卫星高度计定标现状

定标是卫星高度计数据精度的重要保障,随着高度计卫星HY-2A的发射及后续卫星组网规划,中国将获取长时间序列的自主高度计观测资料,定标对数据精度和长期一致性的重要性日益凸显。总结了卫星高度计定标常用技术方法的国内外研究进展和现状,阐述了中国自主海上定标场的建设和应用情况,重点对青岛千里岩定标场的大地基准测量、地壳沉降监测及HY-2A等多颗卫星高度计的定标结果进行总结分析,并对规划建设中的珠海万山海上综合定标场和中国沿海定标场网做了介绍。此外利用GNSS水汽反演技术对星载微波辐射计观测的大气湿延迟开展了精度检核实验,得到了Jason-2卫星2010年—2016年微波辐射计大气湿延迟观测精度,证明了利用中国沿海GNSS连续运行站标定星载微波辐射计大气湿延迟的可行性,对于充分了解和认识卫星高度计定标的研究现状和发展趋势有一定的借鉴和指导意义。

Research status of satellite altimeter calibration

Satellite altimetry is one of the most important remote sensing technologies used over oceans, and it can dramatically promote ocean science in different disciplines. Since 2011, China has launched the HY-2A and HY-2B satellite altimeters to provide spatially dense data with a 14 day-time frequency to the international altimetry community. Calibration is an important work to maintain the high accuracy of the satellite altimeter data. Following the launch of HY-2A and HY-2B, as well as new satellites to be launched in the near future, the long time series of altimetry data will likely be achieved. The importance of altimeter calibration in guaranteeing the accuracy of satellite data and the consistency of long time series measurements will also likely become prominent.
This paper summarizes the research progress and the status of the main calibration technology at the global level. The calibration methods are generally categorized into absolute and relative sets. Each method is briefly described along with its calibration principle and its merits and demerits. The instructions for the methods of tide gauge, GNSS buoy, and the crossover calibration between different satellites are given in detail, especially since they have been discussed comprehensively in the operational calibration literature. The calibration methods based on the transponder, ARGO, and tide gauge networks are briefly described given their supplementary roles.
The existing progress and application of Chinese calibration sites are also presented. The geodetic survey and the surface subsidence over the Qianliyan calibration site and the calibration results for HY-2A, Jason-2 and Jason-3, Saral, and Sentinel-3A are demonstrated in detail. Then, the Wanshan sites and the planning calibration network in the Chinese coastal area are introduced. Furthermore, the wet delay of the troposphere, as measured by Jason-2 AMR in 2010-2016, is evaluated by considering one site from the Chinese coastal GNSS network, thus proving the feasibility of calibrating the microwave radiometer wet delay through the Chinese coastal GNSS network.
In the last section, we summarize the problems obtained from the present research and provide suggestions for calibrating and correcting the domestic satellite altimeter data. This section is relevant because, in the near future, the surface water and ocean topography (popularly known as SWOT) and the Chinese "Guan Lan" and HY-3C missions, which adopt the new altimetry concept by using the sensors of the synthetic aperture radar interferometer, and which can provide 2D oceanic topography, will likely bring new challenges to present-day altimetry calibration technologies. The paper ends with a brief discussion on the anticipated new challenges on altimeter calibration. This work will bring remarkable contribution to the understanding of the present situation, considering that the paper focuses on the development trend of satellite altimeter calibration.