# ISS orientation

#### MaxBuzz

##### Well-known member
The ISS always has one side facing the Earth. For the same reason as the moon. That is, the period of revolution around its own axis is equal to the period of revolution around the Earth. (e.g. the Cupola module always points to the Earth)
what value of rotation along the axis should be set in Orbiter?

#### DaveS

Donator
Beta Tester
The ISS always has one side facing the Earth. For the same reason as the moon. That is, the period of revolution around its own axis is equal to the period of revolution around the Earth. (e.g. the Cupola module always points to the Earth)
what value of rotation along the axis should be set in Orbiter?
0.067°/s in pitch. This mostly cancels out the orbital pitch rate.

#### MaxBuzz

##### Well-known member
legal education allowed me to derive the formula
93x60 = 5580
360/5580 = 0,06451612903

#### Kyle

##### Armchair Astronaut
First, calculate semi-major axis. Then calculate orbital period using Kepler's third law. Convert to seconds. 360 divided by that answer should be your answer for any orbit.

#### N_Molson

Donator
There's no funny stuff like precession ?

#### Kyle

##### Armchair Astronaut
There's no funny stuff like precession ?

Precession, rotation, and nutation neglected of course

#### PhantomCruiser

##### Wanderer
Moderator
Tutorial Publisher
Gyros. Gyros solve a lot of problems (and is the reason the ISS is oriented in the way that it is).
IIRC, the ISS goes into "free drift" when a visiting vehicle is on approach?

#### MaxBuzz

##### Well-known member
orbital period can be viewed in the SCN editor

#### MaxBuzz

##### Well-known member
unfortunately after a couple of days of simulation, the station loses orientation

#### N_Molson

Donator
orbital period can be viewed in the SCN editor
View attachment 30728

The problem I see is that the orbital period is in practice a variable, as the station is subject to atmospheric drag and tidal forces. So it makes sense that with time, things get less and less accurate.

#### MaxBuzz

##### Well-known member
The problem I see is that the orbital period is in practice a variable, as the station is subject to atmospheric drag and tidal forces. So it makes sense that with time, things get less and less accurate.
or Scn Editor trims the value (-0,06456125248) in the input field too many signs

#### Max-Q

##### 99 40
The problem I see is that the orbital period is in practice a variable, as the station is subject to atmospheric drag and tidal forces. So it makes sense that with time, things get less and less accurate.
Correct. As PhantomCruiser said, the real ISS uses rate gyros to compensate.
Take a look at my Better ISS addon for an example of how to implement in Orbiter; source code is included.

#### MaxBuzz

##### Well-known member
Correct. As PhantomCruiser said, the real ISS uses rate gyros to compensate.
Take a look at my Better ISS addon for an example of how to implement in Orbiter; source code is included.
approximately once a month the ISS orbit is corrected by the spacecraft "Progress". in 2002 to 2005 CMG were broken. correction by the spacecraft "Progress" has become more frequent

#### N_Molson

Donator
approximately once a month the ISS orbit is corrected by the spacecraft "Progress". in 2002 to 2005 CMG were broken. correction by the spacecraft "Progress" has become more frequent

Orbit and attitude are 2 very different things. The orbit is the "ellipse" the station draws when it revolves around Earth. Attitude is the orientation, or angles relative to a reference point (Apollo used stars). AFAIK Progress is used to "re-boost" the station orbit, that decays mostly because of atmospheric drag, which is a natural and "normal" phenomenon.

CMGs (Control Momentum Gyroscopes) are gyroscopes (electrical motors) that can provide torque, but no thrust.

#### Max-Q

##### 99 40
approximately once a month the ISS orbit is corrected by the spacecraft "Progress". in 2002 to 2005 CMG were broken. correction by the spacecraft "Progress" has become more frequent
There are also thrusters on the russian side that can be used for attitude control instead of the CMGs, but the principal is the same. Something is constantly keeping ISS in the correct attitude.

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