Operations in Three Gyro mode provide for a 2 degree radius cap around the anti-sun direction in which observations at any roll orientation can take place. This had occasionally been useful for observations of planets at opposition. There are several pointing control options. These have been used rarely in recent cycles.
- observing in Gyro-only mode.
- starting observations under FGS control and transfer to Gyro-only mode as the guide stars leave the FGS field-of-view.
- starting observations under FGS control and "hand-off" to a second pair of guide stars as the observations proceed.