working papers Envisioning a Future GNSS System of Systems Günter W. Hein, Jose Angel Avila Rodriguez, Stefan Wallner, Part 1 Bernd Eissfeller, Thomas Pany, and Philipp Hartl Russian Federal Space Agency/LockheedMartin/ESA Space RussianFederal
Seven years ago, the U.S. Global Positioning System was the only real GNSS around. The GLONASS constellation had dwindled to seven satellites. Final approval and funding of Europe’s Galileo program was yet to be achieved. Since then, Russia has gone a long way toward rebuilding and modernizing GLONASS. Galileo has put its first experimental GNSS satellite, GIOVE-A, into space. And China has announced plans to build a full-fledged NG SS of its own — Compass — building on three Beidou satellites that it has launched in recent years. With those activities under way, it’s not too early to begin thinking about what a multisystem GNSS might look like and mean for users, receiver manufacturers, and service providers.
e have just made the tran- era with the Global Positioning System Is it not time, therefore, to pause and sition into the new year of (GPS) as the result of efforts that began think for a moment about where we want 2007. Most of us probably in the late 1960s. The Russians followed GNSS to move? Is it not already time to Walready have our eyes focused soon afterwards (or did they do it in really “think global” and to coordinate onto the next 12 months along with parallel?) with GLONASS. Both of these and harmonize all the existing and pro- some wishes and perspectives that we systems are now undergoing extensive jected navigation satellite systems? If so, would like to have fulfilled in the com- modernization. Moreover, the European then the question naturally arises: what ing 365 days. Galileo system is joining the GNSS club, should the “Global Navigation Satellite In the same spirit, over the next two and China is now planning its own ver- System of Systems” look like? issues of Inside GNSS this column will sion called Compass. GPS | GALILEO | GLONASSThis column will try to shed some take a look into the near future and — In the meantime lots of augmenta- light on the fascinating new world of what is even more exciting — into the tion and regional systems have been GNSS in which we will live around the further future of satellite navigation. But developed or are currently under con- year 2020 if all the currently modern- what that future will look like depends sideration. From military to civil sig- izing and planned new systems come to an enormous extent on what the past nals, from medium Earth orbit (MEO) into reality. It will be a complex world was; so, we should have first a look back to geostationary Earth orbit (GEO) and where the word “coordination” will be into the roots of GNSS. inclined geosynchronous orbits (IGSO), the key and from which, if we do it right, Long ago the Americans entered the the palette of systems and offered ser- users will be the ones that will profit the global navigation satellite system (GNSS) vices is as wide as imagination allows. most. After all, why should a GNSS user
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really care about whether one of his or U.S. Department of her signals comes from GPS, the other Defense. Although from Galileo, the third from GLONASS originally devel- and the fourth from Compass as long as oped for military the GNSS receiver works well? applications (we can also find some state- Scenes from the Present ments that GPS was Today only GPS is fully operational. intended to be a civil Nevertheless, Russia hopes to return as well as military GLONASS to full operation capability system from the very (FOC) with a completed constellation by beginning), the U.S. 2009, and Galileo’s FOC is now expected government made in 2012. Compass is already knocking GPS available to FIGURE 1 Launch history of GPS on the door, and in spite of the fact that civilians, transform- China has still a long way to go and ing it into the dual-use system it is today. of both civil and military users. To that lengthy negotiations will be needed, a Accordingly, certain signal capabilities objective the GPS Modernization plan scenario of four global coverage satel- are reserved for U.S. and allied military can be timely divided in