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My country’s first Mars planetary probe is about to launch. Mars is the planet most similar to the Earth in the solar system. The prospect of "migrating to Mars" appeared in science fiction novels. The interesting "Mars Archaeology" believes that Mars was hundreds of millions of years ago. It is a blue ocean planet like the earth. Scientific research has also shown that Mars indeed once had an environment suitable for life-with a thick atmosphere and a large amount of liquid water on the surface, but after hundreds of millions of years of denudation by solar wind, today's Mars is only composed of CO2 The thin atmosphere.
Since the 1960s, mankind has embarked on the brave journey of exploring Mars. Countries that have taken steps to explore include the United States, the Soviet Union/Russia, Europe, China, Japan, and India. In 44 exploration missions, step by step attempts were made to approach Mars, orbit Mars, land on Mars, and carry out Martian ground exploration. However, 48% of the exploration missions fully or partially achieved their goals (including 16 in the United States, 2 in the Soviet Union/Russia, 2 in Europe, and 1 in India). Among them, the four U.S. exploration missions Mariner 4, Mars3, Mariner9 and Sojourner respectively created the first history of mankind’s first successful approach to Mars, orbiting Mars, landing on Mars, and conducting Mars ground exploration. Mars rover about to embark on a journey(hermes outlet) From July to August this year, three countries started their journey to Mars-the United States, China and the United Arab Emirates. Among them, my country's "Tianwen-1" Mars rover is expected to be the first in human history to achieve the three goals of orbiting Mars (orbiter), landing on Mars (lander), and carrying out Martian ground exploration (rover) at one time. Deep space exploration mission. In order to achieve this goal, the orbit of "Tianwen No. 1" is divided into five stages as shown in Figure 2: the Earth-Mars transfer stage for 7 months, and about 10 days to enter Mars capture stage (Mars capture stage), 2-3 months Mars orbit parking stage (Mars orbit parking stage), about 5 hours satellite and Mars rover separation and landing stage (Deorbit and landing stage), a period of 90 The ground exploration of the rover on Mars Day and the scientific exploration stage of 1 Mars year. Here, taking the moon exploration as a comparison, so far, the only countries in human history that have successfully sent a lunar rover to the moon are the United States, the Soviet Union, and China, which shows the difficulty of landing on the moon. However, exploration of Mars is more difficult than exploration of the moon. So, why is Mars exploration so difficult? One of the important reasons is that deep space exploration faces very complex environmental challenges. In interplanetary space, deep space probes face the threat of radiation environment, solar wind plasma environment, and electromagnetic radiation environment, while in near Mars space, deep space probes face challenges from the Martian ionosphere, neutral atmosphere, and surface radiation environment. . NASA Chief Engineer Terry Onsager said: "In order to realize Mars exploration, both the probe and human beings are facing severe challenges in the heliosphere environment, and we are ready." The threat of radiation environment First of all, the safety of deep space probes in orbit is facing the threat of radiation environment. The main radiation sources are high-energy particles of the sun and galactic cosmic rays. The moon is about 400,000 kilometers away from the earth, and the farthest distance between Mars and the earth has reached 400 million kilometers. It took seven months for the deep space probe to reach the first stage of Mars orbit. At this stage, due to the shielding and protection of the earth’s magnetic field and atmosphere, high-energy charged particles (and a small amount of neutral particles) can directly bombard deep space detectors without hindrance, which will cause considerable damage to the normal operation of deep space detectors. Large hazards can cause spacecraft single event effects, displacement damage, etc. Therefore, particle radiation protection is a very important part of the deep space exploration program. In addition, the radiation environment of the fire planet is also very important. The radiation dose on Mars orbit is about 2 to 3 times that of the International Space Station orbit, which will also bring huge pressure on radiation protection for manned Mars exploration in the future. The challenge of the plasma environment Secondly, the measurement and control communication of deep space probes faces the challenge of the deep-space plasma environment. The main source is the solar wind that fills the entire heliosphere. The only connection between the deep space probe and the earth after it is launched is the deep space measurement and control communication system, which is responsible for the transmission of scientific data and remote sensing data, tracking the deep space probe and directing it to perform important tasks. The measurement and control communication relies on the propagation of electromagnetic waves between the probe and the earth. The communication between the earth and the probe on the moon takes only 1.35 seconds. When the radio signal travels from the earth to the Mars probe, the distance It takes up to 22 minutes to communicate once. The solar wind plasma on the line from the detector to the earth has a significant impact on the transmission of electromagnetic waves. Irregular plasma clusters may cause electromagnetic waves to be refracted and reflected, causing electromagnetic wave amplitude flicker, spectrum expansion, phase flicker, etc. Therefore, the solar wind plasma environment, especially the solar eruptive activities such as interplanetary coronal mass ejection, has a very important impact on the measurement and control communication of the deep space exploration program. The influence of solar electromagnetic radiation environment Furthermore, the measurement and control communication of the deep space probe is also affected by the solar electromagnetic radiation environment. Due to the difference in revolution orbits, within 20 days of Mars being near the back of the sun (in the black area as shown in the figure), electromagnetic waves will pass through the strong radiation area near the sun, the communication signal will be blocked or interfered by the sun, and the probe will be "lost" If you encounter a dangerous situation or require precise orbital operations, the earth cannot issue any effective instructions to reach the detector. Everything depends on the detector’s "autonomous intelligence". The moon does not have an atmosphere. The lunar rover’s landing process is to slow down and land on the surface of the moon from an altitude of 15 kilometers in about 12 minutes. The environment that the Mars rover needs to face and land on Mars is much more complicated. The Mars lander needs It decelerated and landed on the surface of Mars from an altitude of 125 kilometers in about 7 minutes. Due to insufficient data to support the simulation of the Martian atmosphere, sand and dust, unknown environmental factors have brought more technical challenges; When nearby, the probe's orbit determination accuracy and velocity measurement error are about 100 kilometers and 1-10m/s respectively (data quoted from 1). With such a large error and the length of communication, landing on Mars obviously requires the probe's autonomous control system. high. Blessing: The Space Environmental Prediction Center of the Chinese Academy of Sciences has undertaken the space environmental protection of my country's space missions, including manned spaceflight, lunar exploration projects, and space science satellites. It is now working closely with user units to provide deep-space environmental prediction and support services related to Mars exploration . The human history of deep space exploration is advancing arduously step by step. Each deep space exploration mission carries the dreams and efforts of generations, overcomes countless difficulties and obstacles, and the precious data obtained has greatly promoted scientific development. Let us bless the three warriors who are still rushing to Mars through the epidemic-my country's "Tianwen No. 1", the United States' Perseverance, and the UAE's Hope! Both the United States and China have announced plans to take samples from Mars and return to Earth by 2030. In the farther future, maybe we can really build a Mars space station and a Mars ecological warehouse, and finally realize the human dream of "immigrant to Mars"!
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