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My country’s first Mars exploration mission to orbit Mars successfully
Shijiazhuang News Network
Time: 2021-02-14 09:12:08
source:Beijing Youth Diary
At 7:52 p.m. on February 10, the first probe of China’s Mars exploration mission “Tianwen-1” implemented a close-fire catch braking. The 3000 N orbit-controlled orbital engine fired for about 15 minutes and the probe entered the near-fire altitude. A large elliptical orbit of about 400 kilometers, with a period of about 10 Earth days and an inclination of about 10 °, has become the first artificial satellite of Mars in my country, achieving the first step of “orbiting, traversing and patrolling “. Mars is a hit.
The Beijing Youth Daily reporter learned from the National Space Administration that after the first Mars exploration mission entered the capture phase of Mars from the ground fire transfer phase, medium resolution cameras, cameras high resolution, magnetometers and magnetometers carried by the “Tianwen-1 Orbiter” Charges such as mineral spectrometers, ion and neutral particle detectors and energetic particles will start working one after another to carry out multidimensional detection of Mars.
Since its successful launch on July 23, 2020, the “Tianwen-1” probe has flown for 202 days, completed 1 deep space maneuver and 4 midway corrections, and had a flight mileage of approximately 475 million kilometers when it reached Mars, which was far from Earth. At approximately 192 million kilometers, the one-way delay for device-ground communication is approximately 10.7 minutes, and each system is in good condition.
The tracking “Tianwen-1” is reported to go through many orbital adjustments, enter the mooring orbit of Mars and conduct a pre-selected landing zone scan. It is planned to choose an opportunity to land on Mars and carry out exploration inspection from May to June 2021.
The Mars capture brake reportedly means that when the probe approaches Mars, the main engine turns on for a long time, causing the probe flying at high speed in interplanetary space to slow down by a large increment. speed so it can be captured. through the Martian gravitational field and into orbit. As one of the most technically risky and technically difficult links in the Mars exploration mission, the opportunity to catch brakes is the only one, which is related to the success or failure of the entire engineering mission.
A reporter for the Beijing Youth Daily learned from the National Space Administration that during the capture process, the Mars orbiter must be turned on and stopped precisely. Only when the ignition time and duration are within minutes can an ideal capture orbit be formed.
Secret
Various “black technologies” help spacecraft fly to Mars
In the process of “Tianwen-1” successfully implementing near-fire braking, completing the capture of Mars and accurately entering the Martian orbit, the communication between “Tianwen-1”, which is 190 million kilometers from the land, and land was delayed for nearly 11 minutes. How does the earth know if the Mars rover has entered the correct orbit? Where is your exact location? How is the working condition? Can you communicate correctly and accurately execute the instructions sent to you from the ground? These key links are based on the numerous “black technology” products of the China Aerospace Science and Technology Corporation with independent intellectual property rights.
How to ensure that the detector enters the capture corridor smoothly?
During the capture of this Mars exploration mission, the probe’s target orbit was only 400 kilometers from the closest point on Mars, and it would collide or fly away from Mars if care was not taken. The deep-space measurement and control network of the ground-based measurement and control system receives highly stable radio signals continuously emitted by the probe and obtains high-precision orbit data through continuous calculations, to ensure that the probe can enter without problems captures the corridor at a predetermined time and at a predetermined height, and implements the action of changes of orbit.
Since the detector is 192 million kilometers from the ground during capture and braking, the delay of one-way communication has reached 10.7 minutes and the ground cannot monitor the whole process in real time, and can only trust the detector to execute the capture strategy autonomously.
Since its launch on July 23, 2020, the development team has continued to conduct 202 days of in-orbit flight control missions, completed four intermediate fixes and a deep space maneuver, carried out various self-checks and functional verification, and monitored and controlled the detector Communication capabilities, energy security capabilities and autonomous management capabilities have been tested to ensure that the functions and performance involved in the capture and braking process are fully tested.
How to “hit the brakes”?
Brake capture, in simple terms, is to slow down the detector via deceleration control of the motor thrust so that it can be captured by the gravitational force of the target star. This action is also vividly called “brake on.” But how do you “hit the brakes”? Faced with this difficult problem, “Tianwen No. 1” handed out a high-scoring answer sheet.
