Preliminary Evaluation and Correction of Sea Surface Height from Chinese Tiangong-2 Interferometric Imaging Radar Altimeter

Abstract

In this study, we performed preliminary comparative evaluation and correction of two-dimensional sea surface height (SSH) data from the Chinese Tiangong-2 Interferometric Imaging Radar Altimeter (InIRA) with the goal of advancing its retrieval. Data from the InIRA were compared with one-dimensional SSH data from the traditional altimeters Jason-2, Saral/AltiKa, and Jason-3. Because the sea state bias (SSB) of distributed InIRA data has not yet been considered, consistency was maintained by neglecting the SSB for the traditional altimeters. The results of the comparisons show that the InIRA captures the same SSH trends as those obtained by traditional altimeters. However, there is a significant deviation between InIRA and traditional altimeter SSHs; consequently, systematic and parametric biases were analyzed. The parametric bias was found to be related to the incidence angles and a significant wave height. Upon correcting the two biases, the standard deviation significantly reduced to 8.1 cm. This value is slightly higher than those of traditional altimeters, which typically have a bias of ~7.0 cm. The results indicate that the InIRA is promising in providing a wide swath of SSH measurements. Moreover, we recommend that the InIRA retrieval algorithm should consider the two biases to improve SSH accuracy.

Simulation research on the whole process of spaceborne XTI-SAR oceanic eddy detection

“…In recent years, the use of interferometric SAR to observe the ocean has gradually become a research hotspot. Many research teams have carried out corresponding research plans, such as the Tiangong-2 in China [4], and the surface water and ocean topography (SWOT) mission jointly developed by NASA, JPL and CNES [5]. However, there is little research on the signal-level whole-process simulation of oceanic eddy by InSAR.…”

New Ku-Band Geophysical Model Function and Wind Speed Retrieval Algorithm Developed for Tiangong-2 Interferometric Imaging Radar Altimeter

“…TG2-InIRA works at 13.58 GHz with 40 MHz bandwidth, it is the first wide-swath ocean altimeter [2]. TG2-InIRA aims to validate the working principle for realizing wide-swath measurement of sea surface height (SSH) and the payload design as well [3]- [5]. Different from traditional altimeters, TG2-InIRA takes a short interferometric baseline and adopts small incidence angles from 1°to 8°along with synthetic aperture imaging technique to obtain amplitude images and wideswath SSH at the same time.…”

Overlapping-calibration of wide-swath altimeter baseline errors using two satellites formation flying design

“…To achieve such oceanography objectives, high-precision sea surface height (SSH) observation is required (Archer et al, 2020). However, multi-source errors of wide-swath altimetry, including random noise (RN), baseline roll and length errors, dry and wet troposphere delay, and sea state bias (Ren et al, 2020), will directly limit the precision of the retrieved SSH data. As a result, one of the most critical studies on the wide-swath altimetry mission is how to reduce the SSH errors (Chen et al, 2021), and for each error source, specific reduction methods should be developed according to the corresponding error model.…”