"Start the Beidou navigation and positioning test!"
Chen Zhongyan was constantly conducting various tests in the lobby of the satellite control center.
After the Beidou Phase I system entered the geostationary orbit, it has relied on its own power to move to its predetermined position.
And unfolded its own solar wing sail and officially started work.
Beidou Phase I mainly provides positioning, communication, and timing functions.
If the positioning function wants to achieve high accuracy, it must rely on a highly accurate atomic clock.
Because the implementation of the Beidou positioning function simply calculates the user's position through the time difference between the two satellites receiving ground signals.
Therefore, if the error of the rubidium atomic clocks on the two satellites exceeds 1ns (billionth of a second), the difference can be 0.3 meters for ground positioning.
The reason why the positioning accuracy of the later Beidou Phase III navigation system was much higher was largely due to the localization of domestic rubidium atomic clocks and cesium atomic clocks, which made the timing accuracy much higher.
As for the two rubidium atomic clocks on Beidou 1 and 2, because the country is still relatively backward in this regard, they cannot be independently produced and can only be imported from abroad at high prices. And even so, these two rubidium atomic clocks can only be regarded as It barely meets the application requirements.
"The ground control system has obtained the positioning data sent back by Beidou-1 and Beidou-2."
An engineer wearing a blue and white uniform handed Chen Zhongyan the latest positioning information sent back by Beidou.
"Going out so much?!"
Chen Zhongyan looked at the data report in his hand and frowned.
Although it was expected that the positioning accuracy would not be too high before the satellite was launched into the sky, when the real situation came out, it was still a bit shocking.
The positioning accuracy of the Beidou Phase I positioning and navigation system can only be maintained within an error range of 20-100 meters.
You must know that the positioning accuracy of Yingjiang's GPS positioning and navigation system at this time can reach 10 meters.
"Is it really the problem with the atomic clock?"
Chen Zhongyang looked at the errors in several positioning marks and couldn't help but think to himself.
"Has the timing function been tested?"
Hiding the problem of the atomic clock in his heart, Chen Zhongyan asked about the timing issue.
"Testing is ongoing and results will be available soon."
After the engineer finished speaking, he immediately returned to his job and continued working.
Looking at the busy people, Chen Zhongyan fell into deep thought.
Atomic clocks are actually a big problem that navigation systems must face.
At this time, the road to domestically produced rubidium atomic clocks is not very smooth. It is not known how many years it will take to truly achieve localization.
And when the domestic Beidou navigation system is actually built in the future, it is still a question whether they will continue to sell you rubidium atomic clocks!
"Mr. Chen, the timing accuracy results are out."
At this time, another engineer ran over and handed the timing accuracy results of Beidou Phase 1 to Chen Zhongyan.
The accuracy of satellite timing is actually controlled by the theory of relativity.
According to the time dilation effect in Einstein's theory of relativity, the faster an object moves, the slower time will appear.
Beidou satellites fly at a speed of 4km/s in space. According to the special theory of relativity, time every day will slow down: (4×4)/2(c×c)×60×60×24=7.68 microseconds. The satellite is from the ground 20000km, the gravity is much smaller than the ground. According to the general theory of relativity (the difference between the gravitational potential of the satellite and the ground)/(the square of the speed of light), the time every day will be faster: [(GM/6371km)-(GM/26371km)]/c /c=45.58 microseconds. In other words, satellites in the sky are 38 microseconds faster than those on the ground every day.
That is to say, if the satellite does nothing in the sky every day, it will produce an error of 38 seconds. Therefore, if you want to maintain the accuracy of the time, you need to calibrate the time of the atomic clock every 1.5 seconds.
"The timing accuracy is not very different from the experiments we did on the ground, and the error is about 20ns."
The engineer looked at the timing accuracy report in Chen Zhongyan's hand and said helplessly.
"Well, it is indeed not much different from the experiments we did before, but this is a two-way timing accuracy, and the one-way timing accuracy is still somewhat unsatisfactory!"
Chen Zhongyan agreed with the engineer's statement, but also pointed out the difference here.
Generally speaking, the one-way timing function does not require the Beidou terminal on the ground to send signals to the satellite, but only needs to receive the timing signals broadcast by the Beidou satellite.
Although the accuracy of this timing method is lower, it does not need to occupy the communication band of the Beidou satellite system.
The number of users that Beidou can receive transmission at the same time is limited, no more than 540,000 users per hour.
Most of them are used in various positions that require precise timing.
It is simply impossible for most industries or units to use it.
Therefore, the one-way timing accuracy is the real accuracy of Beidou timing!
"Mr. Chen, under our current conditions, this is the limit." The engineer felt that achieving the current accuracy is almost the limit of the entire Beidou project team.
You must know that if other countries were to do this, using atomic clocks with such accuracy, the accuracy would definitely be much lower than theirs.
Chen Zhongyan also knows that everyone has put in a lot of time and energy to achieve this.
So I didn’t criticize him too much, but gave him some comfort:
"Everyone is working hard for Beidou in the sky!"
"The results of the communication function test are probably coming out soon, so go ahead and get busy."
At this time, Chen Zhongyan walked next to the engineer responsible for communication function testing.
Watching the data exchange between the stars and the earth, it was displayed on the big-ass computer that was still very backward.
The communication function of the Beidou system can be regarded as the first in China.
At this time, two satellite systems have been completed, whether it is Maozi's GLONASS system or Yingjiang's GPS system.
They all have no communication function.
However, because the low-orbit satellite communication system has been officially approved and construction work has begun, the communication functions originally reserved for the Beidou Phase II system to be built later have been cut off.
Only the positioning and timing functions are retained.
"Mr. Chen, the test results are better than the experiments we did on the ground!"
The female engineer in charge of communication testing turned her head and looked at Chen Zhongyan very happily.
"A single transmission of 36 Chinese characters, a continuous transmission of 120 Chinese characters, and a two-way transmission of 36 Chinese characters have all reached the results of our ground tests."
"However, the transmission response effect is better than when we tested before."
Chen Zhongyan pushed up his glasses and said happily looking at the results on the screen.
Because the launch was carried out three years in advance, Beidou in this world has seized a better orbit.
Therefore, the signal transmission effect is even better than in previous lives.
(End of chapter)
