE EIRP.  THESE TOLERANCES ARE COMPUTED
      USING  ALL POSSIBLE COMBINATIONS Of THE MOD IND.  VARIANCE OF  TRANS
      CARRIER  POWER (dBW) IS COMPUTED BY USING EIRP AND THE FAV  AND  ADV
      TOLERANCES OF Pc/Pt.  TOLERANCES ARE COMPUTED BY USING ALL  POSSIBLE
      MOD INDEX COMBINATIONS.
 2A   A TRIANGULAR DENSITY USED IS FOR THE Pc/Pt RATIO.
 3    DESIGN  TRANSMITTED CARRIER POWER (dBW) IS COMPUTED BY USING  DESIGN
      VALUE  OF Pd/Pt AND THE EIRP.  DESIGN VALUE OF Pd/Pt IS COMPUTED  BY
      USING THE DESIGN VALUES Of MOD INDICES.
 4    MEAN  TRANSMITTED DATA POWER (dBW) IS COMPUTED BY USING FAV AND  ADV
      TOLERANCE  OF  Pd/Pt  AND THE EIRP.  THESE TOLERANCES  ARE  COMPUTED
      USING  ALL POSSIBLE MOD INDEX COMBINATIONS.  VARIANCE OF TRANS  DATA
      POWER  (dBW) IS COMPUTED BY USING EIRP AND THE FAV AND ADV TOLERANCE
      OF  Pd/Pt.  TOLERANCES  ARE COMPUTED USING ALL  POSSIBLE  MOD  INDEX
      COMBINATIONS.
 4A   A TRIANGULAR DENSITY USED IS FOR THE Pd/Pt RATIO.
 5    DESIGN TRANSMITTED RANGE POWER (dBW) IS COMPUTED USING DESIGN  VALUE
      OF  Pr/Pt AND THE EIRP.  DESIGN VALUE OF Pr/Pt IS COMPUTED USING THE
      DESIGN VALUES OF MOD INDICES.
 6    MEAN  TRANSMITTED RANGE POWER (dBW) IS COMPUTED USING  FAV  AND  ADV
      TOLERANCE OF Pr/Pt AND THE EIRP.  TOLERANCES ARE COMPUTED  BY  USING
      ALL  POSSIBLE MOD INDEX COMBINATIONS.  VARIANCE OF TRANS RANGE POWER
      (dBW)  IS  COMPUTED  USING EIRP AND THE FAV  AND  ADV  TOLERANCE  OF
      Pr/Pt.  TOLERANCES  ARE  COMPUTED  USING  ALL  POSSIBLE  MOD   INDEX
      COMBINATIONS.
 6A   A TRIANGULAR DENSITY USED IS FOR THE Pr/Pt RATIO.
 7    THE SPACE LOSS USING FAVORABLE TOLERANCE.
 8    THE SPACE LOSS USING ADVERSE TOLERANCE.
 9    LINK  AND ATMOSPHERICS ARE ASSUMED TO BE INDEPENDENT.  THIS  IS  THE
      WORST  CASE.   MEAN AND VARIANCE ARE COMPUTED USING THE  APPROPRIATE
      WEATHER MODEL.
 10   SAME AS REMARK 1 BUT APPLIED FOR THE DOWNLINK.
 11   SAME AS REMARK 2 BUT APPLIED FOR THE DOWNLINK.
 11A  SAME AS REMARK 2a BUT APPLIED FOR THE DOWNLINK.
 12   SAME AS REMARK 3 BUT APPLIED FOR THE DOWNLINK.
 13   SAME AS REMARK 4 BUT APPLIED FOR THE DOWNLINK.
 13A  SAME AS REMARK 4a BUT APPLIED FOR THE DOWNLINK.
 14   SAME AS REMARK 5 BUT APPLIED FOR THE DOWNLINK.
 15   SAME AS REMARK 6 BUT APPLIED FOR THE DOWNLINK.
 15A  SAME AS REMARK 6a BUT APPLIED FOR THE DOWNLINK.
 16   SAME AS REMARK 7 BUT APPLIED FOR THE DOWNLINK.
 17   SAME AS REMARK 8 BUT APPLIED FOR THE DOWNLINK.
 18   SAME AS REMARK 9 BUT APPLIED FOR THE DOWNLINK.


4.1.2     TELECOMMUNICATIONS LINK DESIGN CONTROL TABLE (Continued)


 NOTES:::::::
 UPLINK:
 1. REQUIRED TONE 1 SNR MEANS THE REQUIRED TONE / CODE 1 RANGING POWER
     DIVIDED BY THE NOISE POWER IN THE RANGING BANDWIDTH.  THE USER IS
     EXPECTED TO INPUT THE SNR VALUE IN SHEET 3, LINE 32.
 2. WHEN THE RANGING MARGIN IS COMPUTED, THE RANGING BANDWIDTH IS USED TO
     CONVERT THE REQUIRED POWER-TO-NOISE DENSITY RATIO AND, THEREAFTER, IT
     IS COMPARED WITH THE RECEIVED RANGING POWER-TO-NOISE DENSITY RATIO.
 
 DOWNLINK:
 1. REQUIRED RANGING POWER-TO-NOISE DENSITY RATIO IS TO BE SPECIFIED TO
     PROVIDE THE NEEDED RANGING ACCURACY.  THE STEPS ARE:
     a.              SPECIFY INTEGRATION TIME NEEDED MEET ACCURACY
         REQUIREMENTS.
     b.              COMPUTE EFFECTIVE BANDWIDTH (e.g., 1/INTEGRATION
         TIME).
     c. USING CURVES IN TRK-30 Of DSN DOCUMENT 810-5, FIND REQUIRED Pr/No
         AND ENTER ON SHEET 4, LINE 79.
          DENSITY RATIO AND PROVIDE THIS IN SHEET 4 PLACE 79
 2. RANGING MARGIN IS BASED ON EFFECTIVE BANDWIDTH COMPUTED ABOVE.


4.1.3     STANDARD TERMINOLOGY FOR TELECOMMUNICATIONS LINK PERFORMANCE
          CALCULATIONS

The CCSDS,

considering

(a)  that   a   uniform   method  for  computing  telecommunications   link
     performance  is  desirable  in order to  facilitate  the  exchange  of
     information among agencies;

(b)  that  it  is  necessary to agree upon the definitions of  certain  key
     terms  before  a uniform method for computing telecommunications  link
     performance can be adopted;

(c)  that definitions which have been adopted by internationally recognized
     organizations for such key terms should be used whenever possible;

recommends

(1)    that the terms listed in Article 1 of the Radio Regulations and in
       the Annex below be used together with the meaning ascribed to them
       in the corresponding definition.

(2)    that the telecommunications link, together with the noise sources
       and losses, be described as shown in Figure 4.1.3-1.


                                  [IMAGE]

4.1.3     ANNEX AID RECOMMENDATION

TELECOMMUNICATIONS  LINK  DESIGN  CONTROL  TABLE  (Link  and  Weather   Not
Combined):   A set of informational and input data tables for the  user  to
provide  the  salient earth-to-space and space-to-earth  telecommunications
equipment  and  link  characteristics together with tables  containing  the
computed  performance  of  these links without regard  to  weather  induced
effects.


                            GENERAL INFORMATION

(1)    OWNER CCSDS AGENCY:  The CCSDS member agency having primary
       responsibility for the success or failure of the mission.

(2)    NAME OF MISSION:  The name given to the mission by the CCSDS member
       agency owner.

(3)    NAME OF SPACECRAFT:  The name given to a specific spacecraft, which
       is part of the named mission, by the CCSDS member agency owner.

(4)    MISSION CATEGORY:  The mission's category, either Category B for
       deep space missions (missions whose altitude above the earth's
       surface exceeds 2 x 10**6 km) or Category A for non-deep space
       missions (those whose altitude above the earth's surface are less
       than, or equal to, 2 x 10**6 km).

(5)    LINK BUDGET NUMBER:  A number which is assigned to this link budget
       study under the conditions and with the configuration stated on the
       following pages to distinguish it from other such studies.

