bias

This term is defined in ECSS-E-ST-60-20C Rev. 1 as
error on the knowledge of the orientation of the BRF including: • the initial alignment measurement error between the Alignment Reference Frame (ARF) and the sensor Boresight Reference Frame (BRF) (on ground calibration) • the Alignment Stability Error (Calibration to Flight )witch is the change in the transformation between the sensor Mechanical Reference Frame (MRF) and the sensor Boresight Reference Frame (BRF) between the time of calibration and the start of the in-flight mission