Tidal force

firavia

some telecomunication satellites in orbits are made to be kept oriented in a certain way where their reception and broadcasting antenna or whatever is called should awalys face the earth so while orbiting the satellite has to be interlocked with the surface of the earth.
My question is: can the tidal force of gravity due to the shape of the satellite exerce a torque on the latter in a way that changes the orientation of the satellite while orbiting to preserve the interlock of the antenna and the surface of the earth ? disregarding any mechanical intervention through rocket thrust or anything else ?.

Nik_2213

IIRC, it can be done using a long boom. However, small corrections may still be required to suppress 'pendulum' swinging...

zhermes

The tidal force goes like [tex]\frac{l}{R^3}[/tex] for an object of length 'l' in the radial direction, and a distance R from the center of mass. For something like a satellite, this force would be extremely small, and I would guess entirely negligible in comparison to other effects.

You can easily do the calculation to check.

Nik_2213

http://space.skyrocket.de/doc_sdat/ggse-1.htm

Google found a trove...

firavia

Thank you guys.