Studies of the lunar surface from Synthetic Aperture Radar (SAR) data have played a prominent role in the exploration of the lunar surface in recent times. This study uses data from SAR sensors from three Moon missions: Chandrayaan-1 Mini-SAR, Lunar Recon-naissance Orbiter (LRO) Mini-RF and Chandrayaan-2 Dual Frequency Synthetic Aperture Radar (DFSAR). DFSAR sensor is the first of its kind to operate at L-band and S-band in fully and hybrid polarimetric modes. Due to the availability of only L-band data out of the two bands (L-and S-band) for the study site, this study only used DFSAR's L-band data. The dielectric characterization and polarimetric analysis of the lunar north polar crater Hermite-A was performed in this study using Chandrayaan-1 Mini-SAR, LRO Mini-RF and Chandrayaan-2 DFSAR data. Hermite-A lies in the Permanently Shadowed Region (PSR) of the lunar north pole and whose PSR ID is NP_879520_3076780. Because of its location within the PSR of the lunar north pole, the Hermite-A makes an ideal candidate for a probable location of water-ice deposits. This work utilizes S-band hybrid polarimetric data of Mini-SAR and Mini-RF and L -band fully polarimetric data of DFSAR for the lunar north polar crater Hermite-A. This study characterizes the scattering mechanisms from three decomposition techniques of Hybrid Polarimetry namely m-delta, m-chi, and m-alpha decompositions, and for fully polari-metric data Barnes decomposition technique was applied which is based on wave dichotomy. Eigenvector and Eigenvalue-based decom-position model (H-A-Alpha decomposition) was also applied to characterize the scattering behavior of the crater. This study utilizes the hybrid-pol and fully polarimetric data-based Integral Equation Model (IEM) to retrieve the values of dielectric constant for Hermite-A crater. The dielectric constant values for the Hermite-A crater from Chandrayaan-1 Mini-SAR and LRO Mini-RF are similar, which goes further in establishing the presence of water-ice in the region. The values of the dielectric constant for Chandrayaan-2 in some regions of the crater especially on the left side of the crater is also around 3 but overall the range is relatively higher than the com-pact/hybrid polarimetric data. The dielectric characterization and polarimetric analysis of the Hermite-A indicatively illustrate that the crater may have surface ice clusters in its walls and on some areas of the crater floor, which can be explored in the future from the synergistic use of remote sensing data and in-situ experiments to confirm the presence of the surface ice clusters.(c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.

Permanently shadowed regions (PSRs) at the poles of the Moon are potential reservoirs of trapped volatile species, including water ice. Knowledge of the distribution and abundance of water ice at the poles provides key scientific background for understanding the evolution of volatiles in the Earth-Moon system and for human exploration efforts. The Lunar Reconnaissance Orbiter Camera (LROC) acquired images of the terrain within PSRs to search for indications of water ice. In addition, the LRO Miniature Radio-Frequency (Mini-RF) instrument acquired S-band radar observations to further characterize these regions. Specifically, the m-chi decomposition was used to assess the distribution of materials within and around PSRs based on the type of backscatter. Double-bounce backscatter is indicative of water ice, but could also be produced by randomly distributed blocks at the wavelength scale. To ascertain whether these signatures are due to water ice or blocks, we quantified the abundance of detectable blocks in areas with double-bounce backscatter using the LROC Narrow Angle Camera (NAC). Block populations were measured for a suite of craters with different ages, sizes, and radar characteristics. For fresh craters, a correlation between block size, block density and double-bounce backscatter was found. Within PSRs exhibiting double-bounce backscatter, no blocks were found. Additionally, no albedo variations were observed at PSRs, in contrast to observations of PSRs on Mercury. While the possibility of water ice in some lunar craters still exists, these results indicate that they are likely small-scale, and that the observed radar anomalies at PSR-bearing craters are most likely due to the presence of wavelength-scale blocks.

