Most embarrassing, their Phobos probe spun out of control because one technician sent a command that was wrong by one digit. But when they failed, too, NASA began to worry. The case of the September 1999 Mars Climate Orbiter is embarrassing, for many reasons. Until now and the reasons why are instructive. True, but not the whole story.
All spacecraft have to keep their bearings against deflecting forces.
That's why most spacecraft spin, to keep their direction more or less fixed. These little tops spin at up to 3000 revolutions per minute, one gyroscope for each of three axes in direction. Another way to move a spacecraft is to thrust with gas jets. The ground team turns on a jet for a few seconds, calculated to correct a straying aim. Both methods get used to make the complicated changes along a long interplanetary orbit.