完形填空satellite navigation system
China is to contribute to a new global satellite navigation system being developed by European nations. The Galileo satellite system 1 will offer a more accurate civilian alternative to the Global Positioning System(GPS)， operated by the US military. China will provide 230m Euros (USD 259m) in 2 funding and will cooperate with technical， manufacturing and market development. “China will help Galileo to 3 become the major world infrastructure for the growing market for location services，” said Loyola de Palacio， EU transport commissioner.
A new center that will coordinate co-operation was also announced 4 by the European Commission， the European Space Agency (ESA) and the Chinese Ministry of Science and Technology not long 5 ago 。The China-Europe Global Navigation Satellite System Technical Training and Cooperation Center will be 6 located at Beijing University. China has a substantial satellite launch industry and could potentially help the Galileo satellites.
The US has claimed that Galileo could interfere 7 with the US ability to downgrade the GPS service during military conflicts. European officials say this is unfounded and counter that US opposition 8 is due to the commercial challenge Galileo would present to GPS. Galileo will be precise to within a meter， while civilian GPS service is accurate to around 10 meters.
The Galileo satellite constellation will 9 consist of 27 operational and three reserve satellites orbiting the Earth at an altitude of 23， 600 km. The satellites will be strung along three medium-Earth orbits at 56 degrees inclination to the equator and will provide global coverage. The system should be operational by 2008 and the entire project is expected to 10 cost around 3.2 billion Euros(USD 3.6 billion)。
The European Commission has said Galileo will primarily be used for transportation technology， scientific research， land management and disaster monitoring.
Galileo will provide two signals; a standard civilian one and an encrypted， wide-band signal 11 called the Public Regulated Service (PRS)。 This second signal is designed to withstand localized jamming and will be used by police and military services in Europe. European Commission __12_officials_ have said China will not be given access to the PRS.
The first Galileo satellite is scheduled to launch late in 2004， Clocks on board the 13_satellite_ Will be synchronized through 20 ground sensors stations， two command centers and 15 uplink stations.
Receivers on the ground will use time signals from the satellites to precisely calculate their 14 location 。 A “search and rescue” function will also 15 let distress signals be relayed through the constellation of satellites.
中國幫助歐洲發(fā)展全球定位系統(tǒng)的競爭 (B)
中國要捐助歐洲國家正在開發(fā)的全新的全球衛(wèi)星定位系統(tǒng)。伽利略人造衛(wèi)星系統(tǒng)將提供了一個較美國軍事機構(gòu)使用的全球定位系統(tǒng)更為精確的民用系統(tǒng)。中國將提供兩億三千萬歐元（兩億伍千九百萬美元）的資金，并且協(xié)助技術(shù)、制造以及市場拓展的開發(fā)。歐洲交通委員羅瑤拉德帕若索說：“中國將幫助伽利略（人造衛(wèi)星）成為成長中的定位服務(wù)市場的主要世界基礎(chǔ)設(shè)施。”
不久前，歐洲貿(mào)易委員會、歐洲航天局和中國科技部還宣稱將建立一個新的中心來協(xié)助合作。中國——歐洲全球定位衛(wèi)星系統(tǒng)技術(shù)培訓和合作中心將座落于北京大學。中國具有一個非常有實力的衛(wèi)星發(fā)射工業(yè)。有可能幫助發(fā)射伽利略衛(wèi)星。
美國聲稱伽利略會在軍事斗爭中干擾美國的能力并消減全球定位系統(tǒng)的使用。歐洲官員稱這種說法無事實根據(jù)，并對美國所謂的伽利略（人造衛(wèi)星）會對全球定位系統(tǒng)的商業(yè)上構(gòu)成挑戰(zhàn)的說法持反對意見。伽利略（人造衛(wèi)星）將精確到一米，而民用全球定位服務(wù)只精確到10米。
伽利略人造衛(wèi)星群由27個運用衛(wèi)星和3個儲備衛(wèi)星構(gòu)成，并在地球表面23 600千米的高度運行。衛(wèi)星將與三個中等地球軌道并排在與赤道56度的傾斜角度上運行，并且可以覆蓋全球。這個系統(tǒng)將在2008年啟動，整個項目將耗資32億歐元（36億美元）。
歐洲貿(mào)易委員會說伽利略（人造衛(wèi)星）最初將被用于交通技術(shù)、科學研究、陸地管理和自然災害監(jiān)控兩種信號：一種是加密信號，稱為標準民用信號，另一種是公共調(diào)控服務(wù)系統(tǒng)加密信號。第二種信號是為抵抗地方交通堵塞而設(shè)計的，將被用于歐洲公安和軍事事業(yè)。歐洲貿(mào)易委員會官員說中國將無權(quán)使用公共調(diào)控服務(wù)系統(tǒng)。
第一個伽利略人造衛(wèi)星將在2004年底發(fā)射。這架衛(wèi)星上的鐘表將與20個地面感應(yīng)站、2個指揮中心和15個上行站時間同步。
地面的接收器將利用衛(wèi)星上的時間信號準確地計算出它們的方位。“搜索救援”功能也會通過衛(wèi)星群傳遞遇難信號。