(6)    REVISION NO/CONDITIONS:  The most recent revision of this
       telecommunications link budget study, which is contained in this
       table, for the named spacecraft and mission together with a short
       description of the study conditions (e.g., transmitter power,
       station used, etc.).

(7)    DATE:  The date that this study or revision was made.

(8)    FILE NAME:  The name or number of the file, whether on a computer
       disk or other media, where this DCT is stored.

(9)    PROJECT COGNIZANT PERSON:

     Name:  The name of the person in the owner agency with whom inputs to,
     or  outputs  from  this Design Control Table should be  discussed  and
     approved.

     Title:  The position or title of the person named in above.

     Address:   The full agency center's name and address which is required
     to contact the cognizant person in an efficient manner.

     Telephone:  The telephone number, including country and area codes  of
     the cognizant person.

     FAX  Number:  The FAX number, including country and area codes of  the
     cognizant person.

     Telemail/Telex  No.:   The  full  Telemail  box  name,  including  the
     relevant node, and/or the Telex number of the cognizant person.

4.13      ANNEX TO RECOMMENDATION (Continued)


                      GENERAL INFORMATION (Continued)


(10)   NETWORK COGNIZANT PERSON:

     Name:   The  name of the person in the agency operating the supporting
     network with whom inputs to, or outputs from this Design Control Table
     should be discussed and approved.

     Address:   The full network agency center's name and address which  is
     required to contact the cognizant person in an efficient manner.

     Telephone:  The telephone number, including country and area codes  of
     the cognizant person.

     FAX  Number: The FAX number, including country and area codes  of  the
     cognizant person.

     Telemail/Telex  No.:   The  full  Telemail  box  name,  including  the
     relevant node, and/or the Telex number of the cognizant person.

4.1.3     ANNEX TO RECOMMENDATION (Continued)


                COMMUNICATIONS SYSTEM OPERATING CONDITIONS


                            EARTH-TO-SPACE LINK


EARTH STATION (E/S) TRANSMITTING RF CHANNEL

(1)    RF CARRIER MODULATION:

(1a)   Ch 1 Type:  The earth station's carrier modulation method.
       Generally, only phase modulation is recommended by the CCSDS for
       the RF carrier.

(1b)   Ch 1 Format:  The method used in the earth station to represent the
       modulated Telecommand symbols on the carrier (e.g., NRZ-L, NRZ-M,
       SP-L, etc.).

(1c)   Ch 2 Type:   Same definition as (1a) above except that it is
       applicable to RF channel 2.

(1d)   Ch 2 Format:  Same definition as (1b) above except that it is
       applicable to RF channel 2.


EARTH STATION (E/S) TRANSMITTING DATA CHANNEL

(2)    BASEBAND DATA:

(2a)   Ch 1 Bit Rate, b/s:  The rate, usually the maximum, at which uncoded
       telecommand or other data on channel 1 is to be transmitted from
       the earth station and for which the link performance is to be
       evaluated, expressed in b/s.

(2b)   Ch 1 Bit Err Rate:  The maximum information bit error rate providing
       acceptable performance for data channel 1 under consideration,
       expressed as a dimensionless fraction less than 0.5.

(2c)   Ch 2 Bit Rate, b/s:  Same definition as (2a) above except that it is
       applicable to channel 2.

(2d)   Ch 2 Bit Err Rate:  Same definition as (2b) above except that it is
       applicable to channel 2.

(3)    DATA CODING:

(3a)   Ch 1 Type:  The type or name (e.g., block, Reed-Solomon, etc.) of
       the error detecting-correcting code used on data channel 1 by the
       earth station.

(3b)   Ch 1 No. Info Bit:  The number of information bits contained in a
       block code on data channel 1 which is transmitted from the earth
       station, expressed as a number.

(3c)   Ch 1 Block Length:  The total length of the block used on data
       channel 1 from the earth station, expressed as a number.

(3d)   Ch 2 Type:  Same definition as (3a) above except that it is
       applicable to data channel 2.

(3e)   Ch 2 No. Info Bit:  Same definition as (3b) above except that it is
       applicable to channel 2.

(3f)   Ch 2 Block Length:  Same definition as (3c) above except that it is
       applicable to channel 2.

(4)    SUBCARRIER:

(4a)   Ch 1 Waveform:  The earth station's subcarrier waveform on data
       channel 1.  Sine wave subcarriers are recommended by the CCSDS for
       telecommand.

(4b)   Ch 1 Frequency:  The earth station's subcarrier frequency on data
       channel 1, expressed in kHz.

(4c)   Ch 1 Mod Type:  The method used by the earth station for modulating
       the subcarrier with the data. PSK modulation is recommended by the
       CCSDS for telecommand subcarriers.

(4d)   Ch 2 Waveform:  Same definition as (4a) except that it is applicable
       to channel 2.

(4e)   Ch 2 Frequency:  Same definition as (4b) above except that it is
       applicable to channel 2.

(4f)   Ch 2 Mod Type:  Same definition as (4c) above except that it is
       applicable to channel 2.


EARTH STATION (E/S) TRANSMITTING RNG CHANNEL

(5a)   System Type:  The name, or descriptive term used to identify the
       specific ranging equipment (e.g., sidetone, square wave, DLR sine
       wave, CNES sine wave, ESA sine wave, DSN square wave, etc.).

(5b)   Tone/Code Wavfm:  The ranging tone or code waveform (e.g., sine or
       square).

(5c)   Highest Frequency:  The highest ranging tone or code frequency to be
       used for this mission, expressed in kHz.

(5d)   Lowest Frequency:  The lowest ranging tone or code frequency to be
       used for this mission, expressed in kHz.

(5e)   Tot Comp No.  The total number of ranging tone or code components
       which will be used in measuring the range, expressed as a number.


EARTH-TO-SPACE PATH PERFORMANCE

(6a)   Weather Avail: The amount of time that the earth-to-space link must
       be available when considering the degradation due to weather,
       expressed as a percent.

(6b)   S/C Distance (km): The distance, measured along a ray path, between
       the earth station transmitting antenna's radiation point and the
       spacecraft receiving antenna's reference point, expressed in
       kilometers (km).

4.13      ANNEX TO RECOMMENDATION (Continued)


            COMMUNICATIONS SYSTEM OPERATING CONDITIONS (Cont.)


                            SPACE-TO-EARTH LINK


SPACECRAFT (S/C) TRANSMITTING RF CHANNEL

(11)   RF CARRIER MODULATION:

(11a)  Ch 1 Type:  The spacecraft's carrier modulation method. Generally,
       only phase modulation is recommended by the CCSDS for the RF
       carrier.

(11b)  Ch 1 Format:  The method used by the spacecraft to represent the
       modulated Telemetry symbols on the carrier (e.g., NRZ-L, NRZ-M, SP-
       L, etc.).

(11c)  Ch 2 Type: Same definition as (11a) above except that it is
       applicable to RF channel 2.

(11d)  Ch 2 Format:  Same definition as (11b) above except that it is
       applicable to RF channel 2.


SPACECRAFT (S/C) TRANSMITTING  DATA CHANNEL

(12)   BASEBAND DATA:

(12a)  Ch 1 Bit Rate, b/s:  The rate, usually the maximum, at which uncoded
       telemetry or other data on channel 1 is to be transmitted from the
       spacecraft and for which the link performance is to be evaluated,
       expressed in b/s.

(12b)  Ch 1 Bit Err Rate:  The maximum information bit error rate providing
       acceptable performance for data channel 1 under consideration,
       expressed as a dimensionless fraction less than 0.5.

(12c)  Ch 2 Bit Rate, b/s:  Same definition as (12a) above except that it
       is applicable to channel 2.

(12d)  Ch 2 Bit Err Rate:  Same definition as (12b) above except that it is
       applicable to channel 2.

(13)   DATA CODING:

(13a)  Ch 1 Rate:  The number of data bits compared the total number of
       convolutionally encoded symbols transmitted from the spacecraft,
       generally expressed as a fraction (e.g., 1/2 for the CCSDS
       recommended code).

(13b)  Ch 1 Constr Lngth:  The constraint length of the convolutional
       encoder on the spacecraft, expressed as a number (e.g., 7 for the
       CCSDS recommended code).

