APOD: A Perseid Below (2014 Aug 10)

Comments and questions about the APOD on the main view screen.
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APOD: A Perseid Below (2014 Aug 10)

Post by APOD Robot » Sun Aug 10, 2014 4:09 am

Image A Perseid Below

Explanation: Denizens of planet Earth typically watch meteor showers by looking up. But this remarkable view, captured on August 13, 2011 by astronaut Ron Garan, caught a Perseid meteor by looking down. From Garan's perspective onboard the International Space Station orbiting at an altitude of about 380 kilometers, the Perseid meteors streak below, swept up dust left from comet Swift-Tuttle heated to incandescence. The glowing comet dust grains are traveling at about 60 kilometers per second through the denser atmosphere around 100 kilometers above Earth's surface. In this case, the foreshortened meteor flash is right of frame center, below the curving limb of the Earth and a layer of greenish airglow, just below bright star Arcturus. Want to look up at a meteor shower? You're in luck, as the 2014 Perseids meteor shower peaks this week. Unfortunately, the fainter meteors in this year's shower will be hard to see in a relatively bright sky lit by the glow of a nearly full Moon.

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Re: APOD: A Perseid Below (2014 Aug 10)

Post by JohnD » Sun Aug 10, 2014 12:15 pm

Now that we have the permanent (?) on-board ISS view of Earth, we need not rely on the astronauts on board to catch a meteor from above.
I cannot, but can those with astronavigational skills tell when the ISS would be in postion to see them? During a meteor storm, on the right side of Earth, near to or within night side and with a camera pointing the right way. It's not much to ask, is it?

John

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Re: APOD: A Perseid Below (2014 Aug 10)

Post by Boomer12k » Sun Aug 10, 2014 2:23 pm

Great shot....

Sooooo romantic....ahhhhhh....


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Re: APOD: A Perseid Below (2014 Aug 10)

Post by Chris Peterson » Sun Aug 10, 2014 3:00 pm

JohnD wrote:I cannot, but can those with astronavigational skills tell when the ISS would be in postion to see them? During a meteor storm, on the right side of Earth, near to or within night side and with a camera pointing the right way. It's not much to ask, is it?
As with any meteor shower, it is simply necessary that the radiant be above the horizon, and the Sun below it. There's really no favored position or camera angle.
Chris

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Re: APOD: A Perseid Below (2014 Aug 10)

Post by JohnD » Sun Aug 10, 2014 3:28 pm

So simple, Chris?
The ISS cameras seem to switch at random, so now help there, but surely meteors come in from a preferred angle, hence their various names, and are moving so fast relative to the Earth that they won't curve around and come in from another place? I was thinking that looking out via the ISS when it had the radiant at the zenith would optimise sightings, but would have no idea how to work out where that would be.

To see a metor in that way would be a wonderful thing, almost better than by direct sight!
JOhn

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Re: APOD: A Perseid Below (2014 Aug 10)

Post by Chris Peterson » Sun Aug 10, 2014 3:44 pm

JohnD wrote:So simple, Chris?
The ISS cameras seem to switch at random, so now help there, but surely meteors come in from a preferred angle, hence their various names, and are moving so fast relative to the Earth that they won't curve around and come in from another place? I was thinking that looking out via the ISS when it had the radiant at the zenith would optimise sightings, but would have no idea how to work out where that would be.
The orbit of the Earth intersects the orbit of the meteoritic debris. This results in a parallel field of meteoroids, larger than the Earth. If one comes in at the zenith it will be at a different ground angle than one that comes in near the edge (at the very edge you get an Earth-grazer).

During a meteor shower, if the radiant (the apparent vanishing point for the stream of debris) is above the horizon, you can see a meteor anywhere in the sky. Near the radiant they will tend to be shorter and slower (because they are moving towards you), and far from the radiant they will tend to be longer and faster (because they are moving orthogonal to you). Not much is different if you're viewing from above, except the slightly altered geometry of having the radiant behind you and the meteors in front.
Chris

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Re: APOD: A Perseid Below (2014 Aug 10)

Post by zbvhs » Sun Aug 10, 2014 7:53 pm

As long as a Perseid is seen "down there", it's fine. A Perseid "here" from an astronaut's perspective could be bad, indeed.
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Re: APOD: A Perseid Below (2014 Aug 10)

Post by JohnD » Sun Aug 10, 2014 8:11 pm

Thanks, Chris, got it now!

Next time there is a shower, I think I'll High me up to the ISS, instead of hoping to see oene from'sunny' north-west England!
Oh! There's one on right now? The Perseids? Where are my space boots?
JOhn

PS And ... and ... and ... The Link to the ISS cameras is broken. Bother.
Last edited by JohnD on Sun Aug 10, 2014 10:04 pm, edited 1 time in total.

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Re: APOD: A Perseid Below (2014 Aug 10)

Post by hoohaw » Sun Aug 10, 2014 9:01 pm

This picture seems familiar - has it appeared on APOD before?

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Re: APOD: A Perseid Below (2014 Aug 10)

Post by bystander » Sun Aug 10, 2014 9:12 pm

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: A Perseid Below (2014 Aug 10)

Post by MarkBour » Mon Aug 11, 2014 3:02 am

This got me to thinking that some "man-made meteors" might be spectacular, if the ISS were lucky enough to catch a view of them. It turns out (as always) that NASA ad APOD are way ahead of me on that. There's a nice video of a Soyuz re-entry:
https://www.youtube.com/watch?v=WmEzR3dGru4 ,
and on an historic occasion, they obtained some nice images of the shuttle Atlantis re-entering for the last time. It became a beautiful APOD:
http://apod.nasa.gov/apod/ap110801.html
I did not find any examples of ISS catching a rocket launch streak. The closest example I found of that was a contrail, referenced here:
http://ext-cms.dp.discovery.com/dnews/f ... 131011.jpg
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Re: APOD: A Perseid Below (2014 Aug 10)

Post by JohnD » Thu Aug 14, 2014 12:56 pm

Continuing to try and see a meteor below, from the ISS, but does anyone know about this live feed?

Try as I might, I can't get to see the Earth's night side from the ISS
I've tried leaving it on in a reduced window, while I get on with something else, and intending to wait until the ISS goes into Night. Then, watching, with my finger poised over the Print Screen button, I'll catch a falling star! But every time, after a while, the view disappers and the message appears that the signal has been lost or the camera is being changed - and it never comes back!

Is there some reason why a computer on the net - mine - should time-out after a while from this?
Or has the system been programmed to cease broadcast if the ISS is over the night side, to save bandwidth or costs?

John