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Tsinghua University Successfully Launched Gravity and Atmospheric Science Satellite

Tech.China.Com.cn's August 7, 2020 article Tsinghua University Successfully Launched Gravity and Atmospheric Science Satellite (Chinese, title translated to English) includes the image above of what I believe to be 2020-054B or 46026 or "Q-SAT" or "Tsinghua Gravity and Atmospheric Science Satellite".

From Space.com's China launches 2 satellites from desert launch site

Riding along with the Gaofen 9 payload was the Tsinghua gravity and atmosphere scientific satellite, or Q-SAT, which was developed by Tsinghua University in Beijing. The project will verify technology and will measure atmospheric density and collect gravity field data, according to

See also Xinhuanet.com's China launches new optical remote-sensing satellite

Question: Why does Q-SAT look like a buckyball? It appears to have a spherical surface but with subsections that follow the faces of a truncated icosahedron (12 pentagons & 20 hexagons), which is also the shape of a C60 "buckyball" or buckministerfullerene. Why? Is this just convenience or is there some reason for this that we can read further about?

Note that there is one difference between this pattern and that of the "Humanity Star"

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    If football (soccer) is a popular sport in China, creating a sphere from hexagons and pentagons would seem the first / natural choice to the engineers. According to Wikipedia: "... spherical truncated icosahedron design, brought to prominence by the ..., has become a symbol of the sport." – AJN Jan 30 '22 at 02:54
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    It seems somewhat appropriate given it's nearly 60 years since the launch of the first Telstar satellite., on July 10, 1962. – Fred Jan 31 '22 at 00:04
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    The arrangement (layout) of the small square "solar panels" is interesting. They are not the same for each hexagonal frame visible in the picture. – Fred Jan 31 '22 at 00:08

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A little googling turned up a few tidbits about this satellite. From the launch announcement, "Tsinghua Scientific Satellite developed by Tsinghua University is China's first satellite dedicated to the scientific measurement of gravity and atmosphere, and its main goal is to jointly detect the atmospheric density and gravity field in low orbit."

The second link says (thanks to Google Translate) " 'Outer space is not an absolute vacuum, and there is still an extremely thin atmosphere. Measuring its density will help the precise orbit determination of spacecraft and the precise tracking and prediction of space debris.' Wang Zhaokui, head of the Gravity and Atmospheric Science Satellite Team [said]. ... The satellite can obtain centimeter-level precise orbit determination data, realize high-precision atmospheric density and gravity field measurement, and establish my country's own independent space mechanics environment model. At the same time, this mission will also verify the theoretical research results of my country's gravity satellite technology for decades in orbit. The satellite adopts a novel configuration of pure spherical shape, which can ensure that the atmospheric resistance has nothing to do with the attitude of the satellite, thereby greatly improving the accuracy of atmospheric density measurement. In order to ensure sufficient power supply for the satellite, the team designed a spherical solar cell array and overcome the difficulty of small curvature spherical surface mounting process." The article goes on to describe some of the new technology (for space) such as graphene batteries.

According to the third link, it's currently in a 476x500 km orbit. Lowish, but at that altitude it will probably stay in orbit for 20 years or so.

The key point here, I think, is that it is intended to study atmospheric density. That explains its spherical shape, because you don't want solar panels and what not sticking out and complicating the drag you're trying to measure very precisely.

It looks like a buckeyball for the same reason soccer balls do: that pattern of hexagons and pentagons tiles a sphere quite nicely.

I should also mention that getting high resolution gravity field maps also means flying low. Others have flown similar missions. ESA's GOCE mission flew much lower, around 250 km, low enough to require nearly-constant ion engine thrust to maintain altitude. The Tsinghua approach is elegantly simple and low cost, although I have no insight into the quality of the data it will return.

https://www.linkedin.com/pulse/china-launched-gf-no9-04-satellite-successfully-cosats-space/

http://tech.china.com.cn/roll/20200807/368543.shtml

https://orbit.ing-now.com/satellite/46026/2020-054b/q-sat/

https://earth.esa.int/eogateway/documents/20142/37627/GOCE-ESAs-Gravity-Mission.pdf

John McCarthy
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