Chapter 1005 Network Coding Technology

The idea proposed by Chang Haonan is not difficult to understand.

In fact, some countries have actually begun to demonstrate the feasibility of such satellite gazing technology internally.

Of course, it is also not a simple matter for the device to continuously adjust the angle while maintaining the image quality.

But compared with large-load satellites, heavy-lift rockets carry these things that require strong comprehensive national strength to support them. A single movable equipment platform is not enough for most countries with limited size but certain high-precision technologies on hand. Something you can achieve if you work hard.

To put it bluntly, the basic principles of this thing and the multi-degree-of-freedom gimbal on the aiming pod are the same, and the associated front-end technology is relatively small.

For China, whose current external environment is relatively good, it can also take the path of introduction-digestion and absorption.

There are no technical barriers that are completely insurmountable.

"In this case... it can indeed extend the effective monitoring time of each satellite on key areas."

No need for Chang Haonan to explain too much, Luan Wenjie quickly figured out the joints:

"But the key point of military reconnaissance is timeliness. If a warship sails at full speed, it can travel about 100 kilometers in an hour and a half, so it is definitely not enough to take effective pictures. You must also ensure that the things you take can be transmitted back in real time. OK..."

"If the satellite is photographing the western Pacific Ocean over our country, that's fine, but if the satellite itself is in the eastern Pacific Ocean, or even south of the equator... Even if the reconnaissance data can be obtained, it will have to wait for almost ten hours before re-entering. Data transfer window..."

Everyone who had just become excited suddenly calmed down again.

However, Chang Haonan's mentality was very stable, and he just sighed slightly:

"There is no way. Satellite surveillance is something that only superpowers can handle. Even if some efficiency can be improved through some tricks, core technologies such as inter-satellite links cannot be avoided... "

"..."

In any case, it was an unexpected surprise to be able to capture the location of Kitty Hawk today.

As for the 24-hour surveillance of the waters surrounding China, it was entirely due to Chen Dazhi's temporary expansion of mentality.

Therefore, after some mental ups and downs, everyone finally entered the celebration session that was prepared before but was postponed to the present due to the interlude.

Only Zhang Weiyong followed quietly at the back of the crowd, lowering his head as if thinking about something.

"Mr. Zhang?"

After chatting with Chen Dazhi and other acquaintances, Chang Haonan quickly noticed the slightly lonely figure behind him.

After calling three times, the other party finally responded:

"Oh...Mr. Chang"

Zhang Weiyong showed a somewhat embarrassed smile:

"Sorry, I was thinking about something just now, so I slipped away a little and didn't hear you."

"Still thinking about the ocean surveillance system?"

Chang Haonan himself has actually been thinking about this matter, but he has become accustomed to multitasking, so outwardly everything seems to be normal.

"Ah...that's right."

Zhang Weiyong nodded:

"Or strictly speaking, I'm thinking about what you mentioned last about satellite relay communications."

"Based on our current launch capabilities, it is indeed difficult to launch a large-scale reconnaissance satellite like a keyhole into geosynchronous orbit, but if it is just a communication relay satellite, only 3-4 are needed. , it can meet the communication requirements between low-orbit satellites and between low-orbit satellites and the ground.”

"If such a relay constellation can be built, then in many aspects we can no longer pursue a single all-powerful satellite, but split different functions into a large number of low-cost small satellites, which is more in line with our current carrying capacity. level……"

"..."

After listening to the other party's explanation, Chang Haonan couldn't help but admire in his heart——

This idea of ​​"exchanging quantity for quality" is still a very advanced concept even if it is put aside more than ten years later.

Although the most famous thing under this guiding ideology in the future may be Starlink, in fact, China had already introduced the same idea in the field of remote sensing satellites as early as 2014 before the SpaceX incident.

The product produced is the "Jilin-1" optical remote sensing satellite constellation. It is ultimately planned to deploy more than 300 satellites to achieve the goal of revisiting any point in the world with a revisit period of less than 30 minutes.

Almost as close to real-time reconnaissance as possible.

And Zhang Weiyong's ideas are even wilder.

We must not only pursue efficiency at the information acquisition level, but also pursue efficiency at the information transmission level.

For example, a satellite acquires a valid image information on the other side of the earth.