(13c)  Ch 1 Concat Code:  The type or name of the code which is
       concatenated with the convolutional code on the spacecraft (e.g.,
       Reed-Solomon, Golay, block, etc.). The CCSDS recommends Reed-
       Solomon.

4.13      ANNEX TO RECOMMENDATION (Continued)


(13d)  Ch 1 Data/Tot Bit:  The number of data bits to total bits in a
       spacecraft block code, expressed as a ratio (e.g., 223/255 for the
       CCSDS recommended Reed-Solomon code).

(13e)  Ch 2 Rate:  Same definition as (13a) above except that it is
       applicable to channel 2.

(13f)  Ch 2 Constr Length:  Same definition as (13b) above except that it
       is applicable to channel 2.

(13g)  Ch 2 Concat Code:  Same definition as (13c) above except that it is
       applicable to channel 2.

(13h)  Ch 2 Data/Tot Bit:  Same definition as (13d) above except that it is
       applicable to channel 2.

(14)   SUBCARRIER:

(14a)  Ch 1 Waveform:  The spacecraft's subcarrier waveform on data channel
       1 (e.g., sine or square).

(14b)  Ch 1 Frequency:  The spacecraft's subcarrier frequency on data
       channel 1, expressed in kHz.

(14c)  Ch 1 Mod Type:  The spacecraft's method used for modulating the
       subcarrier with the data.  PSK modulation is recommended by the
       CCSDS for telemetry subcarriers.

(14d)  Ch 2 Waveform:  Same definition as (14a) above except that it is
       applicable to channel 2.

(14e)  Ch 2 Frequency:  Same definition as (14b) above except that it is
       applicable to channel 2.

(14f)  Ch 2 Mod Type:  Same definition as (14c) above except that it is
       applicable to data channel 2.


SPACECRAFT (S/C) - EARTH STATION (E/S) RNG CHANNEL

(15a)  Code Regenerate:  A statement (Yes or No) indicating whether the
       spacecraft regenerates the ranging code prior to transmitting it to
       the earth station.

(15b)  Coh Ops Reqd:  A statement (Yes or No) indicating whether the earth
       station's ranging equipment requires a coherent spacecraft RF
       channel.

(15c)  Reqd Accuracy (m):  The required ranging measurement accuracy,
       expressed in meters.

(15d)  Bandwidth T/C 1:  The earth station's effective bandwidth
       (1/integration time) required to obtain the ranging measurement
       accuracy stated in 5c, above, with the P[sub]r/N[sub]o stated on
       the Input Data Sheet, expressed in Hz.

(15e)  Bandwidth T/C 2:  The earth station's effective bandwidth
       (1/integration time) required to obtain the required probability of
       success in the ranging measurement, expressed in Hz.

SPACE-TO-EARTH PATH PERFORMANCE

(16a)  Weather Avail:  The amount of time that the space-to-earth link must
       be available when considering the degradation due to weather,
       expressed as a percent.

(16b)  S/C Distance (km):  The distance, measured along a ray path, between
       the spacecraft transmitting antenna's radiation point and the earth
       station receiving antenna's reference point, expressed in
       kilometers (km).


                 INPUT DATA SHEET FOR EARTH-TO-SPACE LINK


EARTH STATION (E/S) TRANSMITTING RF CARRIER CHANNEL PARAMETERS

(1)    TRANSMITTER POWER:  That power actually produced at the transmitter
       power amplifier's output terminals, expressed as a positive or
       negative value in dBW (10 Log[sub]10 [Watts]).

(2)    TRANSMITTER FREQUENCY:  The unmodulated transmitter carrier
       frequency, expressed in Megahertz (MHz).

(3)    ANT GAIN (ITU/RR/154):  "The ratio, usually expressed in decibels,
       of the power required at the input of a loss-free reference antenna
       to the power supplied to the input of the given antenna to produce,
       in a given direction, the same field strength or power flux-density
       at the same distance. When not specified otherwise, the gain refers
       to the direction of maximum radiation." In this application, the
       reference antenna is an isotropic antenna located in free space.
       The gain of the subject antenna is expressed as a positive or
       negative value in dBi.

       Placing the network's name (e.g., DSN) in the box to the right of
       Antenna Gain and the antenna's diameter (e.g., 70) in box to the
       right of the network in row 3 will cause the computer program to
       consult its data base for all required information regarding that
       station.

(4)    ANTENNA CIRCUIT LOSS:  The attenuation in rf power occurring between
       the output terminals of the transmitting power amplifier and the
       point of electromagnetic radiation from that antenna, expressed as
       a negative value in dB.

(5)    ANTENNA POINTING LOSS:  The reduction in signal power at the
       receiving antenna resulting from imperfect pointing of the
       transmitting antenna such that the actual ray path from
       transmitting antenna to receiving antenna differs from the optimum
       ray path containing the point of maximum transmitting antenna gain,
       expressed as a negative value in dB.

EARTH STATION (E/S) TRANSMITTING DATA CHANNEL PARAMETERS

(6)    INFORMATION BIT RATE:  The rate at which uncoded Telecommand
       information bits are to be sent from the transmitting station to
       the receiving station, expressed in bits per second (b/s).

(7)    SUBCARRIER FREQUENCY:  The unmodulated Telecommand subcarrier's
       frequency, either 8 kHz or 16 kHz, expressed in kHz.

(8)    SUBCARRIER WAVEFORM:  The Telecommand subcarrier's waveform is
       always sine wave.

(9)    RF MODULATION INDEX:  The angle by which the rf carrier is phase
       shifted, with respect to the unmodulated rf carrier, as a result of
       the data on Telecommand channel of the modulator, expressed in
       radians peak.

EARTH STATION (E/S) TRANSMITTING RANGING CHANNEL PARAMETERS

(10)   SIMULTANEOUS WITH DATA:  A statement showing whether the computed
       performance is based upon simultaneous ranging and telecommanding
       operations ( e.g., Yes or No).

(11)   RANGING WAVEFORM:  The waveform of the ranging modulation, sine wave
       for tone modulation, square wave for code modulation, expressed as
       Sin or Sq.

(12a)  MOD INDEX TONE / CODE 1:  The angle by which the rf carrier is phase
       shifted, with respect to the unmodulated rf carrier, as a result of
       the highest frequency (major) ranging Tone / Code modulation,
       expressed in radians peak (Rad-pk).

(12b)  MOD INDEX TONE / CODE 2:  The angle by which the rf carrier is phase
       shifted, with respect to the unmodulated rf carrier, as a result of
       the lower frequency (minor) ranging Tones / Codes modulation,
       expressed in radians peak (Rad-pk).


EARTH-TO-SPACE PATH PARAMETERS

(13)   TOPOCENTRIC RANGE:  The distance, measured along a ray path, between
       the earth station transmitting antenna's radiation point and the
       spacecraft receiving antenna's reference point, expressed in
       kilometers (km).

(14)   ATMOSPHERIC ATTENUATION:  The reduction in signal power at the
       receiving antenna, considering such factors as the earth station's
       antenna elevation angle, weather, and geographical location, which
       results from absorption, reflection, and scattering of the rf
       signal as it passes through the Earth's atmosphere, expressed as a
       negative value in dB.

(15)   IONOSPHERIC LOSS:  The reduction in signal power at the receiving
       antenna, considering such factors as the earth station's elevation
       angle and communication's frequency, resulting from the dispersive
       loss in radiated signal as it passes through the Ionosphere of the
       Earth and/or other bodies, expressed as a negative value in dB.

(16)   ANTENNA ELEVATION ANGLE:  The angle between a ray, representing the
       boresight of the earth-station's antenna beam pattern, and a
       locally horizontal line, when both ray and line are contained in a
       vertical plane which also contains the center of the earth,
       expressed in degrees (deg).


SPACECRAFT (S/C) RECEIVING CARRIER RF CHANNEL PARAMETERS

(17)   ANTENNA GAIN:  The ratio of the power flux density required at the
       input of a loss-free isotropic antenna to that power flux density
       needed at the input of the spacecraft's receiving antenna which
       produces the same output at the antenna's terminals for a source
       which is at equal distance from both antennas. The gain of the
       spacecraft's receiving antenna refers to the direction of maximum
       sensitivity, except in the case of a non-directional antenna in
       which case the gain refers to a minimum value corresponding to the
       antenna's specified coverage. The gain of the subject antenna, at
       the receiving frequency, is expressed as a positive or negative
       value in dBi.

