News Weekly丨“Tianwen No.1” sent back a group photo of the Earth and the Moon, the affectionate look back at 1.2 million kilometers away
On July 27, the fourth day of flying to Mars, the "Tianwen-1" Mars probe took a look back affectionately at its homeland while flying 1.2 million kilometers from the earth. Because of the long distance, the earth looks only the size of a fingernail, and the moon is even smaller. "Tianwen" left home and didn't know when it would come back. Before the hometown flew out of sight, it hurriedly pressed the shutter and used this photo to report to his family that it was safe for the first time after going out. After the photo was sent back to the earth, many people left messages on the Internet. Some people asked it "has it already flown out of the galaxy?", some encouraged it to "don't be afraid", and some kindly reminded it to "watch the road slowly"!
Earth and moon photo
Zhang Yuhua, deputy commander-in-chief of the probe system for China's first Mars exploration mission: We actually designed it in advance and wanted to take this photo. But being able to shoot so perfect, is also a little overjoyed. We have seen this group photo of Earth and Moon from various places on Weibo, everyone is very concerned.
When Tianwen took this photo, he was on the side where the earth and the moon were both at night, but part of the earth and moon on this side was in the bright part of the day, so it was taken in a crescent shape. According to human visual habits, the original image should be rotated 90 degrees to the left: let the bright hemisphere face the right and the dark hemisphere face the left, which is in line with human understanding of the sun rising and setting west. But the researchers did not rotate the photo in the end, because Tianwen's flying posture at that time, its big eyes saw the two smiling faces now, and people wanted to keep a memory of their hometown for Tianwen. And Tianwen, the 5-ton fat man, can change his posture to take pictures and transmit during the flight of 300,000 kilometers per day, behind which is high-tech support.
Zhang Yuhua, deputy commander-in-chief of the probe system for China's first Mars exploration mission: In order to take this photo, we have to calculate in advance how many degrees I have to adjust before I can get to the earth, and by how many degrees can I put both the earth and the moon in. One is that I must calculate it correctly; the other is that I control it correctly; the third is that when I control it in place, I must ensure stability; and fourth, its automatic exposure data must be correct. This series of control, measurement and control, data storage and data processing to the ground, this series must be correct and perfect to get such perfect photos.
The meaning of the photo: many firsts
The part of Tianwen wearing golden material is called the orbiter. In the next six months or so, it will take Tianwen to fly to Mars. The eyes that took the group photo have a very professional name: the optical navigation sensor, which is located on the golden surround. In addition to the camera function, there are star maps of various stars hidden in this eye. Tianwen can correct its direction and speed according to the star maps while flying, which can realize automatic driving. Tianwen carried a white cauldron with a diameter of 2.5 meters, called a directional antenna, which allowed Tianwen to hear the request to take pictures in his hometown and send them back photos, equivalent to Tianwen's ears and mouth.
This photo was also a health test specially designed by researchers for Tianwen during the flight. Scientists looked at the photos as if the doctor saw the test sheet. Judging from the photos, Tianwen had a clear eye, the flying posture was correct, and the coordination with the ground would be more likely to complete the Mars exploration mission.
Zhang Yuhua, deputy commander-in-chief of China's first Mars exploration mission probe system: This photo has both emotional and scientific significance. It is our first time to go to Mars, and many things are our first time.
Mars exploration symbolizes human courage, dreams and passion
The photo taken after the successful take-off on July 23, although the Chinese spacecraft took a photo with the Earth and the moon farthest from the earth, in fact, as early as 2017, the Fengyun-4 meteorological satellite was about 36,000 kilometers away from the earth. I also took a group photo in 2018. Then, in 2018, the Chang'e-4 relay star "Magpie Bridge" also took pictures of the Earth and Moon in an orbit about 450,000 kilometers from the earth; and now, a smiling group photo of 1.2 million kilometers from the earth. The spacecraft is getting farther and farther from the earth, and the images of the earth and the moon are clear, and the angle of shooting can also be taken into account. It is not difficult to see that technology is advancing.
China's first exploration of Mars, the 400 million-kilometer expedition of "Heavenly Questions" has just taken a small step, facing the global Mars exploration failure rate as high as 50%, the way forward is unknown. But perhaps because there are too many unknowns and dangers, Mars exploration activities not only become a major technological event, but also symbolize human courage, dreams and passion.