the following lite systems seems to be very likely in a applications while the civilian signals are three blocks. future not so far away from today. open and free for worldwide use. Block IIR-M (replenishment-modern- From the experience with Gali- The GPS baseline constellation con- ized) satellites. This generation of space- leo, we know how important the roles sists of 24 satellites (21 + 3 active spares) craft introduced a second civil signal of interoperability and compatibility in six circular MEO planes at a nominal with improved services (L2C) reaching with GPS were from the very begin- average orbit semi-major axis of 26559.7 the 24-satellite FOC around 2012. Addi- ning. Unfortunately, major differ- kilometers with an inclination of the tionally, for military purposes the mod- ences between those two systems and orbital planes of 55 degrees with refer- ernized M-code — BOC(10,5) — will GLONASS still exist. ence to the equatorial plane. be placed on L1 and L2. Block IIR-M However, also on the GPS/GLONASS side, work on attaining real interoper- Is it not already time to really “think global” and ability is continuing. Just recently dur- to coordinate and harmonize all the existing and ing the GPS/GLONASS Working Group projected navigation satellite systems? 1 meeting in December 2006, both sides emphasized the benefit to the user com- munity that a common approach con- The first developmental satellites satellites also have antijam flex power cerning FDMA/CDMA would bring in were launched beginning in 1978, and capabilities for military needs. Figure terms of interoperability. The Russian the first operational satellites went into 4 provides more details on the signal side announced that they will come to orbit in 1989. The system reached initial structure. The first operational IIR-M a decision on adding or converting to a operational capability (IOC) in 1993 and satellite was launched on December 16, CDMA format by the end of 2007. The achieved FOC in 1995. The present GPS 2005. formal U.S.-Russia statement can be view constellation exceeds the baseline con- Block IIF (follow-on) satellites. The at < http://www.glonass-ianc.rsa.ru/i/ stellation with 30 orbiting satellites after third civil signal (L5) – BPSK(10) glonass/joint_statement_eng.pdf>. the last successful launch on November — begins with the IIF satellites. The The direction in which COMPASS 17, 2006. The history of all GPS launches FOC with 24 satellites is expected to be will go remains a large unknown. In can be seen in Figure 1. reached around 2015 fact, if the need of standardization was Block III. Still in the design phase, GPS always there, it seems that the concept GPS Modernization Block III includes prospective improve- is gaining in interest the more systems Before December 2005GPS the | basicGALILEO GPS | GLONASSments to both the ground and space come into play. capability consisted of the Standard segments. These will most likely include But before dreaming with our ideal Positioning Service (SPS) provided by increased anti-jam power, increased GNSS, let us first look more closely into the C/A-code on the L1 frequency and security, increased accuracy, navigation what the current reality is and what the the Precise Positioning Service (PPS) surety, backward compatibility, assured plans for new GNSS systems are. provided by the P(Y)-code on L1 and L2. availability, system survivability, and Although those services are of relatively controlled integrity — among other Global Positioning System good quality, the United States envis- improvements. The fourth civil signal GPS is made up of a network of initially aged modernizing the signals in order (L1C) will probably be introduced with 24 active satellites placed into orbit by the to improve the quality and protection this block.
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100
80 27 60 24 21 40 18 SV Number SV 15 Active Satellite 20 Decommisioned Satellite 12 9 0 6 3 Jan-92 Jan-94 Jan-82 Jan-84 Jan-02 Jan-04 Jan-96 Jan-86 Jan-90 Jan-98 Jan-06 Jan-88 Jan-00 0 Date 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
FIGURE 2 Launch history of GLONASS FIGURE 3 Plans to re-establish full operation capability of GLONASS
