Galileo IOV-3 Broadcasts E1, E5, E6 Signals; Russian SBAS Luch-5B in Orbital Slot; EGNOS and Galileo in Emergency Call, Road Tolling; Compass ICD Rumored
Galileo IOV-3 Broadcasts E1, E5, E6 Signals
By Oliver Montenbruck, German Space Operations Center and Richard B. Langley, University of New Brunswick
After reaching its final position, the Galileo IOV-3 satellite started transmitting its first ranging signals on December 1. Within three days, the various carriers (E1, E5, E6) and associated modulations were activated, and full in-orbit testing is now in progress. Anyone with commonly available GNSS receivers can presently access the open signals in the E1, E5a, and E5b frequency bands as well as the wide-band E5 AltBOC signal.
According to statements made at the recent 6th ESA Workshop on Satellite Navigation Technologies (Navitec 2012) in Noordwijk, The Netherlands, the IOV-3 satellite, which is also identified as Flight Model 3 (FM3) and E19 after its pseudorandom noise code, will continue to use binary offset carrier modulation — specifically BOC(1,1) — on the E1 Open Service signals for the time being. In contrast to this, the first pair of IOV satellites has already started to use composite binary offset carrier modulation, which offers better multipath suppression in the received signal.
Right after its activation, IOV-3 could be tracked immediately by the global network of stations participating in the Multi-GNSS Experiment (MGEX; http://www.igs.org/mgex) initiated by the International GNSS Service (IGS).
Figure 1. Pseudorange errors of IOV-3 tracking at Tanegashima, Japan, using the E1 BOC(1,1) signal (top) and the E5 AltBOC signal (center). The elevation angle over time is shown in the bottom panel.
The high quality of the IOV-3 signals is illustrated by measurements collected by the Tanegashima station during a 10-hour pass of the satellite over Japan (see Figure 1). The E5 AltBOC pseudorange measurements in particular exhibit an exceptionally low noise and multipath level of better than 10 centimeters at mid- and high-elevation angles.
An attractive feature of the Galileo system is the availability of multiple signal frequencies, which opens up numerous prospects for precise positioning and scientific investigations.
Carrier-Phase Measurements
While the E6 signals foreseen for a future Commercial Service are not presently supported by geodetic receivers due to the lack of information on the transmitted codes and possible licensing issues, users can already benefit from the E5a and E5b signals in addition to E1. By way of example, the ionosphere-free and geometry-free linear combination can be formed from carrier-phase measurements on these frequencies. Results of some first tests using this combination for IOV-3 are shown in Figure 2, based on measurements made at four MGEX stations: CUT0 (Perth, Australia), GMSD (Tanegashima, Japan), KZN2 (Kazan, Russia), and SIN1 (Singapore).
The results provide an indication of carrier-phase noise and multipath effects but are free of long-term variations that have earlier been found in GPS L1/L2/L5 signal combinations.
It is anticipated that similar measurement quality will be obtained with the E1 and E5 signals of IOV-4, which were activated on December 12 and 13.
This level of performance highlights the potential benefit of Galileo signals in advanced triple-frequency techniques such as undifferenced ambiguity resolution and ionospheric monitoring.
Figure 2 The difference between the ionosphere-free carrier-phase combinations formed from E1/E5a and E1/E5b signals received at four MGEX stations: CUT0 (Perth, Australia), GMSD (Tanegashima, Japan), KZN2 (Kazan, Russia), and SIN1 (Singapore).
Russian SBAS Luch-5B in Orbital Slot
The second Russian satellite-based augmentation system (SBAS) satellite, Luch-5B, has now been positioned at its designated orbital slot of 16 degrees west longitude. The satellite had been in a drift orbit since its launch on November 2 at 21:04:00 UTC along with the domestic communications satellite Yamal-300K.
NORAD/JSpOC tracking data showed Luch-5B arriving at its geostationary position by about December 13. Figure 3 shows the footprint of the satellite with the elevation-angle contours at 30-degree intervals.
Luch-5B, the second of a set of three geostationary satellites being launched to reactivate Roscosmos’s Luch Multifunctional Space Relay System, is expected to use PRN code 125.
The Luch system will relay communications and telemetry between low-Earth-orbiting spacecraft, such as the the Russian segment of International Space Station, and Russian ground facilities. The system’s satellites also carry transponders for the System for Differential Correction and Monitoring (SDCM), Russia’s SBAS. The transponders will broadcast GNSS corrections on the standard GPS L1 frequency.
