  SOFIA is an airborne, gyroscopically stabilized 2.5m infrared telescope,
mounted to a spherical bearing. Unlike its predecessors, SOFIA will work in
absolute coordinates, despite its continually changing position and attitude.
In order to manage this, SOFIA must relate equatorial and telescope coordinates
using a combination of avionics data and star identification, manage field
rotation and track sky images. We describe the algorithms and systems required
to acquire and maintain the equatorial reference frame, relate it to tracking
imagers and the science instrument, set up the oscillating secondary mirror,
and aggregate pointings into relocatable nods and dithers.
