请输入或粘贴题目内容
搜题
拍照、语音搜题，请扫码下载APP
题目内容
（请给出正确答案）
Laser-doppler radar is especially valuable in space missions because ______. ()
A．it is one thousand times more precise than microwave radar
B．it provides precise measures of the velocity of space vehicles
C．it is a new system of radar
D．it can measure the movement of a spaceship less accurately than a microwave radar
答案
更多“Laser-doppler radar is especially valuable in space missions because ______. （)A．it is on”相关的问题
第1题
The model has shown that this radar system, known as laser-doppler radar, can measure with absolute precision speeds varying from spaceship orbital injection (进入) 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 (对接) 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 could knock the station out of its orbit.
The light-beam radar, which operates at a frequency of trillions (百万兆) of cycles per second, could easily detect and measure the movement of a vehicle edging up to a satellite space station. 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 ______. ()
A．measures the movements of a spaceship by means of light beam
B．makes use of microwaves
C．makes use of sound waves
D．Both A and B
第2题
Implied but not stated is that ______. ()
A．laser-doppler radar is more accurate than microwave radar
B．microwave radar may not ensure absolute precision in measuring varying speeds
C．the light-beam radar can measure only slow speeds with accuracy
D．microwave radar operates at a higher frequency than laser-doppler radar
第3题
Which of the following statements is not true according to the passage ______. ()
A．accuracy ill speed measurement is essential to spaceships
B．the speeds of space vehicles will vary
C．inaccuracies in measurement could cause accidents in space missions
D．a bump could affect the preciseness of the laser-doppler radar
第4题
By moving the radar beam around slowly in circles, we can ______ the surroundings.
A．explore
B．expose
C．exploit
D．expand
第7题
An appropriate title for this passage would be ______. ()
A．Rendezvous in Space
B．Landing at a Space Station
C．New Radar for the Space Age
D．Space Navigation
第9题
A.want their pigeons to win the race
B.are sending radar signals to their pigeons
C.do not know whether the race began on time
D.do not trust the rules set down by the judges
第10题
A.WINDSHEAR AHEAD在起飞过程中，低于RA1500可用
B.两声警笛后，紧接WINDSHEAR，是GPWS探测到当前位置风切变过大，不高于RA1200可用
C.抬轮时，GPWS开始探测风切变工作
D.MONITOR RADAR DISPLAY 是探测前方3NM之内有风切变
