A Cascaded Autofocus Method for Earth-Based Radar Moon 3-D Imaging under Multisource Phase Errors Based on Entropy Gradient

TY - JOUR

T1 - A Cascaded Autofocus Method for Earth-Based Radar Moon 3-D Imaging under Multisource Phase Errors Based on Entropy Gradient

AU - Ding, Zegang

AU - Yang, Yuewen

AU - Dong, Zehua

AU - Wang, Zhen

AU - Liu, Peiyao

AU - Zhou, Ziyi

N1 - Publisher Copyright: © 1980-2012 IEEE.

PY - 2026

Y1 - 2026

N2 - The Moon is Earth's only natural satellite, and observation of the Moon is of great importance in scientific research and engineering applications. Earth-based radar is a powerful approach for Moon observation, and is capable of acquiring a Moon 3-D radar image. However, various nonideal factors lead to intratrack and intertrack phase error, which degrade 3-D imaging quality. To address this issue, this article proposes a novel cascaded autofocus method for Earth-based radar Moon 3-D imaging. The contribution of the article mainly consists of two parts. The first is the comprehensive modeling for complex phase errors, where different types of phase errors are modeled as a polynomial or periodic function of azimuth time. The impact of complex phase errors on Moon 3-D imaging is analyzed. The second is the error estimation and compensation algorithm for multisource complex phase errors that does not rely on strong scatters. This algorithm uses the image energy maximization criterion to truncate the optimal imaging region for autofocus. The analytical iteration format based on the partial derivation of distributed target entropy is given. In addition, the 2-D and 3-D autofocus is performed in cascade to separately estimate errors in the time-domain, which does not rely on a certain coordinate system property. Computer simulations and real data experiments based on an Earth-based radar system are conducted to validate the proposed method.

AB - The Moon is Earth's only natural satellite, and observation of the Moon is of great importance in scientific research and engineering applications. Earth-based radar is a powerful approach for Moon observation, and is capable of acquiring a Moon 3-D radar image. However, various nonideal factors lead to intratrack and intertrack phase error, which degrade 3-D imaging quality. To address this issue, this article proposes a novel cascaded autofocus method for Earth-based radar Moon 3-D imaging. The contribution of the article mainly consists of two parts. The first is the comprehensive modeling for complex phase errors, where different types of phase errors are modeled as a polynomial or periodic function of azimuth time. The impact of complex phase errors on Moon 3-D imaging is analyzed. The second is the error estimation and compensation algorithm for multisource complex phase errors that does not rely on strong scatters. This algorithm uses the image energy maximization criterion to truncate the optimal imaging region for autofocus. The analytical iteration format based on the partial derivation of distributed target entropy is given. In addition, the 2-D and 3-D autofocus is performed in cascade to separately estimate errors in the time-domain, which does not rely on a certain coordinate system property. Computer simulations and real data experiments based on an Earth-based radar system are conducted to validate the proposed method.

KW - Earth-based radar

KW - Moon 3-D imaging

KW - phase error compensation

KW - synthetic aperture radar

KW - time-domain autofocus

UR - https://www.scopus.com/pages/publications/105028387680

U2 - 10.1109/TGRS.2026.3656358

DO - 10.1109/TGRS.2026.3656358

M3 - Article

AN - SCOPUS:105028387680

SN - 0196-2892

VL - 64

JO - IEEE Transactions on Geoscience and Remote Sensing

JF - IEEE Transactions on Geoscience and Remote Sensing

M1 - 5202618

ER -