As has been widely reported, China plans to construct its own global satellite navigation network. Or so it would appear. No ones quite sure. The system, dubbed Compass, is mired in confusion, with possible intentions ranging from a modest upgrade of their regional Beidou system to a full blown competitor to GPS and Galileo.China invested in the European Galileo system through the Galileo Joint Undertaking. Remarkably, this investment will not allow the Chinese any role in Galileo when it transitions to the Supervisory Authority at the end of the year, likely due to the sensitive nature of Galileos encrypted signals. Its no surprise, then, that China would feel betrayed by its partnership in the Joint Undertaking. Compass may be a result of Chinas desire to strike out on its own or a bluff aimed at wrangling a more substantive role in Galileo.The business case for Galileos commercial signals is questionable, since most people are content with using GPS and the free Galileo signals. Another commercial competitor, such as Compass, would surely hurt Galileo. As such, China can easily use Compass as leverage for better standing within the Supervisory Authority.China has ordered 18-20 rubidium atomic clocks, a key component of satellite navigation systems. However, this is nowhere near enough to create a global constellation, which requires at least 21 satellites, especially since there are usually multiple clocks per satellite, with GPS satellites having at least three and Galileo having four.At best, China would be able to build eight or nine satellites with just two clocks each, which would allow for a regional navigation system for East Asia and the Indian subcontinent. Such a system would not be a commercial threat to Galileo, but has potential to become a global competitor fairly quickly if China buys more clocks; this initial order may only represent a first installment.The International Telecommunications Union (ITU) database has 36 satellite slots registered to Compass. Fourteen are in geosynchronous orbits, and the remaining 22 are in the medium orbits traditionally used for navigation systems. While there is a tendency to register more slots with the ITU than will realistically be filled, such a large number of registrations for a regional system would be excessive and place China in a poor position with the ITU for future registrations.What is Europe to do? The economic returns on Galileo must be protected if the project is to succeed. China could be given rights under the Supervisory Authority, minimizing its need for Compass. However, this would probably allow Chinese companies to build Galileo ground receivers, a potentially lucrative market that Europe would like to keep for itself. It would also give China access to the encrypted, and sensitive, public-safety signals. The stakes are high, but can Europe afford to call Chinas bluff?An interesting aside: there is no guarantee that the clocks would be used for Compass. Another possible application is naval signal reconnaissance satellites similar to the Navys Ocean Surveillance Satellites program. In that case, the clocks are used for radio inferometery, in turn determining the origin of the intercepted signals. Such a capability for the Chinese would undoubtedly have significant military implications. That possibility, however, is a subject for another day.Another consideration: there is a possibility that Compass could jam GPS and Galileo. Even as a regional system, Compass could have significant military implications. These aspects will be discussed in another entry tomorrow.-- Ryan Caron
Compass - Chinese SatNav or Galileo Bluff?
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