Global Navigation Satellite Systems Engineering, Policy, and Design
For the complete story, including figures, graphs, and images, please download the PDF of the article, above.
Galileo receiver designers require formal interface specifications for the Galileo signal-in-space (SIS) in order to write unambiguous and accurate specifications for Galileo receivers. To compute their positions, Galileo receivers must be able to retrieve timing and orbital information from the data stream conveyed in Galileo analog signals.
By Inside GNSS
FIGURES 1, 2 & 3For the complete story, including figures, graphs, and images, please download the PDF of the article, above.
In satellite navigation, a GNSS receiver must account for several sources of error such as relativistic effects, atmospheric propagation delay, offset of satellite clocks from system time and satellite ephemeris. In order to accurately compute user position, velocity, and time (PVT), these errors need to be predicted/estimated precisely.
By Inside GNSS
The GPS program continues progress on several fronts — in space and on the ground.
During fall 2010, the U.S. Air Force and the Raytheon Company team developing the GPS Advanced Control Segment (OCX) successfully carried out an integrated baseline review (IBR) for the next-generation system on schedule.
When completed in 2015 under the current schedule, GPS OCX will deliver control segment enhancements designed to provide secure, accurate and reliable navigation and timing information to military, commercial and civil users.
By Inside GNSS
One of 12 magnetograms recorded at Greenwich Observatory during the Great Geomagnetic Storm of 1859
1996 soccer game in the Midwest, (Rick Dikeman image)
Nouméa ground station after the flood
A pencil and a coffee cup show the size of NASA’s teeny tiny PhoneSat
Bonus Hotspot: Naro Tartaruga AUV
Pacific lamprey spawning (photo by Jeremy Monroe, Fresh Waters Illustrated)
“Return of the Bucentaurn to the Molo on Ascension Day”, by (Giovanni Antonio Canal) Canaletto
The U.S. Naval Observatory Alternate Master Clock at 2nd Space Operations Squadron, Schriever AFB in Colorado. This photo was taken in January, 2006 during the addition of a leap second. The USNO master clocks control GPS timing. They are accurate to within one second every 20 million years (Satellites are so picky! Humans, on the other hand, just want to know if we’re too late for lunch) USAF photo by A1C Jason Ridder. 
Detail of Compass/ BeiDou2 system diagram
Hotspot 6: Beluga A300 600ST
1. STORMY WEATHER
Belgium and Brazil
A: GPS receivers built for various applications, such as handhelds, automobiles, mobile phones, and avionics, all have a method for indicating the signal strength of the different satellites they are tracking. Some receivers display the signal strength in the form of vertical bars, some in terms of normalized signal strength, and others in terms of carrier-to-noise density (C/N0) or signal-to-noise ratio (SNR).
By Inside GNSS
Return to main article: Military PNT — The Way Ahead
By Inside GNSS
Return to main article: Local Oscillator Phase Noise
In 1966 D.B. Leeson proposed an empirical linear model for the noise spectrum of an oscillator, which has been extensively cited in the literature since then. G. Sauvage generalized this model to other resonant circuits in 1977, providing a deeper mathematical background. In 1998 A. Hajimiri and T.H. Lee proposed a linear time variant model (LTV) to explain the effect of each of the noise sources of an oscillator on its phase noise.
By Inside GNSS
Frank & Jeanine at the Wild Animal ParkSIDEBAR: Frank Czopek’s Compass Points
Frank Czopek and his brothers used to go to the 1970s Detroit version of Craigslist — Trading Times — to buy two or three non-functioning Chevrolet Corvairs (air-cooled rear engine-mounted) cars, at $25 apiece.
They hoped to turn the junkers into a single functioning automobile over a weekend. Unfortunately, the results did not last long; so, the process was repeated often. But they sure had fun!
By Inside GNSS
Engineering Specialties
Mechanical space hardware, real-time embedded programming, Boolean Logic, Assembly Language.
His Compass Points
By Inside GNSS
Antonio TajaniAmid continuing debate over how to handle budgetary shortfalls in building a European GNSS, the European Space Agency (ESA) signed a €194 million ($270.5 million) contract on October 25 with SpaceOpal to provide space- and ground-based services to operate the Galileo constellation once it has been fully deployed.
By Inside GNSS
A Salzburg, Austria–based start-up company, Mobilizy, took home the €20,000 grand prize in the European Satellite Navigation Competition 2010 (ESNC 2010) for its revolutionary navigation system Wikitude Drive, which uses augmented reality (AR) to superimpose driving directions over live street video on smartphones.
Wikitude Drive also won the prize for the best application leveraging EGNOS, the European satellite-based augmentation system that aims to add even more speed, precision, and reliability to GPS. The European GNSS Agency (GSA) sponsored the EGNOS prize.
By Inside GNSS
FIGURE 1: Block-diagram of a GNSS direct-conversion receiver
For the complete story, including figures, graphs, and images, please download the PDF of the article, above.
GNSS systems rely on direct sequence spread spectrum (DSSS) transmissions to achieve high receiver sensitivity. Typically, GNSS user equipment compares the signal received from a satellite with an internally generated replica of its corresponding code until the maximum correlation for a given delay is achieved. This provides an indirect measurement of the satellite-receiver range.
By Inside GNSS
FIGURE 1: The three foundations of C2 and how they are “changing the game” in an electronic battlespace: spectrum (communications media), yellow; computers (digital data), green; PNT (precise position and timing), blue.With thanks to Yogi Berra, it’s “déjà vu all over again” for the Global Positioning System, but this time with a twist.
Twenty-five years ago, the question asked by U.S. military commanders and combat personnel in the field was, “Why should I go to the trouble to use this space-based system called GPS?” Today, the question being asked is, “GPS is vital to the success of my mission; so, why are you asking me to consider using something else?”
By Inside GNSS
