Pang Xuelin and Watney worked again, first using the Sojourner rover as the center of the circle, and drawing a circle around it, which was very simple.

But the next step is a bit troublesome, because they need to place 16 cards (hexadecimal) and a blank card (starting point) with 0~9 and A~F written on them evenly around the Sojourner's unmanned vehicle, so that each card passes about 21 degrees of space to ensure that the camera rotation is not ambiguous.

This kind of work is more difficult to place by feel, and at this time Pang Xuelin needs to show his professional knowledge.

Placing the seventeen cards evenly on the circle around the Sojourner unmanned vehicle is essentially a matter of making a regular seventeen-sided ruler.

This problem has plagued the mathematical community for more than 2,000 years, and was finally solved by Gauss, the famous little prince of mathematics.

Gauss directly gives a sufficient condition for the number of sides of a regular polygon to be graphed with a ruler: that is, the power of a non-negative integer of 2 multiplied by the product of any (which can be 0) different Fermat primes.

Pang Xuelin's grandfather taught him to solve this problem when he was in junior high school, so he is familiar with the road.

With the help of Watney, Pang Xuelin spent more than ten minutes dividing the circle into seventeen equal parts with the tools at hand, and then placed the card on the equal points of the circle.

Everything was ready, and after about half an hour, the camera turned again.

"Watney, you record, I'll translate!"

"Good!"

Soon, Pang Xuelin and Watney converted the string into the corresponding information.

"The question has been learned and an answer will be given within two days. Best wishes! ”

's very concise reply, but Pang Xuelin and Watney looked at each other and smiled, high-fived in celebration.

……

JPL Mars Pathfinder Command Center.

Venkat pressed a desk for himself in the accusation center, which was converted into a temporary warehouse, and Tian Mu sat across from him.

Since contacting Pang Xuelin and Watney through the Mars Pathfinder landing module, in the past two days, Venkat and Tian Mu have almost pressed their homes here, waiting for news from Mars at any time.

Except for being too sleepy to take a break in the lounge next to them, they spent most of the time staring at the scene.

Although the communication with Pang Xuelin and Watney is still relatively inefficient under the existing conditions, in the past two days, they still basically know the situation of Pang Xuelin and Watney.

For example, how they survived a sandstorm and were knocked unconscious by a blown off dish-shaped satellite dish.

For example, how they use residual hydrazine from MDVs (Mars landing vehicles) to make water, and then transform the Martian soil to grow potatoes, etc.

Even if Pang Xuelin did not say anything about the various difficulties experienced during this period, everyone here could imagine it.

The only regret is that they couldn't move the rover to the planting module to photograph the potatoes that have already emerged (the perching module shields the signal), otherwise this photo alone would have won this year's Pulitzer Prize.

Even so, after the news of Pang Xuelin and Watney planting potatoes on Mars came out, it became popular in major media around the world.

This was the first time in history that humans carried out real agricultural activities on an alien planet, and Pang Xuelin and Watney went down in history because of this move.

Knock knock knock...... Knock knock knock......

Vencarter, who was resting on his desk, was woken up by the sound of a knock on the desk, and saw Bruce leading a slender man to the desk.

Bruce said, "Karp, sorry to interrupt, this is Jack Trick from our software engineering department, who got the source code for the communication system of the Sojourner's unmanned vehicle!" ”

"Treve, great work!"

Venkat was stunned when he heard this, and quickly got up and shook Trim's hand, then drank the remaining coffee in the cup in one gulp, rubbed his temples and said, "Bruce, then arrange it as soon as possible and pass the code to Pong!" ”

Trive said, "Dr. Karp, I did get the source code for the Sojourner's unmanned vehicle, but there is a problem with it. ”

"What's the problem?"

Venkart was slightly stunned.

Trick said: "Although the source code of the communication system of the Sojourner unmanned vehicle is not large, it also has three megabytes, and we can only transmit one byte to Pang every four seconds on average, even if we don't sleep, it will take at least half a year to transmit all the files, this plan is obviously not feasible!" ”

Venkart was slightly stunned, couldn't help frowning, pondered for a moment, he turned to Bruce and said, "Go and get me the field!" ”

Soon, Tian Mu, who had slept in the lounge for less than an hour, yawned and appeared in front of Vencarter.

Venkat repeated the current predicament to Tian Mu and asked, "Tian, do you have any other solutions?" ”

Tian Mu frowned and said: "Karp, the solution was proposed by Pang, let's listen to Pang's opinion, he is our most outstanding mathematician and communication expert, maybe he has a way to solve it!" ”

"Hmm...... That's fine, too! ”

Venkart pondered for a moment with his chin under his wing, then nodded.

