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China Moon Space Technology

Chinese City 'Plans To Launch Artificial Moon To Replace Streetlights' (theguardian.com) 196

The south-western Chinese city of Chengdu is planning to launch an illumination satellite in 2020 that is "designed to complement the moon at night," though it would be eight times as bright. "The 'dusk-like glow' of the satellite would be able to light an area with a diameter of 10-80km, while the precise illumination range could be controlled within tens of meters -- enabling it to replace streetlights," reports The Guardian. From the report: The vision was shared by Wu Chunfeng, the chairman of the private space contractor Chengdu Aerospace Science and Technology Microelectronics System Research Institute Co (Casc), at a national mass innovation and entrepreneurship event held in Chengdu last week. Wu reportedly said testing had begun on the satellite years ago and the technology had now evolved enough to allow for launch in 2020. It is not clear whether the plan has the backing of the city of Chengdu or the Chinese government, though Casc is the main contractor for the Chinese space program.

The People's Daily was quick to reassure those concerned about the fake moon's impact on night-time wildlife. It cited Kang Weimin, director of the Institute of Optics, School of Aerospace, Harbin Institute of Technology, who "explained that the light of the satellite is similar to a dusk-like glow, so it should not affect animals' routines."

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Chinese City 'Plans To Launch Artificial Moon To Replace Streetlights'

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  • by Anonymous Coward

    If they can pull off such a power hungry and yet precise lighting system, that will be amazing in itself. Of course the environmental impact will be 'interesting'. Most of the Chinese cities are over lighted, so no big deal right?

    • Power hungry? I'd bet dollars to donuts that this is a mirror.
      You'd need a little power to orient the mirror, but hey, a little solar pannel would do that.

      I'd also presume that this thing will be in geo-sync orbit, making it a un-moving "moon" in the sky. If so, it too would go dark for a short time around midnight, when the earth's shadow blocks it.

      • You likely have the orbit tilted in a way, that it only hits the earth shadow like the moon does during an eclipse, that means roughly once a year.

      • by ShanghaiBill ( 739463 ) on Thursday October 18, 2018 @01:57AM (#57496498)

        I'd bet dollars to donuts that this is a mirror.

        According to TFA, it is based on mirrors. It will be in GEO, with is at 42,000 km, so it would have to be aimed with extreme accuracy, and to light an entire metropolitan area, it would have to be enormous.

        And it is supposed to be ready-to-go in 2020. That is wildly implausible.

    • by viperidaenz ( 2515578 ) on Wednesday October 17, 2018 @11:06PM (#57496088)

      They plan on using mirrors, and I assume a geo orbit that doesn't get eclipsed by the Earth.

      Even if they did get it up there, I doubt it would last long.

      Hubble has had all its gyros replaced already and the replacements are failing again.

      This is something that needs precise control, every night, continuously. It doesn't have to just point itself somewhere and stay still for a long period of time, it needs to constantly move the mirror to keep the desired spot illuminated as it orbits. That's going to require the gyros and reaction wheels to be on 24/7.

      • That's going to require the gyros and reaction wheels to be on 24/7.
        In theory you only need to notch it once in a precise rotation ... then it will always beam at the same spot.

        • by WhiplashII ( 542766 ) on Wednesday October 17, 2018 @11:44PM (#57496204) Homepage Journal

          Nope, GEO wobbles. Satellites up there require station keeping and direction pointing thrusters. (There are some clever ways to limit the directional thrusters, but in GEO there is no way to avoid needing position thrusters and for precise pointing like this you'll need pointing thrusters.)

        • That's going to require the gyros and reaction wheels to be on 24/7. In theory you only need to notch it once in a precise rotation ... then it will always beam at the same spot.

          And how do you do that? Are you thinking about a globe [wikipedia.org] which is sitting on a table, and then you stick a pin representing the satellite on it, so that it is precisely fixed to the location and rotation of the earth?

          • No, the pin, or end of the pin, would oscilate south and north.

