Science Big Bang Tianwen No. 1 clocked 100 million kilometers-
"Fire detection" still has a few hurdles
On August 28, my country’s first Mars exploration mission, the Tianwen-1 probe, flew a total of 100 million kilometers.
Since its successful launch on July 23, Tianwen-1 has been in orbit for about 36 days.
Compared to flying around the earth and landing on the surface of the moon, flying to Mars is not easy.
This will be a long journey to the solar system. According to expert estimates, when it reaches Mars, Tianwen-1 is about 195 million kilometers away from the earth, and the actual flight distance is about 470 million kilometers. The entire process will have to undergo orbit correction and braking capture. Wait for difficulties.
The current Tianwen No.1 has become an artificial planet. It revolves around the sun together with the earth and Mars in the earth-fire transfer orbit, and gradually moves away from the earth and flies towards Mars.
What did Tianwen No. 1 have gone through in the previous 100 million kilometers, and how many hurdles will it take in the future 300 million kilometers?
Finally, here is a photo of Earth and Moon
The Chinese astronauts' pursuit of Mars has already begun during the flight of the rocket.
At 12:41 on July 23, Tianwen-1 carried a dozen scientific payloads with different functions and embarked on a long journey to Mars in anticipation of all.
"Directional antenna deployment!" This is a very critical control. At a distance of 400 million kilometers, the radio signal transmitted between the ground and the detector will become very weak, and this "cauldron" of nearly 6 square meters is deployed. Very important, it can greatly increase the transmission signal strength.
Once in Mars orbit, long-distance communication with the ground depends on it.
After the antenna is deployed, it means that China's fire detection journey has a "lifeline" from then on.
On the fourth day of the long journey, everything was normal during the flight of Tianwen-1, but without the familiar atmosphere of the earth around it, it traveled alone in the black universe and ocean, while the earth and moon became smaller and smaller.
Tianwen 1 took out the optical navigation camera it carried and took a picture of the earth and the moon.
In this black-and-white photo, the earth and the moon are large and one small, both in the shape of a crescent. They accompany each other in the vast universe, as if they are smiling at people.
Research and development experts of the Eighth Academy of China Aerospace Science and Technology Corporation told reporters that the probe is in space, just like a ship sailing on the vast sea, except that there is no satellite navigation system guidance after it leaves the earth.
Unlike traditional radio navigation, optical autonomous navigation can acquire navigation information such as position and speed through image target recognition and feature extraction.
"The optical navigation sensor is like the'eyes' of the detector." The optical navigation expert of the Eighth Hospital Control Institute drew an analogy, "With these bright'eyes', the detector has the ability to be autonomous and can see by itself. Flying towards the destination".
In the process of Tianwen-1's approach to Mars, Chinese astronauts regarded the navigation sensor equipped with a telephoto lens as a "clairvoyance", which can identify Mars at a distance of up to 10 million kilometers and can adapt to Mars autonomously. From the point target to the area target, from the weak target to the strong target Mars image extraction, even without external navigation information, it can autonomously find the way forward in deep space flight.
Become an artificial planet
According to the definition of the International Telecommunication Union, the deep space boundary is the space 2 million kilometers away from the earth. On July 29, 6 days after Tianwen-1 entered orbit, it successfully broke through this boundary and officially became a solar system. An artificial planet traveling in deep space.
As of 23:00 on August 25th, Tianwen-1's distance away from the earth exceeded 10 million kilometers, with a cumulative travel distance of 93.29 million kilometers.
Cui Xiaofeng, the chief model officer of the first Mars exploration mission at the Beijing Aerospace Flight Control Center, said that the boundary means that the limit is challenged to a certain extent. The deep space boundary is the same. The difficulty that the flight controller must overcome.
Although all roads lead to Rome, a scientific and rigorous attitude is necessary to successfully complete the long space journey.
At present, Tianwen-1 is in a state of unpowered flight. During the flight, small deviations will gradually accumulate and amplify due to factors such as orbit deviation and control accuracy deviation. Therefore, timely correction and adjustment are necessary.
On August 2, the 3000 Newton engine of the Tianwen-1 probe worked for 20 seconds to complete the first midway correction of the orbit.
Zhu Qinghua, vice president of technology for my country's first Mars exploration mission probe system, said that many cars have lane keeping functions. If the car deviates from its lane, it will automatically correct the direction and return the car to its original lane.
The orbit correction of the Mars rover is similar, but the difference is that the Mars rover needs to correct not only the flight direction, but also the flight speed and other variables.
He told reporters that the startup time of Tianwen No. 1 engine was determined to be 20 seconds, and the orbital experts finally came up with a control strategy that can not only meet the engine calibration but also achieve the optimal ground-fire transfer energy.
According to Cui Xiaofeng, the unknown space means risks and challenges. It is very important to hold the "communication line" between the ground and the spacecraft.
While taking good care of Tianwen-1, the flight controller must also make reasonable use of deep-space measurement and control resources to implement the dormant wake-up of the Chang'e-4 lander, patrol and relay star, and take care of the "old birthday star" Chang'e on the moon. The No. 3 lander allows the Chinese "Jade Rabbit" to continue to patrol and explore the back of the moon.
The future will pass five hurdles and six generals
According to Zhang Yuhua, deputy commander-in-chief of China’s first Mars exploration mission probe system and commander-in-chief of the orbiter, Tianwen-1 will undergo 3-4 midway corrections and one deep-space maneuver correction during its flight in the next few months. , The orbiter gradually flew closer to Mars and entered the Mars capture section.
Among them, Mars capture is one of the highest technical risks in Mars exploration missions. Due to the uniqueness of the Mars capture window, the success or failure of capture determines the success or failure of Mars exploration missions.
This ignition and braking process is usually referred to as "braking".
Zhang Yuhua said that if the "brake" is stepped on early and the probe's speed drops too low, the probe will fall into the atmosphere and hit Mars; if stepped on too late, the probe will not be captured by Mars' gravity and fly away from Mars.
After successfully capturing and entering the ring fire orbit, the Mars rover will perform a series of orbit adjustments, enter the parking orbit, adjust the near-fire point to near the landing point, and conduct detailed inspections of the rover’s landing area every time it passes the near-fire point , To prepare for the next landing of the landing patrol.
Zhang Yuhua said that after the probe enters the Mars capture orbit, after 3-4 orbit adjustments, it will enter a moored orbit with a period of about two Martian days.
The Mars rover will operate in orbit for about 75 days, carry out 12 pre-landing zone imaging detections, and return the imaging data to the ground to complete the pre-detection of the landing zone pre-selected by the landing patrol.
She told reporters that after completing the three-month Mars relay mission, the Tianwen-1 Mars Orbiter will brake and descend near the fire point, enter the scientific exploration orbit, and continue to operate in this orbit for one Martian year. , The implementation of Mars global remote sensing mission.
But all this will not happen until a few months later.
A young science and technology worker at Beijing Flight Control Center said that the first month was fresh and tense for Tianwen-1 and the astronauts on the ground. Tianwen-1 is like a newborn baby. The new location, facing the new environment.
The aerospace people are like new parents, to guard it, to deal with every possible challenge.
Although it is difficult, all this will be full of meaning-condensed in more than a dozen months, witnessing China's road to heaven.
China Youth Daily · China Youth Daily reporter Qiu Chenhui Source: China Youth Daily