I Can a Gyroscope in a Satellite Detect Orbit?

[Sagittarius A-Star]

In this video at 06:30 the astronaut places the gyroscope on the string attached to the walls of the ISS cabin. I'm not sure whether the gyroscope was rotating about itself when placed on the string or was not.

It's the ISS, which rotated, not the gyroscope axis:

The ISS rotates about its center of mass at a rate of about 4 degrees per minute so that it will complete a full rotation once per orbit. This allows it to keep its belly towards the Earth.

Source:
https://www.forbes.com/sites/quora/2017/10/03/how-does-the-iss-travel-around-the-earth/

 

[cianfa72]

It's the ISS, which rotated, not the gyroscope axis:

Yes, definitely. What I can't see clearly from the video is: was the gyroscope spinning about its axis when the astronaut placed it on the string ?

 

[A.T.]

was the gyroscope spinning about its axis when the astronaut placed it on the string ?

What would be the point of a non-spinning gyroscope?

 

[cianfa72]

What would be the point of a non-spinning gyroscope?

Yes, indeed (maybe it wasn't that evident in the video, though).

As far as I understand, the ISS's center of mass (CoM) is free-falling, i.e. it travels along a geodesic in spacetime. ISS rotates about its CoM at a rate of 4 degree/minute. The spinning gyroscope's gyro-stabilized axis -- by definition -- is Fermi-Walker transported along the gyroscope's CoM worldline (since this is geodesic, then FW transport coincides in this case with parallel transport along it).

As you said, it is the ISS which rotated (since the gyroscope axis actually defines locally what "non rotating" means).

P.s. very basic notion: the gyroscope's axis is gyro-stabilized only when the gyroscope is spinning about it