(18)   POLARIZATION LOSS:  The reduction in transferred signal power
       between transmitting and receiving stations resulting from
       differences in the radiated and received polarization patterns
       between the two antennas, expressed as a negative value in dB.

(19)   ANTENNA POINTING LOSS:  Same definition as (5) above except that it
       is applicable to the pointing error of the spacecraft's receiving
       antenna, expressed as a negative value in dB.

(20)   ANTENNA CIRCUIT LOSS:  The attenuation in rf power occurring between
       the point of electromagnetic radiation on the spacecraft's antenna
       and the input terminals of the low noise amplifier, expressed as a
       negative value in dB.

(21)   CARRIER CIRCUIT LOSS:  The sum of resistive (cable and circuitry),
       transmission line mismatches, and other implementation losses,
       expressed as a negative value in dB.

(22)   TOTAL NOISE TEMPERATURE:  The sum of the following noise temperature
       components (a) + (b) + (c), expressed in dBK.   This sum is a
       computed entry and is not supplied by the user.

  (a) Rcvr Operating Temp:  Overall Noise Temperature (CCIR/Rec 573-1):
          "For an antenna, or a receiving system including the antenna, the
          value to which the temperature of the resistive component of the
          source impedance should be brought, if it were the only source of
          noise, to cause the noise power at the output of the receiver to
          be the same as in real case."

      In the Link Design Control Table, this parameter represents a
          receiving system reference temperature, at the received
          frequency, which excludes all contributions enumerated in (b),
          and (c), below, expressed in Kelvin. The reference temperature is
          measured at the input to the low-noise amplifier with the antenna
          viewing a cold sky background and which includes contributions
          from the: 1) cosmic background; 2) low noise amplifier and/or
          receiver; 3) circuit losses before the low-noise amplifier and/or
          receiver.

  (b) Feed Through Noise: The increase in the receiver's operating
          temperature resulting from a portion of the transmitted signal
          leaking into the receiver's low-noise amplifier, expressed in
          Kelvin (K).

  (c) Hot Body Noise:  The predicted increase from the reference
          temperature (Tr), resulting from the receiving antenna being
          directed toward a body having a temperature greater than that of
          the cold sky reference, expressed in Kelvin (K).

(23)   THRESHOLD LOOP NOISE BW:  The total (2-sided) bandwidth of the rf
       carrier's phase-locked-loop, measured at the point when the SNR in
       that phase-locked-loop is +10 dB (carrier threshold), expressed in
       Hz.

(24)   REQD THRSHLD SNR IN 2 B[sub]LO:  The ratio of received carrier power
       in 2 B[sub]LO to the noise power density required to maintain
       receiver lock at threshold which has been defined to be +10 dB,
       expressed as a positive or negative value in dB.

SPACECRAFT (S/C) RECEIVING DATA CHANNEL PARAMETERS

(25)   PHASE JITTER LOSS:  The loss in symbol detection efficiency
       resulting from phase noise on the received rf carrier, which
       produces a non-orthogonal, noisy phase relationship between the
       demodulator's reference and the rf carrier to be demodulated, plus
       losses from the partial tracking of the modulated symbols by the rf
       carrier phase locked loop, expressed as a negative value in dB.

(26)   DEMOD / DETECTOR LOSS:  The loss in data demodulation and detection
       efficiency resulting from phase noise on the demodulated
       subcarrier, which produces a non-orthogonal, noisy phase
       relationship between the demodulator's reference and the subcarrier
       to be demodulated, plus losses from the partial tracking of the
       data bits by the subcarrier loop, plus losses due to timing errors
       in the symbol synchronizer's tracking loop, plus losses from
       nonlinearities in the demodulator, which reduce the device's
       efficiency, expressed as a negative value in dB.

(27)   WAVEFORM DISTORTION LOSS:  The loss in the recovered data signal
       power resulting from distortion in the modulated signal's
       (subcarrier and data) waveform, which has been introduced by
       filtering and non-linearities in the data channel or medium,
       expressed as a negative value in dB.

(28)   MAX RNG INTERFER TO DATA:  The ratio of the ranging modulation's
       maximum spectral power level, lying within the data spectrum
       bandwidth [data spectrum bandwidth equals the data symbol rate in
       Hz], to the total ranging power level, expressed as a negative
       value in dB.

(29)   REQD DATA E[sub]b / N[sub]o: The energy per data bit divided by the
       noise spectral density which is required to obtain the stated Bit
       Error Rate, considering the improvement due to coding, expressed in
       dB.

SPACECRAFT (S/C) RECEIVING RANGING CHANNEL PARAMETERS

(30)   RANGING DEMODULATOR LOSS: The loss in ranging demodulation and
       detection efficiency resulting from phase noise on the demodulated
       subcarrier, which produces a non-orthogonal, noisy phase
       relationship between the demodulator's reference and the i.f.
       carrier to be demodulated, plus losses from non-linearities in the
       demodulator, which reduce the device's efficiency, expressed as a
       negative value in dB.

(31)   RANGING FILTER BAND WIDTH:  The bandwidth of the ranging channel
       filter in the spacecraft receiver, expressed in Megahertz (MHz).

(32)   REQD TONE/CODE 1 SNR:  The ranging tone/code 1 signal-to-noise ratio
       required in the spacecraft's transponder to achieve the desired
       ranging measurement accuracy, expressed as a positive or negative
       number in dB.

(33)   REQD TONE/CODE 2 SNR:  The ranging tone/code 2 signal-to-noise ratio
       required in the spacecraft's transponder to achieve the desired
       ranging ambiguity resolution, expressed as a positive or negative
       number in dB.

                 INPUT DATA SHEET FOR SPACE-TO-EARTH LINK


SPACECRAFT (S/C) TRANSMITTING RF CARRIER CHANNEL PARAMETERS

(51)   TRANSMITTER POWER:  That power actually produced at the transmitter
       power amplifier's output terminals, expressed as a positive or
       negative value in dBW (10Log[sub]10 [Watts]).

(52)   TRANSMITTER FREQUENCY:  The unmodulated transmitter carrier
       frequency, expressed in Megahertz.

(53)   ANTENNA GAIN:  The ratio of the power required at the input
       terminals of a loss-free isotropic antenna to the power supplied to
       the input terminals of the spacecraft's transmitting antenna which
       is needed to produce, in a specified direction, the same field
       strength (power flux density at an equivalent distance). The gain
       refers to the direction of maximum radiation except for non-
       directional antennas, in which case, the gain refers to a minimum
       value corresponding to the specified antenna coverage. The gain of
       the subject antenna, at the transmitting frequency, is expressed as
       a positive or negative value in dBi.

(54)   ANTENNA CIRCUIT LOSS:  The attenuation in rf power occurring between
       the output terminals of the transmitting power amplifier and the
       point of electromagnetic radiation from that antenna, expressed as
       a negative value in dB.

(55)   ANTENNA POINTING LOSS:  The reduction in signal power at the
       receiving antenna resulting from imperfect pointing of the
       transmitting antenna such that the actual ray path from
       transmitting antenna to receiving antenna differs from the optimum
       ray path containing the point of maximum transmitting antenna gain,
       expressed as a negative value in dB.


SPACECRAFT (SIC) TRANSMITTING DATA CHANNEL PARAMETERS

(56)   INFORMATION BIT RATE:  The basic telemetry data rate generated by
       the flight data system, prior to any encoding or spectrum spreading
       procedures, for transmission to the receiving earth station,
       expressed in kilo-bits per second (kb/s).

(57)   SUBCARRIER FREQUENCY:  The unmodulated Telemetry subcarrier's
       frequency, expressed as a positive value in kilo-Hertz (kHz).

(58)   SUBCARRlER WAVEFORM:  The waveform of the Telemetry subcarrier,
       either sine wave or square wave, expressed as Sin or Sq.