In the 2004 GNSS cooperation agree- As can be seen in Figure 2, the cur- January 18, 2007, and in spite of the ment between the United States and the rent GLONASS status is far away from additional three recently launched sat- European Union (EU), the two parties its nominal numbers and as of Janu- ellites that should become operational, agreed to have BOC(1,1) as the baseline ary 18, 2007 only 9 active GLONASS the fulfilment of the GLONASS pro- waveform on both the GPS L1C and satellites were transmitting from gram objectives is still difficult. Galileo E1 Open Service (OS) signals. space. Seven additional space vehicles GLONASS Service Modernization. As Nevertheless, a group of experts from are on orbit but have been temporar- with GPS, GLONASS is on the way to Working Group A set up under the 2004 ily switched off and are currently not modernization of the system. Apart agreement has proposed to optimize this broadcasting any signals. On December from the signals in the L1 band, the signal using MBOC(6,1,1/11) instead, 25, Russia launched three additional Russian system has already established as previously discussed in this column GLONASS-M (modernized) satel- a second civil signal at L2 upon launch in the May 2006 issue of Inside GNSS. lites from Baikonur Cosmodrome in of the first GLONASS-M satellite in Although an earlier schedule is under Kazakhstan that are currently in the 2003. A third civil signal at L3 band consideration, the first Block III satellite commissioning phase. is expected to start in 2008 aboard launch will probably occur somewhere The initial GLONASS Program Bud- GLONASS-K satellites. For more details around 2013 with FOC being reached get of 2001 was designed for achieving on the GLONASS signal structure refer by about 2020. FOC in 2011. However the GLONASS to Figure 4. We should note that the program appears to be speeding up on definition of the GLONASS L3 signals GLONASS its course in accordance with a presi- is still subject to changes. The GLObal NAvigation Satellite Sys- dential directive issued January 18, tem (GLONASS) is the Russian navi- 2006. Europe’s Galileo System gation satellite system and, like GPS, it As announced in September 2006 Galileo is the European global navigation defines itself as a dual-use system. Its at the 46th Civil GPS Service Interface satellite system, designed to provide a nominal constellation is composed of Committee (CGSIC) Meeting in Fort highly accurate, guaranteed global posi- 24 satellites in three orbital planes with Worth, Texas, current moderniza- tioning service under civilian control. ascending nodes 120 degrees apart. tion plans of GLONASS envision the According to the Galileo SIS ICD, the Eight satellites are equally spaced in achievement of minimal operational system will be interoperable with GPS each plane with argument of latitude capability (18 satellites) again by the and, at least to some extent — excluding displacement of 45 degrees. The orbital end of 2007 and FOC by end of 2009 the real-time high-precision services of planes have 15 degrees argument of (See Figure 3). the systems — with GLONASS, the two latitude displacement relative to each For realizing thisGPS ambitious | GALILEO sched- | GLONASSother global satellite navigation systems other. ule for constellation deployment, an available today. The satellites operate in circular extra budget for the GLONASS pro- The fully deployed Galileo system 19,100-kilometer orbits at an inclina- gram has been set up for the years 2007 will consist of 30 satellites (27 opera- tion of 64.8 degrees, and each satellite to 2011. In addition to reaching FOC, tional + 3 non-active spares), posi- completes the orbit in approximately by 2010 Russia wants to achieve a per- tioned in three circular MEO planes at 11 hours 15 minutes. The spacing of formance of GLONASS comparable to a nominal average orbit semi-major axis the satellites allows for continuous and that of GPS and Galileo. of 29,601.297 kilometers, and at an incli- global coverage of the terrestrial surface Nevertheless, with only nine satel- nation of the orbital planes of 56 degrees and the near-earth space. lites being in complete operation as of with reference to the equatorial plane.
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FIGURE 4 GPS, GLONASS, Galileo, and planned Compass signals.
