This answer to the question Is there really no difference between up and down in ISS? says:

ISS does have a sort of 'up and down', deliberately created as part of the design. All the modules apparently have a consistent 'up' orientation in one direction. The majority of lights are in the 'ceiling' and are set up to shine 'downward'. Furthermore, all the writing on the walls is pointed in the same direction, so that it is 'right side up' in relation to the 'floor' and 'ceiling'.

But it doesn't say what directions those are.

Question: When reading "the writing on the wall" and other signage and posted messages inside the ISS, which way is up? Which direction do the lights generally come from? Direction meaning nadir, zenith, cross-track, port, stern, starboard, but please not X, Y, Z because after seeing @OrganicMarble's artwork I'll never be able to get them straight.

  • $\begingroup$ You want to hear Earth facing as the reference, since that is easiest to visualize. $\endgroup$
    – geoffc
    Feb 14, 2019 at 15:02
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    $\begingroup$ Why the hurtful omission of forward and aft? $\endgroup$ Feb 14, 2019 at 15:22

1 Answer 1


Forward is toward the US segment, +X in the ISS coordinate system.

Aft is toward the Russian segment, -X in the ISS coordinate system.

Starboard is toward the AMS, +Y in the ISS coordinate system.

Port is toward the Cupola, -Y in the ISS coordinate system.

Down or Deck is toward the Nadir, +Z in the ISS coordinate system.

Up or Overhead is toward the zenith side, -Z in the ISS coordinate system.

  • $\begingroup$ I thought the cupola was on the bottom of the station, ie in nadir direction? $\endgroup$
    – Hobbes
    Feb 14, 2019 at 16:40
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    $\begingroup$ It certainly started out on Node 3 nadir, but I haven't necessarily been keeping up with current events. en.wikipedia.org/wiki/Tranquility_(ISS_module). I think he means "towards the cupola when moving laterally away from the fore/aft axis", not "in the direction the top of the cupola is facing". $\endgroup$ Feb 14, 2019 at 19:03
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    $\begingroup$ It is on N3N, but N3 is on the port side of the module stack. The cupola was chosen as the unique piece of hardware that is on the port side but not the starboard side of the XZ plane. $\endgroup$
    – Tristan
    Feb 14, 2019 at 19:53
  • $\begingroup$ JEM, is further port, but also further forward, and BEAM is roughly the same place as the cupola, but points aft $\endgroup$
    – user20636
    Feb 14, 2019 at 23:27
  • $\begingroup$ @uhoh Things are oriented internally precisely as I stated. The Cupola is an exception, as it's generally treated as facing "up". $\endgroup$
    – Tristan
    Feb 15, 2019 at 15:15

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