CCSDS Optical Communications Working Group
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 may operate in space, e.g. inter-satellite links and
between space and Earth. The latter have to operate through Earth’s atmosphere,
which can be severely impacted by weather (clouds, optical turbulence, and other
atmospherics); the result is that a typical spacecraft in space-ground
communications 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, for space-to-space and space-Earth configurations.
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 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. The maturity of space optical
communications terminals that are already realized (e.g., for Earth-orbit intersatellite 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
 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 at least one 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 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.
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)
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 for space-Earth communications 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. Equally, it is a motivation to also
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 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 may be used with optical
communications systems and thus negate the need for specific optical communications
standards at the Data Link Layer and above. This activity will culminate in two Blue Books.
Another goal is to investigate 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:

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Green Book for the elaboration of link budgets, atmospheric models, handovers, and
concept of operations
Blue Book for Low Signal Photon Flux Optical Communications
Blue Book 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
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.
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: 10 man months
comprised of 6 man months plus 2 man months for two contributors plus 2 man
months for two monitors
Proposed Book Editor:
B) Blue Book for Low Signal Photon Flux Optical Communications
Title: Low Signal Photon Flux Optical Communications Standard
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: 30 man months
comprised of 10 man months plus 16 man months for 2 prototypes (To Be
Reviewed) plus 2 man months for two contributors plus 2 man months for
two monitors
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
 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: 30 man months
comprised of 10 man months plus 16 man months for 2 prototypes (To Be
Reviewed) plus 2 man months for two contributors plus 2 man months for
two monitors
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
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: 10 man months
comprised of 6 man months plus 2 man months for two contributors plus 2
man months for two monitors
Proposed Book Editor for Version 1: TBD
Proposed Book Editor for Version 2: TBD