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This answer to Is the ISS going to yaw and assume the XPOP attitude for Nauka docking? contains lots of information on the attitude trajectory in yaw-pitch-roll space, but from those I can't envision how the attitude evolved over time.

Question: Did the ISS just turn upside-down? Nauka docking attitude maneuvers; did the cupola come close to pointing zenith and therefore show only black sky w/ stars?

Usually the cupola points nadir and is mostly filled by the Earth below.

plot of ISS Roll/Pitch/Yaw July 18, 2021

https://twitter.com/ISSAboveYou/status/1417257264646299661/photo/1

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  • $\begingroup$ Check out this video and the notes underneath: youtu.be/EXv5q7_PoyI "At times you'll see the rear-facing camera ends up pointing AT the earth! and towards the end of the sequence, you will see the nadir (down-facing) camera has been pointing away / up from the earth." $\endgroup$ Jul 27 at 8:25
  • $\begingroup$ @blobbymcblobby I think an answer can be written based on the video, but it's a 1 hour video and I really don't understand what it's showing at all. Explaining the video in a comment is not really helpful to me. Thanks! $\endgroup$
    – uhoh
    Jul 27 at 8:28
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    $\begingroup$ Are you missing a word (perhaps "cupola"?) in the title and body question? $\endgroup$ Jul 27 at 22:01
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    $\begingroup$ this question didn't age well :P $\endgroup$
    – 0xDBFB7
    Jul 30 at 4:25
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    $\begingroup$ I just spent an hour observing the ISS do a combined yaw pitch and roll all at the same time... Its back to standard TEA after flying backwards for a bit, even after Nauka did its thing. Numbers were like -155 -63 -67 to -55 -61 115 to -150 51 19 then -26 -43 61 till it got to -3 -4 0. Quite the spinning rolling top. $\endgroup$ Jul 30 at 6:08
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No. The ISS yawed 180 degrees, stayed like that for ~ a week, then yawed back around.

You can see a simulation of the maneuver in this official engineering video from NASA. The video is cued to start just before the maneuver.

Other 180 degree yaw and 90 degree pitch maneuvers have been executed recently and are planned for the near future, but none are planned to bring the cupola zenith-facing.

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  • $\begingroup$ What's confusing me about the plot in the question is the apparent -360 degree roll; on 18-July-2021 at about 15:45 roll starts to decrease from zero and accelerates until about 16:15, then roll continues to decrease linearly with time, crossing -180 degrees at 16:25, begins to slow at 16:40 and stopping back at zero roll at 16:25. That gives me and my limited 3D skills the impression that the ISS did more of a "barrel roll" than a pirouette about local vertical as the video is suggesting to me. Help me Mr. Wizard! $\endgroup$
    – uhoh
    Jul 27 at 23:40
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    $\begingroup$ @uhoh I suspect the answer lies in how the Euler angles are calculated from the telemetry data rather than anything physical. Nothing in the official engineering video shows any roll maneuvering at all. $\endgroup$ Jul 28 at 0:08
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    $\begingroup$ @uhoh only a suspicion, but if that Twitter person does the Euler angles the same way as this page telemetry.space I wouldn't be surprised if that is the explanation. $\endgroup$ Jul 28 at 0:34
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    $\begingroup$ The ISS rotates to keep the cupola pointing down. I heard it stops rotation during docking, so that would make it "turn" 360° per orbit. $\endgroup$
    – darsie
    Jul 28 at 1:10
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    $\begingroup$ @darsie you're describing the normal 1 complete pitch/ orbit the ISS does to maintain an LVLH attitude. This question and answer are about something completely different. It takes an XPOP attitude for these Russian module additions and subtractions, but that attitude is also rotating in the inertial frame, to keep the x axis pointed at the center of the Earth. $\endgroup$ Jul 28 at 1:22
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note: not an answer and too long for a comment...

Did the ISS just turn upside-down? Nauka docking attitude maneuvers; did the cupola near pointing zenith and therefore show only black sky w/ stars?

As @OrganicMarble points out:

No. The ISS yawed 180 degrees, stayed like that for ~ a week, then yawed back around.

But frighteningly, just a short time later it DID

...though this was not a maneuver related to docking, nor was it even planned.

From Gizmodo's The ISS Backflipped Out of Control After Russian Module Misfired, New Details Reveal:

At a press conference held later that day, NASA said the space station shifted by around 45 degrees. “That’s been a little incorrectly reported,” Zebulon Scoville, the NASA flight director in charge at the time, told the New York Times. The actual figure, he said, is closer to 540 degrees, which means the ISS performed 1.5 backflips, in an impromptu performance that would make an Olympic athlete jealous. When the ISS stopped spinning, it was fully upside down, requiring a 180-degree forward flip to regain the outpost’s original position, as the New York Times reports.

