中華衛星一號離子漂浮向量儀之主要任務為測量電離層中離子橫豎面漂移速度，而速度主要是依據離子入射角度來判定。如果中華衛星一號受到外力擾動而造成姿態偏移時，便會對離子漂浮向量儀所量測之離子入射角度，及之後的速度判定產生誤差。本篇研究將深入探討衛星姿態受到軌道面逐漸西移的影響，以及考慮橢圓地球、大氣阻力與太陽輻射壓等外力擾動所產生的效應。我們利用座標轉換求得衛星受軌道面西移干擾時三軸的角度誤差，再用剛體力學的方法，將橢圓地球的外力項代入衛星座標之Euler’s Moment Equation以求得角度偏差，此解與利用座標轉換所得之結論相符。 The major mission of the ion drift meter (IDM) on ROCSAT-1 is to compute the plasma flow velocity by measuring arrival angles of ions with respect to the sensor look direction. The deviation of the satellite attitude due to any external forces could cause errors in the arrival angles of ions measured from IDM, and the faulted data would bring about the inaccuracy in the plasma flow velocity. In this study, we will determine the disturbed angles of the satellite axes by conferring the spacecraft attitude drift caused by the nodal regression and perturbations due to the equatorial bulge, atmospheric drag and solar radiation pressure. By transferring the satellite coordinate, we can obtain three axes error from the nodal regression, and the inference is tally with the resolution of the Euler’s Moment Equation by considering the external force for the Earth oblateness. With adequate understanding of these disturbances, it is effortless to correct the inaccuracies from the IDM, and the more accurate information must be valuable for the researches of the ionosphere and the plasma physics.