Everyone who drives knows that when coming off a ramp on a freeway, you must slow down your car to do so safely. For a probe approaching Mars at a high speed of 28 kilometers per second, if it wants to be captured by Martian gravity, it must also precisely, autonomously and reliably complete its “brake” in the arc of the orbit corresponding to the “Capture window”. ”. In theory, by giving the detector a reverse thrust, its speed can be reduced. But in the process of realizing the project, many problems will still be encountered.
The Mars rover is equipped with a 3000 N orbit control motor to control braking and deceleration during gravity capture. The Martian gravitational capture window is limited, requiring the probe to slow down by about 1 kilometer per second in 10 minutes. In the process, the detector must be completely dependent on itself to complete engine startup and shutdown, overcome disturbance during engine startup, and achieve precise control of ignition duration and direction.
“In the absence of real-time measurement and control on the ground, we can only implement precise trajectory control autonomously through schematic design, fully considering motor thrust deviation and continuous change of detector center of mass,” and then through the combined analysis of testing and multi-factor simulation, the control scheme is more reliable, “said Zhu Qinghua, deputy chief designer of the Eighth Academy of China Aerospace Science and Technology Corporation.
What “black technologies” help spacecraft fly to Mars?
Capturing and braking the Mars orbiter is one of the difficulties of this Mars exploration mission. When the Mars orbiter captures the orbit of Mars, to ensure that the Mars orbiter can accurately enter orbit, the combination of the GNC subsystem and the Mars orbiter meter developed by the Ninth Institute is required. It can accurately measure the acceleration of the orbiter, and the control system controls the motor to implement braking operations by returning the parameters, so that the probe can accurately enter the orbit of Mars.
Upon entering the orbit of Mars, the probe needs to implement near-fire braking. At this time, the detector is almost 190 million kilometers from the ground and the engine ignition time is more than 1000 seconds. At that time, the communication delay is almost 11 minutes and the ground cannot monitor the braking process in real time. . At this time, the X-band deep space transponder independently developed by the Ninth Academy came out. In order to develop the first national X-band high-sensitivity digital transponder in the deep space field, developers have overcome a number of key technical problems, such as 400 million kilometers of ground fire long-distance communication technology, reaching the international advanced level. .
As the distance between Tianwen-1 and the ground continues to increase, the signal received by the ground becomes extremely weak. This is an unprecedented test for the measurement and control communication system. To this end, my country has independently developed a deep space measurement and control system that uses antenna array technology to receive signals sent by the detector from hundreds of millions of kilometers away and, at the same time, send ground and control commands to the detector. The Ninth Institute has developed world-class data acquisition and signal acquisition signal synthesis and demodulation processing equipment for two key subsystems for this system. At the same time, the deep space transponder and the deep space measurement and control antenna array equipment together constitute the only information bridge between the Mars rover and Earth, which is related to the success or failure of all The mission.
Link
Mars has been a bit “crowded” recently
Mars will fill up a bit anytime soon: the United States, China and the United Arab Emirates have launched Mars probes during the Earth-Mars launch “window period” in July 2020, and all three probes are scheduled to arrive. on Mars this month.
Among them, the UAE’s “Hope” Mars rover entered the orbit of Mars on February 9 and officially began its two-year orbital exploration activity. Unlike the Martian surface exploration missions in China and the United States, the “Hope” will only conduct various studies around Mars, study the Martian atmosphere and the daily and seasonal cycles of Mars, and obtain the general laws of climate change. Martian.
The US “Perseverance” rover is expected to land on the surface of Mars on February 18, becoming the fifth rover that the United States has launched to Mars. There are currently two Mars probes on Mars, the US Opportunity and Valor, and the United States has obtained a wealth of Mars data from these two Mars probes. According to foreign media reports, “Perseverance” will directly implement a soft landing in the Jezero crater on Mars. The goal is to find signs of life on Mars and collect Martian geological samples.
China’s “Tianwen-1” also has landing and rover activities on Mars. After flying around Mars for a period of time, “Tianwen-1” plans to choose the opportunity to land on Mars from May to June this year and conduct inspections. (Reporter Lei Jia, correspondent Yang Lu)
Editor: Zhao Yuheng
