Release date：2021-12-29Author source：KinghelmViews：1603
June 23, 2020
Xichang Satellite Launch Center
The long march rocket carriesmostafteroneBeidou networking satellite
Cut through the sky
(at 9:43, the last global networking satellite of Beidou 3 was launched, photographer @ Nan Yong）
subsequently
The satellite will reach an orbit about 36000 kilometers from the earth's surface
Its stable operation
Mark
ChinaBeidou satellite navigation systemUnifiedFully completed
This isOnehugeEngineering
In space46 navigation satellites
Around the earth day and night
More than 2700 reference stations on the ground
It is distributed in the north and south of the river
A "dragnet" spread out
This is also adifficultEngineering
More than 80000 staff
More than 300 R & D units
Fought for more than 20 years
Finally the dream came true
(in the past 20 years, the long march rocket, as the only carrier of the Beidou satellite, has been launched 44 times. The following figure shows the scene of the long march 3B rocket carrying the 39th and 40th Beidou satellites waiting to be launched, photographer @ Shi Yue)
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This is aessentialEngineering
Now Beidou has been widely used in
Power, finance, communication and transportation
Agriculture, surveying and mapping, disaster reduction and relief, etc
All aspects of production and life
China will get rid of
Global positioning system (GPS)Dependence of
(the Beijing Zhangjiakou high-speed railway running at the speed of 350 km / h can realize the parking accuracy error from driving once braking to parking, which is less than 10 cm. The following figure shows the Beijing Zhangjiakou high-speed railway crossing the river, photographer @ Zhao Bin)
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And with the help of Beidou
Chinese missiles haveUltra high precision guidance capability
The sharp weapon of national defense is becoming sharper and sharper
(on October 1, 2019, julang-2 missile team in the military parade of the General Assembly celebrating the 70th anniversary of the founding of the people's Republic of China, photo source @ People's vision)
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nowadays
Beidou System (BDS)It has covered the whole world
Global positioning system with the United States（GPS）
GLONASS system in Russia
OhAllianceGalileo
It is also known as the world's four major satellite navigation systems (GNSS)
Grinding a sword in 20 years
How did China do it?
01
NavigationsatelliteSecret of
To get our location
Need to be deployed in space
At least 3 navigation satellites
They constantly emit electromagnetic signals
We use navigation equipment to receive signals
The signal is generated between sending and receivingtime difference
Multiplied by the propagation rate of the electromagnetic wave (speed of light)
We can calculate our distance from the satellite
When there is only one navigation satellite
Satellite centric
WeThe distance from the satellite is the radius
You get onesphere
Any point on the sphere
Could be our location
（The speed of light is about 3 & times;teneightm/s. Position determined by a navigation satellite -- sphere, cartography @ Zheng Borong / Institute of planetary Research)
If there are 2 navigation satellites
Two spheres intersect to get onecircumference
Any point on the circumference
Could be our location
(two navigation satellites)Fixed position - circumference, cartography @ Zheng Borong / Institute of planetary Research)
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If there are 3 navigation satellites
Three spheres intersect to get a and BTwo points
Any of two points
It could also be our location
(location determined by three navigation satellites - two points), cartography @ Zheng Borong / Institute of planetary Research)
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And between the two points
have onlyPoint B is near the surface
So we locked our only position
(there is only one intersection with the earth's surface, cartography @ Zheng Borong / Institute of planetary Research)
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That's itIt's the secret of navigation satellites
NamelyThree ball intersection positioningprinciple
actually
stayWhen measuring time
There will be various errors
To eliminate errors
Often also needThe fourthSatellite assistance
meanwhileIn order to ensure that we can
Can receive more than four navigation satellite signals
The total number of satellites orbiting the earth is often much higher than four
For example, GPS in the United States and GLONASS in Russia
The number of navigation satellites is more than 24
(GPS system positioning diagram. There are more than 4 satellites above the same point. The original image is from @ Wikipedia, reproduced @ Zheng Borong / Institute of planetary Research)
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however
In the 1990s
Want a short timeLaunch the same number of navigation satellites
For China, which is relatively backward in aerospace and navigation technology
It's almost an impossible dream
Can I use itleastSatellite
Achieve the goal of positioning?