(59)   RF MODULATION INDEX:  The angle by which the rf carrier is phase
       shifted, with respect to the unmodulated rf carrier, as a result of
       the data on Telemetry channel of the modulator, expressed in
       radians peak.

4.13      ANNEX TO RECOMMENDATION (Continued)


SPACECRAFT (S/C) TRANSMITTING RANGING CHANNEL PARAMETERS

(60)   SIMULTANEOUS WITH DATA:  A statement showing whether or not the
       computed performance is based upon simultaneous ranging and
       telemetry operations (e.g., Yes or No).

(61)   MOD INDEX TONE / CODE:  The angle by which the rf carrier is phase
       shifted, with respect to the unmodulated rf carrier, as a result of
       the ranging Tones / Codes modulation, expressed in radians peak
       (Rad-pk).


SPACE-TO-EARTH PATH PARAMETERS

(62)   TOPOCENTRIC RANGE:  The distance, measured along a ray path, between
       the spacecraft antenna's radiation point and ground station
       antenna's reference point, expressed in kilometers (km).

(63)   ATMOSPHERIC ATTENUATION:  The reduction in signal power at the
       receiving antenna, considering such factors as the earth station's
       antenna elevation angle, weather, and geographical location, which
       results from absorption, reflection, and scattering of the rf
       signal as it passes through the Earth's atmosphere, expressed as a
       negative value in dB.

(64)   IONOSPHERIC LOSS:  The reduction in signal power at the receiving
       antenna, considering such factors as the earth station's elevation
       angle and communication's frequency, resulting from the dispersive
       loss in radiated signal as it passes through the Ionosphere of the
       Earth and/or other bodies, expressed as a negative value in dB.

(65)   ANTENNA ELEVATION ANGLE:  The angle between a ray, representing the
       boresight of the earth-station's antenna beam pattern, and a
       locally horizontal line, when both ray and line are contained in a
       vertical plane which also contains the center of the earth,
       expressed in degrees (Deg).


EARTH STATION (E/S) RECEIVING RF CARRIER CHANNEL PARAMETERS

(66)   ANT GAIN:  Same definition as (3) above except that it is applicable
       to the earth station's receiving frequency. See second paragraph of
       (3) above to access earth station data base.

(67)   POLARIZATION LOSS:  The reduction in transferred signal power
       between transmitting and receiving stations resulting from
       differences in the radiated and received polarization patterns
       between the two antennas, expressed as a negative value in dB.

(68)   ANTENNA POINTING LOSS:  Same definition as (5) above except that it
       is applicable to the pointing error of the earth station's
       receiving antenna.

(69)   ANTENNA CIRCUIT LOSS:  The attenuation in rf power occurring between
       the point of electromagnetic radiation on the earth station's
       antenna and the input terminals of the low noise amplifier,
       expressed as a negative value in dB.

(70)   TOTAL NOISE TEMPERATURE:  The sum of the following noise temperature
       components (a) + (b) + (c) + (d), expressed in dBK.  This sum is a
       computed entry and is not supplied by the user.

  (a)     Rcvr Operating Temp:  Overall Noise Temperature (CCIR/Rec 573-1):
          "For an antenna, or a receiving system including the antenna, the
          value to which the temperature of the resistive component of the
          source impedance should be brought, if it were the only source of
          noise, to cause the noise power at the output of the receiver to
          be the same as in real case."

          In the Link Design Control Table, this parameter represents a
          receiving system reference temperature, at the received
          frequency, which excludes all contributions enumerated in (b),
          and (c), below, expressed in Kelvin. The reference temperature is
          measured at the input to the low-noise amplifier with the antenna
          viewing a cold sky background and which includes contributions
          from the: 1) cosmic background; 2) low noise amplifier and/or
          receiver; 3) circuit losses before the low noise amplifier and/or
          receiver.

  (b)     Feed Through Noise:  The increase in the receiver's operating
          temperature resulting from a portion of the transmitted signal
          leaking into the receiver's low-noise amplifier, expressed in
          Kelvin (K).

  (c)     Hot Body Noise:  The predicted increase from the reference
          temperature (Tr), resulting from the receiving antenna being
          directed toward a body having a temperature greater than that of
          the cold sky reference, expressed in Kelvin (K).

  (d)     Weather Temp Increase:  The predicted increase from the reference
          temperature, resulting from the selected ground station weather
          model, and which excludes contributions from atmospheric
          attenuation (63), Ionospheric loss (64), and from (b) and (c)
          above, expressed as a positive value in Kelvin.

(71)   THRESHOLD LOOP NOISE BW:  The total (2-sided) bandwidth of the rf
       carrier phase-locked-loop, measured at carrier threshold, expressed
       in Hz.

(72)   REQD THRSHLD SNR IN 2 B[sub]LO: The ratio of received carrier power
       in 2 B[sub]LO to the noise power density required to maintain
       receiver lock at threshold which has been defined to be + 10 dB,
       expressed in dB.

EARTH STATION (E/S) RECEIVING DATA CHANNEL PARAMETERS

(73)   PHASE JITTER LOSS:  The loss in symbol detection efficiency
       resulting from phase noise on the received rf carrier, which
       produces a non-orthogonal, noisy phase relationship between the
       demodulator's reference and the rf carrier to be demodulated, plus
       losses from the partial tracking of the modulated symbols by the rf
       carrier phase locked loop, expressed as a negative value in dB.

(74)   DEMOD / DETECTOR LOSS:  The loss in data demodulation and detection
       efficiency resulting from phase noise on the demodulated
       subcarrier, if any, which produces a non-orthogonal, noisy phase
       relationship between the demodulator's reference and the subcarrier
       to be demodulated, plus losses from the partial tracking of the
       data bits by the subcarrier loop, plus losses due to timing errors
       in the symbol synchronizer's tracking loop, plus losses from non-
       linearities in the demodulator, which reduce the device's
       efficiency, expressed as a negative value in dB.

(75)   WAVEFORM DISTORTION LOSS:  The loss in the recovered data signal
       power, which results from distortion in the modulated signal's
       (subcarrier and data) waveform, which has been introduced by non-
       linearities in the data channel or medium, expressed as a negative
       value in dB.

(76)   MAX RNG INTERFER TO DATA:  The ratio of the ranging modulation's
       maximum spectral power level, lying within the data spectrum
       bandwidth [data spectrum bandwidth equals the data symbol rate in
       Hz], to the total ranging power level, expressed as a negative
       value in dB.

(77)   REQD DATA E[sub]b / N[sub]o:  The energy per data bit divided by the
       noise spectral density which is required to obtain the stated Bit
       Error Rate, considering the improvement due to coding, expressed in
       dB.


EARTH STATION (E/S) RECEIVING RANGING CHANNEL PARAMETERS

(78)   RANGING DEMODULATOR LOSS:  The loss in ranging demodulation and
       detection efficiency resulting from phase noise on the demodulated
       subcarrier, which produces a non-orthogonal, noisy phase
       relationship between the demodulator's reference and the i.f.
       carrier to be demodulated, plus losses from non-linearities in the
       demodulator, which reduce the device's efficiency, expressed as a
       negative value in dB.

(79)   REQD TONE/CODE 1 PWR/N[sub]o:  The magnitude of range tone/code 1
       ST/N[sub]o required to achieve the desired Range accuracy,
       expressed as a positive or negative value in dB-Hz.

(80)   REQD TONE/CODE 2 PWR/N[sub]o:  The magnitude of range tone/code 2
       ST/N[sub]o required to achieve the desired probability of error in
       the ranging measurement, expressed as a positive or negative value
       in dB-Hz.

4.1.3     ANNEX TO RECOMMENDATION  (Continued)


                 LINK COMPUTATIONS FOR EARTH-TO-SPACE LINK


EARTH STATION (E/S) TRANSMITTING RF CARRIER CHANNEL PERFORMANCE

(101)  TRANSMITTER POWER:  That power actually produced at the transmitter
       power amplifier's output terminals, expressed as a positive or
       negative value in dBW (10 Log[sub]10 [Watts]).

