Quasi Zenith and Beidou2 Satellite systems - Essay Example

Quasi Zenith and BeiDou-2 Satellite System 0 Aim and Objectives 1 Quasi-Zenith Satellites System (QZSS). The QZSS is a satellite-based positioning system that enhances GPS services by (1) enhancing the availability of GPS signals, and (2) enhancing the accuracy and reliability of GPS signals. 1 1.2 The BeiDou-2 Satellite System The BeiDou-2 Satellite Navigation System, also known as Compass Navigation Satellite System (CNSS), is a second generation satellite navigation system of China that provides “continuous, real-time passive 3-D geo-spatial positioning and speed measurement.” It has two goals, (1) short-term, which is to provide high-accuracy positioning services for China users and surrounding regions within 120 degrees longitude in the Northern Hemisphere, and; (2) long-term, which is to develop a global satellite network similar to GPS and GLONASS. 2 2.0 Introduction The GPS or Global Positioning System, which first became popular as a means of car navigation have become widespread with their integration in mobile phones. A navigation signal can point to an exact location with the help of at least four satellites but in areas whose geographical terrains are populated with mountains, the satellites signals can be hampered by their presence and the same is true in urban areas where skyscrapers abound. Mountains, skyscrapers and other tall structures, manmade or otherwise, can cause signal errors. The QZSS and the BeiDou-2 Satellite Systems were launched to remedy such situations. In 2003, Japan launched the Quasi-Zenith Satellite System that will provide a regional satellite positioning service in addition to communication and broadcasting services. This is the first satellite positioning of Japan and it is a joint effort of government and private sectors. The Advanced Satellite Business Corporation or ASBC is a private company that is tasked with the development and operation of the communications and broadcasting functions of the satellite system. Four ministries of the Government, on the other hand, are tasked with the development of the satellite positioning system. JAXA or Japan Aerospace Exploration Agency and the CRL or Communications Research Laboratory built and developed the onboard equipment of the satellite based modules, whilst the ground-based modules such as the master control station and monitoring stations are a joint effort of JAXA, CRL and other institutes. 3 On the other hand, China launched its regional satellite navigation system with BeiDuo-1 in early 2000, but this year, the BeiDuo-2 or COMPASS-2, which is planned to be a global satellite navigation system, was launched. It is China’s first entry into the Global Navigation Satellite System or GNSS. As early 2006, China has declared through the State Council Information Office that it is developing “application technologies and products in applying satellite navigation, positioning and timing services.” 4 The Chinese navigation system was likewise rooted in military application operated by its defence mapping agency and before 2006, the system was thought to continue operating only in the regional realm augmenting only the operational GNSS. In 2003, for example, China invested in the Galileo, the EU GNSS with $290 million but as earlier stated, indicated a change of plans in 2006. 5 3.0 Characteristics and Uses 3.1 QZSS The QZSS consists of both ground-based and space-based modules (see Fig. 1). The space module has three satellites and at least one of the three is always located above Japan. It is created to be compatible and interoperable with the GPS. To compliment the said system, the QZSS broadcasts L1, L2 and L5 signals with the last two signals having the same structure and characteristics as GPS’ L2C and L5 signals. L1 is currently investigates as it presents many possibilities whilst an additional signal, Lx, with a global beam is being considered. The time of QZSS, viz. UTC (CRL) corresponds to the GPS’ UTC (USNO) and the QZSS broadcast coefficients of af0, af1 and af2 allows users to obtain GPS-equivalent timing (CCTF 2004 1). As illustrated by Fig. 1, the two components of the QZSS are the space segment with the constellation of satellites orbiting the earth that transmit the QZS signals, which are monitored by the monitoring system on the ground and the ground segment. The master control station (MCS) on the ground collects the results and approximates the orbits and QZS time. The tracking control station (TCS) on the ground keeps watch over the QZS status and once a year, secures the orbital position of the QZS by controlling its orbit. 6 Fig. 1 QZSS System Configuration Since the purpose of the QZSS is to provide signal stability in high elevation areas, such as canyons and intermountain areas, the QZS is maintained at a seamless positioning service with certain orbits and terrestrial trajectories (see Figs 2 and 3). Three of the satellites in the QZSS constellation orbit in an elliptical shape (see Fig. 3) in various orbital planes and their orbit is designed in such a manner as to ensure that at any time, there is always a satellite hovering over the Japanese region. Fig. 2 QZSS Orbit Fig. 3 QZSS Terrestrial Trajectory The first QZSS satellite is the Michibiki, which was launched on September 11, 2010 via the H-IIA Launch Vehicle No. 18 and is presently under an initial functional verification stage, which will go on for three months. The Michibiki goes by the International Code 2010-045A and consists of two box shapes with wing-type solar array paddles, together