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I noticed this in the launch of Nauka MLM to the ISS.

(Previously I had assumed it would dock in a similar manner to Progress or Soyuz, that is coming from behind and underneath - this says the station will change its whole attitude, something not seen since the early years of construction)

xpop

Image is from me screen capping my monitor!

NASA video feed.

https://civiliancomms.tripod.com/spacecomms/iss/iss_appendix_c.html

XPOP means that the ISS X axis is perpendicular to the orbital plane.

The X-Axis Perpendicular to Orbit Plane (XPOP) reference frame is shown. XPOP is a quasi-inertial reference frame that can be visualized by a 90° yaw of the LVLH frame at orbital noon. The X-axis points out of plane, while both the Y- and Z-axes lie in the orbital plane. Note that unlike LVLH, which is rotating with the Station as the Station rotates about the Earth, XPOP remains fixed with the Station X-axis pointing out of plane and the Z-axis is aligned with the orbit noon vector. XPOP is a “quasi-inertial” reference frame, because as the orbital plane slowly regresses, the XPOP reference frame also regresses to keep the X-axis pointing out of the orbital plane.

Is the new ISS attitude for Nauka's docking going to be thus:

-XLV ZVV ? (assuming ISS negative X axis is pointed to the local vertical and the positive Z axis is pointed into the velocity vector)

Previously, during stages of construction I recall the station held -XLV -ZVV X-POP attitude.

And then I am assuming again that the ISS will reverse its movement to regain TEA position.

Or will it 'follow through' with the yaw direction instead (completing a circle, if you will)?

So I guess my questions are:

  1. Will the ISS adopt a -XLV ZVV X-POP attitude for the Nauka docking?
  2. How will it achieve this?
  3. Will it yaw to starboard or port?
  4. Will it yaw and pitch separately or all at the same time (unlikely)?
  5. Will the Solar Array spend a little time during this manoeuvre not in its optimum sun-facing attitude.
  6. How long will it take?
  7. Are they only using the CMG's for this?
  8. When it goes back to TEA, does it simply reverse its motions or will it carry them on through?
  9. Who is in charge during this - Russian module so the Russians or Houston for overall ISS control?
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    $\begingroup$ Should be fixed, thanks, trying to get it out in a hurry.. $\endgroup$
    – blobbymcblobby
    Jul 21, 2021 at 23:02
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    $\begingroup$ Thanks! That page looks interesting, I hope it becomes archived! $\endgroup$
    – uhoh
    Jul 21, 2021 at 23:06
  • $\begingroup$ Watching the undocking of Pirs was interesting. Shame there is no external craft to watch the attitude change. $\endgroup$
    – blobbymcblobby
    Jul 26, 2021 at 17:47
  • $\begingroup$ The station does rotate for Soyuz undocking, always to point the Soyuz prograde. $\endgroup$
    – SF.
    Jul 27, 2021 at 11:48

2 Answers 2

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That's a whole lot of questions for one post. So consider this a partial answer.

  1. Yes.

Here's the official MAGIK video showing the maneuvers. My former coworker made the video. Some of the other answers can be derived from the video.

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  • $\begingroup$ Yeah, had a headache formulating it in a hurry. I hoped that one would lead into the other, that they weren't too disparate from each other regarding the subject. Great video - guess my terms weren't right for google... Q3,4,8 are definitely answered. Q1 seems to be not "-XLV ZVV X-POP" at all but just simply "-ZVV". Thanks! $\endgroup$
    – blobbymcblobby
    Jul 21, 2021 at 23:30
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    $\begingroup$ @blobbymcblobby She posted the video on Facebook, that's the only way I knew about it. $\endgroup$
    – Organic Marble
    Jul 21, 2021 at 23:32
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    $\begingroup$ Thanks for the MAGIK link - i assumed they were presentation videos farmed out for production, not the actual tools used. Takes me back though - I used SGI's in the 90s - in 2 different industries, aerospace and broadcast... the last I used were the Onyx RM's... PS. Your colleague had awesome timing! :) $\endgroup$
    – blobbymcblobby
    Jul 21, 2021 at 23:33
  • $\begingroup$ @blobbymcblobby at ~1:25 in the video (MLM docking) it sure looks -XLV to me $\endgroup$
    – Organic Marble
    Jul 21, 2021 at 23:37
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    $\begingroup$ ah, i did pull that from the page description.. That looks like quite a lot of attitude changes over a limited period of time - I am presuming it is not not always like that (and that the Soyuz flyaround at 2:35 is to get photos for analysis of Nauka) - and interesting the attitude change is for each 'visit', ie. they didn't leave it in that attitude for both undocking Pirs and docking Nauka.. $\endgroup$
    – blobbymcblobby
    Jul 22, 2021 at 0:05
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Also a partial answer:

The maneuver is called an OPM (Optimal Propellant Maneuver) which means very little fuel is needed. The space_station moves in all three axes of motion (called Yaw/Pitch/Roll) to complete the flip-around.

The plots shown below are for the 180 degree yaw maneuver carried out in the past week. This led to the station looking like it was flying backwards for a while.

EDIT:

In relation to the answer below and todays coverage of the Pirs module undocking:

  1. How will it achieve this?

Yaw, pitch.

  1. Will it yaw to starboard or port?

Starboard. Always..?

  1. Will it yaw and pitch separately or all at the same time (unlikely)?

Separately

  1. Will the Solar Array spend a little time during this manoeuvre not in its optimum sun-facing attitude.

The solar arrays will be ineffective. The SARJ gets locked for the duration of the maneuvering.

(Solar Arrays are always locked for these types of maneuvers)

  • I feel a question coming on for how they make the choice.

Today it looked like (hard to see) they feathered the array. This might be to present the least amount of drag possible presented by the arrays during the maneuver.

  1. How long will it take?

about 2 hours for the maneuver which is apparently average. (I saw another quote which must be dated saying 30 minutes)

Sat at 180 for the longest time and the 90 pitch for the shortest.

  1. Are they only using the CMG's for this?

use of the 4xCMGs (Control Moment Gyroscopes) with some help from the thrusters on a Progress

  1. When it goes back to TEA, does it simply reverse its motions or will it carry them on through?

Reverses.

  1. Who is in charge during this - Russian module so the Russians or Houston for overall ISS control?

for the attitude control:

These OPM (Optimal Propellant Maneuver) maneuvers are controlled by ADCO (Attitude Determination and Control Officer - Flight Operations Division) in mission control NASA Johnson

https://twitter.com/ISSAboveYou/status/1417260086741803044

180 Yaw pitch roll plots:

enter image description here

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

ypr for some of the panels during maneuver:

enter image description here

https://twitter.com/ISSAboveYou/status/1417258046623940608/photo/1

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