So it had a pure inertial guidance system which got deviated by 20 degrees? How common is that? I always assumed that , aside from the pre-programmed trajectory. modern rockets would be "aware" of their position. Perhaps even with calculations as to what corrections would be needed to stay on course.
They are "aware" of their position relative to their entered initial state due to their accelerometers.
I'm still struggling to picture where the mistake was made and why it wasn't caught. If it had a strapped down guidance system, and it launched from a known pad with a known orientation, physical mis-rotation of the vehicle seems impossible.
Is it simply that someone typed 70 instead of 90 into the guidance code? That would seem to be a ridiculous error that should have been easy to check with any rudimentary QC.
I'm just struggling with what was incorrect and how was it hidden.