"I don't understand, the history books clearly say that Beidou navigation is a double star positioning, why do you need four when you come here?"

Whether it makes sense or not, it is Fang Yuan's ability to always find a point to go back.

"The double satellite positioning is talking about [Beidou-1], of course, this is a relatively popular saying, and the scientific name is [Beidou Satellite Navigation Test System]."

"Speaking of which, isn't two enough?"

If the general direction is not correct, the right part of the general direction will be intercepted.

Staying the course is victory.

"The dual-satellite positioning system, in fact, has three satellites, two working satellites and one backup satellite."

Fang Yuan finally couldn't even find an excuse, and began to obediently listen to Liang Tian tell the story.

The accuracy of the dual-satellite positioning system is within 100 meters, and if calibrated, the accuracy can reach 20 meters.

Such accuracy is definitely not as good as the later [Beidou No. 2] and [Beidou No. 3].

However, under certain historical conditions, dual-satellite positioning is the fastest way for a country to have an independent satellite navigation system.

In the eyes of astronauts, the first step of three steps, starting from scratch, is the most important.

Without Beidou-1, there is no way to legally have your own satellite navigation system.

However, Beidou-1 was experimental, and the three satellites were launched on October 31, December 21, 2000 and May 25, 2003.

The scope of use is limited to the territory of our country, and after the expiration of the life of the satellite, the service is discontinued.

At this point, it is still not possible to legally own a global satellite navigation system.

According to ITU regulations, two conditions need to be met in order to legally use a frequency band.

First, apply to ITU.

ITU will inform the requester of the timing of the acceptance of the application.

The applicant is required to start using this frequency band within 7 years based on this notification time.

If the application is not successfully used, the application will be deemed invalid.

The application for the frequency band of China's Beidou navigation system was made on April 18, 2000.

The frequency band application for the European Galileo navigation system was made on 5 June 2000.

The time frame for filing the application is similar.

Because the good frequency band was already occupied in the eighties of the last century.

There is a high degree of overlap in the frequency bands applied by Beidou and Galileo.

The second condition of ITU is particularly important at this time – when multiple parties request the same frequency, they can be coordinated with each other and shared as long as the user feels that there is no interference.

If it is coordinated, it can be used legally by all parties.

At first, the idea of the Beidou people was, [Hello, hello, everyone].

There are so many frequency bands left, try to cooperate and find a way not to interfere with each other.

In 2003, after the launch of the last test satellite of Beidou-1, China invested 230 million euros and signed an agreement with the European Union to participate in the Galileo project.

In the following two years, the Beidou people gave everything, and the gain was almost nothing.

The first is the core accessory, the rubidium atomic clock.

According to the original idea of the Beidou people, each Beidou satellite will carry four rubidium atomic clocks.

One is domestically produced and three are imported.

At that time, our country did not yet have the ability to manufacture rubidium atomic clocks with an accuracy of navigation satellites (an error of less than one second in a million years).

From the beginning he agreed to sell it to us, and then he didn't.

Finally, after many negotiations, there was a company willing to sell, and the delivery time and accuracy were greatly reduced.

I don't know if it's really a technical reason, or if it's deliberately not allowing us to legally own the frequency band.

The time came in 2005, and the Beidou people reluctantly withdrew from Galileo.

[Hello, hello, everyone] This road is no longer working.

Only by creating the Chinese's own rubidium atomic clock can we have the Chinese's own navigation.

This process has seriously slowed down our country's legitimate access to ITU frequency resources and orbital positions.

Galileo launched his first test satellite, Galileo-A, on 28 December 2005, and half a month later, on 12 January 2006, Galileo launched a navigation signal.

At this time, the Beidou people were still working day and night for the rubidium atomic clock.

"Old man Liang, what you said here is that the navigation signal was launched on January 12, 2006, does that mean that it is officially used?"

