Current Science

Prakash Chauhan ¹, Prabhjot Kaur ¹, N. Srivastava ², Rishitosh K. Sinha ², Nirmala Jain ¹, S. V. S. Murty ²

Affiliations
1 Space Applications Centre, (ISRO), Ahmedabad 380 015, IN
2 Physical Research Laboratory, Ahmedabad 380 009, IN

Abstract

Space exploration missions of planetary bodies in our solar system have provided new insights to understand their formation and evolutionary processes that such bodies have undergone leading to their current geological state. Remote sensing from orbiter mission has helped in identifying surface features, delineating surface topography, mapping surface composition and deriving reliable age estimates of different planetary surfaces. In particular, high spatial and spectral resolution spacecraft observations have significantly contributed to our current understanding of the geological, physical and chemical processes that resulted in divergent evolutionary paths undertaken by different planetary objects such as inner and outer planets, dwarf planets, the moons and small solar system bodies (asteroids and comets). Hyperspectral remote sensing has been an emerging field of space-based reflectance spectroscopy and in recent years many imaging spectroscopy instruments have flown on different planetary missions, e.g. Moon Mineralogy Mapper on-board Chandrayaan-1, VIMS on Cassini mission, CRISM on Mars Reconnaissance Orbiter (MRO) mission, etc. This article provides a review on imaging reflectance spectroscopy for understanding the surface composition through mineralogy for different planetary bodies.

Keywords

Hyperspectral Remote Sensing, Mineralogy, Planetary Surfaces, Solar Systems.

Full Text

   

Ami J. Desai ¹, S. V. S. Murty ¹

Affiliations
1 PLANEX, Physical Research Laboratory, Ahmedabad 380 009, IN

Abstract

Wind is currently the dominant active geological agent bringing about constant changes over the Martian surface. One of the most conspicuous resultant morphology derived is the formation of slope streaks, highly transient features that tend to develop and may completely disappear within a few ten of years. In this article a detailed analysis on the pattern, morphology and appearance of slope streaks within the central mound of the Nicholson crater on Mars, has been made and plausible reasons for their formation as well as darkening and fading mechanisms are discussed. We focus on some observations which indicate the role of wind in carving specific streak patterns. The morphological observations discussed, strongly support active aeolian processes and provide evidences in favour of the dust avalanche theory for the formation and current morphology of slope streaks in the Nicholson crater.

Keywords

Aeolian Activities, Craters, Morphology, Slope Streaks.

Full Text

   

M. Shanmugam ¹, S. V. Vadawale ¹, Arpit R. Patel ¹, N. P. S. Mithun ¹, Hitesh Kumar Adalaja ¹, Tinkal Ladiya ¹, Shiv Kumar Goyal ¹, Neeraj K. Tiwari ¹, Nishant Singh ¹, Sushil Kumar ¹, Deepak Kumar Painkra ¹, A. K. Hait ², A. Patinge ², Abhishek Kumar ³, Saleem Basha ³, Vivek R. Subramanian ³, R. G. Venkatesh ³, D. B. Prashant ³, Sonal Navle ³, Y. B. Acharya ¹, S. V. S. Murty ¹, Anil Bhardwaj ¹

Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN
2 Space Applications Centre, Ahmedabad 380 015, IN
3 U.R. Rao Satellite Centre, Bengaluru 560 017, IN

Abstract

Alpha Particle X-ray Spectrometer (APXS) is one of the two scientific experiments on Chandrayaan-2 rover named as Pragyan. The primary scientific objective of APXS is to determine the elemental composition of the lunar surface in the surrounding regions of the landing site. This will be achieved by employing the technique of X-ray fluorescence (XRF) spectroscopy using in situ excitation source ²⁴⁴Cm emitting both X-rays and alpha particles. These radiations excite characteristic X-rays of the elements by the processes of particle induced X-ray emission and XRF. The characteristic X-rays are detected by the ‘state-of-the-art’ X-ray detector known as Silicon Drift Detector, which provides high energy resolution, as well as high efficiency in the energy range of 1–25 keV. This enables APXS to detect all major rock forming elements such as, Na, Mg, Al, Si, Ca, Ti and Fe. The flight model of the APXS payload has been completed and tested for various instrument parameters. The APXS provides energy resolution of ~135 eV at 5. 9keV for the detector operating temperature of about –35°C. The design details and the performance measurement of APXS are presented in this paper.

Keywords

Alpha Particle X-Ray Spectrometer, CSPA, Silicon Drift Detector, X-Ray Spectrometer.

Full Text