A big country of aerospace with black technology

"Begin the Beidou navigation and positioning test!"

Chen Zhongyan was constantly conducting various tests in the satellite control center hall.

After the Beidou Phase I system entered the geostationary orbit, it has moved to the predetermined position relying on its own power.

And launched its own solar wing sails, officially started work.

The first phase of Beidou mainly provides positioning, communication and timing functions.

If the positioning function wants to achieve high precision, it must rely on highly accurate atomic clocks.

Because the realization of the Beidou positioning function is simply to calculate the user's position through the time difference between the two satellites receiving the ground signal.

Therefore, if the error of the rubidium atomic clocks on the two satellites exceeds 1 ns (one billionth of a second), it can be out of 0.3 meters for ground positioning.

The reason why the positioning accuracy of the later Beidou Phase III navigation system was much higher is largely because the domestic rubidium atomic clock and cesium atomic clock have been localized, and the accuracy of time service is much higher.

As for the two rubidium atomic clocks on Beidou-1 and Beidou-2, because the country is still relatively backward in this area, they cannot be produced independently, and can only be imported from abroad at a high price, and even so, these two rubidium atomic clocks can only be regarded as Barely met the application requirements.

"The ground control system has obtained the positioning data sent back by Beidou-1 and Beidou-2."

An engineer in a blue and white uniform handed over the latest positioning information sent back by Beidou to Chen Zhongyan.

"It's so far away?!"

Chen Zhongyan frowned as he looked at the data report in his hand.

Although it was expected that the positioning accuracy would not be too high before the satellite was launched into the sky, after 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 at this time, the positioning accuracy of Yingjiang's GPS positioning and navigation system can reach 10 meters.

"Is it still an atomic clock problem?"

Chen Zhongyang looked at the errors of several positioning punctuation points, and couldn't help but think in his heart.

"Has the timing function been tested?"

Hiding the question of the atomic clock in his heart, Chen Zhongyan asked about timing.

"Tests are underway and results will be available soon."

After the engineer finished speaking, he immediately returned to his work station and continued to work.

Looking at the busy crowd, Chen Zhongyan fell into deep thought.

The atomic clock is actually a big problem that the navigation system must face.

At this time, the road to domestically produced rubidium atomic clocks is not very smooth, and it is not known how many years it will take to achieve localization.

And when the Beidou navigation system in China is really going to be built in the future, it is still a question whether people will continue to sell you rubidium atomic clocks at that time!

"Old Chen, the timing accuracy results are out."

At this time, another engineer ran over and handed over the timing accuracy results of Beidou Phase I to Chen Zhongyan.

The accuracy of satellite timing is actually controlled by the theory of relativity.

According to the time dilation effect in Mr. Einstein's theory of relativity, the faster an object moves, the slower time will be.

The Beidou satellite flies in space at a speed of 4km/s. According to the special theory of relativity, the daily time will slow down: (4×4)/2(c×c)×60×60×24=7.68 microseconds from the ground 20000km, the gravity is much smaller than the ground, according to the general theory of relativity (the difference between the satellite and the ground gravitational potential) / (the square of the speed of light), the daily time will be faster: [(GM/6371km)-(GM/26371km)]/c /c=45.58 microseconds That is to say, the satellite in the sky will be 38 microseconds faster than the ground every day.

That is to say, if the satellite does nothing in the sky every day, there will be an error of 38 seconds, so if you want to maintain the accuracy of the time, you need the atomic clock to perform time calibration every 1.5 seconds.

"The timing accuracy is not very different from the experiments we did when we were on the ground, and the error is about 20ns."

Looking at the timing accuracy report in Chen Zhongyan's hand, the engineer said helplessly.

"Well, it is indeed not that far from the experiment we did before, but this is the two-way timing accuracy, and the one-way timing accuracy is still a bit 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 signal broadcast by the Beidou satellite.

Although the accuracy of this timing method is lower, it does not need to occupy the communication frequency band of the Beidou satellite system.

The number of users that Beidou can receive transmissions at the same time is limited, no more than 540,000 users per hour.

Most of them are also 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!

"Old Chen, with our current conditions, it is the limit to be able to do this." 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 do it, and use atomic clocks with such precision, the precision will definitely be much lower than theirs.

Chen Zhongyan also knows that everyone has put in a lot of time and energy to make it like this.

So there is not too much harshness, but a little comfort:

"Everyone is for the Big Dipper in the sky, you have worked hard!"

"The results of the communication function test are probably coming out soon, so go get busy."

At this time, Chen Zhongyan walked to the engineer in charge of the communication function test.

Looking at the data exchange between the stars and the earth, it is displayed on the computer with a big butt that is 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 established, 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 in the second phase of the Beidou system that will be built later have been cut off.

Only the positioning and timing functions are retained.

"Old Chen, the test results are even better than the experiments we did on the ground!"

The female engineer in charge of the communication test turned her head and looked at Chen Zhongyan very happily.

"Single transmission of 36 Chinese characters, continuous transmission of 120 Chinese characters, and two-way transmission of 36 Chinese characters have all reached the results of our ground test."

"However, the transmission response effect is better than when we tested it before."

Chen Zhongyan pushed his glasses, looked at the results on the screen and said a little happily.

Because of the launch three years earlier, the Beidou in this world has seized a better orbit.

Therefore, the transmission effect of the signal is also better than in the previous life.