Chapter 1005 Network Coding Technology
The idea proposed by Chang Haonan is not difficult to understand.
Even now, some countries have actually begun to demonstrate the feasibility of this type of satellite gazing technology internally.
Of course, it is 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 suitable for most satellites with limited size but certain high-precision technologies on hand. As far as the country is concerned, they are all things that can be achieved with hard work.
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 there are relatively few associated front-end technologies.
For China, whose current external environment is relatively good, it can also take the path of introduction-digestion and absorption.
There are no completely insurmountable technical barriers.
"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 it out. joints:
"But the key point of military reconnaissance is timeliness. If a warship sails at full speed, it can travel about 100 kilometers away in an hour and a half, so it is definitely not enough to take effective pictures. You must also ensure that what 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...then even if the reconnaissance data can be obtained, We have to wait for almost ten hours before we can re-enter the data transmission window..."
Everyone who had just become excited suddenly calmed down.
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 it passes Some small tricks can improve some efficiency, but core technologies such as inter-satellite links cannot be avoided after all..."
"..."
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.
So, after some mental ups and downs, everyone finally entered the celebration that was prepared before entering, but was postponed to the present due to the interlude.
Only Zhang Weiyong, quietly following the crowd, lowered his head and seemed to be 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 reacted:
"Oh...Mr. Chang"
Zhang Weiyong showed a somewhat embarrassed smile:
< br>
"Sorry, I was thinking about something just now. I slipped away and didn't hear you."
"Still thinking about the ocean surveillance system?"
Chang Haonan himself has actually been thinking about this matter. , it’s just that he has become accustomed to multitasking, so everything appears to be normal.
“Ah...that’s right.”
Zhang Weiyong nodded:
"Or strictly speaking, we are considering what you mentioned last about satellite relay communications."
"From our current launch capabilities, if we want to launch a satellite into geosynchronous orbit, It is indeed difficult to build a large reconnaissance satellite like a keyhole, but if it is just a communication relay satellite, only 3-4 are needed to meet the communication needs between low-orbit satellites and between low-orbit satellites and the ground. Contact us.”
“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 satellites. On small satellites, it 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 Space X picture.
The product 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 close to real-time reconnaissance.
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 and wait for the communication window that can be as short as 90 minutes or as long as several hours. Instead, the information is immediately transmitted back to the control center on the ground through 2-3 relay communications.
Completely reduce the timeliness of satellite reconnaissance 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 the 921 project, in order to solve the problem of insufficient coverage of measurement and control stations and measurement 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, even know this?"
"Uh..."
Chang Haonan touched his chin awkwardly.
Of course it was impossible for him to say that he knew this twenty years later, so he had to prevaricate casually:
"You know, I have a good relationship with the Science and Technology Commission, and I gave a When the project applied for the payload space of Shenzhou-2, I read some information from Director Luan..."
Not a single punctuation mark in this sentence is false, so Zhang Weiyong did not delve into it further:< br>
“Yes, there is.”
He replied:
“And the project was only established at the beginning of this year. The internal plan is called Tianlian-1.”
“I was just thinking about whether we could rely on these few satellites of the 921 project. Satellite, let me verify my idea in detail.”
For the Chinese astronauts who have almost started from scratch and have been frugal in the past few decades, they have made full use of existing resources to improve the project. Cost-efficiency has almost become an instinct.
But on the other hand, the 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 the space observation and control window period. The data bandwidth is quite average. I am afraid it is not suitable for low-orbit satellites. There is a need for information flow between the group, both image and voice..."
"There is no way...Actually, I am also struggling with this matter now."
Zhang Weiyong sighed softly. Tone:
"The synchronous orbit is too far from the low Earth orbit, which limits the bandwidth and delay from a physical level..."
Chang Haonan opened his mind directly:
"Have you considered it? Let the relay satellite also operate in low orbit? ”
“Huh? ”
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 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 there. It’s good to have a small number of geostationary satellites.”
As he spoke, Zhang Weiyong looked at Chang Haonan with a slightly confused look.
At the end of the sentence, 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 entered 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 he was talking and poured a little for each of them.
Zhang Weiyong took the 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?"
"I'm a bit impressed."
He put down the wine glass that had been brought to his mouth. To the side:
“But I remember it seems to be used on routing equipment?”
“Yes, but it is essentially effective 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 a generalized code that introduces different information into the communication relay node. Technology changes the original meaning of the transmission of special data in the network into the transmission of network data streams, which can greatly reduce the occupation of network bandwidth when transmitting information, and 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 have not studied it in depth, I 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 am better at..."
(This chapter End)