Re: "One-gyro mode uses magnetometers, sun sensors, and star trackers for the failed gyros"
>How's that for cunning engineering? Ideally uses six gyros, but can work with one
Seems wasteful !
" engineering is the art of doing that well with one dollar which any bungler can do with two after a fashion" Arthur M. Wellington
ps It needs 3 gyros so had 6 - cos the call-out fee for replacements is rather high.
It can 'work' with one by basically arranging observations by waiting until they drift into view and then using the magnetometer to hold it still for a while and then use the last gyro to unload the magnetometer. It's like saying a car with no steering but a handbrake that can lock up one wheel is controllable
pps. you can't really add extra gyros, they have to be pretty much at the center to control the pointing. For all the talk of a service mission, it would be better to spend the money on a new cheaper telescope
ppps. that statement migtt also apply before it was launched