CHANGELOG.md

@@ -27,6 +27,10 @@ will consitute of a breaking change warranting a new major release:
 
 - PUS timeservice relative timeshift.
 
+## Fixed
+
+- Fixed wrong order in quaternion multiplication for computation of the error quaternion.
+
 # [v7.7.4] 2024-03-21
 
 ## Changed

mission/controller/acs/Guidance.cpp

@@ -303,9 +303,9 @@ void Guidance::comparePtg(double currentQuat[4], double currentSatRotRate[3], do
   // First calculate error quaternion between current and target orientation without reference
   // quaternion
   double errorQuatWoRef[4] = {0, 0, 0, 0};
-  QuaternionOperations::multiply(currentQuat, targetQuat, errorQuatWoRef);
+  QuaternionOperations::multiply(targetQuat, currentQuat, errorQuatWoRef);
   // Then add rotation from reference quaternion
-  QuaternionOperations::multiply(refQuat, errorQuatWoRef, errorQuat);
+  QuaternionOperations::multiply(errorQuatWoRef, refQuat, errorQuat);
   // Keep scalar part of quaternion positive
   if (errorQuat[3] < 0) {
     VectorOperations<double>::mulScalar(errorQuat, -1, errorQuat, 4);