            But the rotation of the satellite would keep it aimed on the same spot (during the time it is north enough to shine on the cities in question).

            The problem of the rotation is: it needs not only to be semi geostationary but also follow the earth around the sun, that it is always on the night sie of he planet when it is needed. (So it is not a 24h orbit but something like 23h ... oops, or is it 25h, I forgot and it is to late to the math in my head

            • then you need to counter the force from the light hitting the massive mirror.
              Don't forget they're targeting 10m accuracy from 36,000km away. That's 0.0000159 degrees of rotation on the satellite

  • by mark-t ( 151149 ) <markt AT nerdflat DOT com> on Wednesday October 17, 2018 @10:19PM (#57495928) Journal

    In-city viewing is less than ideal, of course, but it's not impossible to find darker areas, even within a metropolis city limits.

    I can't imagine that hobbyist astronomers are going to be very thrilled about this.

    • by SuperKendall ( 25149 ) on Wednesday October 17, 2018 @11:07PM (#57496094)

      The nice thing about the moon is the cycle - when it's full it's nice illumination and the world looks interesting, but a new moon is almost as great with a fairly starry sky even in a city if the air is really clear.

      What they could do to help this though, is to turn off the light very late - say midnight or 1am. That way you still get the safety benefits of good illumination, but you also can still stay up late to see stars if you like.

      I wonder how safe this will be compared to real street-lights though - one of the issues with moonlight even when it is bright, is that the light is so flat with poor shadowing that depth perception is hampered. Maybe since this is brighter it will be a lot better.

      • by AmiMoJo ( 196126 )

        Most places in China have really poor, inadequate street lighting anyway. I don't know why, maybe there are issues installing it or something. But anything they can do with this is probably better than what they have currently.

      • The nice thing about the moon is the cycle - when it's full it's nice illumination and the world looks interesting, but a new moon is almost as great with a fairly starry sky even in a city if the air is really clear.

        The most amazing that I've seen for it was when up in the mountains, miles from any city. Completely clear night. I've been at this location during a full moon and an almost new moon. Really amazing, especially since most of those nights were cloudless.

        But speaking of moon cycles, it always reminds me of a scene from that dumb Angels in the Outfield movie. Where the little brother sees the moon as a sliver and goes: "Look, it's God's thumbnail!"

        But the older brother is all salty and mad about someth

    • Stargazing. .... Are we talking about a different China here? The people in Chengdu should be lucky enough to see to the end of the street to say nothing on the few days where they could look up they couldn't see squat anyway.

      Signed: A hobby astronomer who put his hobby on hold while living in China.

    • by jdavidb ( 449077 )
      And what about the impact on human sleep quality?
    • by Anonymous Coward

      Stargazing is probably already illegal in China, it leads to contemplation and contemplation leads to new ideas and independent thought.

      Why launch a fake moon? Why not just have the government impose an earlier curfew, and have the media declare that it is always daytime and that night is a european myth?

  • Ahh, the whole town illuminated, when it needs it the most, on dark and cloudy nights, when nary a star is to be seen, ohh wait ;D.

    • by quenda ( 644621 ) on Wednesday October 17, 2018 @11:30PM (#57496158)

      No, a bigger problem: Chengdu smog is as bad as Beijing. They rarely see the moon, and often you can't tell where the sun is.

      Will the fake moonlight be able to penetrate thick smog?

      • Reminds me of the surface of Venus. Based on those pollution levels it sounds like that's what they're aiming for.
  • by Arzaboa ( 2804779 ) on Wednesday October 17, 2018 @10:25PM (#57495940)

    It never dawned on me that someone lighting up the earth with satellites would ever make sense. Man will run this earth, without looking back, until it bites him in the ass.

    --
    Walking with a friend in the dark is better than walking alone in the light - Helen Keller

  • by careysub ( 976506 ) on Wednesday October 17, 2018 @10:30PM (#57495954)

    That this won't see the light of day.

    • by Anonymous Coward

      I predict version 2 will have the functionily to focus the light. Ouch.

