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An Update on the CCSDS Optical Communications Working Group Interoperability Standards

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An Update on the CCSDS Optical Communications Working Group Interoperability Standards An Update on the CCSDS Optical Communications Working Group Interoperability Standards Bernard L. Edwards Robert Daddato NASA Goddard Space Flight Center European Space Agency Greenbelt, MD 20771 USA Darmstadt, Germany Klaus-Juergen Schulz Randall Alliss European Space Agency Northrop Grumman Corporation Darmstadt, Germany McLean, VA 22102 USA Jon Hamkins Dirk Giggenbach NASA Jet Propulsion Laboratory DLR Pasadena, CA 91109 USA Oberpfaffenhofen, Germany Bryan Robinson Lena Braatz MIT Lincoln Laboratory Booz Allen Hamilton, Inc. Lexington, MA 02420 USA McLean, VA 22102 USA Abstract – International space agencies around the one space agency’s spacecraft could be served by world are working together in the Interagency another space agency’s ground antennas. Operation Advisory Group (IOAG) and the Consultative Committee for Space Data Systems The overall development of international space (CCSDS) to develop interoperability standards for optical communications. The standards support communication standards for cross support is optical communication systems for both Near Earth coordinated by the Interagency Operations and Deep Space robotic and human-rated spacecraft. Advisory Group (IOAG) [1]. The IOAG is an The standards generally address both free space links organization made up of international space between spacecraft and free space links between agencies that provides a forum for identifying spacecraft and ground. This paper will overview the common needs and coordinating space history and structure of the CCSDS Optical communications policy, high-level procedures, Communications Working Group and provide an technical interfaces, and other matters related to update on the set of optical communications interoperability and space communications. The standards being developed. The paper will address the ongoing work on High Photon Efficiency IOAG considers the future requirements and trends communications, High Data Rate communications, in spacecraft communications needs and assigns and Optical On/Off Keying communications. It will priorities for the development of cross support also cover the work being done within CCSDS on standards. The standard development is then documenting atmospheric measurement techniques accomplished by the Consultative Committee for and link operations concepts. Space Data Systems (CCSDS), a multi-national forum comprised of the world’s major space I. International Interoperability of Radio agencies and observer agencies. The stated goal of Frequency Communications the CCSDS is to enhance governmental and commercial interoperability and cross support, Civil space agencies can increase communications while also reducing risk, development time, and coverage and availability by sharing space-based project costs. Consensus must be reached by the and ground-based communications and navigation member agencies before a CCSDS standard can be infrastructure around the world. The key to published. allowing this “cross support” is communications standards; by developing interoperability standards, As the standards have been developed, the international civil space agencies have gradually 1 International Conference on Space Optical Systems updated their ground space communication describing their applicability, overall antennas and ground data systems to implement the architecture, concept of operations, etc. cross support standards. As more and more systems have adapted the CCSDS standards, the agencies • Red Books are working copies of the have begun to enjoy the benefits of cross support. recommended standards before they are Options for spacecraft communications have promoted to the Blue Book or Magenta increased and the cost of supporting a single Book level. These should be used with agency’s spacecraft has been reduced, as agencies caution as they can change before use the communications assets of other entities to officially released. fulfill their spacecraft’s communication needs. • White Books are the initial conceptual In recent years, there have been significant working draft documents in a topic area. advancements in the development of laser-based communication systems for space applications. • Orange Books document experimental These optical communication systems hold the work. They are normative, but generally promise of better than an order of magnitude higher cover very new technology that does not data rates over radio frequency (RF) space yet have consensus of enough member communications, while using less power, having agencies to standardize. lower mass, and occupying less space than comparable RF communication systems. These • Yellow Books are administrative books. new communication systems will need They document CCSDS procedures, corresponding standards to allow and promote proceedings, test reports, etc. international cross support [2]. • Silver Books are historical books. They are II. The Consultative Committee for Space retired documents that are kept available Data Systems (CCSDS) to support existing or legacy The CCSDS member and observer agencies implementations. The implication is that contribute technical experts to develop space data other agencies may not provide cross- standards. The CCSDS has established a number of support. Working Groups that are focused on specific topics. Each CCSDS Working Group has a leader, • Pink Books/Pink Sheets are draft revisions chosen from a member agency, and a group of to Blue or Magenta Books that are experts contributed by member agencies interested circulated for agency review. Pink Books in the products being produced by that Working are reissues of the full book while Pink Group. The products are documents that Sheets are change pages only. recommend standard communication protocols, procedures, and concepts that will enable cross Once Blue Books are finalized they are brought to support in the particular area of interest of the an ISO Standards subgroup where they are Working Group. The products from the Working promoted to ISO Standards. ISO Technical Groups are color-coded according to the following Committee 20 Subcommittee 13 (TC 20/SC 13) is guide: the ISO administrative subcommittee of CCSDS. By special arrangement with ISO, CCSDS • Blue Books are completed recommended documents are processed as ISO TC 20/SC 13 standards that become ISO standards. projects at the Draft International Standard (DIS) They are normative, sufficiently detailed, stage. Effectively, the CCSDS membership now and pre-tested so they can be used to has a dual role, functioning as the CCSDS directly and independently implement standards body and as the ISO TC 20 /SC 13 interoperable systems. standards body. • Magenta Books describe recommended III. The CCSDS Optical Communications practices. They are normative, but at a Working Group level that is not directly implementable for interoperability. These are reference The CCSDS Optical Communications Working architectures, application program Group was formed in January 2014 and it is chaired interfaces, operational practices, etc. by NASA with a deputy from ESA. The working group is developing: • Green Books are informational reports. These are not normative. These may be • New standards in wavelength, modulation, foundational for Blue and Magenta Books, coding, interleaving, synchronization, and 2 International Conference on Space Optical Systems acquisition, which are best suited for free- where there is limited mass and power to support space optical communications systems. communications, such as on a CubeSat. It is expected that the underlying technologies and • New standards for definition, exchange, and techniques for modulation, coding, and archiving of weather data for predicting and synchronization will be significantly different operating optical communication links between the two signal cases. Finally, the working among optical ground stations and their group has identified a need for a standard that is network operations centers. less complex and less costly to implement than the High Data Rate standard. The first Standards specifically for free space optical recommendation that meets this desire for a less communications are required that account for the complex and costly implementation is the Optical severe impact of the Earth’s atmosphere on space- On/Off Keying recommendation currently in to-ground links. The standards currently cover the development. The Working Group hopes this will wavelength, modulation, coding, interleaving, and be used in those applications where cost or synchronization of optical communications signals. simplicity is more important that high performance, The atmospheric impacts on the link are typically efficiency, or data rate. more severe than the corresponding impacts on RF links, and thus the standards being developed by In addition to the typical standards that have to be the Working Group are different from the existing developed for any communications system, such as RF standards. Several space agencies are modulation and coding, space optical developing optical communications terminals that communications also require a standard for the can support both space-to-ground and space-to- definition, exchange, and archiving of weather and space links and the objective is to develop atmospheric data. That is because optical space maximum synergy, as far as practical, between the communications through Earth’s atmosphere are various scenarios. adversely affected by the presence of cloud cover and optical turbulence, and to a lesser extent, by The working group
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