Unlike the U.S. Global Positioning System (GPS), which was financed by the U.S. Department of Defense and can be accessed at no charge, the European GIOVE-A satellite and the Galileo navigation system is being funded by a joint venture consisting of the European Union, the European Space Agency and private investors. To reimburse the investors, the joint venture presumably planned to charge for access to the codes needed to use the system. Last week Cornell University announced that members of its Global Positioning System Laboratory cracked the pseudo-random number (PRN) codes of the GIOVE-A satellite. GIOVE-A, as detailed in a previous RF Report, is a prototype for the future Galileo satellites that will make up the Galileo constellation.
Under a 2004 agreement between the United States and the European Union--in addition to procedures for avoiding interference between the Galileo and GPS satellites, which share the same frequencies--the agreement called for some of the PRN codes to be "open source."
Mark Psiaki, co-leader of Cornell's GPS Laboratory, requested the codes for the GIOVE-A satellite from Martin Unwin at Surrey Space Technologies Ltd., but the request was refused. Later, when Galileo published the PRN codes, they weren't the codes being used by the GIOVE-A satellite. Galilieo said the open source codes were intellectual property and claimed a license was required for any commercial receiver using them.
Psiaki and his team at the GPS Laboratory responded by developing a basic algorithm to extract the codes and within two weeks had their first signal from the satellite, with cooperation from Oliver Montenbruck, a friend and colleague in Germany who also wanted the codes. After some additional work, the final version of the PRN codes was posted online. Engineers at NovAtel Inc., a GPS manufacturer, downloaded the codes and, according to Cornell, were able to begin tracking GIOVE-A within 20 minutes.
What about the legal ramifications of cracking the code and publishing it under the Digital Millennium Copyright Act and other restrictions on code breaking? Cornell University's attorneys didn't see a problem with it.
"We were told that cracking the encryption of creative content, like music or a movie, is illegal, but the encryption used by a navigation signal is fair game. Imagine someone builds a lighthouse, and I've gone by and see how often the light flashes and measured where the coordinates are," Psiaki said. "Can the owner charge me a licensing fee for looking at the light? No. How is looking at the Galileo satellite any different?"
After cracking the PRN codes, the Cornell team learned that the GIOVE-A codes and navigation messages are not meant to be the same as the final Galileo codes and messages. This explains why the codes released by Galileo did not work with the GIOVE-A satellite.
For additional information, refer to the Cornell University news story, "Cornell Sleuths Crack Secret Codes of Europe's Galileo Satellite." Detailed technical information is available online, including information on GIOVE-A signal strength and potential minor errors due to sign ambiguities and a secondary code phase ambiguity.
For detailed information on the Galileo system, including the primary codes released in April, go to the Galileo Joint Undertaking Web site and select "Standardization Docs" under the "Publications and Links" tab. The Cornell University Galileo Web page said that sources within the Galileo project indicated the GIOVE-A interface control documentation would be released in June 2006, but I did not see it on the Galileo Joint Undertaking Web site.
