Re: Superbird A secondary flashes
Jim Varney (jamesv@softcom.net)
Mon, 22 Jun 1998 23:17:12 -0700
On 22 Jun 98, rkresken@esoc.esa.de wrote:
> I am sure Rob's assumption about the spin axis orientation of Superbird A
> is correct.
> Energy dissipation will make any object that spins in an uncontrolled way
> spin about the body axis with the highest moment of inertia. In the case of
> Superbird A, this axis must be perpendicular to the solar panels.
I think there was a different type of energy dissipation. It's my guess
that Superbird A spun around its current axis from the moment the satellite
went dead, when the reaction wheel motors stopped applying torque. Since
the axis of the reaction wheel that had to do the most work is aligned with
the current spin axis, it's also my guess that there was never an
"uncontrolled" multi-axis spin (tumble).
To go farther, I also wonder if the opposite effect is occurring: Superbird
will go from a flat spin to a wobble. Those big solar panels experience a
lot of solar radiation pressure, and if the pressure is not applied
precisely through the satellite's center of mass then nutation would be
induced. I believe Rob Matson has reported that Superbird's axis does
drift.
__________________________________________________________
Jim Varney
Member, Sacramento Valley Astronomical Society
Sacramento Iridiums www.softcom.net/users/jamesv/index.htm