of which has a total length of 25.3 metres. It is 2.9 m in depth and 3.1 m in width and has a height of 6.2 m (see Fig. 4). Fig. 4 The Michibiki Quasi-Satellite 3.2 BeiDou-2 On the other hand, China had already launched its own satellite system that constitutes the Compass Navigation Satellite System (or CNSS), more popularly known as the BeiDou-2. BeiDou-2 is also positioned to provide geo-spatial positioning like the QZSS. The first quasi-satellite was launched on April 14, 2007 with Compass-M; the second, Compass-G2 on April 15, 2009; Compass-G1 January 17, 2010, and; Compass-G3 last June 2, 2010. All were launched from Xichang via Launch Vehicle CZ-3A and based on the DongFangHong satellite bus at 58.75° E, 80° E, 110.5° E and 140° E positions, respectively. All quasi-satellites are expected to have a life span of eight years. 7 Other specifications for the system are: 27 SVs; 3 orbital planes; 55° inclination; 27840 semi-major axis; 12h 50m period; uses the Beijing 1954 coordinate frame; uses the China UTC time frame; with CDMA coding; and broadcasts at the following frequencies, B1-2:1589.74 (E1), B-1:1561.1 (E2’), B2:1207.14 (E5b) and B3:1268.52 (E6). 8 Fig. 5 Comparative Frequencies of GPS, Galileo & COMPASS 9 Figure 5 shows the comparative frequencies of GPS, Galileo and COMPASS. COMPASS satellites are broadcasting in the four frequency bands shown above: E2; E1; E5b, and; E6. The COMPASS panel integrates the frequency bands of both GPS and Galileo, which appear in gray whilst COMPASS appears in beige. The BeiDuo-2, which is developed from the DHF-3 satellite platform, is planned to ultimately comprise a constellation of satellites that will include about 30 vehicles, with 27 Medium Earth Orbit (MEO) satellites, 9 satellites for each orbit and 4 Geostationary Earth Orbit (GEO) satellites (see Fig.6). The first phase of BeiDuo-2 is the coverage of China and a planned second phase will cover the global sphere. 10 The current design is for the operation of the MEO satellites in six orbital planes for the purpose of a global navigation exposure. Fig. 6 The QZSS Constellation The CNSS or BeiDuo-2 is being developed to provide two kinds of services: free, and; authorised. The free service, with positioning accuracy of within 10 metres, velocity accuracy of within 0.2 m/s and timing accuracy of within 50 nanoseconds, will cater to civilian users whilst the authorised service, which will have higher accuracy rates, will deliver services to the military. 11 4.0 Recent Data and Future Plans 4.1 QZSS The QZSS has further enhanced its system, particularly its standalone aspect and reliability, by “ranging correction data provided through transmission of submeter-class performance signals L1-SAIF and LEX” and by failure monitoring and data notifications of system health. In addition, it provides user support as a means of helping them attain improved GPS signal acquisition. 12 The last phase of the QZSS development is set to start in 2011 when the global positioning service is set to commence. 13 4.2 BeiDuo-2 The NORAD announced recently that the G4 satellite, which is positioned the farthest to the east and was recently launched in October, had already attained geostationary orbit as of November 6. Its exact position is 160° E longitude. 14 The three-step development of the BeiDuo-2 is partially completed with the launching of the three COMPASS test satellites from 2000 to 200. In 2012, the second step of the development will commence by the anticipated coverage of the satellite system of the Asia-Pacific region with respect to “positioning, navigation, timing, and short-message service capabilities.” By 2020, COMPASS shall have launched its third phase with the full launching of all MEO and GEO satellites in space which shall by then total 35. 15 5.0 Other Similar Satellites Satellite navigation originated during the Cold War and was used solely for military applications such as missile guidance. Today, the USA operates the most popular ‘sat nav’ which is fully operational. Other GPPS are Russia’s GLONASS, the EU’s Galileo and recently China’s second generation satellite system, the COMPASS or the BeiDuo-2. Other navigation satellites, like Japan’s QZSS, are also operating but they are only regional navigation satellite systems. Other regional systems include: BeiDuo-1; France’s DORIS, and; India’s IRNSS. The GPS, which is operated by the USA, has been in operation since thirty years ago from its strictly military use that later evolved to include civilian use as well. The system comprises satellites, ground structures and user equipment to establish specific geo-spatial locations for navigational purposes. In the 1990s, a modernization program for the GPS was launched initiated by the cancellation of Selective Availability (SA) in 2000 and followed by scheduled series of enhancements such as new L2 civil signals in 2005, 2008 and in 2013. All of these enhancements are aimed to increase accuracy, integrity, better service and flexibility even for civil users. 16 Russia’s satellite navigation system GLONASS was originally conceived as an answer to GPS. It broadcasts using the FDMA or Frequency Division Multiple Access as opposed to the GPS’ CDMA or Code Division Multiple Access although Russia is preparing for the launching of a CDMA broadcast. FDMA is differentiated from CDMA in that in the latter, each satellite of the system broadcasts its own frequency with identical code as the others whilst in the CDMA all satellites broadcast the same frequencies, which are differentiated by a receiver that identifies one from the other by the satellites’ codes. The collapse of the USSR has greatly affected the operation of the GLONASS, which has suffered budgetary deficiencies with only 6 to 8 satellites deployed, the system’s lowest, in 2001. Russia, however, is currently rehabilitating the system through the launch of GLONASS-M satellites with life span of 7 years. 