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Inside GNSS: Engineering Solutions from the Global Navigation Satellite System Community
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Galileo
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.

GNSS Solutions • April 2006

Adaptive Antenna Arrays, Multi-GNSS Tropospheric Monitoring, and High-Dynamic Receivers

Q: What is adaptive nulling vs. adaptive beamforming? What are the advantages and disadvantages?

A: Adaptive arrays are perhaps the single most powerful antijamming tool in the GNSS systems engineer’s toolkit. They can provide anywhere from 15 to 90 dB of jamming rejection depending on the specific architecture used. Their main disadvantage is that they require an array of antenna elements, each spaced about four inches apart (center to center), and thus are physically large.

GNSS Solutions • March 2006

Carrier Phase Ambiguity Resolution, GNSS Use In Cellular Telephone Systems, and New Antennas?

Q: Will I need a new antenna for the new GPS and Galileo signals? Will one antenna work for both systems?

A: To answer these questions, information will be presented on the GPS and Galileo signal formats, some antenna basic fundamentals with various user applications in mind, followed by some predicted performance assessment.

Inside GNSS • January/February 2006

New EC DG-TREN Director-General

Matthias Ruete has been named as director-general of the European Commission’s Directorate- General for Energy and Transport (EC DG-TREN), which has overall responsibility for implementation of the Galileo program on behalf of the European Union (EU). He replaces François Lamoreaux.

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