02
Stagger start
A bold plan
Born in the sky
Chen Fangyun
"Two bombs and one satellite" meritorious service, famous electronics scientist
Proposed for the first timeConsisting of two satellites
Double star positioning system
The subtlety is
A "brain" is set on the ground
Ground control center
Using ground control center
People can be around the earth"Virtual" a sphere
And through the interaction between control center, satellite and user
Calculate the user's location
(the ground control center can provide the user's elevation and other known data, and has strong solution ability. Schematic diagram of double star positioning principle and mapping@Zheng Borong / Institute of planetary research）
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meanwhile
Both satellites are in geostationary orbit
Its orbital height is 35786 km
The operation cycle is consistent with the earth's rotation cycle
Can always face the same side of the earth
It ensures the signal coverage in the whole period
（Geostationary orbit diagram,drafting@Zheng Borong / Institute of planetary research）
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Since 1994squareThe project was officially approved
By 2000Two Beidou satellitesSuccessful orbit
More than 6 years of research and development
The idea of the Big Dipper
Finally became a reality
This isBeidou 1
Its signal
It can basically cover the whole territory of China
(Beidou-1 covers 70 & deg; - 145 & deg;, north latitude5°- 55°， Drawing @ Wang Chaoyang & Zheng BoRong / Planetary Institute）
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Users can not only receive location information
Still like“send message”Actively send text messages as well
This is particularly critical when seeking help and assistance
And for like“radio”General
GPS and other systems receiving data in one direction
This is impossible
(the advantage of "texting" is that it can not only know its own location, but also tell others, which is of great significance in some dangerous situations such as earthquake and ocean going. The following figure shows the rescue scene in the Wenchuan earthquake in 2008, photographer @ Jia junyang)
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This feature is an international initiative
The father of American GPSParkinsonprofessor
Later, he praised this function
I can know where you are and where I am
What a wonderful experience
however
Defects of Beidou-1
It's also obvious
Its positioning accuracy is 20-100 meters
The time accuracy is 20-100 nanoseconds
It is significantly different from the 10 meters and 20 nanoseconds of GPS in the same period
And only 150 users can be online at the same time
It is also far from the goal of global coverage
also
"Texting" interactive mode
The process is cumbersome and the signal is easy to be intercepted
It not only leads to a delay of about 1 second in positioning
It is also easy to expose its position
For high-speed aircraft and missiles
Every second is life and death
Confidentiality is even more important in military operations
(comparison of positioning operation between Beidou-1 and GPS system,Drawing@Zheng Borong / Institute of planetary research）
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Beidou 1
Although the performance is a little simple
But it basically solved the problem of our navigation system from scratch
Beidou's dream has begun to falter
Will it be all right next?
03
Overcome difficulties
Since 2010
Xichang Satellite Launch Center has become very busy
In less than three years
14 navigation satellites will be launched from here
Five satellites were launched in 2010
Three satellites were launched in 2011
Six satellites were launched in 2012
(in 2007 and 2009, one beidou-2 experimental satellite has been launched respectively. The following figure shows the same frame of the two launch towers of Xichang Satellite Launch Center and the rocket transport locomotive, photographer @ Yu Ming)
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meanwhile
Ground supporting systems such as operation and control are also spread out
Satellite and ground adjustment tests are also being carried out simultaneously
End of 2012
Successful networking of the new system
This is it.Beidou 2
(operation diagram of beidou-2 system,Drawing@Zheng Borong / Institute of planetary research）
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Compared with Beidou-1
Its coverage has expanded significantly
Expand to most regions of the Asia Pacific Region
The positioning accuracy has also been improved from 20m to 10m
The time accuracy is up to 10 nanoseconds
(beidou-2 covers 70 & deg; - 150 & deg;, 55 & deg; - 55 & deg;, mapping @ Wang Chaoyang&Zheng Borong / Institute of planetary research）
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Beidou-1's unique communication function
It has also been completely inherited
It can help more people in emergency communication
(on April 25, 2015, a magnitude 8.1 earthquake occurred in Nepal, and rescue workers carried out search and rescue with the help of Beidou. The following figure shows the post earthquake scene in new tubalchak area, Nepal,Picture source @ People's vision)
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However, such an upgrade
It's not plain sailing
In front of scientists
numerous crises
One of the difficulties is
How are satellites laid out
Optimal orbit for navigation satellite
It's about 20000 kilometers high
Mid circular orbit
It is the best choice to achieve global coverage
Satellites of GPS and other systems are distributed here
(schematic diagram of different orbit types and satellites,drafting@Chen Siqi & Chen Sui / Institute of planetary Research)
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however
Medium circular orbit satellite
Flying over the target areaShort time
That means
Want to achieve stable coverage of this area
Enough satellites must be launched
But then
Technology for launching such satellites
It is not yet mature in China
If all medium circular tracks are used
It is undoubtedly full of risks
In order to achieve the goal in the short term