Luch-5A, launched in December 2011, resides in an orbital slot at 95 degrees east longitude. It began transmitting corrections on July 12, 2012 using PRN code 140.
Figure 3. Geostationary position of Luch-5B, carrying a transponder for the Russian System for Differential Correction and Monitoring.
EGNOS and Galileo in Emergency Call, Road Tolling
The Intelligent Transport Systems (ITS) World Congress in Vienna this fall drew attention to the multi-constellation advantages provided by Galileo during a session on eCall, the European initiative for safer mobility. “Galileo will provide accuracy and reliability in all the transport markets, but in the case of emergency rapid assistance, the positioning need is even more critical,” said Fiammetta Diani, market development officer at the European GNSS Agency (GSA).
A multiconstellation approach for eCall and similar initiatives will deliver better performance without additional costs. Yaroslav Domaratsky from NIS-GLONASS, the Russian national navigation services provider, confirmed that ERA-GLONASS, the Russian version of eCall, will benefit from multiconstellation. “Solutions including also Galileo are welcome in the Russian initiative.”
Satellite ITS applications in road transport cover much more than in-car navigation. They include road-user charging with satellite-based toll collection systems; in-vehicle dynamic route guidance for drivers; intelligent speed adaptation to control the speed of vehicles externally; traveller information systems; and fleet-tracking systems for better management of freight movements and goods delivery.
Road Tolling
European road-toll operators outlined how they plan to emply the European Geostationary Navigation Overlay Service (EGNOS) and Galileo to provide new tolling solutions.
Luigi Giacalone, managing director of Autostrade Tech, which provides the technology for the French Ecomouv project, said EGNOS will contribute to reliably collect taxes on the heavy trucks using the road charging scheme. “This is a tax, not a toll. It aims to collect a new tax reliably and fairly according to distance travelled, while dissuading fraud,” he said. “Thanks to GNSS multi-constellation, only 10 locations out of the 15,000-kilometer network need support beacons.”
Ecomouv, which Includes anti-jamming and anti-spoofing mechanisms, covers 600,000 French lorries and 200,000 foreign ones, and will run from July 2013 for 11.5 years. Giacalone said its performance target was 99.75 percent accuracy of the entire collection chain, and its trials had already 99.8 percent accuracy.
Miroslav Bobošík from SkyToll, which operates Slovakia’s electronic tolling operations, explained how the system was able to cover not only 570 kilometers of motorways, but also 1,800 kilometers of first class roads in the country. “We needed a flexible system to cover different roads in different circumstances. And also to be fair to drivers, so they pay only for what they use,” said Bobošík. “We cover all services, not just toll collection, but enforcement, and technological maintenance and repair.”
GNSS tolling means flexibility as well as feasibility for SkyToll: since its launch in mid-2010, many changes have been made to the operation of the network, but thanks to the technology, they were easy to make. And they were cheap, he said. “While it is difficult to compare costs with other country, SkyToll has the lowest cost per kilometer to operate,” he said. “GNSS is the best possible solution for electronic tolling system in Slovakia, and GNSS is the most suitable for ITS.”
Changing the Game
Volker Vierroth from T-Systems, the German IT services subsidiary of Deutsche Telekom, explained GNSS’s game-changing role: the availability of a huge variety of additional data linked to actual positions; more computing power, notably mobile and cloud-based; fast and reliable networks available now with broad coverage, most recently with the shift from 3G to 4G; and smartphones, powerful and versatile, surging to the fore.
“GNSS [in the form of EGNOS] has proved to be a reliable technology for large-scale road charging on complex networks,” he said. “Galileo will bring further improvements, and may become the cornerstone of future road applications.”
Compass ICD Rumored
As this magazine goes to press, unconfirmed reports from Shanghai state that the Compass Interface Control Document (ICD) will be released on December 27.
Such rumors surfaced in late 2010 and again in late 2011. An October 2011 GPS World newsletter reported “The long-awaited signal ICD for China’s growing GNSS will appear this month, according to representatives of the system who spoke in a “Compass: Progress, Status, and Future Outlook” workshop in September [2011].
“The ICD has been rumored to be available previously to receiver manufacturers within China, creating some disgruntlement among companies outside the country. A workshop panelist affirmed that GPS/Compass chips and receivers are being actively developed by many Chinese manufacturers and research institutes.”
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