    • by Anonymous Coward

      Says Chengdu not Chengdon't.

    • by Anonymous Coward on Thursday October 18, 2018 @12:57AM (#57496372)
      But if it does, that old copypasta 'The Moon: A Ridiculous Liberal Myth' will have become somewhat real. Interesting times.

      It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the last vestiges of control of our public school system from decent, God-fearing Americans (as if any further evidence was needed! Daddy's Roommate? God Almighty!)

      Documentaries such as Enemy of the State have accurately portrayed the elaborate, byzantine network of surveillance satellites that the liberals have sent into space to spy on law-abiding Americans. Equipped with technology developed by Handgun Control, Inc., these satellites have the ability to detect firearms from hundreds of kilometers up. That's right, neighbors .. the next time you're out in the backyard exercising your Second Amendment rights, the liberals will see it! These satellites are sensitive enough to tell the difference between a Colt .45 and a .38 Special! And when they detect you with a firearm, their computers cross-reference the address to figure out your name, and then an enormous database housed at Berkeley is updated with information about you.

      Of course, this all works fine during the day, but what about at night? Even the liberals can't control the rotation of the Earth to prevent nightfall from setting in (only Joshua was able to ask for that particular favor!) That's where the "moon" comes in. Powered by nuclear reactors, the "moon" is nothing more than an enormous balloon, emitting trillions of candlepower of gun-revealing light. Piloted by key members of the liberal community, the "moon" is strategically moved across the country, pointing out those who dare to make use of their God-given rights at night!

      Yes, I know this probably sounds paranoid and preposterous, but consider this. Despite what the revisionist historians tell you, there is no mention of the "moon" anywhere in literature or historical documents -- anywhere -- before 1950. That is when it was initially launched. When President Josef Kennedy, at the State of the Union address, proclaimed "We choose to go to the moon", he may as well have said "We choose to go to the weather balloon." The subsequent faking of a "moon" landing on national TV was the first step in a long history of the erosion of our constitutional rights by leftists in this country. No longer can we hide from our government when the sun goes down..

  • How ?? (Score:5, Interesting)

    by Crashmarik ( 635988 ) on Wednesday October 17, 2018 @10:32PM (#57495958)

    Just how did this make it from story idea someplace in Chengdu to the pages of the Gaurdian or was that the Onion and finally to Slashdot without anyone asking just how the hell it's supposed to work ?

    Just what orbit are they going to put it in where it can cast a 10-80 km diameter circle of illumination and be able to illuminate the city for a significant fraction of the night ?

    • I don't think the "how" is the newsworthy part. It's the "why would you think this is a good idea at all" that is interesting.

      It reminds me of the plan to nuke the moon [wikipedia.org] during the space race.

      • Put it in geostationary orbit. Not difficult to focus a light beam to within a few hundred meters.

        And maybe not even need many batteries as the satellite is normally outside earth's shadow.

        But still a crazy idea.

    • by AmiMoJo ( 196126 )

      Polar orbit, like a weather/spy satellite that passes over the same area regularly. Time it so that it covers the early evening hours in the winter when you really need that extra light, and so it has enough visibility over the horizon of the sun.

      • Err no.

        The Earth isn't transparent. You need the Satellite ahead of the terminator, so it can catch the sun while still having line of sight to Chengdu, then there is second set of constraints between satellite size and height while providing light bright enough to replace street lights.

        Just for reference The Russian stunt to do this produced a spot of illumination that moved at 5km/sec

      • Oh and while I didn't state this explicitly it was implied. The earth not being transparent also means it has to be high enough above the horizon to not be blocked by the earth or the buildings in the city.

  • A horrible idea (Score:4, Insightful)

    by charlie merritt ( 4684639 ) on Wednesday October 17, 2018 @10:37PM (#57495976)

    "...similar to a dusk-like glow, so it should not affect animals' routines."