Chinese scientists find another way
For the first time“Mix and match”Satellite layout
By arranging troops
14 satellites in three orbits
except4 medium circular orbit satellitesOutside
also5 tilt synchronous orbit satellites
Ensure the long-term coverage of the signal to the Asia Pacific region
5 geostationary satellites
Realize the stable coverage of this area all the time
（Tilt synchronizationOrbital satelliteOperating cycle and track heightSame as geostationary satellite.Tilt synchronous orbit satelliteIt is used for positioning and is the first in China. The following figure shows the beidou-2 systemSchematic drawing of three tracks@Zheng Borong / Institute of planetary Research)
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The second difficulty is
How to improve the accuracy
Electromagnetic waves travel at the speed of light
Even if there is a time error of 1 nanosecond
The resulting distance error will also be 0.3m
So the accuracy of satellite navigation and positioning
It mainly depends on the satelliteAtomic clock accuracy
And between satellites, ground stations and users
time synchronization
International universal spaceborne atomic clock
Accuracy needs to reachten-13
It is equivalent to an error of 1 second every 100000 years
And the countries with this technology at that time
Only the United States, Russia and Switzerland
(the following figure is the artistic imagination of the US GPS satellite, photo source @ NASA)
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The atomic clock used by Beidou 1
It is imported from Switzerland
But by Beidou two
Cooperation in the introduction of atomic clocks was interrupted
therefore
If Beidou 2 wants to complete successfully
The Chinese must race against time
Realize the independent development of atomic clock
(the satellites and launch vehicles of the Beidou satellite navigation system are developed and produced by the China Academy of space technology and the China Academy of launch vehicle technology affiliated to China Aerospace Science and Technology Corporation, respectively, as shown in the figure belowThe staff of China Academy of space technology are debugging the equipment, photographer @ Gou Bingchen)
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The urgency of time goes far beyond that
Difficulty 3
It's a satellite
How to launch on time
According to the rules of the International Telecommunication Union
Orbit and signal frequency of satellite operation
Application must be made in advance before use
And must be within 7 years after the application is approved
Complete satellite launch, orbit entry and signal reception
Otherwise, the relevant resources will be recycled
April 18, 2000
China's application was approved
This means that in the next seven years
Satellites and rockets must be foolproof
(the fairing after the docking of satellite and rocket is stretched and deformed at the edge of the picture due to wide-angle shootingShadow master @ Nan Yong)
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Scientists work day and night
Repeated experiments and tests
Master relevant satellite technology within 7 years
Overcome the difficulties of atomic clock in 2 years
even to the extent thatUse onlyMore than 10 days
Complete satellite removal, testing, and then reinstallation
A series of complex operations
FixedSudden failure before launch
(the engine of the satellite has failed. Experts are carefully checking the equipment. The second person from the right is academician sun Jiadong, chief designer of Beidou 1 and 2 systems. Photo)Shadow master @ Nan Yong)
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April 17, 20078 p.m
When people successfully receive the signal
Deadline from track failure
There are only four hours left
thus
Experience and break through the technical blockade
A satellite navigation system covering the Asia Pacific region has been completed
Distance enables global navigation
Only the last step
04
nets above and snares below
Last step
Will be acomprehensiveUpgrade of
Beidou-3 satellite
service lifeFrom 8 years to more than 10 years
Its components
Full implementationMade in China
Atomic clockContinuous performance upgrade
The accuracy has reached 10 million years, with a difference of 1 second
hereRocket technology
It is no longer a constraint
The launch of one arrow and two stars has been "perfect"”
End of 2017
launchoneArrow 2Star
2018
launch9 arrows 17 stars
2019
launch6 arrows and 8 stars
2020
launch3 arrows and 3 stars
Less than 3 years
30satellite
At an unprecedented rate
Launch and complete networking
(on June 23, 2020, the last global networking satellite of Beidou 3 was launched, photographer @ Shi Yue)
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therefore
In space
threeGrainsGeostationary orbit satellite
It is distributed directly over the equator
3 tilt synchronous orbit satellites
Stable coverage of the Asia Pacific Region
24 medium circular orbit satellites
Running around the earth day and night
Together they form
A hugeSatellite network
Hanging in space
It can be called a huge pictureSkynet
from then on
Day or night
Anywhere on earth
People can see 5-6 Beidou satellites when they look up
Global coverageGoal of
Finally realized
(operation diagram of beidou-3 system, cartography @ Zheng Borong / Institute of planetary Research)
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That's not enough
When the satellite flies over China
In the absence of ground control commands
satelliteNormal track operation cannot be guaranteed
to this end
People build bridges between satellites
Communication and ranging can be carried out between each other
Mutual supervision and automatic formation maintenance
Intricate composition
Inter satellite link
This is greatly reduced
System dependence on ground station
even ifAll ground stations failed
The Beidou system can still pass the inter satellite link
Maintain autonomous operation for up to 60 days
(schematic diagram of inter satellite link, cartography @ Zheng Borong / Institute of planetary Research)
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meanwhile
