بـِيْدو، نظام سواتل ملاحية
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شعار نظام بـِيْدو
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| بلد المنشأ | الصين |
|---|---|
| المشغل | CNSA |
| النوع | عسكري وتجاري |
| الوضع | شغال (إقليمياً) |
| التغطية | عالمي |
| الدقة | 10 م (للعامة) 0.1 م (مشفر) |
| حجم الكوكبة | |
| إجمالي السواتل | 35 |
| السواتل في المدار | 21 |
| أول إطلاق | 30 أكتوبر 2000 |
| آخر إطلاق | 12 يونيو2016 |
| إجمالي الإطلاقات | 27 |
| السمات المدارية | |
| النظام | GEO, IGSO, MEO |
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معايير
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بـِيْدو، نظام سواتل ملاحية (BDS, الصينية المبسطة: 北斗卫星导航系统; الصينية التقليدية: 北斗衛星導航系統; پنين: Běidǒu wèixīng dǎoháng xìtǒng؛ بالإنگليزية: BeiDou Navigation Satellite System) هونظام ملاحة ساتلية صيني. يتألف من كوكبتين ساتليتين منفصلتين. نظام بـِيْدوالأول، يعهد رسمياً بنظام بـِيْدوالتجريبي للملاحة الساتلية وبـِيْدو-1، يتألف من ثلاث سواتل والتي وفرت منذ عام 2000 تغطية وخدمات ملاحة محدودة، بصفة أساسية للمستخدمين في الصين والمناطق المجاورة. خرج بـِيْدو-1 من الخدمة في أواخر عام 2012.
نظام الجيل الثاني، يسمى رسمياً "نظام الملاحة الساتلية بـِيْدو"، ويعهد أيضاً باسم كومپاس أوبـِيْدو-2، ولج الخدمة في الصين في ديسمبر 2011 بكوكبة تتألف جزئياً منعشرة سواتل داخل المدار. منذ ديسمبر 2012، وفر بـِيْدو-2 خدمات للمستهلجين في منطقة آسيا-الهادي.
في 2015، بدأت الصين في بناء نظام بـِيْدوالجيل الثالث (بـِيْدو-3) في كوكبة التغطية العالمية. أُطلق ساتل بـِيْدو-3 الأول في 30 مارس 2015. منذ يناير 2018، تم اطلاق تسعة سواتل ضمن المنظومة بـِيْدو-3. وفي نهاية المطاف، سيتألف بـِيْدو-3 من 35 ساتل ومن المتسقط حتى يوفر خدمات عالمية لدى اكتماله في سنة 2020. عندما اكتماله، سيوفر بـِيْدونظام ملاحظة عالمي بديل لنظام تحديد المواقع العالمي الأمريكي (GPS)، ومن المتسقط حتىقد يكون أكثر دقة منه. زُعم في 2016 حتى بـِيْدو-3 سيصل لدقة بمستوى الميلمتر (قبل المعالجة)، والذي يبلغ عشرة أضعاف دقة المستوى الأفضل في نظام تحديد المواقع.
تبعاً لشاينا دايلي، في 2015، بعد خمسة عشر عاماً من اطلاق النظام الساتلي، فقد حقق مبيعات مبيعات قيمتها 31.5 بليون دولار سنوياً لشركات كبرى مثل الصين للعلوم وصناعة الفضاء، أوتوناڤي القابضة، ومجموعة الصناعات الصينية الشمالية.
التسمية
الاسم الرسمي للنظام هونظام الملاحة الساتلية بـِيْدو. والذي سمي على اسم مجمة النجوم المعروفة باسم الغطاس الكبير، والتي تعهد بالصينية باسم بـِيْدو. المعنى الحرفي للاسم هو"الغطاس الشمالي"، الاسم الذي أطلقه فهماء الفضاء الصينيين القدماء على النجوم السبعة الأكثر بريقاً ضمن كوكبة الدب الأكبر. تاريخياً، استخدمت مجموعة النجوم هذه في الملاحظة لتحديد مسقط نجم الشمال. وبالمثل، يستخدم اسم بـِيْدواستعارة للإشارة إلى نظام الملاحة عبر الأقمار الصناعية.
التاريخ
منشأ الفكرة والتطوير الأولي
The original idea of a Chinese satellite navigation system was conceived by Chen Fangyun and his colleagues in the 1980s. According to the China National Space Administration, the development of the system would be carried out in three steps:
- 2000–2003: experimental BeiDou navigation system consisting of ثلاثة satellites
- by 2012: regional BeiDou navigation system covering China and neighboring regions
- by 2020: global BeiDou navigation system
The first satellite, BeiDou-1A, was launched on 30 October 2000, followed by BeiDou-1B on 20 December 2000. The third satellite, BeiDou-1C (a backup satellite), was put into orbit on 25 May 2003. The successful launch of BeiDou-1C also meant the establishment of the BeiDou-1 navigation system.
