From June 9-11, members of the aviation equipment manufacturing industry gathered to move forward on standardising aircraft equipment for European GNSS. The meeting was part of Working Group 62 of the European Organisation for Civil Aviation Equipment (EUROCAE), the organisation responsible for developing aviation standards.
Currently, EGNOS and other Satellite-Based Augmentation Systems provide 
messages to augment GPS in one frequency, called L1. The next generation of EGNOS will be able to provide messages in two frequencies, L1 and L5, augmenting both GPS and Galileo. L5 is part of the aeronautical safety navigation band, which is a protected band of the radiofrequency spectrum for use by aviation safety systems. The Dual-Frequency Multi-Constellation capability is the guiding principle in the evolution of SBAS systems and provides advantages over a single frequency.
The Advantage of Dual Frequency
With Dual-Frequency, users will not be affected by the loss of performance currently experienced in periods of high ionosphere perturbations. Instead, receiving two frequencies gives the receiver enough data to calculate its position and time, resulting in greater precision and better accuracy.
The ionosphere, a layer of the atmosphere with a high concentration of charged particles (ions), is affected by (among others) the solar wind, especially in periods of high solar activity. Turbulent space weather causes unpredictable changes in the behaviour of the ionosphere, which renders the current models of propagation of radiofrequency wave obsolete.
For the past couple of years, GNSS experts from around the world have been working to show what exactly will be in the augmentation messages using the new L5 frequency. GNSS experts from the SBAS International Working Group prepared an Interface Control Document (ICD) and Definition Document to describe the types of messages L5 frequency delivers.
The group, made up of current and future SBAS Systems Owners and Service Providers from around the world, determined that the draft documents were ready for distribution, and they were unveiled during the EUROCAE meeting. With these documents, aviation receiver manufacturers can now begin prototyping user terminals.
What’s Next?
Next, EUROCAE and RTCA (its US equivalent), will use the ICD to write the Minimum Operational Performance Standards (MOPS). These standards define the technical specifications of SBAS receivers, including algorithms and technical specifications of the tests that must be performed to guarantee compliance.
MOPS are developed with receiver manufacturers who develop prototypes, and their publication is the next milestone in standardising DFMC receivers.
The GSA will begin activities to support the development of receiver prototypes, for the next generation of EGNOS, in 2015 and will also encourage progress in producing MOPS.
More Information
DFMC SBAS Receiver Development - Présentation
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