Once FOC is achieved, the Galileo navi- late in 2007. The Galileo In-Orbit Vali- China’s Compass gation signals will provide good coverage dation (IOV) phase is planned to start at Compass is the GNSS system planned even at latitudes up to 75 degrees north the end of 2008 with four satellites and by China. As with GPS, GLONASS, and and 75 degrees south. Galileo provides achieve FOC in 2012. Galileo, the system will provide two enhanced distress localization and call Galileo modernization. Galileo is not navigation services: an open service for features for the provision of a search and yet in operation but already the so-called (commercial) customers and an “autho- rescue (SAR) service interoperable with evolution program for the second gen- rized” positioning, velocity, and timing the COSPAS-SARSAT system. eration is planned to start in the middle communications service. Compass con- The European GNSS approach began of 2007. Galileo II could arrive some- sists of a constellation of 30 non-geosta- with the European Geostationary Navi- where around 2020 andGPS is | expected GALILEO to | GLONASStionary satellites and five GEO satellites gation Overlay Service (EGNOS), which introduce new modernization elements with positions at 58.75° E, 80° E, 110.5° provides civil complements to GPS and analogous to the steps made by its coun- E, 140° E, and 160° E. GLONASS since mid-2005 in its initial terparts GPS and GLONASS. Intersat- Each satellite transmits the same four operation. From the very beginning, ellite links could be introduced at that carrier frequencies for navigational sig- EGNOS was meant to be the bridge time and aeronautical certification could nals. These navigational signals are mod- to Europe’s own full-fledged GNSS. be of relevance. In fact, under current ulated with a predetermined bit stream, Galileo’s first developmental satellite, plans only the first phase of Galileo containing coded ephemeris data and GIOVE-A, was launched in December – EGNOS — will be certified for aero- time, and having a sufficient bandwidth 2005, and GIOVE-B should be launched nautical users. to produce the necessary navigation
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Initially, QZSS was conceived as a government–private sector program aiming for new satellite business, in which the private sector would be responsible for mobile communica- tions and mobile broadcasting while the government would be responsible for the navigation part. Due to the lack of Japanese communication industry participation, however, QZSS satellites will not carry any communication pay- loads but rather will concentrate on the navigation element funded by the gov- FIGURE 5 Ground Tracks of QZSS and IRNSS. ernment alone. QZSS and GPS will be fully interop- precision without recourse to two-way — GPS, GLONASS, Galileo and Com- erable and the first satellite launch date transmission or Doppler integration. pass — are shown in Table 1. is planned for the year 2008. Figure 5 China sent three Compass navigation Finally, Figure 4 shows the sig- shows in detail the ground track of the test satellites into orbit between 2000 nal structure of all the existing and three QZSS satellites. and 2003. The launch of the two “Bei- planned GNSSes. Negotiations among Indian Radionavigation Satellite System dou” (Compass first version) satellites, various countries are still needed to (IRNSS). The IRNSS is an independent scheduled for early in 2007, is expected ensure compatibility (and to fulfil ITU seven-satellite constellation that will to cover China and parts of neighboring regulations) and interoperability of the be built and operated by India. IRNSS countries by 2008, before being expand- signals. will seek to maintain compatibility ed into a global system. with other GNSS and augmentation The will of China to develop its Regional Satnav Systems systems of the region and is planned own global navigation system is clearly In addition to the global satellite-based to provide services for critical national reflected in the policy document released navigation systems already under way, applications (perhaps including mili- by the State Council Information Office two regional satnav systems are also tary uses). on October 12, 2006, which stated that being developed by Japan and India. Of the seven satellites that comprise China will ”independently develop Quasi-Zenith Satellite System (QZSS). the constellation, three are geostation- application technologies and products in QZSS is the Japanese regional system ary (known as GAGAN, see the follow- applying satellite navigation, positioning that will serve as enhancement for GPS ing section of this column) and the other and timing services“ as reported in the in Japan. The constellation consists of four, geosynchronous. The geostation- November 13, 2006, issue of China Daily. three satellites inclined in elliptic orbits ary satellites have designated positions Compass could begin operation in 2012 with different orbital planes in order to at 34° E, 83° E and 132° E, while the geo- if the political statements are brought pass over the same ground track. QZSS synchronous have equatorial crossings into reality. was designed so as to guarantee that at at 55° E (two satellites) and 111° E (two As a summary, the overall constella- any time at least one of its three satellites satellites), with an inclination of 29° and tion parameters of the four global GNSS is close to the zenith over Japan. relative phasing of 56°.