The Lunar Reconnaissance Orbiter's (LRO) Lyman Alpha Mapping Project (LAMP) is a lightweight (6.1 kg), low-power (4.5 W), ultraviolet spectrograph based on the Alice instruments aboard the European Space Agency's Rosetta spacecraft and NASA's New Horizons spacecraft. Its primary job is to identify and localize exposed water frost in permanently shadowed regions (PSRs) near the Moon's poles, and to characterize landforms and albedos in PSRs. LRO launched on June 18, 2009 and reached lunar orbit four days later. LAMP operated with its failsafe door closed for its first seven years in flight. The failsafe door was opened in October 2016 to increase light throughput during dayside operations at the expense of no longer having the capacity to take further dark observations and slightly more operational complexity to avoid saturating the instrument. This one-time irreversible operation was approved after extensive review, and was conducted flawlessly. The increased throughput allows measurement of dayside hydration in one orbit, instead of averaging multiple orbits together to reach enough signal-to-noise. The new measurement mode allows greater time resolution of dayside water migration for improved investigations into the source and loss processes on the lunar surface. LAMP performance and optical characteristics after the failsafe door opening are described herein, including the new effective area, wavelength solution, and resolution.

Knowledge of the amount of water ice on the lunar surface will play a crucial role in future lunar missions. The discovery of large quantities of water ice on the Moon will have very significant implications for human space exploration. In this letter, the methodology for quantification of water ice is developed. Quantification of water ice present in the permanently shadowed region (PSR) of Hermite-A Crater is done by comparing simulated dielectric constant values obtained using the Campbell model and laboratory-measured dielectric constant values of terrestrial analogue of lunar soil for various percentages of water ice content. From this analysis, it is observed that about 66.32% of the total PSR of Hermite-A Crater is covered with different percentages of water ice. In this letter, all the pixels of the PSR of Hermite-A Crater, with a spatial resolution of 7.4 m/pixel, have been mapped with their corresponding water ice content ranging from 0% to 9%.

The Lyman Alpha Mapping Project (LAMP) is a lightweight (6.1 kg), low-power (4.5 W), ultraviolet spectrograph based on the Alice instruments now in flight aboard the European Space Agency's Rosetta spacecraft and NASA's New Horizons spacecraft. Its primary job on NASA's Lunar Reconnaissance Orbiter (LRO) is to identify and localize exposed water frost in permanently shadowed regions (PSRs) near the Moon's poles, and to characterize landforms and albedos in PSRs. In this paper we describe the in-flight radiometric performance and commissioning results and compare them to ground calibration measurements.

The Miniature Radio Frequency (Mini-RF) system is manifested on the Lunar Reconnaissance Orbiter (LRO) as a technology demonstration and an extended mission science instrument. Mini-RF represents a significant step forward in spaceborne RF technology and architecture. It combines synthetic aperture radar (SAR) at two wavelengths (S-band and X-band) and two resolutions (150 m and 30 m) with interferometric and communications functionality in one lightweight (16 kg) package. Previous radar observations (Earth-based, and one bistatic data set from Clementine) of the permanently shadowed regions of the lunar poles seem to indicate areas of high circular polarization ratio (CPR) consistent with volume scattering from volatile deposits (e.g. water ice) buried at shallow (0.1-1 m) depth, but only at unfavorable viewing geometries, and with inconclusive results. The LRO Mini-RF utilizes new wideband hybrid polarization architecture to measure the Stokes parameters of the reflected signal. These data will help to differentiate true volumetric ice reflections from false returns due to angular surface regolith. Additional lunar science investigations (e.g. pyroclastic deposit characterization) will also be attempted during the LRO extended mission. LRO's lunar operations will be contemporaneous with India's Chandrayaan-1, which carries the Forerunner Mini-SAR (S-band wavelength and 150-m resolution), and bistatic radar (S-Band) measurements may be possible. On orbit calibration, procedures for LRO Mini-RF have been validated using Chandrayaan 1 and ground-based facilities (Arecibo and Greenbank Radio Observatories).

The Diviner Lunar Radiometer Experiment on NASA's Lunar Reconnaissance Orbiter will be the first instrument to systematically map the global thermal state of the Moon and its diurnal and seasonal variability. Diviner will measure reflected solar and emitted infrared radiation in nine spectral channels with wavelengths ranging from 0.3 to 400 microns. The resulting measurements will enable characterization of the lunar thermal environment, mapping surface properties such as thermal inertia, rock abundance and silicate mineralogy, and determination of the locations and temperatures of volatile cold traps in the lunar polar regions.