This morning I was watching another video of Soyuz docking to the ISS (Expedition 45/Visiting Crew Docks to the Space Station).

enter image description here

The commentator noted that the two quantities $\rho$ and $\dot\rho$ in the lower-left are the range and range-rate, respectively. Retrospectively this is pretty obvious, but I had never thought about it before. This got me a little curious and I tried to look up what all the other numbers mean, with no luck.

What are the quantities displayed on the Soyuz docking camera? I'm particularly interested in the right-hand side, which looks like something to do with the orientation of the spacecraft or station.

  • 1
    $\begingroup$ Omega (ω) is conventionally an angular rate, so the ω X-Y-Z are probably pitch-yaw-roll rates (maybe not in that order). Gamma, psi, theta (γ, ψ, θ) are conventionally used for angular values (but those three aren't normally used together), and I'm not sure what the angles would be relative to, or the distinction of the psi-swung-dash and theta-swung-dash elements. $\endgroup$ Sep 4, 2015 at 17:31
  • 1
    $\begingroup$ γ, θ and ψ are Euler angles (in degrees), the first three under КУРС (KURS, or course) are LOS (Line of Sight) angles. $\endgroup$
    – TildalWave
    Sep 4, 2015 at 17:38
  • $\begingroup$ What do you mean by line of sight angles? $\endgroup$ Sep 4, 2015 at 17:42
  • $\begingroup$ @RussellBorogove Angle relative to target when in Line of Sight Mode (flight mode is displayed on the left, СБЛИЖЕНИЕ = convergence, approach). $\endgroup$
    – TildalWave
    Sep 4, 2015 at 17:45

1 Answer 1


Thanks to this student's Soyuz simulator:
Top left:
- $\Phi$44 : flight mode (44 is final approach)

Bottom left:
- $\rho$ : range to target
- $\dot\rho$ : range rate (closing speed)
These are calculated parameters

Top right:
- T: time
- $\omega$X, Y, Z: angular rates (roll speed on X, Y, Z axes)

Middle right:
- $\gamma, \psi, \theta$: roll, yaw, pitch attitude
- $\psi_{\pi}, \theta_{\pi}$: heading, pitch bearing angles (Soyuz position relative to ISS)

Bottom right:
- $\rho, \dot\rho$ : range and range rate (closing speed)
- $\Omega Y, \Omega Z$: line of sight angular rates (roll speeds relative to target)
These are parameters measured by Kurs. So they could compare range and range rate between the calculated course and the actual course.

  • $\begingroup$ This is a great find. $\endgroup$ Sep 23, 2015 at 15:03
  • $\begingroup$ I wish I could +1 that student for using Orbiter =) $\endgroup$ Sep 23, 2015 at 19:54
  • $\begingroup$ @RussellBorogove: yes, one was the calculated range (what it should be according to the trajectory they were flying), and the other was the measured range. $\endgroup$
    – Hobbes
    Sep 23, 2015 at 20:04
  • $\begingroup$ Oh, derp, was looking at the wrong thing -- sorry. $\endgroup$ Sep 23, 2015 at 20:42

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