Abstract Details
| Name: P Sreekumar Affiliation: IIA Conference ID: ASI2015_865 Title : Study of lunar surface chemistry using Swept Charge Devices Authors and Co-Authors : Subramania Athiray, Thesis supervisor- Dr. P. Sreekumar Abstract Type : Poster Abstract Category : Sun and the Solar System Abstract : The surface of the Moon is of prime scientific importance as it is very ancient and preserves record of early geological history of the solar system. The lunar surface has been explored extensively at multi-wavelengths through space-based experiments. This thesis deals with understanding the chemical composition of the lunar surface using x-rays. Since the Apollo era, there have been very a few successful observations of the x-ray studies of the lunar surface. The Chandrayaan-1 X-ray Spectrometer (C1XS) onboard Chandrayaan-1 was designed to map the abundances of major rock-forming elements viz., Mg, Al, Si, Ca, Ti and Fe on the lunar surface using the X-ray fluorescence (XRF) technique. In this thesis, we present a comprehensive summary of entire C1XS observations. The first direct spectral evidence of sodium (Na) along with other rock-forming elements from the Moon, as observed by C1XS is demonstrated. A detailed description on the spectral analysis of C1XS data is presented from where XRF line fluxes of major rock-forming elements are derived. An independent XRF inversion algorithm {\it x2abundance} is developed to convert the observed XRF line fluxes to elemental abundances. Algorithm and validation of {\it x2abundance} using laboratory XRF experiments, with metal alloys and lunar analogue rocks are presented. Lunar surface elemental abundances are determined for the C1XS-observed regions using the inversion algorithm. A summary of major findings from the C1XS experiment along with the scientific importance of the discovery of Na on the lunar surface are presented. Due to lack of solar x-ray activity and limited mission life-time, C1XS could not achieve global elemental mapping. Chandrayaan-2 Large Area Soft x-ray Spectrometer (CLASS) is being developed for Chandrayaan-2 to answer the questions raised by C1XS results and complete global mapping with enhanced sensitivity using new generation SCDs (CCD-236). A detailed physical model is developed to simulate x-ray photon interaction in SCDs. This Monte Carlo simulation aims at modeling device level interactions to better understand the spectral redistribution function of SCDs. Algorithm of the model, implementation and comparison with C1XS ground calibration data are presented. At the end, list of science cases for future lunar surface studies are presented. Further, to carry out better scientific investigations in future, a few design aspects which can potentially improve the surface exploration of the Moon/airless planetary bodies in xrays are also presented. |