Then there is no need to store it and wait for a communication window that can be as short as 90 minutes or as long as a few hours. Instead, the information is immediately transmitted back to the control center on the ground through 2-3 relay communications.

The timeliness of satellite reconnaissance is completely reduced to near the theoretical limit (that is, the revisit cycle).

"Communication relay star..."

Chang Haonan lowered his head and thought for a moment:

"I remember that in Project 921, in order to solve the problem of insufficient coverage of measurement and control stations and survey ships in our country, there seems to be a research and development plan for data relay satellites?"

Hearing this question, Zhang Weiyong looked at Chang Haonan with a slightly shocked expression:

"I didn't expect you, Mr. Chang, to know this?"

"Well……"

Chang Haonan touched his chin awkwardly.

Naturally, it was impossible for him to say that he knew this twenty years later, so he could only explain it casually:

"You know, I have a good relationship with the Science and Technology Commission. When I applied for the Shenzhou-2 payload space for a project, I read some information from Director Luan..."

Not a single punctuation mark in this sentence was false, so Zhang Weiyong did not delve into it further:

"Yes, it does."

He replied:

"And the project was only established at the beginning of this year. The internal plan is called Tianlian No. 1."

"I was just wondering if I could use these satellites of the 921 project to concretely verify my idea."

For Chinese astronauts who started from scratch and have been frugal in the past few decades, it has almost become an instinct to make full use of existing resources and improve the cost-effectiveness of the project.

But on the other hand, a high cost-effectiveness ratio means that in most cases the effect itself is mediocre——

Because the effect of reducing the denominator is much more obvious than increasing the numerator.

Chang Haonan frowned after hearing this:

"Tianlian-1 is just to solve the problem of space measurement and control window period. The data bandwidth is quite average. I am afraid it is not very good at meeting the image and voice information flow needs between low-orbit satellite groups..."

"There's no way...Actually, I'm still struggling with this matter right now."

Zhang Weiyong sighed softly:

"The synchronous orbit is too far from the low Earth orbit, which physically limits the bandwidth and delay..."

Chang Haonan opened his mind directly:

"Have you considered having relay satellites also operating in low orbit?"

"ah?"

This method is indeed a bit deviant for Zhang Weiyong:

"Not to mention how many satellites are needed... Even if the number is sufficient, there will be many data relay nodes in the communication network, and each node will cause signal attenuation and data transmission errors..."

"It's easy to say on the ground. Generally, the problem can be solved by repeatedly forwarding the data. But if it is a satellite... it will bring a more serious burden to the network throughput and transmission efficiency... The final transmission effect may not be a small amount. Geostationary satellites are coming well.”

While talking, Zhang Weiyong looked at Chang Haonan with slightly doubtful eyes.

By the end, my voice was a little unconfident.

In his opinion, the latter, as a big man who has made great achievements in many fields such as control and mathematics, seems not to make such a low-level mistake.

Is there anything else that can be done here?

The other party's reaction was just as Zhang Weiyong expected:

"If it is a general communication relay method, then there are indeed the problems you mentioned..."

The group of people had actually walked into the small canteen where the celebration was held. Chang Haonan did not forget to pick up a bottle of low-alcohol red wine from the side while talking and pour a little for each of them.

Zhang Weiyong took the wine glass, but before he could drink it, he heard the second half of Chang Haonan's words:

"But Mr. Zhang may have heard of a new technology that was only proposed last year, called network coding?"

"Some impression."

He put aside the wine glass that had been brought to his lips:

"But I remember it seems to be used on routing equipment?"

"True, but essentially valid for any information transmission node."

Chang Haonan pulled Zhang Weiyong to sit next to him, and then took out the half-used piece of paper from his jacket pocket:

"To put it simply, it is to introduce generalized coding technology of different information at communication relay nodes, changing the original meaning of the transmission of special data in the network into the transmission of network data streams, which can greatly reduce the impact on network bandwidth during information transmission. The occupation can also increase the cost of deciphering information. "

"It sounds... closer to a concept."

Zhang Weiyong was obviously interested in this, but he did not immediately show any excitement:

"Although I haven't studied it in depth, I think... the entire communication effect is probably highly related to the introduced generalized coding, right?"

"Of course."

Chang Haonan picked up the cup and took a sip:

"However, this happens to be the part I'm better at..."