On 2 November 2006, China announced that from 2008 BeiDou would offer an open service with an accuracy ofعشرة meters, timing of 0.2 microseconds, and speed of 0.2 meters/second.[]
In February 2007, the fourth and last satellite of the BeiDou-1 system, BeiDou-1D (sometimes called BeiDou-2A, serving as a backup satellite), was launched. It was reported that the satellite had suffered from a control system malfunction but was then fully restored.
In April 2007, the first satellite of BeiDou-2, namely Compass-M1 (to validate frequencies for the BeiDou-2 constellation) was successfully put into its working orbit. The second BeiDou-2 constellation satellite Compass-G2 was launched on 15 April 2009. On 15 January 2010, the official website of the BeiDou Navigation Satellite System went online, and the system's third satellite (Compass-G1) was carried into its orbit by a Long March 3C rocket on 17 January 2010. On 2 June 2010, the fourth satellite was launched successfully into orbit. The fifth orbiter was launched into space from Xichang Satellite Launch Center by an LM-3I carrier rocket on 1 August 2010. Three months later, on 1 November 2010, the sixth satellite was sent into orbit by LM-3C. Another satellite, the Beidou-2/Compass IGSO-5 (fifth inclined geosynchonous orbit) satellite, was launched from the Xichang Satellite Launch Center by a Long March-3A on 1 December 2011 (UTC).
الانخراط الصيني في نظام گاليليو
في سبتمبر 2003، نـَوَت الصين الانضمام إلى المشروع الأوروبي نظام گاليليوللتمسقط وكانت ستستثمر 230 مليون € (296 مليون USD، 160 مليون GBP) في گاليليو، على مدى بضع سنوات. At the time, it was believed that China's "BeiDou" navigation system would then only be used by its armed forces. In October 2004, China officially joined the Galileo project by signing the Agreement on the Cooperation in the Galileo Program between the "Galileo Joint Undertaking" (GJU) and the "National Remote Sensing Centre of China" (NRSCC). Based on the Sino-European Cooperation Agreement on Galileo program, China Galileo Industries (CGI), the prime contractor of the China’s involvement in Galileo programs, was founded in December 2004. By April 2006, eleven cooperation projects within the Galileo framework had been signed between China and EU. However, the Hong Kong-based South China Morning Post reported in January 2008 that China was unsatisfied with its role in the Galileo project and was to compete with Galileo in the Asian market.
الفترة الثالثة
- In November 2014, Beidou became part of the World-Wide Radionavigation System (WWRNS) at the 94th meeting of The International Maritime Organization (IMO) Maritime Safety Committee, which approved the "Navigation Safety Circular" of the Beidou Navigation Satellite System (BDS).
- At Beijing time 21:52, March 30, 2015, the first new-generation BeiDou Navigation satellite (and the 17th overall) was successfully set to orbit by a Long March 3C rocket.
النظام التجريبي (بـِيْدو-1)
الوصف
BeiDou-1 is an experimental regional navigation system, which consists of four satellites (three working satellites and one backup satellite). The satellites themselves were based on the Chinese DFH-3 geostationary communications satellite and had a launch weight of 1,000 kilograms (2,200 pounds) each.
Unlike the American GPS, Russian GLONASS, and European Galileo systems, which use medium Earth orbit satellites, BeiDou-1 uses satellites in geostationary orbit. This means that the system does not require a large constellation of satellites, but it also limits the coverage to areas on Earth where the satellites are visible. The area that can be serviced is from longitude 70°E to 140°E and from latitude 5°N to 55°N. A frequency of the system is 2491.75 MHz.
الإتمام
The first satellite, BeiDou-1A, was launched on October 31, 2000. The second satellite, BeiDou-1B, was successfully launched on December 21, 2000. The last operational satellite of the constellation, BeiDou-1C, was launched on May 25, 2003.
حساب المسقط
In 2007, the official Xinhua News Agency reported that the resolution of the BeiDou system was as high as 0.5 metres. With the existing user terminals it appears that the calibrated accuracy is 20m (100m, uncalibrated).
المحطات الطرفية
In 2008, a BeiDou-1 ground terminal cost around ¥20٬000RMB ( US$2٬929), almostعشرة times the price of a contemporary GPS terminal. The price of the terminals was explained as being due to the cost of imported microchips. At the China High-Tech Fair ELEXCON of November 2009 in Shenzhen, a BeiDou terminal priced at ¥3٬000RMB was presented.