Parameter Galileo GPS GLONASS Compass Parameter QZSS IRNSS Walker MEO MEO(24/6) MEO(24/3) GEO(5), Constellation GSO(3) GEO(3)+GSO(4) Constellation (27/3/1) plus 3 incl 3 active spares MEO(27),IGSO(3) GEO non-active spares - 34°, 83°, 132° E GPS | GALILEO | GLONASSLongitudes 58.75°, 80°, 110.5°, GEO Longitudes - - - GSO Equatorial 140° and 160° E - 55°(2), 112°(2) Crossing GSO Equatorial Crossing - - - 118° Eccentricity 0.099 0 Eccentricity 0 0 0 0 Inclination 45° 29° GSO Inclination - - - 55° Semi-major 42164.0 km 42164.0 km MEO Inclination 56° 55° 64.8° 55° axis
Semi-major axis 29601.297 km 26559.7 km 25440 km 27840 km TABLE 2. Space Constellation Parameters of QZSS TABLE 1. Space Constellation Parameters and IRNSS
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FIGURE 6 QZSS and IRNSS planned signals. Note that IRNSS is also expected to transmit augmentation signals on L1
Parameter EGNOS WAAS MSAS GAGAN WAAS. The Wide GAGAN. The GPS and GEO Aug- Constellation GEO(3) GEO(4) GEO(2) GEO(3) Area Augmentation mented Navigation system (GAGAN) is System (WAAS) India’s SBAS for the south Asian region. 53° W 15.5° W 34° E 98° W 140° E augments GPS over Established by the Indian Space and GEO Longitudes 64.0° E 83° E 120° W 145° E the North American Research Organization (ISRO) and the 21.5° E 132° E 178° W territory to provide Airports Authority of India to aid civil Semi-major axis 42164.0 km 42164.0 km 42164.0 km 42164.0 km the additional accu- aviation in the country, GAGAN will racy, integrity, and eventually expand into IRNSS. TABLE 3. GNSS Augmentation Systems Constellation Parameters availability needed The first geo-stationary navigation to enable users to payload in C-band and L1 and L5 fre- The first IRNSS payload is expected rely on GPS for safety-critical applica- quencies (L-band) will be carried on an to be put into orbit in 2007 and the sec- tions, particularly in the field of avia- Indian geostationary satellite, GSAT-4, ond, in 2008, reaching FOC in 2009. The tion. Before WAAS, the U.S. National to be placed at 82°E. GSAT-4 is sched- overall constellation parameters of the Airspace System (NAS) did not have uled for launch by mid-2007. Two more two planned regional navigation satellite the capability of providing horizontal satellites, GSAT8 and GSAT9 will follow systems are shown in Table 2. and vertical navigation for aviation pre- it to complete the augmentation system, Figure 5 shows the ground tracks cision approach operations for all users with FOC expected by 2009. of the two regional navigation satellite at all locations. WAAS is constituted by NIGCOMSAT. With its Nigerian Com- systems discussed here. Figure 6 presents four geostationary satellites as shown in munications Satellite (NIGCOM- the signal plan of QZSS and IRNSS. Table 3. SAT-1), Nigeria is the first African coun- MSAS. The Japanese equivalent to try planning to enter the field of GNSS GNSS SBAS Augmentations WAAS and EGNOS incorporates the by transmitting two L-band signals in The European Geostationary Navi- Multifunctional Transport Satellite L1 and L5. gation Overlay Service (EGNOS) is a (MTSAT) into MSAS (MTSAT Space- The manufacturing of the satellite satellite-based augmentation system based Augmentation System). In addi- was assigned to China’s state-owned (SBAS) under development by the Euro- tion to transmitting correction and space hardware manufacturer and is pean Space Agency (ESA), the European integrity data for GPS, the MTSAT sat- thus China’s first satellite export sale. Commission (EC), and EUROCON- ellites are used for meteorological obser- The satellite is to be launched by a Long TROL. EGNOS would supplement GPS vations and communicationGPS | services GALILEO fol- | GLONASSMarch 3B carrier rocket at the Xichang (and perhaps GLONASS in the future) lowing a multi-mission concept. After Satellite Launch Center in mid-2007. by reporting on the reliability and accu- failing with the initial launch of the first Two ground stations are going to be racy of the signals. EGNOS consists of MTSAT satellite in 1999 the substitute built, one each in Nigeria and in China. three geostationary satellites (AOR-E, satellite MTSAT-1R was set into orbit in NIGCOMSAT-1 will be placed in a geo- IOR-W and ARTEMIS) and a network February 2005. An additional satellite stationary orbit at 42°E, although it is of ground stations. The system started — MTSAT-2 — was put into mission a less than optimal location for cover- its initial operations in July 2005, and is in February 2006. (For further details, ing Nigeria. The overall constellation intended to be certified for use in safety see news article on page 16 of the March parameters of all GNSS augmentation of life applications in 2008. 2006 issue of Inside GNSS.) systems are shown in Table 3.