(102)  TRANSMIT ANT GAIN [Effect]:  The computed antenna gain found by
       subtracting the Antenna Circuit Loss and Antenna Pointing Loss from
       the Antenna Gain [(3)]-[(4)+(5)], expressed as a positive or
       negative value in dBi.

(103)  TRANSMITTING E.I.R.P.:  The computed effective isotopically radiated
       power found by adding Transmitter Power and Effective Antenna Gain
       [(101) + (102)], expressed as a positive or negative value in dBW.

(104)  TRANS CARRIER POWER:  The computed portion of the total transmitted
       power remaining in the rf carrier channel after subtracting the
       power in the sidebands due to the modulating signals, expressed as
       a positive or negative value in dBW.

(105)  TRANS CARRIER POWER/P[sub]T: The power computed in (104) above,
       divided by the total earth station transmitted power, expressed as
       a negative value in dB.


EARTH STATION (E/S) TRANSMITTING DATA CHANNEL PERFORMANCE

(106)  TRANS CH 1 DATA POWER:  The computed power in the rf carrier's data
       sidebands resulting from the modulating signal on data Channel 1,
       expressed as a positive or negative value in dBW.

(107)  TRANS CH 1 DATA POWER/P[sub]T:  The Channel 1 data power computed in
       (106) above, divided by the total earth station transmitted power,
       expressed as a negative value in dB.

(108)  TRANS CH 2 DATA POWER:  The computed power in the rf carrier's data
       sidebands resulting from the modulating signal on data Channel 2,
       expressed as a positive or negative value in dBW.

(109)  TRANS CH 2 DATA POWER/P[sub]T:  The Channel 2 data power computed in
       (108) above, divided by the total earth station transmitted power,
       expressed as a negative value in dB.


EARTH STATION (E/S) TRANSMITTING RANGING CHANNEL PERFORMANCE

(110)  TONE - CODE 1 POWER:  The computed power in the rf carrier's ranging
       sidebands resulting from either Tone 1 (major) or Code 1
       modulation, expressed as a positive or negative value in dBW.

(111)  TONE - CODE 1 POWER/P[sub]T:  The Tone or Code 1 power computed in
       (110) above, divided by the total earth station transmitted power,
       expressed as a negative value in dB.

(112)  TONE - CODE 2 POWER:  The computed power in the rf carrier's ranging
       sidebands resulting from either Tone 2 (minor) or Code 2
       modulation, expressed as a positive or negative value in dBW.

(113)  TONE - CODE 2 POWER/P[sub]T:  The Tone or Code 2 power computed in
       (112) above, divided by the total earth station transmitted power,
       expressed as a negative value in dB.


EARTH-TO-SPACE PATH PERFORMANCE

(114)  FREE SPACE LOSS:  The computed loss resulting from the spreading of
       the signal as it propagates from transmitting to receiving
       stations, expressed as a negative value in dB.

(115)  ATMOSPHERIC ATTENUATION:  The reduction in signal power at the
       receiving antenna, considering such factors as the earth station's
       antenna elevation angle, weather, and geographical location, which
       results from absorption, reflection, and scattering of the rf
       signal as it passes through the Earth's atmosphere, placed on this
       page for reference purposes, expressed as a negative value in dB.

(116)  IONOSPHERIC LOSS:  The reduction in signal power at the receiving
       antenna, considering such factors as the earth station's elevation
       angle and communication's frequency, resulting from the dispersive
       loss in radiated signal as it passes through the Ionosphere of the
       Earth and/or other bodies, placed on this page for reference
       purposes, expressed as a negative value in dB.


SPACECRAFT (S/C) RECEIVING RF CARRIER CHANNEL PERFORMANCE

(117)  RECEIVING ANT GAIN [Effect]:  The computed antenna gain found by
       subtracting the Polarization Loss, Antenna Pointing Loss, and
       Antenna Circuit Loss from the Antenna Gain (17)-[( 18) + (19) +
       (20)], expressed as a positive or negative value in dBi.

(118)  NOISE SPECTRAL DENSITY:  The computed noise, generally resulting
       from the receiver's low noise amplifier, in a 1 Hz bandwidth,
       expressed in dBW/Hz.

(119)  THRESHOLD LOOP BW 2 B[sub]LO:  Same definition as (24) above, placed
       on this page for reference purposes.

(120)  RCVD CARRIER POWER:  The computed carrier power in the receiver's
       phase locked loop bandwidth of 2 B[sub]LO, expressed as a positive
       or negative value in dBW.

(121)  CARRIER PERFORMANCE MARGIN:  The computed excess in rf carrier
       signal over +10 dB SNR in the phase-locked-loop, which is defined
       to be carrier threshold, expressed in dB.

SPACECRAFT (S/C) RECEIVING DATA CHANNEL PERFORMANCE

(122)  CH 1 DATA LOSS DUE TO RNG:  The computed loss in data channel's
       performance resulting from the presence of a simultaneous ranging
       signal on the earth-to-space link, expressed in dB.

(123)  RCVD CH 1 E[sub]b / N[sub]o:  The computed received energy per bit
       in Data Channel 1 divided by the noise spectral density, expressed
       in dB.

(124)  REQD CH 1 E[sub]b / N[sub]o:  The computed energy per bit divided by
       the noise spectral density (E[sub]b / N[sub]o) found by adding the
       Phase Jitter Loss, Demod/Detector Loss, Waveform Distortion Loss,
       and Maximum Ranging Interference to Data to the Required Data
       E[sub]b / N[sub]o [(29)] + [(25) + (26) + (27) + (28)], expressed
       in dB.

(125)  CH 1 DATA PERFORM MARGIN:  The computed excess of Channel 1 received
       E[sub]b/N[sub]o over the required E[sub]b / N[sub]o, [(123)-(124)],
       expressed in dB.

(126)  CH 2 DATA LOSS DUE TO RNG:  Same definition as (122) above except
       that it is applicable to data channel 2.

(127)  RCVD CH 2 E[sub]b / N[sub]o:  Same definition as (123) above except
       that it is applicable to data
       channel 2.

(128)  REQD CH 2 E[sub]b / N[sub]o:  Same definition as (124) above except
       that it is applicable to data
       channel 2.

(129)  CH 2 DATA PERFORM MARGIN:  The computed excess of Channel 2 received
       E[sub]b / N[sub]o over the required E[sub]b / N[sub]o [(127)-
       (128)], expressed in dB.


SPACECRAFT (S/C) RECEIVING RANGING CHANNEL PERFORMANCE

(130)  RCVD CODE 1 POWER/N[sub]o:  The computed received power (P[sub]R) in
       the ranging Tone 1 (major) or Code 1 divided by the noise spectral
       density, expressed as a positive or negative value in dB-Hz.

(131)  RCVD CODE 2 POWER/N[sub]o:  Same definition as (130) above except
       that it is applicable to Tone or Code 2.

(132)  RCVD TOTAL RNG POWER/N[sub]o:  The computed total received power in
       all ranging Tones or Codes, if several are present simultaneously,
       or Tone/Code 1 if Tones or Codes are transmitted sequentially,
       divided by the noise spectral density, expressed as a positive or
       negative value in dB-Hz.

(133)  RANGING MARGIN:  The computed excess of received total ranging power
       over the required ranging power, expressed in dB.

                 LINK COMPUTATIONS FOR SPACE-TO-EARTH LINK


SPACECRAFT (S/C) TRANSMITTING RF CARRIER CHANNEL PERFORMANCE

(151)  TRANSMITTER POWER:  That power actually produced at the transmitter
       power amplifier's output terminals, expressed as a positive or
       negative value in dBW (10 Log[sub]10 [Watts]).

(152)  TRANSMIT ANT GAIN [Effect]:  The computed antenna gain found by
       subtracting the Antenna Circuit Loss and Antenna Pointing Loss from
       the Antenna Gain (53)-[(54) + (55)], expressed as a positive or
       negative value in dBi.

(153)  TRANSMITTING E.I.R.P.:  The computed effective isotopically radiated
       power found by adding Transmitter Power and Effective Antenna Gain
       [(151) + (152)], expressed as a positive or negative value in dBW.

(154)  TRANS CARRIER POWER:  The computed portion of the total transmitted
       power remaining in the rf carrier channel after subtracting the
       power in the sidebands due to the modulating signals, expressed as
       a positive or negative value in dBW.