Liang Tian nodded: "That's right." ”

"Huh? Doesn't Galileo legitimately have the right of first refusal to use the frequency band? ”

"Europeans think so, at this pace, it is impossible for China to build its own rubidium atomic clock before the end of the 2007 frequency band."

"I mean what you said before, first-come, first-served, according to this logic, Beidou will have no chance at the beginning of 2006."

"Yes, things have come to this point, and the Galileo people who have won the game are more or less too lazy to take care of it, but don't forget how the second article of ITU is written."

Fang Yuan recalled Liang Tiangang's words: "[When multiple parties apply for the same frequency, they can coordinate with each other, as long as the user feels that there is no interference, they can share it. 】”

After recalling, I still feel that there is a problem: "In this case, people will definitely not say that they think there is no interference." ”

"Little doll, you're right, and this is one of the key factors in Galileo's navigation system thinking that he has a chance to win." Liang Tian fell into memory: "I was already a member of the Beidou people at that time, and I was also worried. ”

"And then?"

Fang Yuan knew that Beidou must have survived this hurdle, but under the historical conditions at that time, the possibility of ITU moving towards Beidou was very small.

Liang Tian did not answer directly, but reminded with a little pride: "You remember the second condition so clearly, you should study and study it carefully." ”

Fang Yuan read it twice, no matter how much he read it, it was still the same.

"Xiao Fangyuan, if you are like this, you are not suitable for studying law."

Liang Tian announced the correct answer before Fang Yuan's explosion: "The second condition, before whether it affects each other, is that all parties need to coordinate with each other when applying for the same frequency. But Galileo never coordinated with us from beginning to end. You haven't coordinated, so we still apply first, why can't we have priority? ”

"Is that all right? You can't have come up with this, right? ”

"Why do you think that?"

"This kind of words can only be thought of by Liang Tian, a rebellious racing driver, right?"

"That's not really." Liang Tian was amused by Fang Yuan: "This is a simple legal issue, what is written in black and white in the ITU charter, you can't slap yourself in the face, right?" The highest level of negotiation is to use the logic of the other party to persuade the other party. ”

"That's just as well." Fang Yuan thought deeply, "But in the end, the other party should still believe that we can't even handle the rubidium atomic clock." ”

"Xiao Fangyuan, what you said is not wrong, according to the normal situation, in three or five years, we can't even make a shadow of the rubidium atomic clock that can meet the requirements. But our country's astronauts have never fought alone. ”

Outside of Liang Tian's words, a familiar feeling came to his face.

Fang Yuan also already has a basic understanding of the chief designer: "Here it is again, the national mobilization, right?" ”

"That's right! Withdrawing from Galileo, the Beidou people made up their minds on the last day of May 2005 to replace the four space-borne rubidium atomic clocks with domestic ones, and in a year and a half, the whole country mobilized to directly dry the domestic rubidium atomic clocks to 3 million years, with an error of no more than 1 second. ”

"This is truly a remarkable achievement." Fang Yuan thought for a while, "A year and a half, even at the beginning of 2007, it has been completely done." You'll have to wait until April 14 for the launch, and the final hours of the 17th for acceptance. You guys did it on purpose, right? ”

"That's not it, our Beidou, there were more than 160 technical problems that needed to be solved at that time. Rubidium atomic clocks are a top priority, but it doesn't mean that they can be launched immediately. We definitely want to launch as soon as possible, you see Galileo from the time of transmitting to receiving the signal, it took half a month in between. ”

"In other words, the on-orbit debugging time must take half a month, right?"

"It's going to take at least seven days."

"If you push forward 7 days, it will have to be launched on April 10, why did it finally delay to April 14?"

"This is not our original intention, the first satellite of [Beidou-2] and the rocket carrying the satellite, on April 2 and 3, were transported to the launch site, and then went to the launch tower to make the final preparations before launch, we carried out three general inspections before and after, the first two times there was no problem, and the third transponder appeared to have an abnormal situation of unstable signal."

