Remote sensing of lunar surface

Abstract

Remote Sensing of Lunar Surface has provided its Topographic, Geo-chemical composition, Radiation dose and Mineralogical information of Lunar Surface. The Indian Space Research Organisation's (ISRO) Chandrayaan-1 and National Aeronautical Space Administration's (NASA) Lunar Reconnaissance Orbiter (LRO) have different type of sensors for measuring and mapping of the entire Lunar Surface. For the Mapping of Topographical features Chandrayaan-1 has Terrain Mapping Camera (TMC), while Lunar Reconnaissance Orbiter (LRO) has Lunar Reconnaissance Orbiter Camera (LROC). For determination of Chemical and Mineralogical features Chandrayaan-1 has Lunar Laser Ranging Instrument (LLRI) and Lunar Reconnaissance Orbiter (LRO) has Lunar Orbiter Laser Altimeter (LOLA) instrument. The mapping of Geo-chemicals has been done by Chandryaan-1 X-ray spectrometer (C1XS) and High Energy X-ray Spectrometer (HEX) onboard Chandrayaan-1 and Lunar Exploration Neutron Detector (LEND) onboard Lunar Reconnaissance Orbiter (LRO). The knowledge of mineral composition has been used for getting information about the evolution history of Moon. For this purpose the Chandrayaan-1 has Hyper Spectral Imager (HySI), near Infrared Spectrometer (SIR-2) and Moon Mineralogical Mapper (M3 ) and Lunar Reconnaissance Orbiter (LRO) has Lyman alpha Mapping Project (LAMP). Radiation dose measurement is also important for designing the sensors and future manned missions. Therefore, Chandrayaan-1 has Radiation Dose Monitor (RADOM) and Lunar Reconnaissance Orbiter (LRO) has Cosmic Ray Telescope for determination of the Effect of Radiation (CRaTER). For the measurement of Backscattered or Energetic Neutral Atoms (ENAs) and predetermination of surface for future landing missions Chandrayaan-1 has Subatomic Reflection Analyser (SARA) and Moon Impactor Probe respectively along with the other payloads. The LRO has the Diviner Lunar Radiometer Experiment (DLRE) for measuring the temperature fluctuations, rough terrain and other landing hazards similar to Moon Impactor Probe (MIP) onboard Chandrayaan-1. The active microwave sensors Miniature Synthetic Aperture Radar (Mini-SAR) onboard Chandrayaan-1 and Mini-RF onboard Lunar Reconnaissance Orbiter (LRO) have been used for identifying the traces of water in form of ice in the permanently shadowed regions at the poles of the Moon. The Mini-SAR instrument onboard Chandrayaan-1 has a primary antenna which transmits single right circularly polarized signal and receives the dual polarized (Left and Right) signal. While the antenna of Miniature Radio Frequency Radar (Mini-RF) onboard LRO transmits either left or right circularly polarized signal and then receives horizontal and vertical polarized signals. The observations based on Circular Polarization Ratio (CPR>1) as well as m-chi (0 to 0.2) parameters and backscattering coefficient less than -15dB have helped in determining the presence of water-ice, differentiate the water-ice from rock abundances, surface and sub-surface characteristics for identifying the Possible landing sites for the future lunar missions. Quantification of water-ice in the Hermite-A crater gives the confirmation that only Circular Polarization Ratio (CPR) is not sufficient for identifying water-ice. The other parameters like m-chi and backscattering coefficient values must be taken into the consideration for distinguishing between water-ice and rocky terrains. The Dielectric properties of Terrestrial Analogue of Lunar Soil (TALS) have been studied and compared with the Apollo samples at different microwave frequencies. The study of variations in complex permittivity of TALS having different percentages of water has been done at different temperatures. The variable Permittivity mapping of lunar surface has been done by using datasets of Microwave Radiometer (MRM) onboard Chang'e-1 and Diviner onboard LRO. The success of Chandrayaan-1 and Lunar Reconnaissance Orbiter (LRO) has greatly helped Scientist to go for further investigations in the areas of water-ice using microwave sensors for future missions for exploration the Moon.