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Galileo
Inside GNSS • October 2006

Progress Amid Criticism: Challenging the Galileo Obstacle Course

As the clock runs out on the Galileo Joint Undertaking (GJU) that has guided the institutional development of the European GNSS program for the past four years, negotiators from the GJU and a consortium seeking to build and operate the system are nearing completion of a “head of terms” agreement.

GNSS Solutions • September 2006

Atomic Clocks on Satellites and Mitigating Multipath

Q: GPS satellites used to carry two cesium and two rubidium atomic standards on board. Subsequently, GPS switched to all rubidium clocks. Galileo plans to use hydrogen masers instead. What are the relative merits of these clocks for use in navigation satellites?

A: It is well recognized that the space-qualified atomic clocks in the GPS satellites are an enabling technology, if not the enabling technology for the system. However, they are also one of the more difficult technologies to acquire.

Inside GNSS • July/August 2006

Industry Sees Galileo Contract Outline in 2006

The consortium negotiating to build and operate Europe’s Galileo system now expects to sign an agreement with the Galileo Joint Undertaking (GJU) by the end of 2006.

GNSS Solutions • July/August 2006

Orbital Precession, Optimal Dual-Frequency Techniques, and Galileo Receivers

Q: Is it true that the GPS satellite geometry repeats every day shifted by 4 minutes?

A: It is true that the GPS satellite orbits were selected to have a period of approximately one half a sidereal day to give them repeatable visibility. (One sidereal day is 23 hours, 56 minutes, and 4 seconds long or 236 seconds shorter than a solar day.) However, because of forces that perturb the orbits, the repeat period actually turns out to be 244 to 245 seconds (not 236 seconds) shorter than 24 hours, on average, and changes for each satellite.

Inside GNSS • July/August 2006

BOC or MBOC?

Europe and the United States are on the verge of a very important decision about their plans to implement a common civil signal waveform at the L1 frequency: Should that waveform be pure binary offset carrier — BOC(1,1) — or a mixture of 90.9 percent BOC(1,1) and 9.09 percent BOC(6,1), a combination called multiplexed BOC (MBOC). The desire for a common civil L1 signal is enshrined in a 2004 agreement on GNSS cooperation between the United States and the European Union (EU).

GNSS Solutions • May/June 2006

New GNSS Frequencies, Advantages of M-Code, and the Benefits of a Solitary Galileo Satellite

Q: What are the major differences between Galileo and GPS current and forthcoming frequencies?

A: Galileo has been designed to be both independent and interoperable with other GNSSes, and particularly GPS. The search for interoperability makes Galileo look like GPS, while the desire of independence of both systems has the opposite effect.

Inside GNSS • May/June 2006

Civil L1 Signals: Galileo ICD, GPS L1C, New MBOC

Within weeks of a bilateral working group’s recommendation for a common civil GNSS signal design, the European Galileo and U.S. GPS programs have filed draft interface specifications (IS) or interface control documents (ICDs) for the new signals planned for the L1 frequency (around 1575 MHZ).

Inside GNSS • April 2006

ICG Working Group Takes On Issues

An ad hoc working group has begun sorting through issues surrounding the recent formation of the International Committee on GNSS (ICG).

Inside GNSS • April 2006

GLONASS: Picking Up the Pace

Russian officials are working to develop a plan that will meet Russian President Vladimir Putin’s directive to have the full GLONASS constellation in place by 2009 instead of 2011.

Inside GNSS • April 2006

Galileo: the Concession Merry-Go-Round

Risk allocation, avoidance, and management are the watchwords of the day as the contract negotiation for the Galileo concession moves into its endgame.

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