(155)  TRANS CARRIER POWER/P[sub]T:  The power computed in (154) above,
       divided by the total spacecraft transmitted power, expressed as a
       negative value in dB.


SPACECRAFT (S/C) TRANSMITTING DATA CHANNEL PERFORMANCE

(156)  TRANS CH 1 DATA POWER:  The computed power in the rf carrier's data
       sidebands resulting from the modulating signal on data Channel 1,
       expressed as a positive or negative value in dBW.

(157)  TRANS CH 1 DATA POWER/P[sub]T:  The Channel 1 data power computed in
       (156) above, divided by the total spacecraft transmitted power,
       expressed as a negative value in dB.

(158)  TRANS CH 2 DATA POWER:  The computed power in the rf carrier's data
       sidebands resulting from the modulating signal on data Channel 2,
       expressed as a positive or negative value in dBW.

(159)  TRANS CH 2 DATA POWER/P[sub]T:  The Channel 2 data power computed in
       (158) above, divided by the total spacecraft transmitted power,
       expressed as a negative value in dB.


SPACECRAFT (S/C) TRANSMITTING RANGING CHANNEL PERFORMANCE

(160)  TONE - CODE 1 POWER:  The computed power in the rf carrier's ranging
       sidebands resulting from either Tone 1 (major) or Code 1
       modulation, expressed as a positive or negative value in dBW.

(161)  TONE - CODE 1 POWER/P[sub]T:  The Tone or Code 1 power computed in
       (160) above, divided by the total earth station transmitted power,
       expressed as a negative value in dB.

(162)  TONE - CODE 2 POWER:  The computed power in the rf carrier's ranging
       sidebands resulting from either Tone 2 (major) or Code 2
       modulation, expressed as a positive or negative value in dBW.

(163)  TONE - CODE 2 POWER/P[sub]T:  The Tone or Code 2 power computed in
       (162) above, divided by the total spacecraft transmitted power,
       expressed as a negative value in dB.


SPACE-TO-EARTH PATH PERFORMANCE

(164)  FREE SPACE LOSS:  The computed loss resulting from the spreading of
       the signal as it propagates from transmitting to receiving station,
       expressed as a negative value in dB.

(165)  ATMOSPHERIC ATTENUATION:  The reduction in signal power at the
       receiving antenna, considering such factors as the earth station's
       antenna elevation angle, weather, and geographical location, which
       results from absorption, reflection, and scattering of the rf
       signal as it passes through the Earth's atmosphere, placed on this
       page for reference purposes, expressed as a negative value in dB.

(166)  IONOSPHERIC LOSS:  The reduction in signal power at the receiving
       antenna, considering such factors as the earth station's elevation
       angle and communication's frequency, resulting from the dispersive
       loss in radiated signal as it passes through the Ionosphere of the
       Earth and/or other bodies, placed on this page for reference
       purposes, expressed as a negative value in dB.


EARTH STATION (E/S) RECEIVING RF CARRIER CHANNEL PERFORMANCE

(167)  RECEIVING ANT GAIN [Effect]:  The computed antenna gain found by
       subtracting the Polarization Loss, Antenna Pointing Loss, and
       Antenna Circuit Loss from the Antenna Gain (66)-[(67)+(68)+(69)],
       expressed as a positive or negative value in dBi.

(168)  NOISE SPECTRAL DENSITY:  The computed noise, generally resulting
       from the receiver's low noise amplifier, in a 1 Hz bandwidth,
       expressed in dBW/Hz.

(169)  THRESHOLD LOOP BW, 2 B[sub]LO:  Same definition as (71) above,
       placed on this page for reference purposes.

(170)  RCVD CARRIER POWER:  The computed carrier power in the receiver's
       phase locked loop bandwidth of 2 B[sub]LO, expressed in dBW.

(171)  CARRIER PERFORMANCE MARGIN:  The computed excess in rf carrier
       signal over +10 dB SNR in the phase-locked-loop, which is defined
       to be carrier threshold, expressed in dB.

EARTH STATION (E/S) RECEIVING DATA CHANNEL PERFORMANCE

(172)  CH 1 DATA LOSS DUE TO RNG:  The computed loss in data channel's
       performance resulting from the presence of a simultaneous ranging
       signal on the space-to-earth link, expressed in dB.

(173)  RCVD CH 1 E[sub]b / N[sub]o:  The computed received energy per bit
       in Data Channel 1 divided by the noise spectral density, expressed
       in dB.

(174)  REQD CH 1 E[sub]b / N[sub]o:  The computed energy per bit divided by
       the noise spectral density (E[sub]b / N[sub]o) found by adding the
       Phase Jitter Loss, Demod/Detector Loss, Waveform Distortion Loss,
       and Maximum Ranging Interference to Data to the Required Data
       E[sub]b / N[sub]o [(77)]+[(73)+(74)+(75)+  (76)], [includes the
       improvement due to coding], expressed in dB.

(175)  CH 1 DATA PERFORM MARGIN:  The computed excess of Channel 1 received
       E[sub]b / N[sub]o over the required E[sub]b / N[sub]o [(173)-
       (174)], expressed in dB.

(176)  CH 2 DATA LOSS DUE TO RNG:  Same definition as (172) above except
       that it is applicable to data channel 2.

(177)  RCVD CH 2 Eb / No:  Same definition as (173) above except that it is
       applicable to data channel 2.

(178)  REQD CH 2 E[sub]b / N[sub]o:  Same definition as (174) above except
       that it is applicable to data channel 2.

(179)  CH 2 DATA PERFORM MARGIN:  The computed excess of Channel 2 received
       E[sub]b / N[sub]o over the required E[sub]b / N[sub]o, [(177)-
       (178)], expressed in dB.


EARTH STATION (E/S) RECEIVING RANGING CHANNEL PERFORMANCE

(180)  RCVD CODE 1 POWER/N[sub]o:  The computed received power (P[sub]R) in
       the ranging Tone 1 (major) or Code 1 divided by the noise spectral
       density, expressed as a positive or negative value in dB-Hz.

(181)  RCVD CODE 2 POWER/N[sub]o:  Same definition as (180) above except
       that it is applicable to Tone or Code 2.

(182)  RCVD TOTAL RNG POWER/N[sub]o:  The computed total received power in
       all ranging Tones or Codes, if several are present simultaneously,
       or Tone/Code 1 if Tones or Codes are transmitted sequentially,
       divided by the noise spectral density, expressed as a positive or
       negative value in dB-Hz.

(183)  RANGING MARGIN:  The computed excess of received total ranging power
       over the required ranging power, expressed in dB.

5.0       TERMINOLOGY AND GLOSSARY

Section   5   is  included  to  assist  the  reader  in  interpreting   the
Recommendations found in Sections 2, 3, and 4 of this document.  It does so
by  providing  an explanation of key words, terms, phrases,  abbreviations,
and  acronyms  used  in these Recommendations.  Presently,  there  are  two
subsections:

     5.1  Terminology         5.2  Glossary

Section 5.1, Terminology, defines specific words, terms, and phrases  which
have  special,  but  uniform, meanings throughout the text.   Additionally,
this  section  also includes quantitative values for some terms  which  are
intended to assist the reader in interpreting the Recommendations.

Section 5.2 contains the full name for the abbreviations and acronyms  used
throughout  this document. If a reader is uncertain as to the  meaning  any
abbreviation  or acronym, this Section should be consulted.  Here,  entries
are arranged alphabetically.

5.1       TERMINOLOGY

Auto track                      A   system  which  causes  earth  station's
                                antenna  to automatically follow [track]  a
                                moving spacecraft.

Bit Rate                        The  baseband data rate exclusive of coding
                                for  either  error correction  or  spectrum
                                shaping purposes.

Category A Missions             Those  missions  whose altitude  above  the
                                earth  is less than, or equal to, 2 x 10**6
                                km.

Category B Missions             Those  missions  whose altitude  above  the
                                earth is greater than 2 x 10**6 km.

Dibit                           A  group of two bits in 4-phase modulation,
                                each  possible dibit is encoded in the form
                                of  one of four unique phase shifts of  the
                                RF carrier.