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Figure 7 shows the coverage region of the satellite-based augmentation sys- tems visible to users at elevations higher than 10 degrees. The Future of GNSS This wide range of activities on exist- ing and new GNS- Ses, regional satel- lite systems, and augmentations raise a number of ques- tions about what the FIGURE 7 Ground tracks of EGNOS, WAAS, MSAS and GAGAN. future directions of a GNSS system of systems should be. ing control centers? This would facilitate problems associated with having mili- Should a future GNSS serve civil, mili- the development of different concepts for tary and civil signals together. tary, or dual-use purposes? GPS and civil and military sectors without having In fact, Galileo had to change its GLONASS were originally intended to depend on what the other does. In the baseline for the public regulated ser- for military applications. In contrast, end, splitting the system into civil and vice (PRS) from the original planned
Galileo stated from the very beginning military from the top would make life BOC(14,2) design to the BOCcos(15,2.5) its intention of being (primarily) a civil much easier. design now in place to meet the NSCC system. The intentions for Compass are Having independent military and requirements. Equally, the Galileo OS unclear in this regard. civil services would open the additional signal had to change from BOC(2,2) to This is the way things are today. possibility of creating true interoper- the current BOC(1,1) baseline Going forward, what should be the ability in GNSS system control. Indeed, What could or should the “satellite navi- approach? And more difficult yet, who the open (civil) services of the various gation system of systems” look like in the should pay for it or in other words how GNSSes could be jointly optimized and year 2020? Let us dare to imagine how should it be financed? Government spon- mission control independently coordi- the different segments of a hypotheti- sorship, as with GPS and GLONASS? Private-public partnership as sought The current scheme of existing dual-use GNSS for Galileo? systems makes interoperability and compatibility Civil and military applications work much more difficult to accomplish. with different standards. Therefore, splitting the civil and military payloads nated to minimize failures and ensure cal GNSS could appear in the future. To could have interesting benefits. Civil and back-up. that objective we will analyze the three military signals now come from one and The current scheme of existing dual- fundamental parts of any satellite navi- the same signal generator; so, inevitably use GNSS systems makes interoperabil- gation system: space, control, and user the greater constraints of the military ity and compatibility much more diffi- segments. requirements have to be applied also to cult to accomplish. Although until now Space Segment. An optimal GNSS civil signal components for which they solutions have been found as we have constellation would be one in which each might not be needed or optimal. recently seen with theGPS agreement | GALILEO on | GLONASSindividual system is optimized in light of Separating military signals from GPS and Galileo regarding L1 signals, the design and operations of all the other the civil signals in the frequency and if more systems begin operating in this systems. This is indeed not the case today signal plan would seem to offer benefits band, as Compass proposes to do, the where the GPS, GLONASS and Galileo to everyone. But wouldn’t a logical con- complexity of the picture might grow to constellations do not take into account sequence of this approach also suggest levels where an optimal solution can no the others. Nevertheless, a real global separating military and civil elements in longer be found. constellation of all the systems together the satellite itself. Further, might not this National Security Compatibility should be the objective because only principle also extend to control of those Compliance (NSCC) is part of the 2004 then could an optimal coverage through elements by separating the correspond- US/EU agreement and deals with the a system of systems be more efficiently
