217: Chapter 217 Ninety-seven days without a reply

The door of the discussion room upstairs was not closed again until evening.

That doctoral student borrowed a whiteboard, Keller, who had rushed over from Bonn, walked downstairs carrying two gray folders, and Gu Mingche stayed by the table, spreading out the seven newly added drafts from the afternoon in numerical order.

When the administrative assistant came in to collect empty paper cups, she noticed that the cardboard box by the wall was still blocking the power outlet.

She picked it up and moved it half a step, and the bottom of the box instantly opened.

A stack of printed materials crashed to the ground, with a red tag pasted on the topmost page.

[A-1: Determination and Recovery Strategy for Lost Contact Status of qingqiong-1 Scientific Satellite]

[Duration: Ninety-seven Days]

[The applicant has submitted complete fault records and data authorization letters]

Gu Mingche squatted down to pick up the papers and first saw a slender high-elliptic orbit diagram.

"Someone sent a satellite right after the center's first public report?"

"It was delivered at noon."

The administrative assistant re-sorted the scattered attachments.

"The technical liaison said it meets the A-1 conditions, the materials are complete, the ownership is clear, and the problem is indeed stuck."

"We really couldn't spare anyone today, so we can only leave it here for now."

The center's open problem portal had just gone live not long ago.

A-1 does not mean the problem is the most important, only that the applicant is willing to hand over sufficient materials and has the right to open them.

Many requests for help read "The result is wrong, please help analyze," with only a screenshot as an attachment.

Yet in this box, there were more than two hundred pages of flight records, ground station logs, successive command tables, onboard software version descriptions, and an encrypted hard drive.

Jiang Lin picked up the last bound booklet from the ground.

The satellite on the cover had only a palm-sized rendering, and even after the solar wings on both sides were deployed, it still looked thin.

qingqiong-1 was jointly developed by three domestic universities and a space technology unit, and entered a high-elliptic Earth orbit three years ago.

It carried a dust impact detector, mainly recording the impact events of micron-level particles in near-Earth space, and then combined with the satellite's attitude to calculate the directional flux, while opening a low-speed beacon for university ground stations and amateur radio enthusiasts to receive.

On August 24, the satellite lost effective telemetry after completing an apogee observation.

In the ninety-seven days thereafter, the ground station issued more than four hundred sets of audited commands.

Onboard computer switching, attitude safety mode, power reconfiguration, transponder reset—every common fault path had been walked through.

Fifteen cooperative stations and amateur receiving stations distributed in six countries had captured thirty-nine suspected carrier waves.

The longest segment was only 11.7 seconds, and the shortest was less than the time required for the decoder to establish synchronization.

The application did not write these thirty-nine segments of signals into hope.

The last page only raised a limited question: Under the existing information, which onboard states still cannot be ruled out, and how can the next command reduce irreversible risks?

Gu Mingche finished flipping through the table of contents and looked at Jiang Lin again.

"The first aerospace problem received by the Math Center."

"The Interdisciplinary Research Center (Preparatory)."

Jiang Lin placed the bound booklet next to the orbit diagram.

"Since the name is long, it's not a waste to use a few more words."

The administrative assistant was worrying about the split cardboard box, and laughed when she heard this.

"Then I will change the long-named center into a sturdy box tomorrow."

Jiang Lin first asked the technical liaison to verify the authorization letter.

The raw telemetry in the hard drive belonged to the satellite mission party, and the center could currently only read desensitized ground station data.

Among the thirty-nine carrier waves, seven retained complete intermediate frequency sampling, which was enough to redo correlation processing.

He copied the seven segments of data into the center's computing environment and copied the phone numbers of three people from the end of the application.

Shao Cen, the chief scientist of qingqiong-1; Xu Kaiyang, the chief designer of the satellite; Song Yao, the person in charge of TT&C.

All three of them signed.

Gu Mingche asked: "Take it?"

"Take it."

"Which layer are you planning to start with?"

