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DW recently met with physicist and astronomer Scott Manley to discuss plans for China's "artificial moon".
DW: What's wrong with the history of "China Daily" ?
Scott Manley: The numbers they give us do not match. They talk about the spacecraft 500 kilometers away [roughly 300 miles] which is good – it's a low Earth orbit. But then, they talk about providing light for an extended period. And the problem is that, at 500 km, satellites move very fast. If you see a satellite, it moves in the sky in a few minutes. Thus, they could only direct light on one point only a few minutes at a time. And that means that if you really want to light a city, you need several satellites, which must also be able to follow the ground position.
Has this ever been done?
The Russians, obviously. tried this in the 1990s, and they did not even adjust the angle of their lighting. They created a bright spot on the earth that was moving at seven kilometers per second. So you had to go after it if you wanted to get a steady light. Otherwise, you will only see a flash of light for a second. The geostationary orbit [36,000 kilometers above the Earth] is traditionally the magical distance to which it could stay above a single area of the Earth.
More about space: The launch of the BepiColombo spacecraft: beginning of a long mission to Mercury
The first tests will be held in a desert, with plans to enlighten Chengdu, population of 14 million
Can not China put the artificial moon in geostationary [19659004TheproblemisthatasyougoalongyouhavetoenlargeyourmirrorSincethereflectedlightscattersthereisakindoffundamentalphysicallimit:ifyouareina500kmorbit[a mirror of] at 25 meters would give you something that is 10 times brighter than the moon. If you plan to cover 36,000 kilometers, you have to travel hundreds of meters. And if you followed the James Webb Space Telescope – NASA's next large space telescope – one of the big problems they face is to unfold their sunshade in space. In fact, it is quite complicated to make a very compact object that can reliably deploy to zero g. all the more so that you can not really test it at zero g on the Earth.
Other projects on Earth's orbit: Are astronauts stranded on the ISS?
Chengdu astronomers should leave the province to observe the stars without light pollution
But the geostationary option would work it, at least in theory, to illuminate a city of average size?
Just light up a city. It would be a fairly large province. If you have a 600-meter mirror, of course … There's this sci-fi trope that allows you to do the "Archimedes light weapon", where you focus the sun on a target. Fortunately, you can not do it from geostationary orbit to a terrestrial target, unless your mirror is really huge – we are talking about hundreds of kilometers or more.
But in geostationary orbit, you also have the other problem your spaceship will reflect the sun. And we think that the sun has just been light . But light exerts a pressure that will act as a force. This means that the rays essentially push your spaceship. And that will change the orbit over time. Thus, the spacecraft should not only reflect the sun. He should also make adjustments for the disturbances that the sun would cause to keep him in that orbit.
So, "China Daily" is he cheated? Would you say that?
I think that they were very enthusiastic. I think that realistically, they will test it in low Earth orbit. They then claim that, if they could permanently, they could save hundreds of millions of dollars in public lighting. But that would require several satellites and very carefully coordinated orbits, all coordinating and ensuring continuous illumination. And I do not think 500 kilometers is a good altitude for that. I think that intermediate orbits could also be used. You can also place it on a synchronous polar solar orbit that flies over the city at the right time.
And of course, even if you find yourself in a situation where you could make the night as bright as the moon, it would disrupt biological processes on Earth. There are animals that would see this thing and disturb their different monthly rhythms, I suppose. So, you know, there are many elements to take into account when you make these big plans
Will the artificial moon change the life of this red panda in danger in Chengdu?
But this is achievable at a certain level
but not as described in their article.
Scott Manley, physicist and astronomer training, is best known online a "rocket specialist on the Internet"
The interview was modified to make it clearer and longer.
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Launching of a BepiColombo spacecraft for the purpose of badyzing Mercury
Meet the BepiColombo spacecraft
The Space Shuttle journey BepiColombo is scheduled for October 20, 2018. This is a joint project of the European Space Agency (ESA) and the Japan Space Agency (JAXA). BepiColombo consists of two satellites: the European Mercury Planetary Orbiter (MPO) and the Japanese Mercury Magnetosphere Organizer (MMO). They will explore Mercury in different orbits from the beginning of 2026.
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The BepiColombo Probe launches a quest to study Mercury (19659029). Unknown beauty
To date, only two space probes have come close to Mercury. . The last was NASA's successful probe, Messenger. He gravitated the planet more than 4,000 times and sent more than 250,000 images to Earth. A crash planned for 2015 due to lack of fuel ended the Messenger mission.
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The BepiColombo satellite launches a quest to study mercury
Long nights
Mercury probes must be able to withstand a lot of things. Above all, extreme temperature differences pose great challenges for engineers and manufacturers here on Earth. Mercury is uninhabitable for another reason: the sun rises once every 176 days. Yes, you read correctly.
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The space probe BepiColombo launches the Mercury satellite quest
Hot, hot, hot – but no atmosphere
On Mercury, it's hot, but not as hot as it is could expect from a planet so close to the sun. Her neighbor, Venus, experiences much warmer conditions. The reason: Mercury, unlike Venus, has no atmosphere and the heat leaves the planet in the form of radiation. Temperatures range from 430 degrees Celsius (806 degrees Fahrenheit) to minus 180 degrees C.
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The spaceship BepiColombo launches the Quest for Mercury [19659029] Unstable and Eccentric [19659030] Mercury is the smallest planet in our solar system and comes closest to the sun. Its orbit around the Sun is unstable and grows all the time as Jupiter slowly pulls Mercury out of its orbit. At one point, Mercury could collide with Earth. But fear nothing, this will not happen before millions of years.
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The BepiColombo probe launches an investigation on mercury
Similarities with the moon
The surface of Mercury is marked and filled with craters like those of our moon . Many meteorites and asteroids crashed on the planet in the past. Some craters are several hundred kilometers in diameter.
Author: Judith Hartl (fs)
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