The article links to this tweet by Scoville:

Lead MLM Flight Director Greg Whitney and I split the shift today. Never have I ever: 1)been prouder of the team that sits in MCC and lives on @Space_Station, 2)had to declare a spacecraft emergency until now, 3)been so happy to see all solar arrays + radiators still attached.

The Gizmodo article says later:

In an email, a NASA spokesperson said the “initial value reported by flight controllers, which was called up to the station astronauts in real time and shared via NASA tweets/live coverage, was 45 degrees.” This value, according to the spokesperson, was being reported as the event was still unfolding, that is, as Nauka, also known as the Russian Multipurpose Laboratory Module (MLM), was still firing its thrusters and as flight controllers were continuing to change the station’s orientation. The value offered by Scoville—540 degrees—was “confirmed only after the post-event analysis was complete,” the spokesperson explained.

and

“And so at first I was like, ‘Oh, is this a false indication?’” Mr. Scoville said. “And then I looked up at the video monitors and saw all the ice and thruster firings. This is no kidding. A real event. So let’s get to it. You get about half a breath of ‘Oh, geez, what now?’ and then you kind of push that down and just work the problem.”

Nauka’s thrusters had started firing, trying to pull away from a space station it was securely docked to.

Worse, there was no way to turn them off.

His counterparts at the mission control in Russia told him that Nauka was configured so that it could receive commands directly only from a ground station in Russia. The next pass over Russia was 70 minutes away.

It also includes the following graphic. If it was thrusting to "pull away from a space station it was securely docked to" that means thrust would have been directed downwards (exhaust: upwards) which is exactly what would cause a "backflip".

Cupola would have pointed roughly upwards for about a few minutes

below that tweet Scoville confirmed the rate was roughly 0.5 degrees per second, so the cupola might have pointed within roughly 30 degrees of the zenith for perhaps two minutes assuming the backflip was executed symmetrically.

Graphic showing the ISS configuration as of July 29, 2021. Image: NASA

Graphic showing the ISS configuration as of July 29, 2021. Image: NASA

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    $\begingroup$ Outside of the safety issue, this was a pretty surprising 'turn' of events! I happened to be watching the apps with the numbers rolling in them at the time, thinking.. why..?! $\endgroup$ Aug 3 at 22:58
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    $\begingroup$ imgur.com/NFGvmZS - 50 minutes squeezed into 29s gif makes it more 'manic' than it would have felt. $\endgroup$ Aug 3 at 23:02
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    $\begingroup$ @blobbymcblobby That's excellent, it must have been quite an experience even to watch in the data stream! But the correction is only ~180°; when will they undo the remaining 360°? (humor) fyi I've just asked Zebulon Scoville “looked up at the video monitors and saw all the ice and thruster firings.” Exactly what ice did Scoville see? Why ice? Where? $\endgroup$
    – uhoh
    Aug 3 at 23:08
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    $\begingroup$ @OrganicMarble I think in situations where the answer post is sufficiently related, of interest to readers of the question, acknowledges another accepted answer first and contains some language identifying the post as providing additional related information, it has seemed to be okay here. Some examples: not an answer and too long for a comment I'll add both for good measure. $\endgroup$
    – uhoh
    Aug 4 at 12:16
  • $\begingroup$ If you want to write an answer to a different question, why not ask it and post the then-completely-appropriate answer? You are demonstrably ok w/ asking questions, $\endgroup$ Aug 4 at 12:54
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ok, another partial answer.

I think what you have plotted there is an OPM.

Introduced a while ago, it makes the station turn on all axis to change from 180 degrees to 0 (or vice versa), with minimal amount of fuel used.

So, for this question:

Did the ISS just turn upside-down?

answer is no.

NASA article on it when it was new:

https://www.nasa.gov/mission_pages/station/expeditions/expedition32/opm.html

CMG visualization of it here:

https://vimeo.com/171416771

ugh, paywall, but you can see some of the figures for it:

https://www.researchgate.net/publication/268469451_Optimal_Propellant_Maneuver_Flight_Demonstrations_on_ISS

developed from:

https://www.researchgate.net/publication/224594118_Zero-propellant_maneuver_guidance

and visually, though pitch can be up or down apparently from looking at ypr's:

https://imgur.com/gwpIvCC

But no, cupola never changes to just looking out at the stars, intentionally.

The reason for this is all the comms and GPS antennae is at the top of the station, so to flip over would put it out of comms with TDRS and lose GPS.

The ypr plots shown here are euler angles and if plotted, quaternion angles would show continuous smooth plots.

Compare the YPR plot above with the Quaternion plot below:

quat-opm Its not the same date, but it is a OPM.

Duration time is 90 minutes.

(i don't have data for the date in question)

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