    Is s/he a fool or does s/he think we are?
    Dusk all night long, no, that wouldn't upset anything.
    Why not a "Natural, noon-like glare" ? Shouldn't upset anything either.

  • Dual purpose (Score:4, Interesting)

    by AlanObject ( 3603453 ) on Wednesday October 17, 2018 @10:40PM (#57495982)

    They can always amp-up the emitters if they have a lawless uprising in the city.

    Don't pretend for even a nanosecond that they didn't think of that, regardless of engineering feasibility.

  • Oh God (Score:5, Funny)

    by WankerWeasel ( 875277 ) on Wednesday October 17, 2018 @10:44PM (#57495998)
    I can just picture the initial testing being like ants under a magnifying glass. Oooops, still trying to get that dialed in guys.
  • by Futurepower(R) ( 558542 ) on Wednesday October 17, 2018 @10:48PM (#57496012) Homepage
    Chengdu weather [google.com]: Of the 8 days shown, 5 are cloudy. No illumination from space then.
  • how do animals cope in places like Alaska in the summertime when the sun almost never set? This will save a ton of electricity and get far way better pictures for the spy programs
  • Is not how to help with climate change, guys. What we need is light being directed *away* from earth.
  • They are going to do this about the time of the Chinese mission to teleport to the Sun (at night, of course). Absurd, technically.

            In any case, street lights are far more practical, and even a moonlight tower is perfectly practical for mostly the same effect - but less so than street lights.

  • How do you get a mirror that big into geostationary orbit?

  • You can't expect dusk-like light to have no impact on wildlife. Just think of the impact it has on humans.

  • Can it work? YES! (Score:5, Interesting)

    by BobC ( 101861 ) on Wednesday October 17, 2018 @11:52PM (#57496220)

    Let's assume, for the moment, that it is a "good idea". How should it be implemented?

    If there is to be only one satellite, then there are only two orbits that can work: GEO and a polar Molniya that has the satellite overhead between dusk and dawn. With more satellites more orbits can work, but let's assume one for now.

    Let's figure out how big a mirror is needed. First, it will need to have at least some degree of focus to keep the spot size bounded. That is, a flat plane won't do. Let's compute the total light needed over a 10 km x 80 km ellipse, an area of about 2500 km^2. Given that 1 lux = 1 lumen / m^2, the lumens we need will be lux * area. Let's assume a partial moon (0.1 lux) is the minimum needed. Multiply those numbers, and that's 250,000,000 lumens. Let's say naked sunlight (allowing for atmospheric losses) is roughly 100,000 lux. Area = lumens/lux, yielding a mirror area of 2500 m^2.

    And that's for a *perfect* mirror: No losses, with perfect focus. Assuming a circular mirror, that's a minimum diameter of about 60 m. That million-to-one illumination ratio really rocks. So, at a first glance, the optics alone says it's doable, at least near the minimums I've used. VERY doable!

    A mirror in a Molniya orbit will have to deal with a rapidly/continuously varying sun angle every night, but there may be rotational tricks to deal with that, *if* we can manage to rapidly change the mirror shape. But it would rapidly complicate things, so let's set the Molniya orbit aside.

    A mirror in GEO need only cope with seasonal variations. While we're at it, let's increase the mirror area by a factor of 10, so we'll be sure to have abundant margin to play with; let's say a nice, round 200 m diameter.

    We already have communication satellites at GEO that stay aimed with precision for 15 years or more. Of course, they're aiming tiny antennas that are a millionth the size of our mirror, so we still must consider the aiming problem.

    Satellites use aiming actuators for the antennas, and thrusters and gyros (torquers) for the satellite body, which combined yield good pointing precision. Our reflector won't have that luxury: The antenna will dwarf any satellite body, and will also have minimal rigidity: It really can't be aimed much at all, and even then not quickly.

    To get some rigidity we can spin the mirror, which should also help with its shape, though that may not be needed. The total range of motion needed to track the sun matches the 23.5 degree tilt axis over a year, which is roughly 0.1 degree per day. (Well, OK, the total wobble is 23.5 degrees in each direction, but we only need to split the difference to bounce the sun toward the ground, which is 11.75 degrees, doubled, which gets us back to 23.5 degrees).