"The transponder is a tool for communication between the satellite and the ground, right? We also have transponders on board the Galactic Ship. ”

"There's nothing wrong with that. We had lost contact with the balloon control center when the magnetic storm disconnected the transponder. ”

"This has been arranged clearly by Old Man Liang." Fang Yuan said back to the point, "If this transponder is broken, even if it is launched, we will not receive the signal, which is equivalent to a vain ride, right?" ”

"Yes."

"Then you just said, it's unstable, it's not broken, and you can still take a risk."

"I did think about it, because it was too late. If we want to zero the problem of the transponder, we must first go to the top of the 60 or 70-meter-high launch tower, and remove the fairing and satellite deck on the premise of zero error, so that the rocket and satellite cannot suffer any slight losses. ”

"And next?"

"The second is that the transponder was developed by me in Shanghai, and the satellite launch center does not have the experimental conditions to zero the transponder problem."

"Uh...... Old man Liang, why does it have anything to do with you......"

"I don't know, maybe it's fate. Dong Ge and they discussed it later, and gave me three days to solve the problem of the answering machine. ”

"And then you're going to fly back to Shanghai with the transponder?"

"How is it possible to bring an answering machine on a plane? Dongge, they found a place in Chengdu with experimental conditions, I held the transponder, and the special truck driver of the base spent five hours sending me to the laboratory. For 72 hours, I didn't close my eyes, and I can't remember how many tests I did. ”

Fang Yuan thought about it, he hadn't experienced it for the time being, and it should be quite difficult to think about it.

praised the chief designer in his heart, but the words that came out of his mouth became: "You were just thirty years old at that time, and it was okay to stay up for three days." ”

"At that time, I really didn't dare to sleep for a second, because when I went to Chengdu, it was already April 11th, not to mention how much time it takes to debug later, before April 17th, only April 14th, there is the closest launch window, miss this, all the previous efforts will be in vain, and there is no chance to take the back commissioning."

Liang Tian explained very seriously that Beidou did not deliberately step on the deadline set by the ITU.

Because the launch was late, the subsequent on-orbit debugging could only be in full swing.

Galileo took half a month, and Beidou only had three days.

Three days later, at 8 p.m. on April 17, 2007, the first satellite of Beidou-2 sent its first set of signals to Earth.

Liang Tian, along with more than a dozen other receiver design manufacturers, lined up the receivers in a row on a huge playground.

As long as one receiver can receive the signal transmitted back from the satellite, it can keep ITU's frequency resources and orbital position, so that Beidou navigation has a legal status.

At 8 p.m. on April 17, 2007, the receivers on the playground, one counted, and all of them received the signal accurately.

China's Beidou, from this moment on, has a legal status, with 100% domestic core components, began to go to the world stage.

China's Beidou has slowly become the world's Beidou.

Galileo, who was full of confidence at the beginning, began to be anxious again at this time.

Galileo repeatedly made representations to Beidou, but they didn't have much to do, and it was the second half of ITU's second condition, repeatedly saying that the same frequency as China's Beidou would interfere with the operation of Galileo in Europe.

Such negotiations were quite serious at the beginning.

After all, Galileo launched satellites earlier than Beidou, completed their use earlier, and had more satellites in the sky at the beginning.

But such negotiations, over time, with the rapid development of China's Beidou, slowly lost their meaning.

As of 2012, the Galileo navigation system has launched a total of 6 satellites, and [Beidou-2] just adds a 1 in front of the European Galileo.

China's Beidou, with 16 navigation satellites, has directly expanded the scope of navigation and positioning services to the entire Asia-Pacific region.

Galileo persevered in negotiations for several more years, and it was not until 2015 that the second condition stipulated by ITU was formally reached with China Beidou - China Beidou and European Galileo applied for the same frequency band, and the two sides negotiated amicably, believing that in use, there was no mutual interference, and the same frequency band could be used together.

From 2007 to 2015, this day, the Beidou people waited for eight years.

In the past eight years, Galileo's reasons for negotiations have not changed in any way.

The only variable is the Beidou speed of the Chinese.