Chapter 1005 Network Coding Technology

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

In fact, some countries have already begun to internally demonstrate the feasibility of this type of satellite staring technology.

Of course, it is not an easy task to allow the device to continuously adjust the angle while maintaining the image quality.

But compared to large-payload satellites and heavy rockets that require strong comprehensive national strength to support, a single movable equipment platform is something that most countries with limited size but certain high-end technologies can achieve with a little effort.

To put it bluntly, this thing is consistent with the multi-degree-of-freedom gimbal on the aiming pod in basic principles, and there are relatively few related pre-technologies.

As for China, where the current external environment is still relatively good, it can also take the path of introduction, digestion and absorption.

There are no completely insurmountable technical barriers.

"In this way... it is indeed possible to extend the effective monitoring time of each satellite over key areas."

Without Chang Haonan's further explanation, Luan Wenjie quickly figured out the key points:

"But the key to military reconnaissance is timeliness. If a warship is sailing at full speed, it can travel about 100 kilometers in an hour and a half. So it is definitely not enough to just be able to take effective pictures. We also have to ensure that the pictures can be transmitted back in real time..."

"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 we can get reconnaissance data, we'll have to wait for more than ten hours before we can re-enter the data transmission window..."

The crowd who had just become excited suddenly calmed down again.

However, Chang Haonan's mentality was very stable. He just sighed slightly:

"There's nothing we can do. Satellite surveillance is something that only superpowers can handle. Even if we can improve efficiency through some tricks, core technologies such as intersatellite links are still unavoidable..."

"..."

In any case, being able to capture the location of Kitty Hawk today was a pleasant surprise.

As for the 24-hour surveillance of the waters surrounding China, it was entirely Chen Dazhi's momentary arrogance.

So, after some ups and downs in mentality, everyone finally entered into the celebration session that they had prepared for before but had been postponed to now because of the episode in the middle.

Only Zhang Weiyong followed quietly at the back of the crowd, with his head lowered, seemingly thinking about something.

"boss Zhang?"

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

After shouting three times, the other party finally responded:

"Oh... Mr. Chang"

Zhang Weiyong gave an embarrassed smile:

"Sorry, I was thinking about something just now and was a little distracted, so I didn't hear it."

"Still considering the issue of the ocean surveillance system?"

Chang Haonan himself had actually been thinking about this matter, but he had become accustomed to multitasking, so outwardly everything appeared 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 reconnaissance satellite like Keyhole into geosynchronous orbit, but if it is just a communication relay satellite, only 3-4 satellites are needed to meet the communication requirements between low-orbit satellites and between low-orbit satellites and the ground."

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

"..."

After hearing the other party's explanation, Chang Haonan couldn't help but exclaim in admiration -

This idea of ​​"trading quantity for quality" is still considered a very advanced concept even after more than ten years.

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

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

Almost close to real-time reconnaissance.

Zhang Weiyong’s ideas are even wilder.

We should not only pursue efficiency in information acquisition, but also efficiency in information transmission.

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

Then, there is no need to store the information and wait for a 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.

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

"Communication relay satellite..."

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 our country's tracking and control stations and survey ships, there seemed to be a plan to develop a data relay satellite?"

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

"I didn't expect that you, Mr. Chang, even knew this?"

"Uh……"

Chang Haonan touched his chin somewhat awkwardly.

Of course, he couldn't say that he found out about this 20 years later, so he just made up an excuse:

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

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

"Yes, there is."

He replied:

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

"I was just thinking, can I use these satellites of the 921 project to verify my idea?"

For the Chinese aerospace people who started from scratch and have been frugal in the past few decades, making full use of existing resources and improving the cost-effectiveness of projects has almost become an instinct.

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

Because reducing the denominator has a much more significant effect than increasing the numerator.

Chang Haonan frowned after hearing this:

"Tianlian-1 is only intended to solve the problem of the space tracking and control window period. The data bandwidth is quite average. I'm afraid it can't meet the information flow requirements of both images and voices between low-orbit satellite groups..."

"I can't help it... Actually, I'm still struggling with this matter now."

Zhang Weiyong sighed softly:

"The synchronous orbit is too far from the low earth orbit, which limits the bandwidth and latency from a physical perspective..."

Chang Haonan opened his mind directly:

“Have you considered putting relay satellites in low orbit as well?”

"what?"

This method is indeed somewhat unorthodox for Zhang Weiyong:

"Let's not talk about how many satellites are needed... Even if there are enough satellites, 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 on the ground. Generally, the problem can be solved by repeatedly forwarding data. But if it's a satellite... it will put a more serious burden on network throughput and transmission efficiency... The final transmission effect may not be as good as a small number of synchronous orbit satellites."

As he spoke, Zhang Weiyong looked at Chang Haonan with a slightly puzzled look.

By the end, my voice sounded a little unconfident.

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

Is there anything that can be done here?

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

"If it is a normal communication relay method, then the problems you mentioned do exist..."

The group had actually already walked into the small cafeteria where the celebration was held. While speaking, Chang Haonan did not forget to pick up a bottle of low-alcohol red wine from the side and poured 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, perhaps you have heard of a new technology that was only fully proposed last year, called network coding?"

"Some impression."

He put aside the glass that was already at his lips:

"But I remember it was used on routing equipment?"

"True, but it essentially works for any information transmission node."

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

"To put it simply, it is to introduce generalized encoding technology for different information at the communication relay nodes, changing the original transmission of special data in the network into the transmission of network data streams. This can greatly reduce the network bandwidth occupied during information transmission and also increase the cost of decrypting information."

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

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

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

"of course."

Chang Haonan picked up the cup and took a sip:

"But this is exactly the part I am good at..."