Consultative Committee for Space Data Systems
Encyclopedia
The Consultative Committee for Space Data Systems (CCSDS) was formed in 1982 by the major space agencies of the world to provide a forum for discussion of common problems in the development and operation of space data systems. The Committee meets periodically to address data systems problems that are common to all participants, and to formulate sound technical solutions to these problems. It is currently composed of eleven member agencies, 22 observer agencies, and over 100 industrial associates.
Since its establishment, it has been actively developing Recommended Standards for data- and information-systems standards to
At the CCSDS' bi-annual meetings, the week-long working committee meetings are followed by a general meeting where the member agencies vote to approve the committees' recommendations and direct the other business of the organization.
These agencies and the nations they represent are:
Report types
If the leading bytes happen to be the codeblock sync marker, two sync markers will appear in each R-S codeblock, leading to confusion in determining which is the correct starting point for the codeblock. The Recommendation indicated that a solution would need to be found.
Various solutions were studied and it was finally decided to adopt the cleanest technical solution: to remove the attached sync marker from the encoding process.
In addition, by steering the 32-bit sync marker away from the R-S encoder, the R-S codeblock now has space for an additional 32 bits of data. This solution was incorporated into Issue 2, References which redefined the "Codeblock" (and "Transfer Frame", for consistency) to exclude their respective "attached sync markers". Of course, an attached sync marker must still precede each uncoded Transfer Frame, or each R-S codeblock.
this only means they do not transmit in the standard CCSDS packet formats. These craft do however use CCSDS standardized error correction formats in the downlink segment.
Since its establishment, it has been actively developing Recommended Standards for data- and information-systems standards to
- reduce the cost to the various agencies of performing common data functions by eliminating unjustified project-unique design and development, and
- promote interoperability and cross support among cooperating space agencies to reduce operations costs by sharing facilities.
Member agencies
There are eleven space agencies with full voting membership in the CCSDS.At the CCSDS' bi-annual meetings, the week-long working committee meetings are followed by a general meeting where the member agencies vote to approve the committees' recommendations and direct the other business of the organization.
These agencies and the nations they represent are:
- Brazil - Instituto Nacional de Pesquisas EspaciaisNational Institute for Space ResearchThe National Institute for Space Research is a research unit of the Brazilian Ministry of Science and Technology, whose main goals are fostering scientific research and technological applications and qualifying personnel in the fields of space and atmospheric sciences, space engineering, and space...
(INPE) - Canada - Canadian Space Agency (CSA)
- China - China National Space AdministrationChina National Space AdministrationThe China National Space Administration is the national space agency of the People's Republic of China responsible for the national space program. It is responsible for planning and development of space activities...
(CNSA) - European Union - European Space AgencyEuropean Space AgencyThe European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
(ESA) - France - Centre National d'Etudes SpatialesCNESThe is the French government space agency . Established under President Charles de Gaulle in 1961, its headquarters are located in central Paris and it is under the supervision of the French Ministries of Defence and Research...
(CNES) - Germany - Deutsches Zentrum für Luft- und Raumfahrt e.V.German Aerospace CenterThe German Aerospace Center is the national centre for aerospace, energy and transportation research of the Federal Republic of Germany. It has multiple locations throughout Germany. Its headquarters are located in Cologne. It is engaged in a wide range of research and development projects in...
(DLR) - Italy - Agenzia Spaziale ItalianaItalian Space AgencyThe Italian Space Agency is a government agency established in 1988 to fund, regulate and coordinate space exploration activities in Italy...
(ASI) - Japan - Japan Aerospace Exploration AgencyJapan Aerospace Exploration AgencyThe , or JAXA, is Japan's national aerospace agency. Through the merger of three previously independent organizations, JAXA was formed on October 1, 2003, as an Independent Administrative Institution administered by the Ministry of Education, Culture, Sports, Science and Technology and the...
(JAXA) - Russia - Russian Federal Space AgencyRussian Federal Space AgencyThe Russian Federal Space Agency , commonly called Roscosmos and abbreviated as FKA and RKA , is the government agency responsible for the Russian space science program and general aerospace research. It was previously the Russian Aviation and Space Agency .Headquarters of Roscosmos are located...
