福爾摩沙衛星三號任務近即時自動化定軌

Abstract

本研究主旨為建立福爾摩沙衛星三號任務近即時自動化定軌處理系統。採用Bernese 5.0進行定軌，以解算出福衛三號近即時軌道的最佳精度。於Linux叢集電腦下，配合佇列排程控管軟體PBS以及例行性工作排程，處理系統可實現福衛三號六枚衛星的自動化定軌。根據近即時軌道重疊分析以及與UCAR近即時軌道差異比較，在未使用final GPS軌道與高取樣率GPS時錶改正的情況下，近即時軌道精度約為20 cm。以15 cm的3D軌道誤差作為評估標準，則近即時軌道的平均定軌成功率（軌道誤差小於15 cm的百分比）約為四成。測試顯示：（1）使用增進GPS軌道（精度由10 cm提升為5 cm），福衛三號近即時軌道精度改善為15 cm且定軌成功率提升為七成；（2）使用30秒一筆的高取樣率GPS時錶改正（精度為0.01 ns），福衛三號近即時軌道精度改善為10 cm且定軌成功率提升為八成。

This research is focused on establishing an automatic near-real time (NRT) system for the orbit determination (OD) of the FORMOSAT-3/COSMIC (F3/C) satellite mission. With Bernese 5.0 for OD, emphasis is on achieving an optimal accuracy of the F3/C NRT orbit. With a portable batch and routine task scheduling under a Linux PC cluster, the system carries out automatic OD for the six satellites of F3/C. Without the final orbits and high-rate clocks of the GPS satellites, the accuracy of the NRT orbits is about 20 cm, based overlapping arc analysis and comparisons with UCAR NRT orbits. With a 15-cm threshold of 3D orbit error, the average success rate of the NRT orbit (percentage of orbit error < 15 cm) is about 40%. Simulations show that, (1) use of improved GPS orbits (from 10 cm to 5 cm), the F3/C NRT orbit accuracy is improved to 15 cm and the success rate increases to 70%. (2) use of 30-s high-rate GPS clocks (with a 0.01ns accuracy), the F3/C NRT orbit accuracy is improved to 10 cm and the success rate increases to 80%.