中華衛星三號軌道擾動力模式

Abstract

中華衛星三號預計於2005年秋天發射，ROCSAT-3計畫大地測量研究團隊有一科學任務，即為衛星精準軌道定位和地球重力場觀測，而衛星擾動力模式之不完整，會使定軌產生誤差，因此在精密定軌的過程中，必須力求擾動力模式之精確。本研究以衛星運動理論為基礎，探討地球非球體引力位擾動、多體擾動、固體潮擾動、海潮擾動、大氣阻力擾動、太陽輻射壓擾動、地球輻射壓擾動、相對論效應引起之擾動等八種擾動力模式，進行程式編輯，以期獲得精密之軌道資料，益於後續地球重力場之求定。目前計算結果已能正確計算海潮擾動力模式、多體擾動力模式及相對論效應引起之擾動力模式等，其餘擾動力模式軌道誤差都已控制在1.3公尺之內，未來工作將針對其它未臻完善之擾動力模式進行修改，最終目的是要建立一套由國人自行開發的精密定軌軟體。

ROCSAT-3 is scheduled to launch in the fall of 2005. The geodesy team of the ROCSAT-3 mission has committed to developing a computer package for precise orbit determination (POD) and gravity determination from the GPS data collected onboard ROCSAT-3. For POD precise knowledge about perturbing forces on orbiting satellite is essential. In this study, we model perturbing forces caused by the earth's non-sphericity, N-body, solid earth tide, ocean tide, air drag, solar radiation pressure, earth radiation and relativity. Acceleration due to these forces are coded in Fortran 90, which are later to used in gravity and orbit determinations. Currently, perturbing forces due to ocean tide, N-body, and relativity are precised computed and the orbital errors due to other forces are under 1.3 meter. With a goal to complete the POD and gravity determination package improvement in modeling these forces will be continued.