How to convert .a file from STK to unitQuaternion in czml file?

CesiumJS
1

Hi, All,
I convert .a file, exported from STK, to unitQuaternion. But when I try it in cesium, the orientation is wrong. Should I change the order of the 4 values of a line? And, what's the 4 values really mean?

Thanks,
-Shawn