التطبيقات
- تم استخدام أكثر من 1.000 محطة تابعة لبـِيْدو-1 بعد زلزال سيتشوان 2008، لجلب المعلومات من مسقط الكارثة.
- في أكتوبر 2009، كان جميع أفراد حرس الحدود الصينيين في يوننان مزودين بأجهزة بـِيْدو-1.
تبعاً لسون جيادونگ، كبير مصممي نظام الملاحة، "الكثير من المنظمات استخدمت نظامنا لفترة وجيزة، وقد أعجبهم كثيراً."
سواتل الجيل الجديد من بـِيْدوتدعم خدمات الرسائل القصيرة.
النظام العالمي (بـِيْدو، نظام السواتل الملاحية أوبـِيْدو-2)
الوصف
BeiDou-2 (formerly known as COMPASS) is not an extension to the older BeiDou-1, but rather supersedes it outright. The new system will be a constellation of 35 satellites, which includeخمسة geostationary orbit satellites for backward compatibility with BeiDou-1, and 30 non-geostationary satellites (27 in medium Earth orbit and ثلاثة in inclined geosynchronous orbit), that will offer complete coverage of the globe.
The ranging signals are based on the CDMA principle and have complex structure typical of Galileo or modernized GPS. Similar to the other global navigation satellite systems (GNSSs), there will be two levels of positioning service: open (public) and restricted (military). The public service will be available globally to general users. When all the currently planned GNSSs are deployed, users of multi-constellation receivers will benefit from a total over 100 satellites, which will significantly improve all aspects of positioning, especially availability of the signals in so-called urban canyons. The general designer of the COMPASS navigation system is Sun Jiadong, who is also the general designer of its predecessor, the original BeiDou navigation system.
الدقة
There are two levels of service provided — a free service to civilians and licensed service to the Chinese government and military. The free civilian service has a 10-meter location-tracking accuracy, synchronizes clocks with an accuracy ofعشرة nanoseconds, and measures speeds to within 0.2 m/s. The restricted military service has a location accuracy ofعشرة centimetres, can be used for communication, and will supply information about the system status to the user. To date, the military service has been granted only to the People's Liberation Army and to the Military of Pakistan.
الترددات
Frequencies for COMPASS are allocated in four bands: E1, E2, E5B, and E6 and overlap with Galileo. The fact of overlapping could be convenient from the point of view of the receiver design, but on the other hand raises the issues of system interference, especially within E1 and E2 bands, which are allocated for Galileo's publicly regulated service. However, under International Telecommunication Union (ITU) policies, the first nation to start broadcasting in a specific frequency will have priority to that frequency, and any subsequent users will be required to obtain permission prior to using that frequency, and otherwise ensure that their broadcasts do not interfere with the original nation's broadcasts. It now appears that Chinese COMPASS satellites will start transmitting in the E1, E2, E5B, and E6 bands before Europe's Galileo satellites and thus have primary rights to these frequency ranges.
Although little was officially announced by Chinese authorities about the signals of the new system, the launch of the first COMPASS satellite permitted independent researchers not only to study general characteristics of the signals, but even to build a COMPASS receiver.
كومپاس-M1
Compass-M1 is an experimental satellite launched for signal testing and validation and for the frequency filing on 14 April 2007. The role of Compass-M1 for Compass is similar to the role of the GIOVE satellites for the Galileo system. The orbit of Compass-M1 is nearly circular, has an altitude of 21,150 km and an inclination of 55.5 degrees.
Compass-M1 transmits in ثلاثة bands: E2, E5B, and E6. In each frequency band two coherent sub-signals have been detected with a phase shift of 90 degrees (in quadrature). These signal components are further referred to as "I" and "Q". The "I" components have shorter codes and are likely to be intended for the open service. The "Q" components have much longer codes, are more interference resistive, and are probably intended for the restricted service.
The investigation of the transmitted signals started immediately after the launch of Compass -M1 on 14 April 2007. Soon after in June 2007, engineers at CNES reported the spectrum and structure of the signals. A month later, researchers from Stanford University reported the complete decoding of the “I” signals components. The knowledge of the codes allowed a group of engineers at Septentrio to build the COMPASS receiver and report tracking and multipath characteristics of the “I” signals on E2 and E5B.