In China
Above the ground
More than 2700 ground reference stations
And several data processing centers
Also spread out on the land of China
Form a ground data processing network
Even if the satellite signal is affected
Various terrain, building occlusion and reflection
It can also provide additional ground information supplement
personFoundation reinforcement system
(Beidou foundation enhancement system consists of frame network and regional enhanced density network, including 155 frame network reference stations and more than 2700 regional enhanced density network reference stations. The following figure shows the distribution of frame website points, cartography @ Wang Chaoyang & Zheng Borong / Institute of planetary Research)
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After this correction and treatment
The error of the whole system is reduced again and again
Accuracy continues to increase
It can be meter level or decimeter level
Even centimeter or millimeter
Can be accurate to
Establishment of electronic fence
Ensure that the shared bicycle stops within the specified range
(a temporary storage place for shared bicycles in Xiangyang City, Hubei Province, photo source @ VCG)
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Can be accurate to
In the parade square
The squadron of various types of equipment marched at a constant speed
Each flight echelon is not bad in meters and seconds
The distance error is within plus or minus 10 cm
(on September 23, 2019, the flight echelon during the rehearsal of the National Day military parade, photographer @ Shicheng Tian Weitao)
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Can be accurate to
Monitoring dams, bridges, etc
Appearance deformation of the project
(please watch the horizontal screen. At the bottom right of the screen is Xiluodu Hydropower Station, the second largest hydropower station in China.At present, more than 150 monitoring points have been installed on the slopes on both sides of the hydropower station, and continuously provide millimeter precision data to find potential safety hazards in time, photographer @ Chai Junfeng)
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in addition
Beidou chip
It can be implanted into a mobile phone
As of the third quarter of 2019
Among the more than 400 mobile phones applied for network access in the Chinese market
Nearly 300 models support Beidou navigation
(the driver is using mobile navigation,Photographer @ Ren bingxu）
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It can be equipped with transportation tools
As of December 2019
More than 6.5 million operating vehicles
40000 postal and express vehicles
More than 3200 inland river navigation facilities
More than 2900 marine navigation facilities
All have been equipped with Beidou system
Become the world's largest dynamic supervision system for operating vehicles
(outside the Niujiaotuo light rail station in Chongqing, a bus runs on the viaduct,Photographer @ Shi Cheng Cui Li）
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thus
It is composed of Tianluo and geonet
This is the ultimate form of Beidou system evolution
Beidou 3
05
Beidou 20 years
2000-2020
Launched from the first star of Beidou-1
To the last satellite of Beidou 3
It's been 20 years
20 years
Face many difficulties
Scientists never retreat
They camped step by step
The first step is for China
The second step is Asia Pacific
The third step, for the world
today
ChinafinallyYes
Own satellite navigation system
future
It will be open to the world
It will also become a part of the lives of more than 7 billion people
(Beidou line fault indicator shall be installed in the power line to accurately find the accident location, eliminate the fault in time and reduce the power failure time.The following picture shows the power transmission towers rising one after another in the valley, photographer @ Qiu Huining)
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In the air
Fugitive pollutants
Incorporated into the environmental monitoring information system
From now on, we will not escape the "eye" of Beidou
(Beidou system can be used to obtain the real-time position of relevant monitoring points of air pollutants, and the communication function of Beidou can be used to send the information to the monitoring center.The following figure shows the factory chimney being discharged as a schematic, photographer @ Qiu Huining）
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Between fields
Through the cooperation between Beidou system and agricultural equipment
It can grasp the information of cultivation depth and row spacing in real time
Increase operation efficiency by 50%
Output increased by 5% - 8%
(the following figure shows the working scene of the planter equipped with Beidou navigation system, located in Jilin Province,Photographer @ Qiu Huining）
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And the border
The harsh environment with high mountains, dense forests and deep valleys
As a result, the communication facilities cannot be fully covered
And the border guards rely on the Beidou system
It can still deliver information in a timely and stable manner
(in areas that cannot be covered by mobile phone base stations, Beidou's positioning and communication functions become very important,The picture below shows border officers and soldiers patrolling the border, photographer@Han Jun Li）
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however
theseIt's not enough
Like the father of Chinese satellites
Chief designer of Beidou 1 and 2 systems
Sun JiadongSaid
The key to building Beidou is still to use it. Only when it is used more widely and deeply, will it be the winner.
yes
Scientists have been arrayed for 20 years
finallyWeave a "dragnet"
China's own satellite navigation system
And finally from imagination to reality
And this
Just the beginning of the story
Every day in the future
Is China's Beidou satellite navigation system
The true place of responsibility and mission
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