Loop Bandwidth                  The  resultant phase locked bandwidth  when
                                the  signal-to-noise  ratio  in  the  phase
                                locked loop is 10 dB.

Loop Threshold                  That     signal    level    producing     a
                                signal-to-noise  ratio  of  10  dB  in  the
                                phase locked loop's bandwidth.

Libration Point                 A  point  of  equal potential gravitational
                                fields  between  two or more  large  bodies
                                such as the Sun and the Earth

Link Design Control Table       A   set  of  tables  used  to  display  the
                                operating       parameters       of       a
                                telecommunications link  and  to  calculate
                                the expected performance of that link.

Link and Weather Not Combined   With   a   Link   Design   Control   Table,
                                calculations  are made assuming  clear  and
                                dry  weather  conditions.  Thereafter,  the
                                values    obtained   under    such    ideal
                                conditions  are adjusted using a correction
                                factor   representing  the  loss   due   to
                                weather effects.

Modulo-2 Addition               Also  called an "exclusive or",  this  term
                                refers  to  the manner in which a  pair  of
                                bits  are added such that like bits  result
                                in a 0 and unlike bits produce a 1.

Occupied Bandwidth              (ITU/RR/147):   "The width of  a  frequency
                                band  such that, below the lower and  above
                                the   upper  frequency  limits,  the   mean
                                powers   emitted  are  each  equal   to   a
                                specified percentage [beta]/2 of the total  mean
                                power   of  a  given  emission."    [Unless
                                otherwise  specified by the  CCIR  for  the
                                appropriate  class of emission,  the  value
                                of [beta]/2 should be taken as 0.5%."]

Radiocommunication Service      (ITU/RR/RR1-3.1)  "A  Service...  involving
                                the     transmission,    emission    and/or
                                reception  of  radio  waves  for   specific
                                telecommunication purposes."

Ranging Measurement             A  process for establishing, usually  by  a
                                time   delay   measurement,   the   one-way
                                distance  between an earth  station  and  a
                                spacecraft.

Symbol Rate                     The   baseband  bit  rate  following  error
                                correction   coding   but   excluding   any
                                spectrum modification encoding.

5.2   GLOSSARY OF TERMS


ACQ or Acq               Acquisition

AGC                      Automatic Gain Control

AM                       Amplitude Modulation

BER                      Bit Error Rate

Bi-[phi]-L               Bi-Phase-Level modulation

Bi-[phi]-M               Bi-Phase-Mark modulation

Bi-[phi]-S               Bi-Phase-Space modulation

B[sub]LO                 Phase Locked Loop Bandwidth

BNSC                     British National Space Centre

bps or b/s               Bits Per Second

BW                       Bandwidth

Cat                      Category

Category A Missions      Those missions whose altitude above the Earth is
                         less than, or equal to, 2 x 10**6 km.

Category B Missions      Those missions whose altitude above the Earth is
                         greater than 2 x 10**6 km.

CCIR                     International Radio Consultative Committee

CCSDS                    Consultative Committee for Space Data Systems

Cmd                      Telecommand

CNES                     Centre National D'Etudes Spatiales

COHER or Coh             Coherent

CRL                      Communications Research Laboratory

CSA                      Canadian Space Agency

dB                       Decibel(s)

dBi                      Decibel(s) relative to an isotropically radiated
                         signal

dB/K                     Decibel(s) per degree Kelvin

dBm                      Decibel(s) relative to one milliwatt

dBW                      Decibel(s) relative to one Watt

DCT                      Design Control Table [Link]

deg                      Degree

DLR                      Deutsche Forschungsanstalt fuer Luft-und Raumfahrt
                         e. V.

DNRZ                     Differential Non-Return to Zero

DOC/CRC                  Department of Communications, Communications
                         Research Centre

DRVID                    Differenced Range vs. Integrated Doppler

E[sub]b                  Energy per data bit

E[sub]b / N[sub]o        Energy per data bit to Noise ratio in a 1 Hz
                         bandwidth

EES                      Earth Exploration Service

EIRP                     Equivalent Isotropically Radiated Power

ELEV                     Elevation

E/S                      Earth-to-Space

ESA                      European Space Agency

exp                      Exponent

f or Freq                Frequency

f[sub]c                  RF carrier frequency

f[sub]d                  Doppler frequency shift

f[sub]sc                 Subcarrier frequency

FM                       Frequency Modulation

FN or Fn                 Footnote

FSK                      Frequency Shift Keying

GHz                      Gigahertz

GND                      Ground

GPS                      Global Positioning System

G/T                      Antenna gain divided by the receiving system's
                         noise temperature in degrees Kelvin (usually
                         expressed in dB).

h                        Hours

Hz                       Hertz

IEEE                     Institute of Electrical and Electronic Engineers

IFRB                     International Frequency Registration Board

INPE                     Instituto De Pesquisas Espaciais

ISAS                     Institute of Space and Astronautical Science

ISRO                     Indian Space Research Organization

ITU                      International Telecommunication Union

ITU/RR                   International Telecommunication Union Radio
                         Regulations

k                        Kilo (thousands)

K                        Degrees Kelvin

kb/s                     Kilobits Per Second

kHz                      Kilohertz

km                       Kilometers

Ku                       Ku-band (approximately 13 to 15 gigahertz)

LCP                      Left Circular Polarization

LIM or Lim               Limitation(s)

LIN or Lin               Linear

L.O. or LO               Local Oscillator

M                        Mega (million)

m                        Meter(s)

MAX or Max               Maximum

MHz                      Megahertz

MIN or Min               Minimum

Mod                      Modulation

n                        Nano

ns                       Nanosecond(s)

NASA                     National Aeronautics and Space Administration

NASDA                    National Space Development Agency of Japan

NOAA                     National Oceanic and Atmospheric Administration

NRZ                      Non-Return to Zero

NRZ-L                    Non-Return to Zero-Level

NRZ-M                    Non-Return to Zero-Mark

NRZ-S                    Non-Return to Zero-Space

P[sub]c                  Carrier power

PCM                      Pulse Code Modulation

PDF                      Probability Density Function

PFD                      Power Flux Density

Pk or pk                 Peak

P[sub]LL                 Phase Locked Loop

PM                       Phase Modulation

PN                       Pseudo Noise

ppm                      Parts Per Million

PRN                      Pseudo Random Noise

PSK                      Phase Shift Keying

PWR                      Power

QPSK                     Quadra-Phase Shift Keying [modulation]

OQPSK                    Offset Quadra-Phase Shift Keying [modulation]

r                         Range

Rad                      Radian

RCP                      Right Circular Polarization

RCVR or Rcvr             Receiver

Rec                      Receive

REF or Ref               Reference

regen.                   regenerative

resid.                   residual

RF                       Radio Frequency

RFI                      Radio Frequency Interference

RLIN                     Rotatable Linear polarization

rms                      Root Mean Square

Rng                      Ranging

RSS                      Root Sum Square

S/C                      Spacecraft

s or sec                  Second(s)

S/E                      Space-to-Earth

SEP                      Sun-Earth-Probe [angle]

seq                      Sequential

SFDU                     Standard Formatted Data Unit (CCSDS)

SFCG                     Space Frequency Coordination Group

SIG or sig               Signal

Sim                      Simultaneous

SNR                      Signal-to-Noise Ratio

SP                       Split Phase

SP-L                     Split Phase - Level

sps or s/s               Symbols Per Second

SSC                      Swedish Space Corporation

STA                      Station

STAB                     Stability

SUBCARR                  Subcarrier

SYM or sym               Symbol

TBD                      To Be Determined

TDRSS                    Tracking and Data Relay Satellite System

Tlm                      Telemetry

Trans or Tr              Transmit

TTC                      Tracking, Telemetry, and Command

UTC                      Universal Time Coordinated

VLBI                     Very Long Baseline Interferometry

w/m**2                   Watts per square Meter

X-band                   Approximately 8000 megahertz

XMIT or Xmit             Transmit

yr                         Year

[DELTA]                  Delta (change or variation)

[phi]                    Phase

[mu]                     Micro