| Parameters | E2-I | E2-Q | E5B-I | E5B-Q | E6-I | E6-Q | GPS L1-CA |
|---|---|---|---|---|---|---|---|
| Native notation | B1 | B1 | B2 | B2 | B3 | B3 | --- |
| Code modulation | BPSK(2) | BPSK(2) | BPSK(2) | BPSK(10) | BPSK(10) | BPSK (10) | BPSK (1) |
| Carrier frequency, MHz | 1561.098 | 1561.098 | 1207.14 | 1207.14 | 1268.52 | 1268.52 | 1575.42 |
| Chip rate, Mchips/s | 2.046 | 2.046 | 2.046 | 10.230 | 10.230 | 10.230 | 1.023 |
| Code period, chips | 2046 | ?? | 2046 | ?? | 10230 | ?? | 1023 |
| Code period, ms | 1.0 | >400 | 1.0 | >160 | 1.0 | >160 | 1.0 |
| Symbols/s | 50 | ?? | 50 | ?? | 50 | ?? | 50 |
| Navigation frames, s | 6 | ?? | 6 | ?? | ?? | ?? | 6 |
| Navigation sub-frames, s | 30 | ?? | 30 | ?? | ?? | ?? | 30 |
| Navigation period, min | 12.0 | ?? | 12.0 | ?? | ?? | ?? | 12.5 |
Characteristics of the "I" signals on E2 and E5B are generally similar to the civilian codes of GPS (L1-CA and L2C), but Compass signals have somewhat greater power. The notation of Compass signals used in this page follows the naming of the frequency bands and agrees with the notation used in the American literature on the subject, but the notation used by the Chinese seems to be different and is quoted in the first row of the table.
التشغيل
In December 2011, the system went into operation on a trial basis. It has started providing navigation, positioning and timing data to China and the neighbouring area for free from 27 December. During this trial run, Compass will offer positioning accuracy to within 25 meters, but the precision will improve as more satellites are launched. Upon the system's official launch, it pledged to offer general users positioning information accurate to the nearest 10 m, measure speeds within 0.2 m per second, and provide signals for clock synchronisation accurate to 0.02 microseconds.
The BeiDou-2 system began offering services for the Asia-Pacific region in December 2012. At this time, the system could provide positioning data between longitude 55°E to 180°E and from latitude 55°S to 55°N.
الإتمام
In December 2011, Xinhua stated that "[t]he basic structure of the Beidou system has now been established, and engineers are now conducting comprehensive system test and evaluation. The system will provide test-run services of positioning, navigation and time for China and the neighboring areas before the end of this year, according to the authorities." The system became operational in the China region that same month. The global navigation system should be finished by 2020. As of December 2012, 16 satellites for BeiDou-2 have been launched, 14 of them are in service.
الكوكبة
| البلوك | الإطلاق الدورة |
إطلاقات السواتل | حالياً في مدار ويعملون |
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|---|---|---|---|---|---|---|
| نجاح | فشل | مزمع | ||||
| 1 | 2000–2007 | 4 | 0 | 0 | 0 | |
| 2 | 2007-2012 | 16 | 0 | 0 | 13 | |
| 3 | From 2015 | 7 | 0 | 18 | 7 | |
| الإجمالي | 27 | 0 | 18 | 20 | ||
| (Last update: January 16, 2017) For a more complete list, see list of BeiDou satellites | ||||||
The regional Beidou-1 system was decommissioned at the end of 2012.
The first satellite of the second-generation system, Compass-M1 was launched in 2007. It was followed by further nine satellites during 2009-2011, achieving functional regional coverage. A total of 16 satellites were launched during this phase.
In 2015, the system began its transition towards global coverage with the first launch of a new-generation of satellites, and the 17th one within the new system. On July 25, 2015, the 18th and 19th satellites were successfully launched from the Xichang Satellite Launch Center, marking the first time for China to launch two satellites at once on top of a Long March 3B/Expedition-1 carrier rocket. The Expedition-1 is an independent upper stage capable of delivering one or more spacecraft into different orbits. On November 29, the 20th satellite was launched, carrying a hydrogen maser for the first time within the system.
In 2016, the 21st, 22nd and 23rd satellites were launched from Xichang Satellite Launch Center, the last two of which entered into service on Augustخمسة and November 30, respectively.
انظر أيضاً
- نظام تحديد المواقع العالمي
- گاليليو
- گلوناس
- NAVIC
- Chinese coordinate systems
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وصلات خارجية
- Official website of BeiDou Navigation Satellite System
- BDstar Navigation
- BeiDou (Big Dipper) - GlobalSecurity.org
- Aviation International News
- Preliminary assessment of the navigation and positioning performance of BeiDou regional navigation satellite system
- Precise orbit determination of Beidou Satellites with precise positioning
- BeiDou-1 - SinoDefence.com
- BeiDou-2 - SinoDefence.com
- Compass on the Chinese Defence Today website
- Compass-M1 orbit details can be found in the Space-Track catalogue with a name "Beidou M1"
- Navipedia information on BeiDou—Wiki initiated by the European Space Agency
