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卫星工作原理 – 译学馆
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卫星工作原理

How do Satellites work? | ICT #10

We live our lives knowing that many satellites orbit our planet every day and
众所周知 每天都有很多卫星围绕着地球运行
that they are helping us in several ways
并在诸多领域给人们生活提供了便利
You might be surprised to know that there are almost
围绕地球飞行的卫星将近有4900颗
4900 satellites orbiting the Earth
你听了可能会大吃一惊
The most obvious questions that come to mind are
脑海中浮现的最清晰的问题是
why are these satellites in totally different orbits?
为什么卫星在完全不同的轨道运行?
how does a satellite carry out all of its functions
卫星如何执行其所有功能?
and what are the components inside them
还有卫星内部帮助其完成
which help them to accomplish all of their allotted tasks?
各自使命的部件又是什么?
Let’s explore the answers to all these questions in detail
让我们一起深入探究这些问题的答案
it’s a well-known fact that a satellite stays in orbit
众所周知 卫星会绕着一个轨道运行
because of the balance between gravitational pull and centrifugal force
是因为万有引力和离心力之间的平衡作用
The angular velocity of the satellite is decided by the force balance equation
卫星的角速度可以由受力平衡方程求出
that balances the gravitational and centrifugal forces
这里卫星所受的万有引力和离心力相等
When the satellite is deployed it
发射升空时
is given sufficient speed to balance these two forces
卫星会获得足够的速度来平衡这两个力
A satellite near to earth requires more speed to resist the gravitational pull
离地面近的卫星比离地面远的卫星需要
than the ones located further from the earth
更大的速度来克服重力作用
Due to the negligible resistance in space
因为太空中阻力可以忽略不计
satellites never lose speed
卫星的速度会保持不变
This means satellites will continue their circular motion around the earth
这意味着即便没有任来自外部的能源供给
without any external energy source
卫星都能继续绕地球做圆周运动
Satellites are placed either in low-earth orbit
卫星要么是在近地轨道
Medium Earth orbit
要么是在中地球轨道
or Geosynchronous Earth orbit,
不然就是在同步地球轨道
these three orbits are illustrated here.
这三个轨道如画面所示
We will get into more details of them later.
稍后我们会更加详细地介绍它们
There is an interesting region in space called the Van Allen belt
太空中有一块有趣的区域叫做范艾伦带
a region full of highly energetic charged particles
这块区域充满着高能带电粒子
Which could seriously damage the electronic section of a satellite
这些粒子会对卫星的电子部件造成严重损害
Generally, it is preferred not to park satellites in the Van Allen belt
一般来说 卫星最好不要放在范艾伦带
the decision on what orbit is to be chosen for placing the satellite
决定把卫星放到哪个轨道上
depends on the application and purpose of the satellite.
取决于这颗卫星的用途和目的
If the satellite is built for Earth Observation
如果这颗卫星是用来地面观测
weather forecasting, geographic area surveying, satellite phone calls, etc
预报天气 测量地理区域 卫星电话通信等
Then orbits closer to the earth are chosen
就会被放置在离地面近的轨道
Leo is the closest to the earth at an altitude
近地轨道是离地球最近的轨道
of between 160 and 2000 kilometers
高度在160到2000千米之间
and it’s orbital period is approximately 1.5 hours
轨道周期约为1.5小时
But these types of satellite cover less area of the earth.
但这些卫星覆盖的地面区域很小
So many satellites are required to obtain global coverage
所以就需要更多的卫星才能覆盖到全球
That’s why in the case of broadcasting
这就是为什么在广播邻域
a high orbit such as Geo is chosen
卫星要放在高轨道 如地球同步轨道
satellites in geosynchronous orbit are at a height of 35,786 kilometers and
地球同步轨道卫星的高度是35786千米
and rotate at the same angular speed as the earth.
并且它旋转的角速度与地球相同
It means the satellite takes exactly
这意味着这颗卫星旋转一周的时间是
23 hours 56 minutes and four seconds to complete one rotation
23小时56分钟4秒
Within the geosynchronous orbit.
在地球同步轨道内
There is a special category of orbit called Geostationary orbit
