Teach you how to make the first map of the moon.

When you look up at the starry sky, from the discussion and imagination of the "Moon Man" to the imagination of the alien moon base, it is not only a general scientific exploration significance, or just to provide entertainment for the public, but also has a very strong symbolic significance-there will really be "Moon Man" in the future.

The most likely "moon man" is actually the earth man-because the competition for the moon among the world's major powers has already begun.

# China Aerospace Day #

On February 7, 65438+2020/kloc-0, Chang 'e V returned to Earth with a sample of 173 1 g, announcing the successful completion of the three-step strategy of "circling, falling and returning" for China's lunar exploration project. In other words, China strode into our cosmic journey with the illusion of the ancient Chang 'e.

This trip to the moon is about to begin. Please keep your seat belt fastened.

Wait, pirates of the Caribbean have a treasure map. Where is our map of the moon? How can we explore the moon without a map? How about being a qualified "Moon Man"?

Don't worry, I'll teach you to make a map of the moon by hand! Before you know how to map the moon, let us know what projection is. Projection is the basic principle that a map can be formed, that is, we should put such a huge moon on a piece of paper that we can see, and this is the role of projection.

The essence of projection is that the points on the object we want to project correspond to the plane we want to project. For the moon, the shape and size of the moon are different from those of the earth. The three-axis radii of the moon are 1738. 1km, 1737. 1km and 1736.0km, which are similar to a sphere, so the surface of the moon can be projected as a sphere.

In China, all kinds of data sources of Chang 'e Project are used to obtain the topographic data of the whole month, and a "full moon orthophoto map" is obtained. Orthographic projection is adopted, that is, the projection plane is tangent to a point on the sphere, the viewpoint is at infinity, and the projected rays are straight lines parallel to each other and perpendicular to the projection plane. The full moon image map with the smallest deformation, the highest position accuracy, the most consistent image tone and the most complete spatial coverage in the world has been obtained, which will become the new "standard image" of the moon-the basic map of the moon.

It can be said that human wisdom is endless. In addition to such a cool projection method, there are many different projection methods, such as Mollweit projection, orthographic projection, azimuth projection, transverse Mercator projection, Lambert equiangular cone projection and equidistant cylindrical projection, which are compared at middle and high latitudes.

Slide down to see the projection method. Why did humans invent so many projections?

In fact, they are all to meet our needs of exploring the mysteries of the moon. We are like navigators, marking our own "treasure map" of the moon in our own language. After understanding the first step of making a map of the moon-projection, we know how to project the moon on the map, and then we will focus on how to draw a map of the moon.

When the lunar probe enters the normal operation stage, the ground application system calculates the switching time of the detector's stereo camera according to the orbit of the lunar probe and its operation state, and mobilizes the stereo camera to shoot. After the stereo camera works, the image data is transmitted back to the earth through the transmitting antenna, and the ground receiving stations in Miyun, Beijing and Kunming, Yunnan are responsible for receiving it on the ground. After receiving the relevant data, the receiving station transmits it to the National Astronomical Observatory through optical fiber and enters the data processing stage. Researchers will further study and process the data, and finally produce the moon image expected by the public. —— Lu Chang, deputy chief designer of ground application system

In a word, the drawing of the moon map needs the combination of remote sensing images and data processing.

It seems too simple to say this, and then some people say it's not very simple. Isn't it just taking pictures +p pictures?

Actually, it is not. Don't underestimate the original picture of the moon. In the universe, it is the image of our "Chang 'e-1" after three days and three nights, shooting around the moon and splicing and correcting 598 times. At the same time, with the help of "laser altimeter", based on the data of 965,438+06,000 points, an accurate moon elevation model map was made, and based on this map, the contour map and real image map of the moon were drawn. Finally, on the basis of these lunar simulation maps, the whole moon is divided into 188 blocks, and then each block of the moon is mapped like a provincial map, forming the best and most comprehensive lunar atlas in the world.

This is a complete map of the moon, all the steps. How's it going? Have you learned?