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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)

uhoh
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WhatOnEarthOrOutsideIt
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    Or it could be something else... – Antzi Oct 07 '16 at 01:07
  • Like what? Those look exactly like two small-diaphragm cardioid condenser microphones or shotgun microphones in shock mounts, facing 180 degrees off from each other and with a basic windscreen foam around their capsules (tip). You can almost spot the XLR cable runs that are going into them! Mind you, it's NOT sufficient if you're anywhere in the regular atmosphere recording audio in even milder wind situations. Could someone just give a straight answer? – WhatOnEarthOrOutsideIt Oct 07 '16 at 01:27
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    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... – PearsonArtPhoto Oct 07 '16 at 01:29
  • @PearsonArtPhoto Did you recognised which module it is attached to ? – Antzi Oct 07 '16 at 01:35
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    @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. https://en.wikipedia.org/wiki/Decca_tree -- An illustration of the array: https://upload.wikimedia.org/wikipedia/commons/thumb/4/48/Decca_Tree.svg/220px-Decca_Tree.svg.png – WhatOnEarthOrOutsideIt Oct 07 '16 at 01:36
  • It's not a microphone because sound doesn't transmit in space. Trying to figure out what module, I think it's the Russian side, maybe Zvezda. – PearsonArtPhoto Oct 07 '16 at 01:38
  • @PearsonArtPhoto. Appreciate the effort, I have no idea what module it is, but this sure caught my attention. I guess the stream I posted originally is still up and running. And please, do not fall into the logical fallacy that it can't be a microphone array just because "there's no sound in the vacuum of space" - which I already pointed out in my original post. It sure looks like a mic array - if I had a higher res image, I could probably even name the brand and the model! I couldn't find anything remotely close to solving this with extensive Google searches etc, so .... – WhatOnEarthOrOutsideIt Oct 07 '16 at 01:39
  • It's a really good question. I can't find the answer, but my guess would be it's some kind of a sensor, either a radar detection, LIDAR sensor of some kind, or magnetometer. – PearsonArtPhoto Oct 07 '16 at 01:46
  • Decca Tree Mic Setup and another one (http://www.harmonycentral.com/forum/filedata/fetch?id=31096419&d=1395258391) – WhatOnEarthOrOutsideIt Oct 07 '16 at 01:52
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    Okay, I found it, still trying to figure out what it is. It's off of the Destiny Module. http://pics-about-space.com/space-station-modules?p=3#img15467219880744011659 – PearsonArtPhoto Oct 07 '16 at 01:52
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    @PearsonArtPhoto - seems plausible, but in the picture you posted, the parts that I recognized as windscreen foam for the mics appear solid white and the whole array is grey-ish, as compared to the the new feed where all the parts are just black. In your photo it almost looks like a dual, hi-gain omnidirectional wi-fi/broadband antenna. Then again, it'd be the weirdest one I've ever seen, and I've worked in that field also. – WhatOnEarthOrOutsideIt Oct 07 '16 at 02:06
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    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. – PearsonArtPhoto Oct 07 '16 at 02:09
  • Video broken and there is no title or other information to look for a new one. https://space.meta.stackexchange.com/q/1356/12102 – uhoh Aug 03 '21 at 23:46

1 Answers1

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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

Organic Marble
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  • Seems to match up with http://www.satellitenwelt.de/iss.htm. You might include the picture there in your answer, and I'll just delete mine, as yours is better than mine. – PearsonArtPhoto Oct 07 '16 at 02:13
  • @Organic Marble - what's the deal with the change in the overall color of the antenna then? Did they replace the whole thing, causing it to turn altogether from light(ish) grey to obviously black? – WhatOnEarthOrOutsideIt Oct 07 '16 at 02:20
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    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. – Russell Borogove Oct 07 '16 at 02:25
  • It's actually grey/white. In the original picture it's backlit. – Organic Marble Oct 07 '16 at 02:31
  • @RussellBorogove , are you serious? The othe visible parts of the ISS in the same shot have not been altered in luminosity in any similar manner (i.e. from light grey to carbon black), so I wouldn't take that as the most plausible main hypothesis, sorry. – WhatOnEarthOrOutsideIt Oct 07 '16 at 02:31
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    @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 – Antzi Oct 07 '16 at 02:37
  • T-shaped UHF antenna could indeed be a plausible option, but I still disagree with the "blackening" of the antenna array. It's so light grey in the original shots and the NASA TV screencap also shows that other parts of the ISS in the same picture are still clearly light grey, this made me wonder whether it's been replaced, and if so, when did it happen? – WhatOnEarthOrOutsideIt Oct 07 '16 at 02:38
  • Anyway - thanks a lot for all your quick answers. I was really baffled by the whole thing for some hours and couldn't find any kind of explanation. Now I wonder what do people who work in the popsicle industry for instance see in that array, hehe ... – WhatOnEarthOrOutsideIt Oct 07 '16 at 02:46
  • @WhatOnEarthOrOutsideIt Welcome to space.stackexchange :) – Antzi Oct 07 '16 at 03:03
  • @WhatOnEarthOrOutsideIt since you may be new to the community, if this post answers your question, please mark it as accepted by clicking the gray check mark to the left of the answer. – Organic Marble Oct 07 '16 at 03:13
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    @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%. – Russell Borogove Oct 07 '16 at 03:31
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    @WhatOnEarthOrOutsideIt: You are a victim of this optical illusion: http://www.dailymail.co.uk/sciencetech/article-2521023/Dont-believe-eyes-These-blocks-SAME-shade-grey.html. 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. – slebetman Oct 07 '16 at 08:23
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    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: http://www.tackyliving.com/tacky-tv-antennas/ - they aren't quite common. – WhatOnEarthOrOutsideIt Oct 07 '16 at 12:23
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    This is 100% the correct answer. I chuckled a bit at "well placed on the Lab to get in the way of robotics ops." To add to the answer, it's used for EVA comms. – Tristan Oct 07 '16 at 14:17
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    @Tristan I was a shuttle robotics instructor so I was very used to avoiding the thing. – Organic Marble Oct 07 '16 at 14:38