2018年CRI China sends twin navigation satellites into space

 

China has launched two satellites into space on a Long March carrier rocket from the Xichang Satellite Launch Center in Sichuan Province. 

The satellites are part of the country's growing BeiDou Navigation Satellite System. 

The launch of the Long March-3B carrier rocket marks the 269th mission for the Long March rocket family.

The satellites, number 30 and 31 in the BeiDou system, entered orbit more than three hours after launch. 

After the satellites pass a series of tests, they will work together with the six BeiDou-3 satellites that have already been launched. 

The new satellites contain a new type of atomic clock that will help to improve the accuracy of the BeiDou Navigation System.

An atomic clock is the most accurate type of timing¹ device available. Accurate timing is essential for measuring the position and velocity² of the navigation satellite, which in turn, provides people using the navigation system with an accurate measurement of their location. 

Li Jing is a researcher at China's Aerospace³ Science and Industry Corporation. Li says that an atomic clock based on hydrogen atoms was used in these satellites, in place of the rubidium type of atomic clock used in previous satellites.

"The hydrogen atomic clock allows for more stability and accuracy compared with a rubidium atomic clock. Its frequency drift rate is also lower. The frequency can be maintained without frequent calibration. These features help improved the performance of the satellites. The U.S.'s GPS satellites use cesium and rubidium atomic clocks. The atomic clock carried by the Beidou system can achieve similar performance as GPS. And the hydrogen atomic clock is 100 percent domestically made."

China has a busy schedule of satellite launches planned for 2018, including 18 of the new type of Beidou-3 satellites. 

By around 2020, when the Beidou system goes global, it will use a network of more than 30 satellites.

Chen Lin, from the China Electronics Technology Group, said the new satellites represent a great improvement in performance.

"The newly launched satellites perform as well as we expected. Some technologies are even better than we expected. In general, we delivered an effectively functioning system. For example, the performance of the atomic clocks matches our expectations."

Named after the Chinese term for the Big Dipper, the BeiDou system started providing satellite navigation services over China in the year 2000. It is due to start serving countries along the Belt and Road by the end of 2018.

1 timing   

n.时间安排，时间选择

参考例句：

• The timing of the meeting is not convenient.会议的时间安排不合适。
• The timing of our statement is very opportune.我们发表声明选择的时机很恰当。

2 velocity   

n.速度，速率

参考例句：

• Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
• The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。

3 aerospace   

adj.航空的，宇宙航行的

参考例句：

• The world's entire aerospace industry is feeling the chill winds of recession.全世界的航空航天工业都感受到了经济衰退的寒意。
• Edward Murphy was an aerospace engineer for the US Army.爱德华·墨菲是一名美军的航宇工程师。