1.   Mission Control chief Vladimir Solovyov said Discovery had to fire its engines to align the station, whose attitude control system was switched off for a computer upgrade.

2.   Mission Control quickly fixed the computer problem, but has failed to switch on the gyroscopes, the preferred, fuel-free way of aligning the station.

3.   The engines keep the station properly aligned toward the sun, allowing the solar panels to soak up the maximum amount of energy.

4.   The engines keep the station properly aligned toward the sun, allowing the solar panel to soak up the maximum amount of energy.

5.   The gyroscopes are the preferred, fuel-free way of aligning the station.