17 The relatively new Galileo, EU’s satellite navigation system started development in 2001 and is meant for global operation and interoperable with GPS and GLONASS. The first phase of its development included the IOV or in-orbit-verification, where four of the 30 satellites of the Galileo constellation were delivered together with the ground control and monitoring stations. On December 29, 2005, GLOVE-A, the first Galileo satellite was launched followed in 2008 by GLOVE-B. The second phase, which is deployment, is set to occur before 2012 and the last phase is the full commercial operation of the system which is set at the start of 2012. 18 The French regional satellite navigation system, DORIS (acronym for Doppler Orbit Determination and Repositioning Integrated on Satellite), is based on the Doppler Effect principle and operates on an uplink system – that is, the transmitters are located on the ground whilst the receivers are on board the satellite, as opposed to other satellite navigation systems. This implies that data and other observation information are processed on the satellite and are downloaded on the ground stations and disseminated. 19 6.0 Conclusion The QZSS of Japan and China’s BeiDuo-2 are two of the satellite navigation systems that are operating in the world today. Whilst QZSS is a regional navigation satellite that augments and enhances the fully operational GPS and other global satellite navigation systems such as EU’s Galileo and Russia’s GLONASS, COMPASS, on the other hand, is China’s official entry into the global satellite navigation arena dominated by the US, Russia and the EU. QZSS specifically works where GPS has difficulty broadcasting signals locally especially in places that are hampered by geographical obstacles. BeiDuo-2, for its part, is still in its infancy stage and is expected to be fully operational as a global player by 2020. From its solely military application, the GNSS has become an important facet of civilian lives, providing convenience as well as functionality to its users. A drive for a more accurate and reliable navigation satellite system has become an important goal for both global and regional satellite navigations systems. The GPS, the only fully functional GNSS, the GLONASS, and the Galileo, which are presently operating global satellite navigation systems, are presently servicing users of satellite navigation. Satellite navigation systems, however, still need a lot of improvement as far as reliability and accuracy are concerned. In addition, this technology despite its global scope is still unavailable in some areas of the world. Regional satellite navigation systems, like BeiDuo-1 and the QZSS, are augmenting the capabilities of the aforesaid global systems. The QZSS of Japan, for instance, has made the GPS system more useful to users in Japan and nearby areas where the four-satellite system signal scheme is hampered by geographical impediments. These two systems help bring satellite navigation into a cutting-edge technology and fill the gaps where the GPS, GLONASS and the Galileo are weak. References: Barbosa. R. (2009). China Open 2009 Schedule with BeiDuo-2 (Compass-G2) Launch, NASA Spaceflight.com. http://www.nasaspaceflight.com/2009/04/china-open-2009-schedule-with-beidou-2-compass-g2-launch/. Canspace (2010). BeiDuo/Compass G4 Achieves Geostionary Orbit. http://www.gpsworld.com/gnss-system/compass/news/beidoucompass-g4-achieves-geostationary-orbit-10719. CASA (2006) Global Navigation Satellite Systems Overview. Civil Aviation Safety Authority. http://www.casa.gov.au/wcmswr/_assets/main/pilots/download/gnssbooklet.pdf. CCTF (2004). Quasi-Zenith Satellite System -A New Satellite Positioning System of Japan. http://www.bipm.org/cc/CCTF/Allowed/16/cctf04-11.pdf. Chen, H-C & Huang, Y-S & Chiang, K-W & Yang, M. & Rau, R. (2009). The Performance Comparison Between GPS And Beidou-2/Compass: A Perspective From Asia. Journal of the Chinese Institute of Engineers, Vol. 32, No. 5. http://www.geomatics.ncku.edu.tw/staff-1.php?download=972. China Successfully launched its Fourth BeiDuo Navigation Satellite. BeiDuo.gov.com. http://www.beidou.gov.cn/2010/06/03/20100603274c47b9bf694731a5dba8476fea35b6.html. Compass (BeiDuo-2) Satellite navigation System. sinodefence. Com. 23 June 2010. http://www.sinodefence.com/space/spacecraft/BeiDou2.asp DORIS, International Earth Rotation and Reference Systems Service. 2010, http://www.iers.org/nn_10404/IERS/EN/Science/Techniques/doris.html. Gibbons, G. (2008). China GNSS: Compass in the Rear View Mirror. GNSS World. http://www.insidegnss.com/auto/janfeb08-china.pdf. Grelier, T. & Dantepal, J. & Delatour, A. & Ghion, A. & Rhies, A (2007). Initial Observations and Analysis of Compass MEO Satellite Signals http://www.insidegnss.com/auto/IG0607_CompassFinal.pdf. Hiroyuki, N. & Satoshi, K. & Motohisa, K. & Hiroshi, S. & Tatsuji, M. & Takeshi, F. (2010). Development of the Quasi-Zenith Satellite System and High Accuracy Positioning Experiment System Flight Model, New Technical Journal, Vol. 5. http://www.nec.co.jp/techrep/en/journal/g10/n03/100317.pdf. Quasi-Zenith Satellites System. JAXA Web. http://qzss.jaxa.jp/index_e.html. Service of QZSS. JAXA Web. http://qzss.jaxa.jp/01_e.html. Read More