At 8: 34 on October 7th, 20071165438, when the 490 Newton high-power engine of Chang 'e-1 satellite was turned off, it was displayed on the big screen of Beijing Aerospace Control Center that the target orbit of the satellite completely coincided with the actual orbit, and Chang 'e-1 officially entered the working orbit at a height of 200 kilometers from the moon.
At this moment, there are still 324 hours 3 1 minute before the launch of Chang 'e-1. The Chinese dream of running to the moon for a thousand years has finally come true. 10 Since June 24th, Chang 'e-1 has achieved its goal again and again on its way to the moon, which not only released the strong national pride of Chinese all over the world, but also tested China's scientific and technological strength.
Like all satellites, Chang 'e-1 is an integration of a large number of key technologies. In its design, research and development, manufacturing, launching and working process, it is its most basic DNA, which is everywhere. Unlike other satellites, Chang 'e will work in a vast universe 380,000 kilometers away from the Earth (the farthest satellite launched by China is 70,000 kilometers away from the Earth), and the conditions are quite complicated, so it is very likely that Chang 'e will lose contact with the ground.
Therefore, Chang 'e must achieve highly reliable self-management, which brings unprecedented challenges to its IT "brain"-interstellar computer (the digital management subsystem inside the satellite). This "brain" must be able to calmly and accurately deal with problems and issue instructions in any harsh environment. How is the IT "brain" tempered? How did it guide Chang 'e to embrace the moon?
"Brain" is practiced like this.
165438+ 10 14, the reporter found in China Academy of Space Technology that most of the staff of the Chang 'e-1 data management subsystem were still nervously observing the satellite's every move in the control center, and only Seimi Zhang, the deputy chief designer, was interviewed in the office.
"In the next year's work of Chang 'e satellite, people can't leave the scene for 24 hours. However, going to heaven means that our most difficult and painful time has passed. " Seimi Zhang told reporters that after the Goddess Chang'e flying to the moon's death, they practiced "three shifts", but in the previous design, development and test stages, they often worked in one shift.
The data management subsystem, also known as the interstellar computer, integrates satellite measurement and control tasks into a computer-based system, and realizes satellite telemetry, remote control, program control, on-board autonomous control, time correction and other whole-satellite control and management functions. It is the "brain" and "central nervous system" of the satellite.
So, compared with the brains of other satellites, what is special about Chang 'e's "brain"? Seimi Zhang told reporters that in the process of building the "brain" of Chang 'e, "we have inheritance and development." In terms of technical architecture, it inherits the previous "Shenzhou V" and "Shenzhou VI" and adopts a two-level distributed fault-tolerant computer system. However, as the first satellite orbiting the moon, it requires very high safety and reliability. In order to adapt to the complex conditions of use 380,000 kilometers away, this "brain" has also adopted some designs different from ordinary satellites.
Because of the long distance between the earth and the moon, the spatial attenuation of TT&C signal increases. "In order to reduce the bit error rate and improve the anti-interference ability of satellite downlink telemetry channel, the digital tube system of Chang 'e-1 satellite not only changed the single bit rate to multi-bit rate, but also increased the coding method." Seimi Zhang said, "The self-management function of satellites has also been greatly enhanced. "
According to the reporter, there are two ways to manage satellites, personnel management and independent management. Personnel management is to send instructions through the ground. However, this method is conditional. It is required that the ground monitoring and control can see the satellites in the sky, and the communication channel cannot go wrong. Chang 'e satellite runs near the distant and vast moon, and the situation is very complicated. It must be considered that it may lose contact with the ground at some point. If there is no self-management, or the self-management ability is not strong enough, the satellite may have problems when it encounters unexpected situations.
Although China Academy of Space Technology has strong technical strength and rich experience in satellite development, it is the first time to independently develop a satellite flying around the moon, and it is the first time to independently develop such a "highly reliable" satellite intelligent "brain". Recalling the development process of Chang 'e's "brain" for more than three years, Seimi Zhang said frankly: "It left many unforgettable memory fragments. Especially in the difficult initial stage. "
Because the data management system is connected with the other eight subsystems in the satellite, and even has to work together with the five systems of the whole "Chang 'e Project", the difficulty of communication and testing can be imagined. In the early stage of satellite component development, data management subsystem can be said to be a constant problem. "Seimi Zhang told reporters.
Because hardware production, software development and test equipment development are all carried out at the same time, software operation and debugging depend on hardware equipment, and subsystem joint test depends on test equipment. However, all components are unstable in the initial stage of development, and various unexpected faults and problems will occur, which increases the difficulty of fault location and solution. In addition, due to the constant change of software requirements, the digital tube software is also changing, and the whole satellite electrical measurement can not be separated from the digital tube platform, which once became the short board of the whole satellite development.
At that time, designers and engineers of data management subsystem were working overtime, and it was common to work overtime until one or two o'clock in the evening. On one occasion, Seimi Zhang and the backbone of the data management subsystem have been running continuously for more than 50 hours without sleeping.
At that time, it was a thermal vacuum experiment, that is, putting the satellite in a big "jar" to simulate various cold and hot environments in space, which took more than 20 days. When the experiment went on for more than 10 days, a strange phenomenon suddenly appeared, and the autonomous management of the satellite "brain" was abnormal. If this problem is serious, it means that all the previous work has been in vain and the experiment must be done again. At that time, the CNC management subsystem was still doing another test at the same time. Seimi Zhang and other technical backbones stayed up all night before and rushed to the scene at one or two in the morning to study how to eliminate the problem.
