Meng Sun

In this article, the results of marine gravity recovery over the South China Sea are reported by using the sea surface height (SSH) data measured by Tiangong-2 interferometric imaging radar altimeter (TG2 InIRA). The high observation efficiency is demonstrated even only single swath is observed. The derived gravity anomalies by TG2 InIRA and by conventional altimeters (CAs) [Jason-2 (J2) and SARAL (SA)] are compared with the published gravity models and shipborne gravity measurements, showing that the accuracy of TG2 InIRA is a little better than that of CAs, although the signal bandwidth of which is only 40 MHz. Besides, the comparisons of the residual gravity anomalies also exhibit finer textural information and higher spatial resolution of TG2 InIRA. More interestingly, the potential for the coastal gravity recovery by TG2 InIRA is presented, although the land influence exists when the track is orthogonal to the coast and when the track is parallel to the coast. The achieved results of TG2 InIRA make us believe that more powerful wide-swath altimeters, e.g., the Surface Water and Ocean Topography (SWOT) mission, can bring a revolutionary contribution to the survey of marine gravity field in the future especially for the coastal areas.

This paper presents for the first time the results of marine gravity recovery using the ocean observation data acquired by Tiangong-2 interferometric imaging radar altimeter (TG2 InIRA) which demonstrate not only the balanced accuracies of the north and east components of deflection of the vertical (DOV) as envisaged, but also the improved spatial resolutions of DOV compared with that by conventional altimeters (CAs). Moreover, much higher measurement efficiency owing to the wide-swath capability and the great potential in accuracy improvement of marine gravity field are also demonstrated. TG2 InIRA adopts the interferometry with short baseline and takes small incidence angles, by which wide-swath sea surface height (SSH) can be measured with high accuracy. Gravity recovery experiments in the Western Pacific area are conducted to demonstrate the performance, advantages and capability of TG2 InIRA. SSH data processing algorithms and DOV calculation have been designed by taking the wide-swath feature into account, based on which, the gravity anomalies are then calculated using the inverse Vening Meinesz formula. The derived gravity anomalies are compared with both the published gravity models and the shipborne gravity measurements. The results show that the accuracy of TG2 InIRA is equivalent to, or even a little better than, that of CAs. The fused gravity result using equal TG2 InIRA data and CAs data performs better than those using TG2 InIRA data alone or CAs data alone. Due to the signal bandwidth of TG2 InIRA is only 40 MHz which is much smaller than that of CAs, much higher accuracy can be hopefully achieved for future missions if larger signal bandwidth is used.