CCSDS Optical Communications Working Group
Concept Paper
Version: see footer
Section I) Background
Several space agencies are working on space based optical communications. The
primary motivation stems from the expectation that substantially higher (at least 10
times) data rates than Radio Frequency (RF) based solutions might be feasible with
similar user spacecraft onboard terminal burden (mass, volume and power). In
addition optical communications can also be used at comparable RF data rates in
order to lower the user communication system’s required mass, volume, and power.
Available RF spectrum is also becoming an issue in high data rate applications.
Optical communications systems that have to operate through Earth’s atmosphere,
however, can be severely impacted by weather (clouds, optical turbulence, and other
atmospherics); the result is that a typical spacecraft has to be supported by several
optical communications ground stations to overcome weather related link outages.
This CCSDS Working Group will establish a common framework within which the
space agencies may develop standardized services for optical communications
interoperability and optical communications cross support.
Cross support is desirable in two broad categories: optical ground stations for spaceEarth optical links and GEO relays for space-space links. Cross support for optical
ground stations is necessary for geographical diversity to mitigate weather and
atmospheric effects in optical propagation as well as to share costs for large (multimeter) class ground stations across agencies. Cross support using GEO relays is also
desirable because it is costly to build, launch and operate such orbiters and provide
full global coverage. The maturity of space optical communications terminals that are
already realized (e.g., for Earth-orbit inter-satellite and through the atmosphere links)
or that are in preparation as demonstrations (e.g., for Moon-to-Earth links through the
Earth atmosphere) leads to the immediate need for standardization as these systems
proliferate.
Previous Interagency Advisory Operations Group (IOAG) Optical Link Study Group
(OLSG) activity [REFERENCE REPORTS] has pointed out the need for
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 New standards in wavelength, modulation, coding, interleaving,
synchronization and acquisition which are likely different from existing RF
standards
 New standards for exchange and archiving of weather data for predicting
and operating optical links among optical ground stations and their network
operations centers
In addition to the typical standards that have to be developed for any communications
system, such as modulation and coding, space optical communications also requires a
standard for the exchange of weather and atmospheric data and a selection method for
determining which available optical communications ground terminal should be used
for a particular transmission. That is because optical space communications through
Earth’s atmosphere is nearly impossible in the presence of most types of clouds.
Therefore, the optical communication system solution for a particular mission has to
utilize optical ground stations that are geographically diverse and in compliance with
the selection method, such that there is a high probability of a cloud-free line of site
(CFLOS) to a ground station from the spacecraft at any given point in time (e.g., at
the same longitude, or at a sufficient number of stations at different longitudes to
allow the stored onboard data to be transmitted within the allocated time). The
exchange of weather and atmospheric data among optical ground stations and network
operations center is critical to maximizing the data return from a mission while
efficiently utilizing the various optical ground stations involved.
This CCSDS Working Group will establish a common framework within which the
space agencies may develop standardized services for free space optical
communications interoperability and cross support. This includes writing the required
CCSDS Blue Books and assessing the performance via CCSDS Green Books.
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SECTION II) Tentative Work Plan
Schedule: [TURN INTO A NICE LOOKING SCHEDULE (PICTURE)]
Green Book on Link Budgets and Support Discussion for Blue Books:
Spring 2014 to December 2015
Blue Book on Low Signal Photon Flux: Spring 2014 to June 2016
Blue Book on High Signal Photon Flux: Spring 2016 to June 2018
Green Book on Weather and Atmospheric Data:
Version 1: Physical Quantities to be Measured Only
Spring 2014 to Spring 2015
Version 2: Concept of Operations for Weather Exchange
Spring 2015 to Spring 2017
(could later be turned into a Blue Book)
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ANNEX A:
Draft Charter
Name of Group: Optical Communications
Area: Space Link Services Area (SLS)
Area Director E-Mail Address: Gian.Paolo.Calzolari@esa.int
Proposed Chairperson:
Proposed Chairperson E-Mail Address:
Proposed Chairperson Agency:
Proposed Co-Chairperson:
Proposed Co-Chairperson E-Mail Address:
Mailing List: sls-opt@mailman.ccsds.org (to be created)
Scope of Activity
Standardization in the field of Optical Communications in space addressing the modulation,
coding, and synchronization sublayer of the Data Link Layer and the Physical Layer and
operations supporting the efficient establishment of optical links. This will be accomplished by
developing, maintaining, and updating a set of space optical communications standards to allow
interoperability and interagency cross support; this will include developing standards for the
exchange of weather and atmospheric data between ground stations.
Rationale for Activity
The primary motivation for optical space communication systems is higher data rates than what
is typically available from RF based systems. However, optical communications systems that
have to operate through Earth’s atmosphere can be severely impacted by weather (clouds, optical
turbulence, and other atmospherics); the result is that a typical spacecraft has to be supported by
several optical communications ground stations to overcome weather related link outages. Space
agencies can share optical ground stations by having the appropriate standards; it would also be
possible to support space-to-space intersatellite links with the appropriate standards. This
CCSDS Working Group will develop standards that can be applied by the space agencies for
space optical communications interoperability and optical cross support.
Cross support is desirable in two broad categories: optical ground stations for space-Earth optical
links and GEO relays for space-space links. Cross support for optical ground stations is
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necessary for geographical diversity to mitigate weather and atmospheric effects in optical
propagation as well as to share costs for large (multi-meter) class ground stations across
agencies. Cross support using GEO relays is also desirable because it is costly to build, launch
and operate such orbiters and provide full global coverage.
Goals
Free space optical communications standards shall be developed only to the extent necessary to
ensure interoperability and cross-support. The Optical Link Study Group identified the following
scenarios for optical communication cross support: LEO-Ground, LEO-GEO, GEO-Ground,
Lunar-Ground (Earth), Sun-Earth L1/L2-Ground and Mars-Ground. Each scenario could have
applications in two regimes where:

Power/aperture is at a premium on the link so we have to be as photon-efficient on the
link as possible, the so-called Low Signal Photon Flux Regime (e.g., Mars-to-Earth or
low data rate cubesats in Earth orbit)

More power/aperture is available which allows a tradeoff of power usage against link
efficiency, data rate, complexity, etc., the so-called High Signal Photon Flux Regime
(e.g., high data rate LEO-to-Earth or LEO-GEO)
The goal is to develop standards for wavelength, modulation, coding, interleaving,
synchronization and acquisition applicable to each regime. Work performed by OLSG indicates
that existing CCSDS standards at the Data Link Layer might be used with optical
communications systems and thus tend to negate the need for specific optical communications
standards at the Data Link Layer and above. This activity will culminate in one or several Blue
Books.
Another goal is to investigate, once the first goal is advanced enough, existing standards for
weather and atmospheric conditions data exchange and archiving and modify if needed or create
new standards if necessary. Furthermore, some kind of optical communications ground station
selection or allocation method needs to be developed. This activity will culminate in the
appropriate Blue Books as needed.
Current goals / projects (pending individual project approval by the CMC) are:




Green Book for the elaboration of link budgets, atmospheric models, handovers, and
concept of operations
Blue Book(s) for Low Signal Photon Flux Optical Communications
Blue Book(s) for High Signal Photon Flux Optical Communications
Green, Magenta, or Blue Book (to be determined by the Working Group) for real-time
weather and atmospheric characterization data
Survey of Similar Work Undertaken in Other Bodies
The Optical Link Study Group has recommended that this CCSDS Working Group focus on
1550 nm and 1064 nm wavelengths. The International Telecommunications Union (ITU) has
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analyzed potential wavelengths that can be used for free space optical communications, but
currently does not consider optical wavelengths within their mandate.
The safety assessment of laser links is a concern of the International Civil Aviation Organization
(ICAO) and the NASA Johnson Space Center Medical Office for human spaceflight. The
Optical Link Study Group recommended to the IOAG that both matters be worked at the IOAG
level and not within CCSDS.
Patent Licensing Applicability for Future Standards: The current Working Group
participants know of no limitations on usage of the planned technology as far as patent
restrictions or licensing requirements are concerned.
Technical Risk Mitigation Strategy: No technical risks have been identified.
Management Risk Mitigation Strategy
The schedule is very dependent upon space agencies commitment of resources and on the
success of several optical communications demonstration missions.
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ANNEX B:
Draft Projects
A) Green Book for Link Budgets, Atmospheric Models, Handovers, and Concept of
Operations
Title: Optical Communications Link Budgets, Atmospheric Models, Handovers, and
Concept of Operations
Document Type: Green Book
Description of Document: This Green Book shall define common terminology and
atmospheric models to be used in link budget calculations and define a basic concept of
operations, including handovers from one location to the next.
Contents of the Green Book:




Terminology Definition
Atmospheric Models
Link Budget Calculation Examples
Concept of Operations
Applicable Patents: None
Patents Comments: None
Book Editor (estimated resources + Agency Volunteering): ….
Prototype 1 (estimated resources + Agency Volunteering): ….
Prototype 2 (estimated resources + Agency Volunteering): …..
Expected Contributing Agencies: CNES, DLR, ESA, NASA
Expected Monitoring Agencies: JAXA, KARI, NICT (Observer)
Resource Needs According to CCSDS Resource Model
Proposed Book Editor:
B) Blue Book for Low Signal Photon Flux Optical Communications
Title: Low Signal Photon Flux Optical Communications Standard
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Document Type: Blue Book
Description of Document: This Blue Book shall define the parameters required
for interoperability of Low Signal Photon Flux forward and return links
including pointing, acquisition, and tracking.
Contents of the Blue Book:




Wavelength
Pointing, Acquisition, and Tracking
Modulation
Coding and Interleaving
Applicable Patents: None
Patents Comments: None
Book Editor (estimated resources + Agency Volunteering): ….
Prototype 1 (estimated resources + Agency Volunteering): ….
Prototype 2 (estimated resources + Agency Volunteering): …..
Expected Contributing Agencies: ESA, NASA
Expected Monitoring Agencies: CNES, DLR, JAXA, KARI, NICT
Resource Needs According to CCSDS Resource Model
Proposed Book Editor:
C) Blue Book for High Signal Photon Flux Optical Communications
Title: High Signal Photon Flux Optical Communications Standard
Document Type: Blue Book
Description of Document: This Blue Book shall define the parameters required
for interoperability of High Signal Photon Flux forward and return links
including pointing, acquisition, and tracking.
Contents of the Blue Book:
 Wavelength
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 Pointing, Acquisition, and Tracking
 Modulation
 Coding and Interleaving
Applicable Patents: TBD
Patents Comments: TBD
Book Editor (estimated resources + Agency Volunteering): ….
Prototype 1 (estimated resources + Agency Volunteering): ….
Prototype 2 (estimated resources + Agency Volunteering): …..
Expected Contributing Agencies: CNES, DLR, ESA, NASA
Expected Monitoring Agencies: JAXA, KARI, NICT
Resource Needs According to CCSDS Resource Model:
Proposed Book Editor:
D) Green Book for Real-Time Weather and Atmospheric Characterization Data
Title: Real-Time Weather and Atmospheric Characterization Data
Document Type: Green Book
Description of Document: This Green Book shall initially define the physical
quantities to be measured at future optical communications ground station sites
resulting in version 1. A future version will define the concept of operations
for weather and atmospheric data exchange.
Contents of the Green Book:
 Physical Quantities to be Measured
 Concept of Operations
o Long term statistics
o Real-time measurements
o Predictive Weather
Applicable Patents: TBD
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Patents Comments: TBD
Book Editor (estimated resources + Agency Volunteering): ….
Prototype 1 (estimated resources + Agency Volunteering): ….
Prototype 2 (estimated resources + Agency Volunteering): …..
Expected Contributing Agencies: CNES, DLR, ESA, NASA
Expected Monitoring Agencies: JAXA, KARI, NICT
Resource Needs According to CCSDS Resource Model:
Proposed Book Editor for Version 1: TBD
Proposed Book Editor for Version 2: TBD
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