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  3. A new kind of radar has been developed for space-age travelers. A working laboratory model of a new system of radar that makes u

A new kind of radar has been developed for space-age travelers. A working laboratory model of a new system of radar that makes u

admin2014-04-23  18
问题     A new kind of radar has been developed for space-age travelers. A working laboratory model of a new system of radar that makes use of a beam of light is said to be ten thousand times more accurate than the best comparable system of radar that uses microwaves.
    The model has shown that this radar system (known as laser-doppler radar) can measure with absolute precision speeds varying from spaceship orbital injection velocities (速度) of five miles per second down to virtual stops—speeds of less than one ten thousandth of an inch per second. According to the scientists who are developing this system, such fine measures of velocity are of prime importance in space missions. In a rendezvous (会合, 会合点) between two spaceships, or in a landing approach by a vehicle onto an orbiting space station, a bump could rip open a ship’s skin, or a nudge (轻触) could knock the station out of its orbit.
    The light-beam radar, which operates at a frequency of trillions of cycles per second, could easily detect and measure the movement of a vehicle edging up to a satellite space station even at a small fraction of an inch per second. A control system using so precise a signal as this would allow a huge vehicle to dock at a space station as lightly as a feather.
Laser-doppler radar makes use of______.
选项 A、light
B、microwaves
C、sound waves
D、both A and B
答案A
解析 这是一道综合理解题。文中第一段第二句说：“据说，一种采用光束的新型雷达系统的实验工作模型比采用微波技术最优的同类雷达系统要准确万倍。”在第二段第一句中说：“模型已经显出这种雷达系统(命名为激光多普勒雷达)能够绝对准确地测量速度变量，从太空飞船每秒五英里的发射速度到实际静止的每秒小于一万分之一英寸的速度。”综合以上内容，我们得知多普勒激光雷达系统是使用光束的。所以A是正确答案。
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