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assured. This means that the number of Of course, some applications exist in nitely not be predicted, we can summa- orbital planes, inclination, and altitude which backward compatibility remains rize key technology trends and discuss should be ideally harmonized, although vitally important — aviation, for exam- their likely effects on future receiver unique features of a sub-constellation (of ple. In such sectors, substantial amounts development. each GNSS alone) could be retained to of money have to be invested every time We focus here on the civil market serve special purposes. a receiver is qualified for aeronautical that, in contrast to military or aviation If a global position dilution of pre- use and certification. Such sectors, applications, has rather short receiver cision (PDOP, a factor of positioning therefore, have a great interest in assur- life-cycles of roughly three years. accuracy derived from satellite geom- ing that, no matter what the future sig- • Size: Current GNSS receiver chips etry) could be assured by any combina- nals or what new technologies are devel- are already quite small; so, further tion of GNSS spacecraft (considering oped, the old receivers will still be able substantial reductions in size are the probability of satellite failures), we to function in the future. difficult to envision. However, GNSS would achieve an ideal global GNSS con- Overall, however, the demand for functionality might by integrated as stellation from the user point of view no backward compatibility will ultimately intellectual property rights (IPRs) matter to which GNSS system a specific depend mostly on the cost of GNSS into systems on a chip. Most likely, satellite belongs. This situation would receivers in a couple of years and the within 20 years most standard GNSS applications will be based on soft- Overall, however, the demand for backward compatibility ware (defined) receiver technology, will ultimately depend mostly on the cost of GNSS taking up no physical space at all. receivers in a couple of years and the extent to which • Power: Signal processing and posi- tioning is generally a well defined the software (defined) radio concept is realized. task requiring a fixed number of computations. The required electri- also simplify many system operations, extent to which the software (defined) cal power to perform these opera- because the need for moving satellites radio concept is realized. tions has been markedly decreasing to optimize a particular constellation Control Segment. As discussed earli- in recent years and will continue to would be eliminated (or much reduced) er, a great advantage of separating civil decrease. and replacement of satellites could be and military GNSS operations would be • Functionality: Current GPS receiv- globally coordinated. that civil users would gain (more) access ers are considered to be quite opti- Backward compatibility — do we really to the control segment, which was mized, but the development of true need it? As we know, until now backward until now reserved to the military sec- GNSS receivers making use of the compatibility has been one of the major tor — at least with respect to GPS and upcoming multitude of signals and drivers in the development of GNSS. GLONASS. Another very important systems is just starting. But technology advances in ever-faster consideration is that in a real GNSS sys- • External data: Assistance data is steps. For example, today customers’ tem of systems, the monitoring stations essential for GNSS positioning, and replacement (“churn”) of mobile phones should be spread all over the world. we expect that the use of this data is increasingly common after only a few GPS and Galileo (will) have a global will definitely increase. Internet- months or two years at the maximum. uniform distribution, but as we know based services such as ESA’s SISNET And the same is true for civil GPS this is not the case for GLONASS, which or the NASA Jet Propulsion Labora- receivers, which for the tax authorities only has stations in the Russian terri- tory (JPL) real-time precise ephem- nowadays have a usable life expectancy tory. The case of Compass is still unclear eris along with commercial counter- of only three years. as no statement has been seen as to parts may also enable mass market Having in mind that a GNSS receiver whether Compass will include a global applications to achieve sub-meter might be implemented in every mobile monitoring network. accuracy. Furthermore, mobile phone, backward compatibility in the User Segment. What will the GNSS phone network providers may equip mass market would no longer be such receiver look like in 20GPS years? | GALILEO Will it be | GLONASStheir base stations with GNSS time a great issue as these gadgets will be a piece of software running on a gener- and positioning sensors, supporting replaced anyway after a very short peri- ic computer implant under our skins centimeter to millimeter positioning od in use. Moreover, going to digital sig- powered by bio-energy, broadcasting accuracy for mobile units by ranging nal generators and receivers enable flex- people’s positions permanently to the to the base stations. ibility and easy changes from one to the government or somebody else? Or will • Other sensors: Today GPS is already other minute. However, communication it be (only) the result of a consequent frequently combined with other standards like CDMA or GSM as well as improvement of already known technol- sensors such as inertial or dead the GPS ICD remained constant during ogies? Whereas cultural/technological reckoning systems, where required the last decades. revolutions of the first kind can defi- to improve positioning robustness
