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)
Image is from me screen capping my monitor!
NASA video feed.
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:
- Will the ISS adopt a -XLV ZVV X-POP attitude for the Nauka docking?
- How will it achieve this?
- Will it yaw to starboard or port?
- Will it yaw and pitch separately or all at the same time (unlikely)?
- Will the Solar Array spend a little time during this manoeuvre not in its optimum sun-facing attitude.
- How long will it take?
- Are they only using the CMG's for this?
- When it goes back to TEA, does it simply reverse its motions or will it carry them on through?
- Who is in charge during this - Russian module so the Russians or Houston for overall ISS control?