China News Service, Shanghai, July 23rd Question: Revealing the new work of China's "Tianwen-1": taking "portrait photos" of the Mars satellite while "running"
Author Zheng Yingying Ma Shuaisha Chen Baojuan
It has been two years since China's Tianwen-1 Mars probe went to space for "work". On the 23rd, it handed in a work - a "portrait photo" of the Mars satellite Phobos that looks like a potato. This is the first time China has implemented Phobos. An imaging detection provides valuable data for scientists to carry out research on its topography and operation laws.
The image shows that Phobos is a small, irregularly shaped object in the shape of a potato.
It is one of the two natural satellites of Mars. To take a "portrait" of it, "Tianwen-1" can work hard.
Filmed at a distance of 5100 kilometers
China started its first autonomous Mars exploration mission on July 23, 2020. The Tianwen-1 probe consists of an orbiter and a landing rover.
The Tianwen-1 orbiter runs on an orbital plane that crosses the north and south poles of Mars.
Phobos circles the planet in an orbit close to the equatorial plane of Mars.
In this way, the artificial satellite Tianwen-1, which orbits vertically around Mars, and the natural satellite Phobos, which orbits horizontally around Mars, will periodically "meet", that is, there will be a window period of "reunion".
This time, the Tianwen-1 orbiter accurately captured the "rendezvous" window, and completed the shooting of this cosmic blockbuster at a distance of 5,100 kilometers from Phobos.
"Photographer" shoots while "running"
This time, the "photographer" is a small area detector inside the surround high-resolution camera, and its effective field of view is less than 0.3 degrees.
The orbiter and Phobos are in a fast flight process. At their periodic "encounter" moments, the "photographer" even if the center of the entire 0.3-degree field of view is completely aligned with Phobos, from Phobos entering the field of view to flying It only takes about 6 seconds to go out of the field of view. If the angle of the surround device is slightly off, it is possible that even the shadow of Phobos may not be captured.
"This is equivalent to a photographer running while carrying a camera while taking pictures of another high-speed moving object, and the camera's field of view is still very small. The difficulty can be imagined." Deputy Mars Orbiter, Eighth Institute of China Aerospace Science and Technology Corporation Chief designer Zhu Qinghua said.
Accurately capture "instant images"
The Tianwen-1 orbiter was developed by the Eighth Academy of China Aerospace Science and Technology Corporation.
Before the mission was implemented, the development team first accurately calculated the orbital "intersection" point, and had to confirm whether the lighting conditions at the corresponding time met the shooting requirements.
During the implementation process, the orbiter is maneuvered through a large-angle attitude, and the angle is adjusted to ensure that the center of the field of view of the small area array detector of the high-resolution camera can be aimed at the shooting window and remain stable.
Moreover, due to the time delay of the Mars mission, the entire process of attitude maneuvering, accurate shooting, and restoration of control was completed by the Tianwen-1 orbiter fully autonomously.
"It can be said that in order to obtain the image of Phobos at this moment, accurate calculation, steady pointing, control, and good shooting are indispensable." Zhu Qinghua said.
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