有一个特殊的轨道叫做地球静止轨道
which is concentric to the equator of the earth
它和地球赤道同轴
These satellites remain stationary with respect to the earth
这类卫星相对于地球是保持静止不动的
due to this
出于这一点
Geostationary satellites are the ideal choice for television broadcasting
地球同步卫星是广播电视最理想的选择
since it means you do not have to adjust
因为这意味着人们不用
the angle of your satellite dish again and again
一遍又一遍地调整卫星天线的角度
This is the reason why the geostationary belt is so crowded with satellites
这就是地球静止轨道中卫星密度很大的原因
and it is managed by an international organization called ITU
这个轨道由一个叫ITU的组织管理
Geosynchronous orbits are occupied by a few navigation satellites also.
地球同步轨道上面还有一些导航卫星
Geo satellites can cover one-third of the Earth’s surface
地球同步轨道卫星可以覆盖全球三分之一的地方
So three satellites are sufficient to cover the entire Earth
所以三颗卫星就足够覆盖全球
For navigation applications such as GPS
对于导航应用如GPS
Meo is the wise option
中地球轨道是明智的选择
even though the Leo is closest to the earth
虽然近地轨道是离地面最近的轨道
Satellites in this orbit revolve at a very high speed
但这个轨道内的卫星的速度是非常快的
Due to this receivers on earth failed to carry out the navigation Calculations accurately
因此 地面的接收器就无法准确地进行导航计算
moreover Leo needs a lot more satellites to cover the entire Earth.
此外 近地轨道内需要更多的卫星才能覆盖全球
Thus GPS satellites used Meo
因此 GPS导航卫星位于中地球轨道
In a typical GPS system 24 satellites can cover the entire earth
一般在一个GPS系统内 24颗卫星就能覆盖全球
and the orbital period is 12 hours
公转周期为12小时
Now let’s look at the main components of a communication satellite
现在让我们来看看通信卫星的主要组件
Along with their functions
基于它们的功能
at the heart of communication satellites are the transponders
通信卫星的核心处是转发器
The main task of a transponder is
转发器的主要任务是
to change the frequency of the received signal remove any signal noise
改变接收信号的频率 消除其它信号噪声
and amplify the signal power
并放大信号功率
on K band satellites, the transponder converts from 14 gigahertz to 12 gigahertz
在K波段卫星内 转发器将140千兆赫转换为12千兆赫
and a satellite can have 20 or more transponders
一颗卫星可以有20个甚至更多的转发器
it is obvious that transponders require a great deal of electrical power
显而易见 转发器需要大量的电能
to handle all of these functions
才能实施这一系列的功能
For power supply
能量提供方面
a satellite has the options of batteries and solar panels
卫星可以选择使用电池或太阳能板
The solar panel is used to power the electronic equipment
太阳能板可以用来为电子设备提供电能
but during an eclipse time.
但碰到月食
The batteries are used
就得用电池
You can see a Sun sensor on the satellite
通信卫星上你还可以看到一个太阳传感器
This Sun sensor helps to angle the solar panels in the right direction
太阳传感器帮助把太阳能板调整到正确的方向
so that the maximum power can be extracted from the Sun
这样 卫星就能从太阳那里获得最多的能量
Now, let’s see how the transponder
现在 让我们看看
receives the input signal from the antenna
转发器如何接收并输入来自天线的信号
The most common antenna fixed to satellites our reflector antenna
固定在卫星上的最常见的组件是反射器天线
a Satellite is supposed to follow its intended smooth orbit
卫星会沿着预定的轨道稳定运行
however the gravitational field around the satellite is not uniform
但是卫星周围的重力场是不均匀的
due to the unequal mass distribution of the earth
因为地球的质量也不是均匀分布的
and the presence of the moon and the Sun
同时还受到月亮和太阳的影响
Because of this sometimes the satellite gets displaced from its intended orbital position
因此 卫星有时会偏离预定轨道
This is a dangerous situation
这是一种很危险的状况
since it will lead to a complete loss of signal
因为这会导致卫星信号完全丢失
To avoid such a situation Satellites make use of thrusters
为避免这种情况 卫星会用到推进器
The thrusters are fired and keep the satellite in the right position
推进器点火后会将卫星推到正确的轨道上
these also help satellites to avoid space junk