    Next is the issue of aiming/pointing. Using gas or chemical thrusters alone may be a non-starter, including ion thrusters. But with a spinning disk, we really should be able to use precession. But precess against what?

    Given the slow rate of angular motion, I suspect a 100-300 km long gravity tether should be able to provide enough restoring force to make the job manageable. The satellite body will then need only to slightly pivot the mirror relative to the tether, an extremely low-energy operation.

    The satellite will still need an ion thruster to stay on-station (very gentle thrust). But even with that, our reflector satellite will be vastly simpler than a communications satellite, and perhaps about the same mass for an equivalent mission duration.

    Oh, almost forgot: Let's put a small hole in the center of the mirror so light can reach some solar cells to power the satellite! No reactors or RTGs here.

    I think that about does it, as an "educated guess". Total mass isn't really an issue: Some member of the Long March family will be able to loft it.

    (Yes, yes, I know I haven't calculated either the atmospheric dispersion or the "f-number" of the optics. But I made the mirror 10x larger so I wouldn't have to!)

    • Re:Can it work? YES! (Score:5, Informative)

      by hankwang ( 413283 ) on Thursday October 18, 2018 @01:53AM (#57496484) Homepage

      Regarding focusing: even with a perfectly shaped mirror, you can't circumvent the fact that the sun is not a point source. Sun diameter D=1.4e+9 m, sun distance L=1.5e+11 m, geostationary orbit distance R=3.6e+7 m. The spot at the earth surface will have a minimum diameter D R/L=340 km, for ideal optics. The claimed diameter of 10 to 80 km is physically impossible from geostationary orbit. They would need to use low-earth orbit, about 1000 km altitude, which would require multiple satellites to illuminate a single town throughout the night.

      By the way, the difference between an ideal focusing mirror and a flat mirror is negligible for illumination purposes. For a 200 m diameter mirror, it would add another 0.2 km to the spot size if it's flat rather than paraboloid.

      • by BobC ( 101861 )

        Yeah, the ~0.5 degree angular width of the sun is certainly an issue, as is the small target size. Fortunately it's one that can be mitigated by adding complexity and reducing efficiency, such as by using 3 reflective surfaces and/or collimation. The use of a long gravity tether in GEO would permit multiple annular reflectors to be kept in tight alignment. Modeling the positioning stability of such a system is difficult, but it's bounded, so the system should be controllable.

        Even with a full Goldberg (ri

        • I think you misunderstood me. It is optically impossible to image an extended light source onto a point, no matter how many fancy lens and mirror elements you combine.

          "[Etendue] is the product of the area of the source and the solid angle that the system's entrance pupil subtends as seen from the source. (...) Etendue is important because it never decreases in any optical system where optical power is conserved. A perfect optical system produces an image with the same etendue as the source." - https://en.m. [wikipedia.org]

  • by MobyDisk ( 75490 ) on Thursday October 18, 2018 @12:00AM (#57496234) Homepage

    With a few alternations, you could make it project ads across the entire city! Alternatively, they could make it look like a giant eyeball, so everyone knew they were being watched.

  • by PopeRatzo ( 965947 ) on Thursday October 18, 2018 @12:33AM (#57496320) Journal

    Back in the late 70s, the city of Chicago replaced all the mercury streetlamps with sodium vapor lights. It was sold as a way to improve visibility at night and make driving safer and everything safer.

    They didn't expect it to completely alter the behavior of birds in the city, messing up their diurnal cycles and screwing with their reproduction. Also, it changed the city's character. Night time used to be this magical silvery place in Chicago. It was just beautiful and romantic. The streetlights were the color of a winter moon, and you could still see stars. After the sodium vapor lamps, it was like this phony daylight all the time and yellow and it's ugly as hell. Also, no more stars.