(RFSA) - United Kingdom - UK Space AgencyUK Space AgencyThe UK Space Agency is a United Kingdom government agency responsible for its civil space programme. It was established on 1 April 2010 to replace the British National Space Centre and took over responsibility for government policy and key budgets for space and represents the UK in all negotiations...
(UKSA) - United States of America - National Aeronautics and Space AdministrationNASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
(NASA)
General Recommendations
The CCSDS develops recommendations, called Blue Books, for standards in order to:- Reduce the cost of performing space missions
- Enable cross support for space missions
- Improve understanding of space related data
- Preserve archived space related data
Report types
- Blue: Recommended Standards
- Magenta: Recommended Practices
- Green: Informational Reports
- Orange: Experimental or ongoing research
- Yellow: Record, but not Historical
- Silver: Historical
Specific Recommendations
The CCSDS recommends for Spacecraft to Earth communications the- avoidance of or the turning off of the 'randomizer', as the CCSDS currently recommends a randomizer similar to the BBC NICAMNICAMNear Instantaneous Companded Audio Multiplex is an early form of lossy compression for digital audio. It was originally developed in the early 1970s for point-to-point links within broadcasting networks...
randomizer - avoidance of transmission downlink waveforms with very poor Doppler performance, like FM
- avoidance of error correction systems with weaker performance than the Voyager ProgramVoyager programThe Voyager program is a U.S program that launched two unmanned space missions, scientific probes Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable planetary alignment of the late 1970s...
code—a (7, 1/2) convolutional code concatenated with (255,223) Reed-Solomon code (typically with 3-bit quantization)- A rate 1/2, constraint length 7 convolutional code with Viterbi (maximum likelihood) decoding is already a standard for both NASANASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
and ESA. It has been used in several missions and has demonstrated the expected coding gain.
- A rate 1/2, constraint length 7 convolutional code with Viterbi (maximum likelihood) decoding is already a standard for both NASA
- use of wavelet encoding of images using ICERICERICER is a wavelet-based image compression file format used by the NASA Mars Rovers. ICER has both lossy and lossless compression modes.The Mars Exploration Rovers “Spirit” and “Opportunity” both use ICER...
or JPEG2000, as opposed to JPEGJPEGIn computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality.... - use of separate Packet and Frame sizes to increase error correction margin in the space channel
- avoidance of the False Sync Problem : Issue 1 of the Telemetry Channel Coding Blue Book (May 1984) made reference to a "False Sync" problem in footnote 5. As defined by the Recommendation at that time, the codeblock "attached sync marker" was included as a part of the Reed-Solomon data space. Various solutions were studied and it was finally decided to adopt the simplest technical solution: to remove the attached sync marker from the encoding process.
False Sync snafu
The Telemetry Channel Coding Blue Book (May 1984) made reference to a "False Sync" problem. It was discovered that under certain repeating data values (like test patterns of "01010101...") the then CCSDS "attached sync marker" encoding algorithm regenerates the pattern of the leading data bytes within in the leading bytes of the check symbol field—a place where they should not be.If the leading bytes happen to be the codeblock sync marker, two sync markers will appear in each R-S codeblock, leading to confusion in determining which is the correct starting point for the codeblock. The Recommendation indicated that a solution would need to be found.
Various solutions were studied and it was finally decided to adopt the cleanest technical solution: to remove the attached sync marker from the encoding process.
In addition, by steering the 32-bit sync marker away from the R-S encoder, the R-S codeblock now has space for an additional 32 bits of data. This solution was incorporated into Issue 2, References which redefined the "Codeblock" (and "Transfer Frame", for consistency) to exclude their respective "attached sync markers". Of course, an attached sync marker must still precede each uncoded Transfer Frame, or each R-S codeblock.
Benefits of CCSDS
- Promotes understanding of exchanged data
- Reduces nonrecurring costs:
- Fewer project-specific developments
- Shorter test times
- Less training of staff is needed
- Reduces recurring costs:
- More commercial off-the-shelfCommercial off-the-shelfIn the United States, Commercially available Off-The-Shelf is a Federal Acquisition Regulation term defining a nondevelopmental item of supply that is both commercial and sold in substantial quantities in the commercial marketplace, and that can be procured or utilized under government contract...