……

Mars, Ashidalia Plain.

In front of the perching module, after translating the hexadecimal message from the JPL accusation center into text, Watney and Pang Xuelin couldn't help but look at each other.

Watney frowned slightly and asked, "Pong, do you have any way?" ”

Pang Xuelin frowned and said: "I have to think about this problem, tell them, give me a little time, and I will go back to the perching cabin to check some information of the communication system!" “

As he spoke, Pang Xuelin returned to the perching capsule ahead of schedule.

Watney used a large pencil to write Pang Xuelin's reply on cardboard and placed it in front of the Sojourner's camera.

Subsequently, he also ended the EVA mission.

As soon as he entered the perching module, Watney saw Pang Xuelin in front of the computer in the perching module, as if he was looking for something.

Watney was curious: "Pang, what are you doing?" ”

Pang Xuelin said: "Let me take a look at the source code of the perched cabin communication system. ”

In reality, Pang Xuelin can't do this kind of work, but after entering the system plane, the system will instill corresponding knowledge in him, but these memories are like a book, which can only be opened when Pang Xuelin needs it, and usually does not appear at all.

Therefore, in the Martian world, Pang Xuelin is really a communication expert.

The only pity is that these memories will be erased by the system after leaving the plane, for example, in the Three-Body World, Pang Xuelin is also a communication expert in the Advent Sect, but after leaving, his knowledge of communication will be completely deleted by the system.

After watching for a while, Pang Xuelin sat on the chair and pondered.

"The Mars Pathfinder landing module has two communication systems, the low-gain one that connects with Sojourner and the high-gain one that connects with Earth. If the landing module wants to recognize the landing module signal, then there will definitely be a special byte sequence in the signal sent by the Sojourner, and if the byte sequence does not match, the landing module will ignore it. This means that there must be a program in the source code of the Sojourner's communication system that encodes the corresponding byte sequence. If I hacked into the secondary communication system of the inhabitation module, and before the system checked the legitimacy, I preemptively wrote the parsed byte sequence into the log, and disguised it as the Sojourner unmanned vehicle, wouldn't I be able to fool the landing module?! And this kind of byte sequence is not too long, at most a dozen or twenty lines, it can be transmitted through the current communication system, yes, that's it! “

Pang Xuelin's eyes lit up, and he snapped his fingers and said, "Watney, I have a way!" ”

"So fast?"

Watney was slightly stunned, it was only less than half an hour, right, and the problem that plagued JPL was solved by Pang Xuelin?

Pang Xuelin quickly wrote his solution on cardboard and carried out another EVA mission to send it back to Earth.

"Dear Dr. Karp and Dr. Tian Mu, I need you to provide the communication serial number code of the Sojourner unmanned vehicle and the control authority of the main system of the perching cabin, I believe that you must have backed up a set of plans for how to hack into the main system of the perching module in an emergency situation, and then I only need to write the communication sequence number into the log of the communication system of the perching module before the system checks the legitimacy, and the problem can be solved perfectly!"

JPL Mars Pathfinder Command Center.

Venkart and Tian Mu looked at the information sent back by Pang Xuelin on the big screen, and couldn't help but look at each other.

Venkart turned his gaze to Jack Trive beside him and asked, "Trive, is this possible?" ”

Treve's eyes sparkled, and he patted his head and said, "Why didn't I think of that!" Pang's plan is great, there are only about twenty instructions for the communication sequence coding of the Sojourner unmanned vehicle, we only need to send these twenty instructions to Pang, and then tell Pang how to hack into the control system of the inhabitation cabin! “

Venkat and Tian Mu glanced at each other, and they both saw a positive look in each other's eyes.

Venkart clapped his hands and said, "Okay, that's it!" Guys, it's time to get started! ”

Although the communication sequence code was only twenty lines, it took a long time to send it, and in addition, Venkart and the others also sent the method of how to hack into the communication system of the perching module to Pang Xuelin and Watney simultaneously.

"Run hexedit in the perch control system, open the file /usr/lib/habcomm.so in this directory, drag it down until the number on the left side of the screen is 2AAE5, and replace the bytes here with the 141-byte sequence sent by JPL!"

This information does not seem to be long, but it took Pang Xuelin and Watney two full EVA hours.

It wasn't until half past ten in the evening Martian time, when the sky was full of stars, that the two ended their long work.

After translating all the hexadecimal information, Pang Xuelin opened the control system of the perching module, hacked into the system according to the method given by JPL, and then wrote the serial number into the log of the perched cabin communication system.

