单选题
China is going to contribute to a new global satellite navigation system being developed by European nations. The Galileo satellite system will 1 a more accurate civilian alternative to the Global Positioning System (GPS), operated by the US military. China will provide 230m Euros in funding and will 2 with technical, manufacturing and market development.
A new center that will coordinate co-operation will be set 3 at Beijing University. China has a substantial satellite launch industry and could potentially help 4 the Galileo satellites.
The US has claimed that Galileo could interfere with the US with 5 to downgrade the GPS service during military conflicts. European officials say this is unfounded (无根据的) and counter that US opposition is caused by the commercial challenge Galileo would present to GPS. Galileo will be 6 to within a meter, while the civilian GPS service is accurate to around 10 meters.
The Galileo satellite constellation (卫星集群) will consist of 27 operational and three reserve satellites 7 the Earth at an altitude of 23,600 kin. The satellites will be strung along three medium-Earth orbits at 56 degrees inclination (倾斜) 8 the equator (赤道) and will provide global coverage. The system should be 9 by 2008 and the entire project is expected to cost around 3.2 billion Euros.
The European Commission has said Galileo will 10 be used for transportation technology, scientific research, land management and disaster monitoring.
Galileo will provide two 11 , a standard civilian one and an encrypted (把……编码), wide-band signal called the Public Regulated Service (PRS). This second signal is 12 to endure localized jamming and will be used by police and military services in Europe.
The first Galileo satellite is 13 to launch late in 2004. Clocks on board the satellites will be synchronized (同步) through 20 ground sensors (传感器) stations, two command centers and 15 uplink (上传) stations.
Receivers on the ground will use time signals from the satellites to precisely calculate their 14 . A "search and rescue" function will also let distress signals be 15 through the constellation of satellites.