International space agencies around the world are currently developing optical communication systems for Near Earth and Deep Space applications for both robotic and human-rated spacecraft. These applications include both links between spacecraft and links between spacecraft and ground. The Interagency Operation Advisory Group (IOAG) has stated that there is a strong business case for international cross support of spacecraft optical links. It further concluded that in order to enable cross support the links must be standardized. This paper will overview the history and structure of the space communications international standards body, the Consultative Committee for Space Data Systems (CCSDS), that will develop the standards and provide an update on the proceedings of the Optical Communications Working Group within CCSDS. This paper will also describe the set of optical communications standards being developed and outline some of the issues that must be addressed in the next few years. The paper will address, in particular, the ongoing work on application scenarios for deep space to ground called High Photon Efficiency, for LEO to ground called Low Complexity, for inter-satellite and near Earth to ground called High Data Rate, as well as associated atmospheric measurement techniques and link operations concepts.

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The Inter-agency Operations Advisory Group (IOAG) established an Optical Link Study Group (OLSG) at its meeting in 2010 to investigate the business case for cross support of spacecraft that may utilize optical communications in the future. This paper addresses the work that was done by the seven international space agency members of the OLSG. It was found that since clouds make optical communications through the Earth atmosphere impossible, in order to maintain high availability of spacecraft communications it is necessary to have weather de-coupling of individual ground stations. Other issues such as aircraft intrusion, atmospheric turbulence, and atmospheric aerosol considerations are also important factors in choosing which optical ground station to use for spacecraft data downlinking. In order to maintain high levels of optical communication capability it was found that numerous ground stations are required. Based on specific mission scenarios from low earth orbit to deep space, and Earth relay inter-satellite links, the feasibility of optical space communication solutions will be discussed and critically assessed for their maturity of being considered for implementation. Due to the cost of establishing optical communication ground stations with appropriate weather diversity around the globe, or to deploy earth relay satellites, the OLSG concluded that cross support based on interoperable solutions implementing international standards is an essential requirement to advancing this new method of spacecraft communication. The OLSG also identified the need to develop a detailed standardisation roadmap in order to enable an efficient standardisation process.

International space agencies around the world are working together in the Interagency Operation Advisory Group (IOAG) and the Consultative Committee for Space Data Systems (CCSDS) to develop interoperability standards for optical communications. The standards support optical communication systems for both Near Earth and Deep Space robotic and human-rated spacecraft. The standards generally address both free space links between spacecraft and free space links between spacecraft and ground. This paper will overview the history and structure of the CCSDS Optical Communications Working Group and provide an update on the set of optical communications standards being developed. The paper will address the ongoing work on High Photon Efficiency communications, High Data Rate communications, and Optical On/Off Keying communications. It will also cover the working being done within CCSDS on documenting atmospheric measurement techniques and link operations concepts. I. International Interoperability of Radio Frequency CommunicationsCivil space agencies can increase communications coverage and availability by sharing space based and ground based communications and navigation infrastructure around the world. The key to allowing this "cross support" (see Figure 1) is communications standards; by developing interoperability standards, one space agency's spacecraft could be served by another space agency's ground antennas.

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