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Re: The Olympics



Herb Schulz's archival statement retrieved by Larry Cartwright caught my
eye:

----- Original Message -----

On Mon, 21 Dec 1998, Herb Schulz wrote:

By changing the moment of inertia of the upper and lower parts of the
body appropriately you can have DIFFERENT and opposite angular
velocities so the different parts of the body will rotate through
different angles in the same amount of time.

"That's how we aim camera's at different points in space without using
fuel 'jets'! Spin an internal body one way and the rest of the
satellite rotates the other way."

In fact, satellite telescopes are not slewed to their target by spinning an
internal body the opposite way. Most satellites achieve attitude control
with gyroscopic reference systems. Three mutually orthogonal gyroscopes are
used to define an inertial reference frame. Torquing motors are then used to
rotate the satellite with respect to this frame. The gyro reference frame is
maintained against the stars.

"When stars are out, they are visible; when other lights are out, they are
invisible."

Paul O. Johnson
Collin County College