This tweet from Expedition 51/52 astronaut Jack Fischer admires the great view straight down from the ginormous Russian porthole of the Progress cargo vehicle on the ISS.

I don't really understand where this porthole is. Is it the porthole part of a docked spacecraft, or is it a permanent part of the ISS?

Is this the same direction that the center, round window of the ISS's Cupola faces?

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    $\begingroup$ I'm also curious why this porthole is covered, then covered again (with some misc equipment inside that second cover)... $\endgroup$
    – Steve
    Commented Jul 26, 2017 at 16:36

1 Answer 1


It's on one of the Russian modules of the ISS, that's why it's a ginormous Russian porthole. Since the porthole is facing Earth, I'd say yes, it's also facing the same general direction as the cupola, but not necessarily the same exact direction.

@Steve the first cover is part of the pressure containment vessel of the station, note the mating seals around its rim and the seat of its closed position. If the glass of the porthole cracks or otherwise starts leaking, the first cover keeps the air in the station from all rushing out. The other cover is the access hatch in the inner walls of the ISS that define the bounds of normal day-to-day operation.

The opinions expressed in this analysis are my own, YMMV.


It's window number 9 (of 14) in the Zvezda module, a 16-inch-diameter (410 mm) window in the main Working Compartment. (N.B. Window No. 11 is "unaccounted for in all available sources" - so it's quite possible there are only 13 windows on the module.)

Russian Space Segment windows
Russian Space Segment windows, from Wikipedia
link to full size (1096 x 823) image

I guess "ginormous" is a matter of opinion - a 16 inch window doesn't seem to be that big - from here on the ground.

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    $\begingroup$ @uhoh I'll get back to you on that... $\endgroup$ Commented Jul 26, 2017 at 19:00
  • $\begingroup$ Wow, very nice indeed! Thank you for the additional material. $\endgroup$
    – uhoh
    Commented Jul 27, 2017 at 4:11
  • $\begingroup$ Btw there's some disagreement about windows 12 and 13 (?) in the discussions connected to the question Does the ISS have zenith-facing windows? if you'd like to take a look there, including the definition of what "zenith-facing" does or does not mean. I tried to clarify the issue with a separate question But does the ISS REALLY have zenith-facing windows? Is there a photo of it? but was shut down, so we now have a stalemate but no clear answer - at least to my question :) $\endgroup$
    – uhoh
    Commented Jul 27, 2017 at 4:23
  • $\begingroup$ See also Were there any STS missions that included maneuvers that might have photographed ISS's top side?; a work in (slow) progress. $\endgroup$
    – uhoh
    Commented Jul 27, 2017 at 4:24
  • $\begingroup$ This window is also made of a special glass (quartz or such) which makes it transparent to (invisible) frequencies that other windows obstruct, so photos in these frequencies can be taken. This also makes it brittle and prone to scratches, though, that's why the cover. The other cover is because the window is located right on the bottom of the training bicycle compartment, which is closed when not in use. (and it's almost never in use because it's the only piece of training equipment firmly coupled with the station, which makes the whole station, esp. the long solar panels shake when used...) $\endgroup$
    – SF.
    Commented Sep 9, 2018 at 21:13

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