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Thread: Disco ball put into orbit.

  1. #1
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    Disco ball put into orbit.

    A highly reflective sphere has been placed in orbit by a New Zealand-launched rocket.
    Akin to a giant "disco ball", the object should be visible to the naked eye as it sweeps across a twilight sky.
    It was lofted by American start-up Rocket Lab, whose Electron boosters operate from the North Island.
    The company said its "Humanity Star" was an attempt to create a shared experience for everyone on Planet Earth.
    "No matter where you are in the world, or what is happening in your life, everyone will be able to see the Humanity Star in the night sky," said Rocket Lab CEO Peter Beck in a statement.
    http://www.bbc.co.uk/news/science-environment-42808180

    will this work? Would it create flashes for all locations on the Earth in a given day? How bright would the flashes be?
    Formerly Frog march..............

  2. #2
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    Well, they say it won't be visible at US latitudes until March, so I'll take a look for you then. ;-)

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  4. #4
    They discussed it this weeks WSH this evening.
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  5. #5
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    perhaps it should be bigger, and assembled from pieces, as a huge buckyball.
    Formerly Frog march..............

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    Where can we get orbital pass info. Doesn't appear to be on Heavens-Above.com yet.

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    And, it'll decay soon. Humanity Star...more like, O The Humanity Star.

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    I'm having a little trouble find the actual orbital altitude; assuming the 500-km sun-synchronous orbit stated as a typical Electron goal, at a zenith pass one of the mirror faces (from photos, about 30 cm on a side) would span 0.12 arcseconds on a side. So a perfectly reflective mirror would direct a fraction ~(0.12/1800)2=4.7 x 10-9 of the Sun's light to a properly positioned observer, which would make a (very brief) flash of apparent magnitude -5. A bit to my surprise, these would indeed be very noticeable - comparable to the inoperative and tumbling members of the old Iridium constellation, which produced extremely brief flashes (I think too short for the eye to actually resolve), some of which seemed roughly this bright.

    (Mirror roughness would decrease this brightness, as would a nonplanar mirror shape if worse than the Sun's angular size).

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    The only bad I see coming of this is getting people used to the idea that this is a good thing.

    This is not a good thing.

    Remember the Coca-Cola orbital advertising attempt? Smaller scale version of the same thing.
    Time wasted having fun is not time wasted - Lennon
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    Thread moved from OTB to Space Exploration, with a redirect. Note that some of the above posts would have been frowned upon had it been in Space Exploration to start with.
    Everything I need to know I learned through Googling.

  11. #11
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    Quote Originally Posted by ngc3314 View Post
    I'm having a little trouble find the actual orbital altitude; assuming the 500-km sun-synchronous orbit stated as a typical Electron goal, at a zenith pass one of the mirror faces (from photos, about 30 cm on a side) would span 0.12 arcseconds on a side. So a perfectly reflective mirror would direct a fraction ~(0.12/1800)2=4.7 x 10-9 of the Sun's light to a properly positioned observer, which would make a (very brief) flash of apparent magnitude -5. A bit to my surprise, these would indeed be very noticeable - comparable to the inoperative and tumbling members of the old Iridium constellation, which produced extremely brief flashes (I think too short for the eye to actually resolve), some of which seemed roughly this bright.

    (Mirror roughness would decrease this brightness, as would a nonplanar mirror shape if worse than the Sun's angular size).
    I got the same even with tweaking to a 32 arcsec Sun, triangle area 75% of a circle, 75% brightness reduction for AM1 atmosphere. For 300km, it would be -6.2 app. mag. An Iridium flare can be as bright as -8, so it should be bright. But I get a time of reflection of under one second (~ 1/2 sec. for 500km, 1/3rd sec at 300km).

    [I suppose we should factor in the phase angle since it will be near the terminator.

    Crunch, crunch... ok, it only changes it slightly. -4.9 peak (500km) when it is just above our atmosphere's shadow.]
    Last edited by George; 2018-Jan-25 at 10:25 PM.
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    "Messages in the sky" stop being cute when you realize that *anybody* with the capability to put something into LEO can put any message they want up.

    This time it's New Zealand. What if next time it's Iran? Or Israel? Or Ireland? Or some other country that begins with the letter I that isn't yours? (Being this is an international board and all.) The Coca-Cola fiasco, for those too young to remember, was to put a Coke symbol shaped billboard the apparent size of the full moon up for several months. (How gosh darn obnoxious would that have been?) So we know that's doable at least.

    I'm sure even the New Zealanders weren't thinking about the commercialization of low Earth orbit but the danger is there!

    (Ack! My brother told me to finish this post with "All you damn kids get off my lawn!")
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  13. #13
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    Quote Originally Posted by BigDon View Post
    The only bad I see coming of this is getting people used to the idea that this is a good thing.

    This is not a good thing.

    Remember the Coca-Cola orbital advertising attempt? Smaller scale version of the same thing.
    I'll buy that.

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    Here's one place you can find orbital pass info. For my area, I'll have to wait 37 days before it will be visible.
    http://www.thehumanitystar.com/ Heavensabove.com doesn't have anything about it yet.
    This reminds of about 10-12 years ago, the shuttle put a disco ball into orbit as a high school science experiment. They asked ground based observers to monitor its passes as exactly as possible, to determine the rate of orbital decay. I took part as a ground observer, but only saw one very tiny flash. If we can get an accurate orbit, perhaps there can be some scientific benefit from this.

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    Heavens-Above now has Humanity Star.
    http://www.heavens-above.com/

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    Quote Originally Posted by Superluminal View Post
    Heavens-Above now has Humanity Star.
    http://www.heavens-above.com/
    That shows a pass in my area every 11-12 hours or so, all in daylight or unlit, for the next few weeks. Directly overhead (altitude 90) around noon today. I went out to September without a single "visible" occurrence.

    ETA: oops, I wasn't logged in, I guess that's the result for 0,0. But, no sightings for next couple of months, slmost directly overhead 3 Feb/4 Feb
    Last edited by grapes; 2018-Jan-28 at 11:41 AM. Reason: ETA

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    According to Heavens Above, visible passes for Humanity Star, at my location in the southern U.S., will start March 8th, and last until March 24. Magnitudes aren't going to be very impressive. 4.2 is the brightest for my location.

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    Just observed Humanity Star. Not very impressive. One little 4th magnitude flicker every few seconds.

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    Quote Originally Posted by Superluminal View Post
    Just observed Humanity Star. Not very impressive. One little 4th magnitude flicker every few seconds.
    I haven't seen it, but I thought the ball looked a bit small....Needs to be made in segments, and a lot bigger.
    Formerly Frog march..............

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    Quote Originally Posted by Superluminal View Post
    Just observed Humanity Star. Not very impressive. One little 4th magnitude flicker every few seconds.
    When it was first put up, there were people complaining about presumed light pollution etc from it.
    Measure once, cut twice. Practice makes perfect.

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    Quote Originally Posted by pzkpfw View Post
    When it was first put up, there were people complaining about presumed light pollution etc from it.
    You should never let facts get in the way of your outrage.


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  23. #23
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    Quote Originally Posted by pzkpfw View Post
    When it was first put up, there were people complaining about presumed light pollution etc from it.
    https://spaceflight101.com/humanity-star-re-entry/
    Well, the threat has been eliminated. Humanity Star has burnt up. No plans the launch another.

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    Disco inferno, as it were.

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