    You can really fuck up artificial lighting. Maybe it's just because it was what I was used to, but if you see any old color photos of Chicago neighborhoods at night, you can really see the difference.

    • The sodium lights mess up human color vision too. A red emergency vehicle would appear orange or something not red. It would be difficult to determine the color of a hit and run vehicle, etc. Sodium lights put out a narrow band of light that can be filtered out in telescopes.
      • They don't mess up vision, they simply provide an unbalanced spectrum to begin with an therefor have poor color rendering.

        • That's what I meant, you expressed it better. The City of San Diego replaced mercury streetlights and a man from Tijuana , Baja California Mexico bought some to install in his Colonia, his neighborhood. It was his urban renewal project as the municipal government wasn't effective and was powered by bribery.
        • Unbalanced is putting it nicely, the spectrum of low pressure sodium lamps is practically monochromatic.

    • chicago is changing to leds now. people are crying about the loss of the yellow glow.
      • chicago is changing to leds now. people are crying about the loss of the yellow glow.

        LEDs are pretty ugly at night and probably unhealthy because they are known to disrupt people's sleep. In a big city, you're going to have to have blackout curtains on the windows to get a good night's rest.

  • Russians deployed some space mirrors before in their Znamya mission:

    https://en.wikipedia.org/wiki/... [wikipedia.org]

    Znamya 2.5 had a bit of a tragic ending as the mirror got ripped by the antenna of the satellite that deployed it.
  • by TeknoHog ( 164938 ) on Thursday October 18, 2018 @06:14AM (#57496922) Homepage Journal
    Yay, more sunlight to heat the Earth! What could possibly go wrong?
    • Sublight is hardly the cause of the problem.
    • That's what I was wondering as well. Would all the extra sunlight reflecting onto what normally would be a darker side of the Earth cause it to heat up even more? Some AC made a comment elsewhere about doing this elsewhere at night. That seems like it'd be a huge hit to the temps of the Earth.
  • They are finally building Elysium [wikipedia.org]!
  • Now with extra light at night, perhaps they will need dusk/night during the day. Someone get in contact with Mr. Burns. We need his sun blocking device! You'll just have to pay his nuclear power bills.
  • That's no moon....

  • Think of the positives of 24/7 light, it won't matter anymore if you work 1st, 2nd, or 3rd shift, spread the workload from 8 hours a day to 24 and no more morning and evening rush hour. Electricity will be saved with no more streetlights. Cars will save on gas with no more headlights. Accidents of all types will go down. Crime will go down. The economy will improve now that you can go about your normal business / entertainment / etc activities at 4 AM. Depression will go away. Life expectancy will rise by 7
  • "... the light of the satellite is similar to a dusk-like glow, so it should not affect animals' routines..."

    I'm pretty sure animals that wait for night don't start until AFTER dusk. If it's always dusk, then...?

    Well, good news for crepuscular [mnn.com] animals, then, though they may get tired from being active for 12 hours instead of 30 minutes...

  • by p51d007 ( 656414 )
    Too damn much light pollution now! I don't live in a "big" city...less than 200,000 but, the only stars you see at night are Venus & Mars. My parents live about 125 miles away in a small town of 4,000. Largest city of 50k is 22 miles away. Once, I took my parents dog after dark, out to do its business and just stared up at the sky. My dad looked out and came outside and said what are you looking at? I said the stars...you could actually see the milky way. He said so? I said in a city, you are luck
  • Comment removed based on user account deletion
  • You think it was bad when Suki took over the paint bots, just wait until some kid gets control of the satellite and realizes it's the ultimate magnifying glass and anthill situation.

  • Moths be going crazy...
  • by WindBourne ( 631190 ) on Thursday October 18, 2018 @04:57PM (#57500110) Journal
    Seriously, we should have several in GEO, but then be able to rotate them with the earth rotation. In particular, use these for disaster areas. This will allow for rescue crews to not have to bring in massive amounts of lights, generators, and fuel. This would save a LOT of lives.

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