"Go to class first."

The table of contents in Gu Mingche's hand paused in mid-air.

Jiang Lin opened the school course system and searched for Spacecraft Overall Design, Satellite Attitude Dynamics, Aerospace TT&C Principles and Flight Control.

In the Wasteland, he had personally built launch vehicles, satellites, and launch sites, and had also finished writing flight software and ground TT&C sequences for the next round of missions.

Those kinds of knowledge spanned long eras, and when landing on specific tasks in reality, they still needed to be connected to real-world interfaces.

How the 2022 telemetry dictionary is arranged, how many layers command approval goes through, which software the ground station uses, what format of flight program attitude disposal is written into, and which button the mission party hands over to whom—these contents would not grow automatically out of orbital mechanics formulas.

He didn't need many classes.

Three were enough.

The next morning, an extra chair was temporarily added to the Spacecraft Overall Design class.

Professor Wen, who taught the class, received the auditing application in advance and casually placed a stack of interface control documents on the back row when entering the classroom.

"Jiang Lin, the current version you wanted."

"Thank you, Professor Wen."

"I originally planned to talk about overall scheme trade-offs."

"With you sitting in the back, the front row feels a bit pressured."

Dozens of graduate students turned around in unison.

Jiang Lin opened the first document.

"Then I'm responsible for taking notes, not for taking roll call."

A burst of laughter rang out in the classroom.

Professor Wen also smiled, turned around, and projected the functional block diagram of a microsatellite onto the screen.

This class was not changed into a report meeting just because Jiang Lin was present.

The constraints among payload, platform, TT&C, thermal control, and power were still unfolded item by item, and students were called up as usual to explain why the weight margin cannot be repeatedly calculated across the five subsystems.

Jiang Lin's notes only took up two pages.

The first page was the document chain of the real-world mission.

The second page was who signed off on each type of judgment after an anomaly occurred.

When the class bell rang, Professor Wen walked down from the podium and saw that he had divided "verified facts," "onboard inferences," and "permitted executable actions" into three columns.

"Do you really treat yourself as a student?"

"Auditing always requires bringing something back."

"qingqiong-1?"

Jiang Lin raised his head.

Professor Wen pointed at the paper bag containing the interface documents.

"Shao Cen called me yesterday."

"They've looked for people in orbit, attitude, power, software, and TT&C, and have done all the routine recoveries they could."

"If you want to enter the mission hall, I can vouch for the research needs on behalf of the center, but the command authority still has to be issued by the mission party themselves."

"It should be like this."

"The TT&C principles class in the afternoon is also in this building."

"The instructor is Song Yao, and she will bring the ground station logs of qingqiong-1."

There were only forty minutes left for the noon attitude dynamics discussion class, so the instructor simply replaced the original exercises with a set of slow-roll data after losing the star sensor.

Jiang Lin finished writing the state transition on the blackboard and casually re-sorted the observables by power consumption.

How much information sun sensors, magnetometers, gyroscopes, and carrier envelopes could each leave behind was compressed into the same table.

At the end of the discussion class, the instructor sent him the permissions for the school's current attitude simulation instance, and also kept that table as a course case for the next generation.

In the afternoon class, Song Yao played a piece of real signal from August 24.

The carrier wave first emerged from beneath the noise, its frequency moving along the orbital forecast, and sank back down eleven seconds later.

She asked the students to judge what this signal could prove.

Some thought the transponder was still working, some thought it was just a ground interference source happening to sweep across the same frequency band, and others supported the former answer from the Doppler shift.

Song Yao wrote several judgments on the blackboard, not crossing out a single one.

"The evidence is only enough to go this far."

"Mission control fears nothing more than writing wishes into conclusions."

She turned to the back row.

"Teacher Jiang, can you take one more step?"

Jiang Lin connected his computer to the projector.

He did not replay those eleven seconds, but instead laid out six blank frequency spectra before and after the same orbital period side by side.

