Abstract
The Moon-based Synthetic Aperture Radar (Moon-Based SAR), using the Moon as a platform, has a great potential to offer global-scale coverage of the earth’s surface with a high revisit cycle and is able to meet the scientific requirements for climate change study. However, operating in the lunar orbit, Moon-Based SAR imaging is confined within a complex geometry of the Moon-Based SAR, Moon, and Earth, where both rotation and revolution have effects. The extremely long exposure time of Moon-Based SAR presents a curved moving trajectory and the protracted time-delay in propagation makes the “stop-and-go” assumption no longer valid. Consequently, the conventional SAR imaging technique is no longer valid for Moon-Based SAR. This paper develops a Moon-Based SAR theory in which a signal model is derived. The Doppler parameters in the context of lunar revolution with the removal of ‘stop-and-go’ assumption are first estimated, and then characteristics of Moon-Based SAR imaging’s azimuthal resolution are analyzed. In addition, a signal model of Moon-Based SAR and its two-dimensional (2-D) spectrum are further derived. Numerical simulation using point targets validates the signal model and enables Doppler parameter estimation for image focusing.
Highlights
Earth observation from remote sensing satellites orbiting in a low Earth orbit provides a continuous stream of data that can enable a better understanding of the Earth with respect to climate change [1]
The performance and potential applications of the Moon-Based Synthetic aperture radar (SAR) were characterized by Moccia and Renga [5], and the scientific and technical issues in the application of lunar-based repeat track and along track interferometry in [6]
This paper aims at deriving a signal model of Moon-Based SAR imaging by considering the more complete, but more complex, geometry of SAR in Moon-Earth orbits
Summary
Earth observation from remote sensing satellites orbiting in a low Earth orbit provides a continuous stream of data that can enable a better understanding of the Earth with respect to climate change [1]. The performance and potential applications of the Moon-Based SAR were characterized by Moccia and Renga [5], and the scientific and technical issues in the application of lunar-based repeat track and along track interferometry in [6] Following this stream of development, an L-band Moon-Based SAR for monitoring large-scale phenomena related to global environmental changes was discussed [9] and the coverage performance of the Moon-based platform for global change detection [10]. The geometric modeling and coverage for a lunar-based observation by using Jet Propulsion Laboratory (JPL) ephemerides data were addressed in [11] These studies are focused on the performance analysis and potential applications with some assumptions, such as a regular spherical Earth, an orbicular circular lunar orbit, a fixed earth’s rotational velocity, and a stationary Moon.
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