201007 July/August 2010 Archives - Inside GNSS - Global Navigation Satellite Systems Engineering, Policy, and Design

GNSS Hotspots | July 2010

Inside GNSS — Fri, 23 Jul 2010 07:01:08 +0000

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. EARTHQUAKE!
Seattle, Washington USA
√ Want to know where an earthquake will occur and how big it will be? The Pacific Northwest Geodetic Array (PANGA) geodesy lab can tell you. They use 350 continuously operating high-precision GPS receivers and can analyze and share quake data in less than a minute. (Fact: A megaquake is likely 50 miles from Seattle).

PANGA’s website

2. TORTS
Park City, Utah USA
√ A young tourist asked Google Maps to plot a safe route during a nighttime walk around a Utah resort. The map guided her to a 4-lane highway, where she was hit by a car and sued Google for $100,000. No word if the driver was relying on his car’s navigation or crash-avoidance technologies at the time.

See the case here

3. 100% COMPLETE
Baikonur spaceport, Kazakhstan
√ Russia’s GLONASS constellation will be complete by the end of December 2010, said a JSC Russian Space Systems spokesman at the APEC/GIT meeting in Seattle in June. Three space vehicles are scheduled to launch from Baikonur on September 2, and another three at the end of December. Russia needs 24 satellites for global coverage.

4. PUMP FAILURE
Satish Dhawan Space Center (SHAR), India
√ Turbo-pump failure caused the April crash of India’s GSLV rocket and the loss of its GSAT-4 satellite that carried the country’s first GPS-Aided Geo Augmented Navigation (GAGAN) payload. On July 9, the Indian Space Research Organization (ISRO) said liquid hydrogen stopped flowing into the rocket’s thrust chamber right after ignition. No word on when, or on which launcher, GAGAN may fly again.

5. QZSS DELAY
Tanegashima Space Center, Japan
√ Japan’s space agency, JAXA, has postponed the August 2 launch of Michibiki, its first Quazi-Zenith Satellite, due to problems with the onboard reaction wheels. JAXA has decided to replace the parts. By 2013, QZSS’s planned three-satellite constellation will augment GPS over Japan, strengthening the signal in mountains and urban areas.

JAXA website

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Interesting. Too Interesting?

Inside GNSS — Wed, 21 Jul 2010 22:44:35 +0000

In the world of GNSS we usually think of more as better. More systems, more satellites, more signals — all contribute to greater availability of robust positioning, navigation, and timing.

Certainly that was the mood at the June meeting of the Asia-Pacific Economic Cooperation — GNSS Implementation Team (APEC-GIT) in Seattle, Washington.

In the world of GNSS we usually think of more as better. More systems, more satellites, more signals — all contribute to greater availability of robust positioning, navigation, and timing.

Certainly that was the mood at the June meeting of the Asia-Pacific Economic Cooperation — GNSS Implementation Team (APEC-GIT) in Seattle, Washington.

Everybody was celebrating progress with their systems: the first GPS Block IIF in orbit, another Compass GEO up, GLONASS constellation nearing completion, Europe’s EGNOS approaching certification, more than 100 satellites expected to be in orbit by 2020.

It all sounded good.

That is, until Tim Murphy came along.

Until then, the reports from representatives of the various GNSS and regional augmentation systems were accentuating the positive: better coverage in urban canyons, improved dilution of precision (DOP) metrics, more signals to use for receiver autonomous integrity monitoring (RAIM), and so on.

But about 21 slides into his Powerpoint presentation, Murphy — a long-time aeronautical engineer at Boeing — puts up a chart titled, “Receivers Are Going to Get Complicated.”

Well, sure, I think to myself, that stands to reason.

His chart lists the various systems and the frequencies that their signals will be on, and then asks the question: How many different kinds of position solutions could there be?

Turns out, by the time all the current and planned signals come on line over the next decade, GPS by itself will have seven different possible combinations for just the signals in protected safety-of-life frequencies (omitting GPS L2): L1 only, L1C only, L5 only, L1 & L5, L1 & L1C, L1C & L5, and L1, L1C, L5.

Then Murphy goes to the next slide: “Receivers Are Going to Get Complicated (2).”

“Uh-oh,” I think to myself.

This slide even starts out with a formula. Total combinations (Nc) for a constellation with n signals is:

See equation here

Bottom line: Murphy’s conservative estimate totals 441 different modes that a receiver could operate in. Toss in a satellite-based augmentation system that adds one signal option to each signal set, and the number doubles. Pity the poor manufacturer who has to sort out the trade-off analysis for that one!

Yeah, we were all thinking this was an interesting twist on Murphy’s Law — “Anything that can go wrong, will go wrong.” Perhaps the “too much of a good thing” variation.

It was almost a relief when he turned to his next slide: “Interoperability — the Political/Institutional Problem.”

Difficult as they now appear, sorting out frequency-sharing issues among the various providers may turn out to be the easy part.

So, initiatives at the highest political levels — such as the more internationalist and cooperative approach outlined by the Obama administration in a recent space policy statement — are sorely needed. So are practical projects such as the proposal for an Asia-Pacific multi-GNSS Demonstration Campaign recently offered by the Japanese Aerospace Exploration Agency (JAXA).

Meanwhile, the efforts of the International Committee on GNSS (ICG), which holds its fifth full meeting in Italy this coming October, may play a more important role than ever. The ICG secretariat, hosted by the UN Office of Outer Space Affairs, recently published a handy compendium outlining where we are now: “Current and Planned Global and Regional Navigation Satellite Systems and Satellite-Based Augmentation Systems.”

Interesting times, and they will require much good will and many solid efforts too keep them from becoming too interesting.

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