When the first carrier wave appeared, the satellite was just entering the sunlight zone from the shadow.

The second segment was forty-seven seconds later than expected.

The third segment had a lower amplitude, but its Doppler slope fit the orbital forecast seamlessly.

After the seven segments of intermediate frequency sampling were aligned one by one, the short lines that originally seemed to pop up randomly turned into a slowly moving envelope.

"It can be proven that the emission source follows qingqiong-1."

Jiang Lin marked seven peaks on the frequency spectrum.

"It can also be proven that the antenna gain changes periodically."

"The period is neither the orbital period nor the scanning period of ground interference."

Song Yao stared at the screen for a few seconds, then walked back to the console and brought up two other sampling records that had never been listed in the public attachments.

"These two segments have worse signal-to-noise ratios."

"As long as the raw samples are still there, it's enough."

The students reopened their computers.

The originally scheduled course content was moved back by half a session, and correlation processing was temporarily done in the classroom.

Jiang Lin broke the algorithm into three parts and asked the front-row students to recalculate the possible contributions of local oscillator drift, orbital Doppler, and antenna pattern respectively.

Song Yao provided the data, not the conclusions.

Forty minutes later, the three sets of results were superimposed on the same graph.

A stable six-minute-thirteen-second period floated out from the noise.

It was close to the slow-roll period in qingqiong-1's last effective telemetry before losing contact, yet nearly twice as long as it was back then.

This difference was sufficient to rule out "repeated recordings appearing," but insufficient to determine which attitude mode was currently controlling the satellite.

Song Yao turned off the classroom loudspeaker and directly dialed Shao Cen's phone with her mobile phone.

"The seven segments of public data have been re-correlated."

"Jiang Lin has found a stable envelope."

The other side of the phone only asked one sentence: "Can we enter the hall?"

"He can go anytime."

"You should add the authorization to the raw database."

At nine o'clock that evening, the qingqiong-1 mission team arrived at the center.

Xu Kaiyang pushed three locked aviation cases into the door.

The cases contained all the raw telemetry before and after the loss of contact, the onboard software image, and the execution records of every command over the ninety-seven days.

Shao Cen, nearly sixty years old, walked in and first looked at the six-minute-thirteen-second period on the whiteboard.

"We also did roll envelope analysis, and the periods we got were between five minutes fifty seconds and seven minutes twenty seconds; the error is too large."

"You estimated each segment of signal individually."

Jiang Lin connected the orbital positions during the seven receptions into a single graph.

"These short segments can be regarded as the same long record cut apart by ground windows."

"First eliminate the local oscillator difference and orbital Doppler, then splice according to the solar incidence direction, and the period will tighten."

Xu Kaiyang opened his computer and pulled up the twenty-seven fault trees that the team had made over the past three months.

"After the period is tightened, which one can be selected?"

"It can't be selected right now."

Jiang Lin turned the fault tree in front of everyone.

"Repeated cold starts of the power controller, the attitude machine entering low-power roll, the onboard computer stopping in the switching process, and intermittent power acquisition by the transponder—these four types of states can all leave similar ground manifestations."

Shao Cen pressed her fingers on the case lock.

"Then what did you see?"

Jiang Lin zoomed in on the timeline below the seven envelopes.

Before each segment of signal began, there was a narrow-band leading edge with approximately equal duration.

Previous decoders treated it as garbage data left by phase-lock failure.

After re-correlation, the interval between the leading edge and the main carrier was changing with sunlight conditions.

"qingqiong-1's power is still accumulating energy, and the timing chain is still running."

Jiang Lin picked up the temporary mission hall pass brought by Xu Kaiyang.

"It has been replying for these ninety-seven days, except that every letter was too short to write the main text."

"The Tianyi team are scalpers, disguised with big bad wolf QQ avatars and screen names, swaggering and swindling! (QQ are 1070240776, 845646066, and 1484608559) Beware of being scammed!"