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and continuity. Since this is often [8] http://gps.losangeles.af.mil/engineer- Bernd Eissfeller is a full the only way to obtain position fixes ing/icwg/Docs/EC%20and%20US%20Joint professor of navigation in poor GNSS signal environments, %20Statement%20on%20GALILEO%20and and vice-director of the Institute of Geodesy and we expect that this trend will gain %20GPS%20Signal%20Optimization%20- %20%2024%20Mar%2006.pdf Navigation at the even more in importance. Future [9] http://gps.losangeles.af.mil/engineering/ University FAF Munich. He receiver platforms (e.g., software icwg/Docs/WGA%20Signed%20Recommendation is responsible for receivers) will definitely alleviate %20on%20MBOC%20-%2023%20Mar%2006.pdf teaching and research in the often cumbersome integration [10] http://pnt.gov//public/docs/2004-US-EC- navigation and signal processing. Till the end of 1993 he worked in industry as a project manager process currently encountered. Inte- agreement.pdf on the development of GPS/INS navigation grating “INS on a chip” and into the [11] http://www.space.com/spacenews/ systems. He received the Habilitation (venia archive05/Nigeria_0221.html tracking loops of a GNSS receivers legendi) in Navigation and Physical Geodesy in [12] IS-GPS-200: NAVSTAR GPS Space Segment will result in a more robust tracking 1996 and from 1994-2000 he was head of the capability of future receivers. / Navigation User Interfaces GNSS Laboratory of the Institute of Geodesy and [13] Revnivykh, S. (2006), “GLONASS Status Navigation. Update”, Proceedings of 46th CGSIC Meeting, 25 Conclusion Thomas Pany has a Ph.D. in September 2006, Fort Worth, Texas, USA Our discussion to this point has focused geodesy from the Graz on the current and relatively near-future Authors University of Technology prospects for moving toward a GNSS and a M.S. in physics from “Working Papers” explore the Karl-Franzens system of systems in light of current pro- the technical and scien- gram plans and evolutionary technology University of Graz. tific themes that underpin Currently he is working at trends. In Part 2, we will examine some GNSS programs and appli- the Institute of Geodesy of the possibilities further “outside the cations. This regular col- and Navigation at the University of Federal box,” including the potential for revo- umn is coordinated by Armed Forces Munich. His major areas of interest lutionary leaps in technology and new Prof. Dr.-Ing. Günter include GPS/Galileo software receiver design, approaches to operational advances and Hein. Galileo signal structure and GPS science. cooperation. Prof. Hein is a member of the European Com- Stefan Wallner studied at mission’s Galileo Signal Task Force and organizer the Technical University of Manufacturers of the annual Munich Satellite Navigation Sum- Munich and graduated Figures 5 and 7 were generated using the mit. He has been a full professor and director of with a diploma in techno- Satellite Tool Kit (STK) from Analytical the Institute of Geodesy and Navigation at the mathematics. He is now University of the Federal Armed Forces Munich research associate at the Graphics, Inc. (AGI), Exton, Pennsylva- (University FAF Munich) since 1983. In 2002, he Institute of Geodesy and nia, USA. received the United States Institute of Naviga- Navigation at the Additional Resources tion Johannes Kepler Award for sustained and University FAF Munich. Wallner’s main topics of significant contributions to the development of interests are the spreading codes and the signal [1] Avila-Rodriguez, J.A. et al. (2005), “Revised satellite navigation. Hein received his Dipl.-Ing structure of Galileo and also interference and Combined GALILEO/GPS Frequency and Signal interoperability issues involving GNSS systems. Performance Analysis”, Proceedings of ION GNSS and Dr.-Ing. degrees in geodesy from the Univer- Phil Hartl has an M.S. in 2005 – 13-16 September 2005, Long Beach, Cali- sity of Darmstadt, Germany. Contact Prof. Hein at electrical engineering and fornia, USA.
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