Although it can be retrieved with the help of the computer system itself, some data errors must be analyzed and judged by the naked eye, so they searched tens of thousands of pieces of data running in the previous 10 day one by one. After a day and a night, I finally found the crux of the problem. "If you can solve it, don't bother!" The excitement almost made these space elites forget that they had been fighting for more than two days and nights.
In the reporter's impression, in some high-tech companies with high work intensity, such as Microsoft and Cisco, technical elites will be equipped with psychological teachers or psychological hotlines to learn to "release stress". Is this also true of our space elite? Seimi Zhang said that they also attended some courses on "psychological stress relief".
"But that's theory. As an aerospace IT worker, one code goes down and one hardware goes down, which is related to a major project of a country. Can it be easy? " Seimi Zhang said, "However, the happiness and sense of accomplishment brought by the whole team overcoming difficulties together are incomparable!"
It seems that the aerospace spirit of "special efforts, special dedication, special research and special fighting" is really not just a slogan, it runs through every detail of the development of Chang 'e satellite, and Chang 'e's "brain" is tempered in such an atmosphere.
Guide the Goddess Chang'e flying to the moon.
The reporter learned that in the process of Chang 'e's lunar exploration, in addition to the data management subsystem, the satellite guidance, navigation and control system (GNC) is also a subsystem composed of a computer system and many sensors, which is mainly responsible for the satellite to find its own running direction at different stages.
The change and control of 22 postures during the Goddess Chang'e flying to the moon, the three braking of satellite's orientation to the moon, the orientation tracking of solar panels to the sun, and the orientation of directional antenna to the ground are all completed by the computer system sending instructions to many sensors.
According to incomplete statistics, the computer of Chang 'e's "brain" (data management system) and GNC system has issued thousands of instructions. However, what Seimi Zhang relishes most is not these complicated instructions, but the powerful self-management ability of Chang 'e's "brain". "When the satellite loses contact with the earth, the data management subsystem can independently manage thermal control and supply satellite energy."
According to Seimi Zhang, thermal control itself is a subsystem, but each system is cross-cutting. Thermal control system mainly includes thermal control coating, thermal insulation material, electric heater, sensor, heat pipe and so on. In view of the complex boundary conditions of thermal design, active temperature control design is widely used in thermal systems. Chang 'e "brain" (data management subsystem) is responsible for the switch control of the heater.
Even in an emergency when the Chang 'e-1 satellite loses contact with the ground, Chang 'e's "brain" can independently control the heater. Because there are many thermal detection devices everywhere in Chang 'e-1 satellite, they can automatically send the sensed temperatures of various points to the computer. The computer identifies and processes these temperature data, and when the temperature is low, the computer software will automatically issue an instruction to turn on the switch of the heating controller; When the temperature is too high, the computer software will automatically issue an instruction to turn off the switch of the heating controller.
Chang 'e's "brain" can also make wise decisions with the cooperation of the energy control of the power supply and distribution subsystem. It is understood that Chang 'e-1 satellite was full of energy before it went into space. Chang 'e satellite consumes a lot of energy during its flight and work, and the computer can judge whether it needs to be supplemented. Seimi Zhang told reporters that the two "wings" of Chang 'e satellite can convert solar energy into electricity and store it. When Chang 'e's "brain" judges that the energy is insufficient, the stored energy will supply power to each subsystem.
"A person can't accomplish his work goals alone with his brain. Similarly, the data management subsystem, as the' brain' of Chang' e-1, cannot accomplish its work goals independently. " Seimi Zhang repeatedly stressed that "the realization of all the work objectives of Chang 'e satellite must rely on the cooperation of various sub-systems within the satellite. At the same time, without the support of the other four systems of the Chang' e Project, it is impossible for Chang' e I to fly around the moon. "
Seimi Zhang gave an example. If there are no accidents, Chang 'e-1 satellite will send back the moon image to Earth in the middle and late of 165438+ year1October. "At that time, we will also pass the next instruction of Chang 'e's brain. Chang' e-1 will play 30 songs in the distant space 380,000 kilometers away, and we can clearly hear them on earth. " Seimi Zhang said, "This seemingly simple work also includes the cooperation of various systems."
It is understood that the songs played by Chang 'e-1 satellite bring the music recorded on the ground to the satellite through a special memory. When the satellite orbits the moon, after receiving the instructions from the digital tube subsystem, this storage device and the transmission device on the satellite are used to transmit these music back to the ground from distant space. The ground receiving system can receive these music, and transmit the music festival from distant space through digital signals, radio, television and networks all over the country.
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Nine subsystems of Chang 'e-1
Structural subsystem: equivalent to the "body plate and skeleton" of Chang 'e-1, which provides installation location and working space for instruments and equipment of other subsystems.
Data management subsystem: the "brain" of Chang 'e-1, which is used to realize satellite telemetry, remote control, program control, on-board autonomous control and time correction.
Guidance, navigation and control subsystem: The "cerebellum" of Chang 'e-1 has a part of "brain function", which is responsible for correcting, measuring and controlling the flight trajectory and attitude of the detector, and controlling solar panels and payload.
Power subsystem: Chang 'e-1' s "Heart and Blood" consists of solar panels, batteries and power regulators.
Thermal control subsystem: temperature regulation system, which consists of sensors and thermal control elements.
Measurement and control and data transmission subsystem: the main function is to complete the tracking, orbit measurement, telemetry, remote control and data transmission tasks of the detector.
Propulsion subsystem: the power system of Chang 'e-1, including rocket engine, propellant tank and various pipelines. It switches various engines according to the instructions of the guidance, navigation and control system.
Scientific detection instrument subsystem: complete the collection, storage and processing of scientific detection data, and complete the on-orbit management of payload.
Directional antenna subsystem: provide antenna gain that meets mission requirements for digital downlink channel and telemetry downlink channel.