The SESAR-LITE (Space Exploration Synthetic Aperture Radar - Lunar Investigations Targeted Experiment) instrument is a compact P-band (70 cm wavelength) polarimetric synthetic aperture radar under development at the NASA Goddard Space Flight Center (GSFC) to measure the surface and upper subsurface of the Moon at full polarimetry and at meter-scale resolution. The radar will use a compact deployable antenna, distributed RF electronics, and multi-channel digital processing system to enable a set of focused mission goals for small payload opportunities. The instrument development leverages proven technology advancements recently developed and demonstrated at NASA GSFC for SESAR (Space Exploration Synthetic Aperture Radar), a flagship version of the instrument that was tailored for larger orbital missions. The development of SESAR-LITE addresses accommodation flexibility on multiple launch vehicle families that require small packages while providing unprecedented surface and subsurface imaging of the Moon as required by NASA’s Artemis program. The goal of this effort is to mature the technology readiness level and to demonstrate the unique features and capabilities of this radar in preparation for upcoming mission opportunities.

This study presents the potential of L- to X-band wideband radiometry to retrieve important geophysical and thermal properties of the lunar regolith through simulated measurements of a 30-channel 1-10 GHz microwave radiometer. It has been demonstrated that regolith thickness, densification with depth, water ice percentage in the regolith, as well as the geothermal heat flux can be estimated with little (95%) confidence if surface brightness temperatures are collected with such an instrument throughout the entire diurnal cycle. On the other hand, ancillary information regarding other regolith properties such as internal layerings, and the surface density and temperature values may be necessary for a nonunique retrieval; thus, deployment of other instruments such as ground penetrating radars with wideband radiometers would be useful during the future lunar missions.

Synthetic Aperture Radar acquisitions in nadir (sounding) and side-looking imaging modes are planned for the International-Mars Ice Mapper (I-MIM) orbiter mission to accurately detect ice buried just below the Martian surface. In an effort to gain a comprehensive understanding of the ice detection capability of the I-MIM L-band polarimetric SAR, we developed a Nadir Scattering Radar Model (NRSM), and evaluated it in comparison to a previously implemented Side-looking Radar Scattering Model (SRSM). Together, these Radar Scattering Models (RSMs) permit a thorough evaluation of key radar performance metrics for given sets of radar parameters and Martian surface and shallow subsurface scenarios, and offer new insights into potential depths of detection of buried water ice on Mars.

The use of polarimetric SAR to detect buried water/ice at shallow depths under the Martian surface is quantitatively explored. An electromagnetic model consisting of a dielectric layer that represents the Martian regolith (upper surface layer), with an underlying half space of water/ice, is considered. The top surface of the regolith and the regolith/ice interface are assumed to be rough at radar wavelength scales. It is also assumed that throughout the regolith, small rock particles with arbitrary shapes and prescribed orientation statistics are randomly distributed. Backscattering with co-polarization and cross-polarization from vertical or horizontal polarized waves incidence at L-band frequencies are considered. The Advanced Integral Equation Method (AIEM) is applied to irregular surfaces and the Distorted Born Approximation (DBA) applied to particle scattering and regolith attenuation.

We implemented a 3-D electromagnetic scattering model to gain a better understanding in the observations of L- and P-band radar returns from the multi-layered Martian upper surface layer. The model, based on the Integral Equation Model (IEM) developed by Adrian Fung, treats the Martian regolith (upper 10-meter layer of surface sediments) as an inhomogeneous medium with irregular boundaries, and employs surface and shallow subsurface parameters representative of a variety of Martian terrains. The model is well-suited to study the near-subsurface ice detection capability of the L-band (32 cm wavelength) Synthetic Aperture Radar (SAR) planned for the international Mars Ice Mapping (I-MIM) mission being considered for launching in the late 2020s.

The Space Exploration Synthetic Aperture Radar (SESAR) is a new P-band radar instrument development for planetary applications that will enable unprecedented surface and near-subsurface measurements of planetary bodies including the Moon, Mars, and asteroids. The radar will measure full polarimetry at meter scale resolution, and achieve beam agility through programmable digital beamforming architecture. The radar features a low power, lightweight, modular design, specifically developed to meet stringent launch and operation requirements of planetary instruments. A prototype SESAR system is currently being developed under NASA's MATISSE (Maturation of Instruments for Solar System Exploration) program.

The Space Exploration Synthetic Aperture Radar is a new radar instrument development for planetary applications that will enable unprecedented surface and near-subsurface measurements of planetary bodies including the Moon, Mars, and asteroids. The radar is based on an advanced multiple-input multiple-output (MIMO) architecture that operates in the P-band (70 cm wavelength), measures full polarimetry at meter scale resolution, and achieves beam agility through programmable digital beamforming. The radar is based on a low power, lightweight, modular design approach specifically developed to meet stringent launch and operation requirements of planetary instruments. Prototype SESAR subsystems have been developed and tested, and a recent MATISSE (Maturation of Instruments for Solar System Exploration) proposal was awarded to build and test a functional radar panel.