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I was watching a feed on the latest footage of Hurricane Matthew as seen from the ISS just now, relayed from NASA TV. Suddenly, I spotted something poking out of the ISS hull in the footage that appeared to be a shockmounted 180-degree-dual-microphone setup. I just can't understand what's it for even though I've worked in the A/V production field for more than 15 years of my life as both an audio and video technician/engineer.

Now, as far as I know, space is supposed to be a vacuum, and what I have been taught all my life and professional career is that sound requires a medium (i.e. air, water) to travel through. Would someone tell me why on earth there's an array consisting of at least two pieces of 180-degree-separated, shockmounted and foam-windscreened (!??!!) microphones sticking out of the ISS that is supposed to be in orbit outside our atmosphere?

It seems to be a permanent installation as well. Only a few M/S microphone setups would make sense in a 180-degree-L-R-setup like that down here, and even in a case of M/S micing, there should be a third condenser mic somewhere.

And that would make remote sense only IF this was taking place inside the atmosphere or somewhere underwater. The mics seem to be shockmounted and have a windscreen foam around their capsules. This makes absolutely no sense either, since as far as I know, no sound is transmitted through the vacuum of space, apart from what's being "amplified" through the so-called artificial atmospheres such as the astronaut suits or the oxygen-pressurized hull of a spaceship or a space station.

180 degree stereo pair microphone setup outside the ISS?

Please see the pic above for reference. Original URL of the live stream relay is/was at https://www.youtube.com/watch?v=9x3HpNaaOVM (broken video link with no title given)

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    $\begingroup$ Or it could be something else... $\endgroup$
    – Antzi
    Commented Oct 7, 2016 at 1:07
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    $\begingroup$ I'm sure it's not a microphone, as you said, it wouldn't make any sense at all. Still trying to figure out what it is, but it's not that easy... $\endgroup$
    – PearsonArtPhoto ♦
    Commented Oct 7, 2016 at 1:29
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    $\begingroup$ @PearsonArtPhoto, why is your first assumption that it's definitely not a microphone array? Throughout my career in the A/V field, I've gone through just about all the brands out there as well as their clamping systems and what have you not. That sure looks like a 180 degree L-R- microphone array with a possible center mic somewhere that's unseen from that view, i.e. a Decca tree microphone array. en.wikipedia.org/wiki/Decca_tree -- An illustration of the array: upload.wikimedia.org/wikipedia/commons/thumb/4/48/… $\endgroup$
    – WhatOnEarthOrOutsideIt
    Commented Oct 7, 2016 at 1:36
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    $\begingroup$ Okay, I found it, still trying to figure out what it is. It's off of the Destiny Module. pics-about-space.com/… $\endgroup$
    – PearsonArtPhoto ♦
    Commented Oct 7, 2016 at 1:52
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    $\begingroup$ Black is just white without any light on it. You can see that most of the ISS is darker in the image you provided, I'm fairly sure it's just a silhouette. $\endgroup$
    – PearsonArtPhoto ♦
    Commented Oct 7, 2016 at 2:09

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That is a UHF antenna. It was well placed on the Lab to get in the way of robotics ops during space station assembly.

This is a picture of a different UHF antenna unit (this one is on the P1 truss segment) but it's clearly the same device. Fortunately this is from a credible source, NASA's ISS Flight Systems brochure (warning, pdf). I can't quite figure out the page numbering in this pdf but I think it's page 60. Anyway, if you search the pdf for "UHF" you will find it quickly.

enter image description here

Incidentally, all the UHF antennas I know of on the shuttle / station look like that "mike" shape. You can see a single one on the shuttle airlock in this picture (the ISS antenna have two of the "mikes" each).

enter image description here

Finally, here is an EVA checklist listing hazards for the crew to avoid. You will note that UHF antennae are listed on the Lab and P1, the exact locations of these antennae shown in my answer.

enter image description here

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    $\begingroup$ I would guess that's just an artifact of automatic gain control in the imaging -- white daylit cloud tops seen from above are very very bright. $\endgroup$
    – Russell Borogove
    Commented Oct 7, 2016 at 2:25
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    $\begingroup$ @WhatOnEarthOrOutsideIt On your own screenshot it is clearly not black. The color on the darker parts of destiny module hull is actually darker than the one on the antenna $\endgroup$
    – Antzi
    Commented Oct 7, 2016 at 2:37
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    $\begingroup$ @WhatOnEarthOrOutsideIt Your eyes are deceiving you, again because of the contrast with the white backdrop. Checking in an image editing program, the lobes of the antenna are between 29%-32% gray, nowhere near "carbon black"; the middle part of the hull area in the lower left is only a little lighter, 30%-37%. The shadowed back side of the cylindrical projection is about 17%. $\endgroup$
    – Russell Borogove
    Commented Oct 7, 2016 at 3:31
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    $\begingroup$ @WhatOnEarthOrOutsideIt: You are a victim of this optical illusion: dailymail.co.uk/sciencetech/article-2521023/…. Look at the picture again, the one you're convinced the antenna is black. Use your fingers to hide the clouds so you can ONLY see the antenna and you will see that it is light grey, not black, not even dark grey. $\endgroup$
    – slebetman
    Commented Oct 7, 2016 at 8:23
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    $\begingroup$ Yep, thanks a lot for the clarification. I really appreciate the thoroughness. I guess I've worked in the field long enough to see mic arrays whenever there's a familiar enough shape, hehe. The reason I didn't think of the UHF T-type array is that although I've also worked with aerial antenna setups down here on Earth, from analog TV antenna installations to outdoor wifi/wireless broadband setups all the way to satellite dishes and , so this just left me a bit boggled. I found a similar T-shaped antenna array from here: tackyliving.com/tacky-tv-antennas - they aren't quite common. $\endgroup$
    – WhatOnEarthOrOutsideIt
    Commented Oct 7, 2016 at 12:23

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