Absolute Calibration or Validation of the Altimeters on the Sentinel-3A and the Jason-3 over Lake Issykkul (Kyrgyzstan)
Absolute Calibration or Validation of the Altimeters on the Sentinel-3A and the Jason-3 over Lake Issykkul (Kyrgyzstan)
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DOI：
10.3390/rs10111679
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发表时间：
2018-11-01
期刊：
影响因子：
5
通讯作者：
Bonnefond, Pascal
中科院分区：
文献类型：
--
作者：
Cretaux, Jean-Francois;Berge-Nguyen, Muriel;Bonnefond, Pascal
利用海洋中的地点进行校准/验证研究有着悠久的历史，而且已有完善的规程。在湖泊上，C/V允许解决诸如各种重跟踪算法的性能和评估大陆沃茨的地球物理校正的精度等问题。这是可以实现的，当测量的具体和众多的领域运动和地面永久网络的水平仪和气象站进行处理。C/V包括安装永久站点（气象站、水位计和全球定位系统参考点）和组织定期的实地活动。伊塞库湖作为C/V的永久场地，用于多任务目的。本文的目的是计算Jason-3和Sentinel-3A的高度计偏差，两者都属于业务卫星系统，用于长期监测湖泊水位变化。我们还确定了这两颗卫星的高度计的精度，通过与现场数据的比较分析。在2016年和2017年，在这个湖上组织了三次活动，以估计Jason-3和Sentinel-3A上的最低点高度计的绝对偏差。实地工作包括使用GPS系统测量水面高度，该系统由船只携带，沿着测高卫星的轨道穿过湖面。它是在高度计通过时进行的。绝对高度计偏差是通过对沿卫星经过的沿着水面高度差求平均值来计算的（船载GPS系统与测高系统）。Jason-3在低分辨率模式（LRM）下工作，而Sentinel-3A在合成孔径雷达（SAR）模式下工作。在本研究中，我们发现使用Ocean Retracker测量的Jason-3的绝对偏差为-28 +/- 40 mm，使用Ice-1 Retracker测量的绝对偏差为206 +/- 30 mm。Sentinel-3A的偏差为-14 +/- 20 mm（Samosa（Ocean like））和285 +/- 20 mm（OCOG（Ice-1-like））。我们还评估了这两个高度计在伊塞库勒湖的精度达到3厘米，这两个仪器，使用海洋retracker。
Calibration/Validation (C/V) studies using sites in the oceans have a long history and protocols are well established. Over lakes, C/V allows addressing problems such as the performance of the various retracking algorithms and evaluating the accuracy of the geophysical corrections for continental waters. This is achievable when measurements of specific and numerous field campaigns and a ground permanent network of level gauges and weather stations are processed. C/V consists of installation of permanent sites (weather stations, limnigraphs, and GPS reference points) and the organization of regular field campaigns. The lake Issykkul serves as permanent site of C/V, for a multi-mission purpose. The objective of this paper is to calculate the altimeter biases of Jason-3 and Sentinel-3A, both belonging to an operational satellite system which is used for the long-term monitoring of lake level variations. We have also determined the accuracy of the altimeters of these two satellites, through a comparison analysis with in situ data. In 2016 and 2017, three campaigns have been organized over this lake in order to estimate the absolute bias of the nadir altimeter onboard the Jason-3 and Sentinel-3A. The fieldwork consisted of measuring water height using a GPS system, carried on a boat, along the track of the altimeter satellite across the lake. It was performed at the time of the pass of the altimeter. Absolute altimeter biases were calculated by averaging the water height differences along the pass of the satellite (GPS from the boat system versus altimetry). Jason-3 operates in a Low Resolution Mode (LRM), while the Sentinel-3A operates in Synthetic Aperture Radar (SAR) mode. In this study we found that the absolute biases measured for Jason-3 were -28 +/- 40 mm with the Ocean retracker and 206 +/- 30 mm with the Ice-1 retracker. The biases for Sentinel-3A were -14 +/- 20 mm with the Samosa (Ocean like) retracker and 285 +/- 20 mm with the OCOG (Ice-1-like) retracker. We have also evaluated the accuracy of these two altimeters over Lake Issykkul which reached to 3 cm, for both the instruments, using the Ocean retracker.