中国最近一次北斗卫星发射为嫦娥4号月背登陆扫清道路 [美国媒体]

HELSINKI —An enhanced Long March 3B with a Yuanzheng-1 upper stage lifted off from the Xichang Satellite Launch Center in southwest China at 2:07 p.m. Eastern Nov. 18 sending two Beidou satellites directly into medium Earth orbits at around 21,500 kilometers altitude.

装载有远征1号上面级的加强型的长征3B在中国东部时间11月18日下午2：07于西昌卫星发射中心升空，将两枚北斗卫星直接送入21500公里的地球中距轨道。



The pair of one-metric-ton Beidou-3 satellites are the 42ndand 43rdlaunched for the Beidou system, China’s answer to the U.S. GPS precision timing and navigation system, and the 18thand 19thof the third-phase satellites for global coverage.

两个一吨重的北斗3号卫星是北斗系统的第42、43颗星，是中国对美国GPS系统的回应，也是目标全球覆盖的北斗3号系统的第18、19颗星。



During 2019 and 2020, China aims to launch six more medium Earth orbit (MEO) Beidou-3 satellites, along with three to inclined geosynchronous orbits and two more satellites to geostationary orbits (GEO).
China’s accelerated launch cadence in 2018, which has seen nine Beidou-related launches, has put the country on course to complete the system of 35 active satellites for global GNSS coverage in 2020, with 27 satellites in MEO, five in GEO and three more in inclined GEO orbits.
Along with civilian uses such as navigation and positioning, Beidou will also provide weapons targeting, guidance and other services for the People’s Liberation Army, removing previous Chinese military reliance on GPS.
The launch was China’s 33rdof 2018, with the maiden orbital launch attempt by startup Landspace bringing the single failure.



The landing will take place in late December or early January, following sunrise over the Von Kármán crater and the beginning of a period of sunlight over the landing area lasting 14 Earth days.
Lunar far side challenges
As the far side of the moon never faces the Earth due to tidal locking, a relay satellite is required to facilitate communications between the spacecraft on the lunar far side and the Earth.
Named Queqiao, a satellite with a 4.2-meter parabolic antenna was launched May 20 from Xichang and entered a Lissajous orbit June 14 beyond the moon around the Earth-moon Lagrange point 2. The orbit will allow Queqiao a constant line of sight with both the lunar far side and terrestrial tracking stations.
Chang’e-4 was originally manufactured as a backup to the Chang’e-3 mission which put a lander and rover on Mare Imbrium on the lunar near side in December 2013 and made China only the third country to soft-land on the moon. The mission followed two lunar orbiter missions, Chang’e-1 and Chang’e-2, launched in 2007 and 2010.
A successful Chang’e-4 mission would also prove useful for future lunar plans, including missions to the lunar poles in the early 2020s.

登陆将会在12月底或1月初进行，此时Von Kármán环形山正值日出，着陆区域将开始一轮持续14个地球日的白昼期。
月球背面挑战
因为潮汐锁定的原因，月背永远不会朝向地球，因此需要一颗中继卫星来帮助在月球背面的航天器与地球之间的通信。
5月20日一颗名为鹊桥的装有4.2米抛物天线的卫星从西昌发射升空，6月14日进入越过月球围绕地月拉格朗日点2的利萨如轨道。这条轨道将给予鹊桥对于月背与地球跟踪站的持续视线。
嫦娥4号最初是作为嫦娥3号任务的备份而制造的，嫦娥3号于2013年12月将登陆器和月球车送上月球正面的雨海，使中国成为第三个月球软着陆的国家。之前还有分别于2007年和2010年发射的嫦娥1号和嫦娥2号月球轨道任务。
一个成功的嫦娥四号任务也将证明对未来的月球计划有用，其中包括2020年以后的月球极地任务。



criticalobserver
This Chang e'4 mission will be amongst the most complex one attempted by mankind. It is hoped that everything will go smoothly.

嫦娥4号是人类尝试过的最复杂的任务之一。希望一切顺利。

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Exciting news, I wish them every success!
China may send up an artificial moon to light up the dark side of the moon.
A real dream with Chinese characteristics...

激动人心的新闻，我希望他们成功！
中国也许会发射一个人造月亮来照亮月球背面。
中国特色的真实梦想。



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That was a geopolitical stunt and not sustainable.

这是地缘政治的噱头，不可持续。

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It was also world-historic and very possibly the event of the Second Millennium. That said, IF the Chinese can pull this first sampling of the lunar far side off, it is our first really good chance to get a sample of the lunar mantle, excavated by South Pole-Aiken impact, and no new exploration comes without at least a few neat surprises. I am very excited about this mission.

这是具有世界性历史意义的，也许会成为第二个千年的重大事件。即是说，如果中国人能成功从月背取样，这是我们第一次有机会获取由South Pole-Aiken撞击挖掘出的来自月幔的样品，所有的探索都会带来至少一点的新惊喜。我对于这次任务非常兴奋。

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The Chinese program is open to others, I heard.
You can be part of it...

我听说中国人的工程是开放的。
你可以加入其中。

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China has already landed on the Moon, in 2013.

中国早在2013年的时候就着陆月球了。
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