DIWATA-2 TARGETING ASSESSMENT AND ATTITUDE ERROR DETERMINATION USING A QUATERNION-BASED TRANSFORMATION SYSTEM
Keywords: targeting assessment; quaternions; transformation system; attitude; vector rotation
Abstract. Target pointing assessment of a space-borne satellite is vital to its operations especially on microsatellites that have limited camera field of view and attitude control components like in the case of Diwata-2. In this study, two scientific payloads of the satellite were used: the Enhanced Resolution Camera (ERC) with a field of view (FoV) of 89.8 × 67.5 km and a resolution of 54.6 m; and the High Precision Telescope (HPT) with a FoV of 3.1 × 2.3 km and a resolution of 4.7 m. Errors in pointing especially on a payload with a small field of view like the HPT could mean the satellite missing its target. The target pointing of Diwata-2 is assessed by firstly, computing the differences in the coordinates of the planned target, the center of the actual image taken by the satellite and the projected target from the satellite’s attitude logs. As such, a quaternion-based transformation system is created to simulate the satellite’s local vertical local horizontal system from a given Earth-centered inertial system. Secondly, the differences were then tabulated, and its averages were computed to derived pointing corrections. Applying the algorithm to the satellite’s images shows that there is an average error in pitch and roll of 0.590° and 0.004°, 6.436° and 6.503°, −5.8465° and −6.499° between the set target to the actual image acquired, between the actual image and from attitude logs and between the set target and from the attitude logs, respectively.