With all that was done, Watney went on another EVA mission, moving the Sojourner rover into the perching module and shutting it down entirely.

Then, Pang Xuelin turned on the perched cabin communication system.

Lines of information began to appear on the computer screen.

The system is initializing......

Initialization complete......

Detect radio signals......

Detect radio signals......

Detect radio signals......

Signal Acquisition ......

The signal is connected!

……

JPL Allegation Center.

"The perched module communication system is online!"

"Oh my God, we can finally type and talk to them easily!"

"Every time I see them send back a lot of information, but we have to type it byte by byte, we are depressed to death!"

The accusation center once again burst into applause, and everyone cheered and hugged each other!

Venkat and Tian Mu shook hands tightly and patted each other on the shoulder.

"Alright, guys, after so many days of dumbness, it's our turn to get to work!"

Soon, Venkart grabbed a computer and typed, "Pong, Watney, hello, I'm Venkart Karp, NASA's Ares Program Director." We've noticed you since Martian Day 39, and now you're in the global media spotlight, and you're doing a great job, whether it's recovering the Pathfinder or planting potatoes on Mars, in short, we're very proud of you. Project Ares Command is trying to rescue you, and our experts plan to modify the Ares 4's MDV to give it some near-Earth flight capability, so that when Ares 4 lands, they will first land on the plains of Ashidalia and then take you to the Schiaparelli crater. We're also putting together resources for a resupply mission that will allow you to make it through to the arrival of Ares 4. ”

Looking at the information that appeared on the screen, Watney's eyes turned slightly red.

Pang Xuelin got up with a smile and said, "Watney, come on!" ”

Watney was slightly stunned, this time he was able to resume communication, Pang Xuelin was a great contributor, he didn't expect that Pang Xuelin actually gave himself the opportunity to communicate with JPL for the first time.

"Hmm!"

Watney nodded, sat down in his chair, and typed, "Hello, Dr. Karp, I'm Watney!" I'm glad to hear this, to be honest, if it weren't for Pang, I'm afraid I would have really died on the day of the sandstorm, my lower abdomen was pierced into an antenna, and it was Pang who saved me. We are in good shape now, the potatoes have sprouted, but we are still more than two months away from the harvest. This accident between me and Pang has little to do with my teammates, they acted correctly, Pang and I don't blame them, I hope they don't have any psychological burden, tell them that I am proud of them. Also, are my wife and kids okay? How are my parents? “

Venkate: "Your parents are fine, your wife and children are overjoyed to learn that you are still alive, and in due course, we will have them come and communicate with you." What are your food reserves, and are you growing enough potatoes to eat? ”

Watney: "Thanks, tell them I miss them too." The potatoes grown are growing well enough to sustain Pong and I for about 1,000 Martian days, and we won't be bothered by food shortages for the time being. I'll give Pang the time next, and you can ask Pang if you have any questions. ”

Soon, new news came from JPL.

Tian Mu: "Xuelin, it's me, Tian Mu, how are you now?" ”

Pang Xuelin: "Lao Tian, I'm fine, it's good to partner with Watney, he is an excellent botanist, without him we might starve to death." ”

Tian Mu: "You did a great job this time, we can restore communications, you are a great contributor, then we will try to restore video and image transmission, our botanists will help you manage your farmland, nutritionists will determine your optimal daily food intake, the supply spacecraft will be launched in the second half of this year, about nine months later, and it is expected to arrive in the plains of Asidalia in two years." Your food reserves give us a lot of extra time. Also, if it's handy, take a picture of you and Watney, and don't forget to take a picture of the plant-pod, the media is driving our Dr. Karp crazy! ”

Pang Xuelin and Watney looked at each other and smiled, and Pang Xuelin typed: "Okay, I'll send you the photo as soon as possible!" That's it for now, we're tired today, we're going to eat first, and then rest! Greetings to everyone on my behalf! “

"Okay, you and Watney have a good rest, good luck!"

Pang Xuelin chose to go offline.

Watney was a little strange and puzzled: "Pang, why don't you greet your family?" “

Pang Xuelin smiled and said: "I was born as an orphan, I grew up in the orphanage since I was a child, and my only relative, the old dean, has passed away......"

"I'm sorry, Pong!"

Watney was a little embarrassed.

Pang Xuelin said nonchalantly: "It's okay, I'm used to it!" ”

Whether it is in the three-body world or the Martian world, the system has arranged the identity of an orphan for Pang Xuelin, and Pang Xuelin is also happy, otherwise if there are a lot of relatives and friends who don't know him in this world, Pang Xuelin will have a headache.