(COTS) hardware is needed - Fewer facilities because of load leveling
- Only selected redundancy is needed
- More automation, less staff
- More commercial off-the-shelf
- Mitigates mission risk
- Enables ingest and access data archives
Important CCSDS standards
Related standards- CCSDS Advanced Orbiting System (AOS)
- CCSDS File Delivery Protocol (CFDP)
- CCSDS Image Compression standard CCSDS 122.0-B-1CCSDS 122.0-B-1CCSDS 122.0-B-1 is a CCSDS Lossless to Lossy Image compression standard released on November 2005.This CCSDS standard is a discrete wavelet transform transform coder followed by a Rice encoder & a Bitplane encoder...
- Packet Telemetry
- Producer Archive Interface Methodology Abstract Standard (PAIMAS)
- Proximity-1 Space Link ProtocolProximity-1 Space Link ProtocolProximity-1 Space Link Protocol is a short haul delivery protocol designed to establish a two-way communications link between a lander and an orbiter, negotiate data rate and communications mode, and reliably deliver data during short orbiter-to-surface contacts.Developed by Consultative Committee...
- Spacecraft Monitoring & ControlSpacecraft Monitoring & ControlThe Spacecraft Monitoring & Control Working Group of the Consultative Committee for Space Data Systems , which sees the active participation of 10 space agencies and of the Space Domain Task Force of the Object Management Group , is defining a service oriented architecture consisting of a set of...
(SM&C) - Space Link Extension Services (SLE)
- Space Communications Protocol SpecificationsSpace Communications Protocol SpecificationsThe Space Communications Protocol Specifications are a set of extensions to existing protocols and new protocols developed by the Consultative Committee for Space Data Systems to improve performance of Internet protocols in space environments...
(SCPS)- SCPS-FP -- A set of extensions to FTP to make it more bit efficient and to add advanced features such as record update within a file and integrity checking on file transfers.
- SCPS-TP -- A set of TCPTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
options and sender-side modifications to improve TCPTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
performance in stressed environments including long delays, high bit error rates, and significant asymmetries. The SCPS-TP options are TCP options registered with the Internet Assigned Numbers AuthorityInternet Assigned Numbers AuthorityThe Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...
(IANA) and hence SCPS-TP is compatible with other well-behaved TCPTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
implementations. - SCPS-SP -- A security protocol comparable to IPsecIPsecInternet Protocol Security is a protocol suite for securing Internet Protocol communications by authenticating and encrypting each IP packet of a communication session...
- SCPS-NP -- A bit-efficient network protocol analogous to but not interoperable with IPInternet ProtocolThe Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
- Telemetry Channel Coding
- XML Telemetric and Command ExchangeXML Telemetric and Command ExchangeXTCE is an XML based exchange format for spacecraft telemetry and command meta-data. Using the format and content of a space systems command and telemetry links can be readily exchanged between spacecraft operators and manufacturers. XTCE was originally standardized by the OMG...
(XTCE)
Pre-CCSDS standards craft in service
There are a few pre-CCSDS standards craft in active service- Voyager 1Voyager 1The Voyager 1 spacecraft is a 722-kilogram space probe launched by NASA in 1977, to study the outer Solar System and eventually interstellar space. Operating for as of today , the spacecraft receives routine commands and transmits data back to the Deep Space Network. At a distance of as of...
- Voyager 2Voyager 2The Voyager 2 spacecraft is a 722-kilogram space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space...
this only means they do not transmit in the standard CCSDS packet formats. These craft do however use CCSDS standardized error correction formats in the downlink segment.
External links
- CCSDS Official Web Site URL accessed 13 March 2006
- CCSDS Documents in PDF format URL accessed 12 April 2006
- An Introduction to CCSDS URL accessed 12 April 2006
- CDSCC, an acronym sometimes confused with CCSDS URL accessed 12 March 2006
- Goddard Space Flight Center URL accessed 12 March 2006
- NASA Jet Propulsion Laboratory
- National Space Science Data Center (NSSDC) at the NASANASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
Goddard Space Flight CenterGoddard Space Flight CenterThe Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...
URL accessed 12 March 2006