利用Lageos 1衛星雷射測距之模擬資料與觀測資料 反算SLR地面觀測站坐標

Abstract

隨著測距精度的增進，衛星雷射測距(Satellite Laser Ranging, SLR)已被應用於許多衛星任務與衛星大地研究領域，例如台灣與美國合作之福爾摩沙衛星七號計畫中將搭載雷射測距反射稜鏡(retro-reflector)。 本研究主要探討SLR觀測資料與模擬資料計算SLR觀測站絕對坐標，利用SLR觀測數據誤差模式化與最小二乘平差法計算地面站坐標。研究中使用澳洲Yarragadee (測站編號：7090) 觀測站對Lageos 1衛星一年的測距資料(Normal point data)反算觀測站每三個月的絕對坐標。 研究結果發現，加入衛星質量中心改正與固體潮位改正對距離有1-5公分的改善，而加入Marini and Murray (1973)大氣折射模式改正對距離有5-10公尺的改善；將所有改正加入後可將點位偏移量降低至4公尺以內。比較模擬資料與觀測資料之結果，得到模擬資料解算結果為公分等級，而觀測資料為10-20公分等級，顯示真實資料存在無法模型化的系統誤差。如欲提高SLR解算坐標成果，應考量資料的數量與品質、以及剔除錯誤資料的方法，或是增加各種軌道傾角衛之星觀測資料共同解算。

With ever-improved ranging accuracies, satellite laser ranging (SLR) has been used in many disciplines of satellite geodesy and in many satellite missions. An example is the Formosat-7 satellite mission, which is a joint Taiwan-U.S. mission equipped with laser retro-reflectors. This study focuses on determinations of SLR station coordinates using real and simulated SLR observations. Errors in the observation are modeled and the least-squares method is used for coordinate determination. One year of real SLR observations to Lageos 1 (Normal point data) at station Yarragadee (ID:7090), Australia, are used to determine quarterly coordinates. By applying center of satellite correction and solid earth tide correction, we achieve 1-5 cm improvements in range observations. Applying the Marini and Murray atmospheric range correction results in 5-10 m improvements in range observations. These corrections also reduce ranging biases by up to 4 m. The accuracies of the Yarragadee station coordinates are at the cm and 10-20cm levels from the simulated data and the observations, respectively. There are still system errors in the real data at Yarragadee that cannot be modeled properly. In order to obtain reliable SLR station coordinates, it is important to use data of long records and good quality, apply effective correction models and data editing to the raw data, and to use SLR data from satellites of various inclination angles.