它也可以让卫星躲避太空垃圾
The fuel needed for the thrusters is saved in tanks in the satellite body
推进器所需燃料会储存在卫星内部的燃料箱里
The position of the satellite and control of the thrusters
卫星的位置和推进器的控制
are continuously monitored from an earth station
都由地面站进行持续监测
Apart from the position controls
除了位置监测
the earth station also monitors the satellites health and speed
地面站还要监测卫星的健康状况和速度
This is done through tracking telemetry and control systems
这都是通过跟踪遥测和控制系统来实现的
These systems continuously send the signal to the earth station
这两个系统不断地向地面站发射信号
and maintain the contact between earth and the satellite.
保持地球和卫星之间的联系
Generally, these signals are exchanged at different frequencies
通常这些信号会变换不同的频率
to distinguish from other communication signals
来区别于其他的通信信号
Have you ever thought what happens to a satellite
你是否有想过这个问题
when it is no longer functional or its lifespan is nearing the end
当一颗卫星不能再发挥功能或者寿命将近时 它会怎样
These satellites could harm other operational satellites or spacecraft
这些卫星会威胁到其它正在运行中的卫星和飞船
to deal with this situation
为了应对这种情况
Inactive satellites are transferred to the graveyard orbit
人们会发动推进器将这些废弃的卫星
by activating the thrusters
推到墓地轨道
Just by increasing the rotational speed of the satellite.
只需通过增加卫星的转速
We will be able to transfer it to a higher radius orbit
我们就能把它转移到更高的轨道上
This operation is made clear in this animation
画面中的动画能清楚演示出这一过程
The graveyard orbit is a few hundred kilometers above the geostationary orbit
墓地轨道比地球静止轨道高几百千米
For this operation the thrusters consume the same amount of fuel
这个过程所消耗的燃料相当于
as a satellite needs for about three months of station keeping
卫星维持轨道位置控制三个月所需的燃料
The satellites we have discussed so far are communication satellites
目前为止 我们提到的卫星都是通信卫星
For GPS satellites the most important components are an atomic clock and the antenna
对于GPS导航卫星 最重要的部件是原子钟和天线
The L band navigation antennas used in these kinds of satellites
L波段导航天线被运用到了这类卫星上
are also illustrated here
即画面上的这个
The earth observation satellites which are mostly in Leo
地面观测卫星大多在低轨道上
carry various types of sensors imagers, etc.
出于不同的功用 它们会携带各种类型的
Depending on their mission
传感器 成像仪等
Now for some interesting information
现在来看看一些有趣的东西
in the visuals of the satellite in this video
就是视频中的卫星照片
You might have observed that they were covered with a gold colored foil
你可能已经发现了它们都被金色的箔纸包着
What is the purpose of this foil in?
这层箔纸有什么作用呢
In fact it is not foil
事实上 乍一看
as it appears to be at first sight
这并不是箔纸
If you take a cross-section of it,
如果你从横截面看过去
you can see it has a multi-layered structure
你可以看到它有多层结构
Satellites face huge temperature variations in space
卫星在太空中要承受巨大的温度变化
where the temperatures varies from minus 150 to 200 degrees Celsius
温度最低零下150摄氏度 最高200摄氏度
moreover satellites face the issue
此外 卫星还要承受
of heavy solar radiation from the Sun
来自太阳的强烈的太阳辐射
This material actually acts as a shield
这层箔纸实际上起着隔离的作用
which protects the satellite components from the heavy temperature variations and from solar radiation
保护卫星部件免受强烈的温度变化和太阳辐射的影响
We hope that you have gained a good insight into different types of satellites
通过本视频 希望大家对不同类型的卫星
and how they work from this video,
和它们的工作原理有了一定的了解
please support our educational service by clicking the support button
点击支持按钮 支持我们的教育服务
Thank you
谢谢

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视频概述

卫星在各个领域让人们的生活变得越来越便利,太空中有成千颗卫星,这些卫星是如何工作的呢?

听录译者

收集自网络

翻译译者

Claudia

审核员

审核员BY

视频来源

https://www.youtube.com/watch?v=ror4P1UAv_g

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