echo

英/ ˈekəʊ /

美/ ˈekoʊ /

CET4/CET6/考研/GRE/SAT/

1
回声
回声（ECHO）：声源发出声音后，经过一定的时间反射回来，又被反射回去，再反射回来，再反射回去，如此反复到没有声音为止。
2
回音
回音，余音绕梁
3
厄科
Echellodna(厄喀德那):厄喀德那(半人半蛇女怪) Echo(厄科):神潘爱她没希望,便指使牧羊狗将她撕成碎片.她的碎片藏在地下时仍在回答潘的疯狂叫喊,于是孕育发生了回声.
4
回波
...：在电视系统中，指摄像机的实用照度范围。在这种情况下，被摄视场中同时存在强光区和阴影区，而所有细节均可看清。数量上一般以允许的最大照度水平与最小照度水平的电压差或功率差来衡量。回波(Echo)：信号传输过程中从一个或多个点反射回来的信号。与原信号相比，具有明显的幅度和时间上的差异。

短语

1
The hills sent back a faint echo.
座座山丘传来微弱的回声。
《牛津词典》
2
There was an echo on the line and I couldn't hear clearly.
电话里有回音，我听不清楚。
《牛津词典》
3
His words were an echo of what she had heard many times before.
他的话是她多次听到过的话的重复。
《牛津词典》

EChO
The Exoplanet Characterisation Observatory (EChO) was a proposed space telescope as part of the Cosmic Vision roadmap of the European Space Agency, and competed with four other missions for the M3 slot in the programme. On February 19, 2014, the PLATO mission was selected in favour of the other candidates in the programme, including EChO.EChO would be the first dedicated mission to investigate exoplanetary atmospheres, addressing the suitability of those planets for life and placing our Solar System in context. EChO is intended to provide high resolution, multi-wavelength spectroscopic observations. It would measure the atmospheric composition, temperature and albedo of a representative sample of known exoplanets, constrain models of their internal structure and improve our understanding of how planets form and evolve. It will orbit around the L2 Lagrange point, 1.5 million km from Earth in the anti-sunward direction.

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