Current Science

Ajay Kumar Patel ¹, Bhavani Kumar Yellapragada ¹, R. Vishnu ², M. V. R. Murti ¹, James Jebaseelan Samuel ³

Affiliations
1 Centre of Studies in Resources Engineering, Indian Institute of Technology-Bombay, Powai, Mumbai 400 076, IN
2 National Atmospheric Research Laboratory, Department of Space, Government of India, Gadanki 517 112, IN
3 Photonics, Nuclear and Medical Physics Division, VIT University, Vellore 632 014, IN

Abstract

We describe an indigenously developed dual polarization lidar (DPL) system for remote sensing of the range resolved properties of non-spherical nature of air borne and cloud particles. The DPL system probes the atmosphere using a linearly polarized second harmoni cNd : YAG laser. The design of receiver optics is such that it separates the collected back scattered light into parallel and perpendicular polarization components.The ratio of intensity of perpendicular to parallel signals is known as the depolarization ratio (DR), which is a gauge for non-spherical particle content in the atmosphere. The DPL employs an external irradiance standard to calibrate the depolarization measurements.Comparison of simultaneous measurements between DPL and a similar instrument validates the utility of the system for cloud and aerosol studies. The altitude profiles of DR derived from lidar signals potentially indicate the type of major particle layers in the atmosphere.

Keywords

Aerosols, Clouds, Laser, Polarization Lidar, Remote Sensing.

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Arindam Barua ¹, M. P. Premchand ¹, R. Vishnu ¹, Prabhat Kumar Dubey ¹, Jayachitra ¹, Ambili K. Gopinath ¹, S. Anitha ¹, Renjith Keezhoth ¹, Anil P. Madeckal ¹, D. Karthikeyan ¹, Sheethal Antony ¹, J. Suresh Babu ¹, R. Manohara Rao ¹, I. Sudar ¹, E. S. Padmakumar ¹

Affiliations
1 Vikram Sarabhai Space Centre, Indian Space Research Organization, Thiruvananthapuram 695 022, IN

Abstract

The navigation, guidance and control (NGC) system of Reusable Launch Vehicle – Technology Demonstrator (RLV-TD) is the most complex system ever flown in ISRO’s launches. It includes a navigation system employing traditional inertial navigation system along with global positioning system aiding and radar altimeter, ceramic servo accelerometer package, angle of attack-based control, different control systems, including secondary injection thrust vector control, reaction control system and aero control surfaces. Closed loop simulations of integrated NGC system of RLV-TD are of utmost importance to ensure mission success by assessment of system performance in nominal and off-nominal flight conditions. Validation is achieved through progressive evaluations in different levels of integrated simulation, namely autonomous simulations, software in loop simulation, on-board processor in loop simulation, hardware in loop simulation and actuator in loop simulation using Iron Bird test facility. This article discusses the overall NGC system, challenges faced during the realization of the simulation test bed, including system design to validate the new on-board elements, commissioning of Iron Bird facility and validation through various phases of simulation. The outcome of these simulations played a crucial role in bringing about improvements and helping in the evolution of the on-board system to the final configuration, ensuring the success of the mission.

Keywords

Control, Guidance, Integrated Simulation, Navigation, Reusable Launch Vehicles, Validation.

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R. H. Rizvi ¹, R. Vishnu ², A. K. Handa ², S. Ramanan ², M. Yadav ², A. Mehdi ², R. K. Singh ³, S. Londhe ³, S. K. Dhyani ³, J. Rizvi ³, Punam ⁴, Rameshwar Kumar ⁴, Naved Qaisar ⁵

Affiliations
1 ICAR-CSSRI Regional Research Station, Lucknow 226 005, IN
2 ICAR-Central Agroforestry Research Institute, Jhansi 284 003, IN
3 World Agroforestry, South Asia Regional Programme, New Delhi 110 012, IN
4 Himachal Pradesh Krishi Vishvidyalay, Palampur 176 062, IN
5 Sher-e-Kashmir University of Agriculture and Technology, Srinagar 190 025, IN

Abstract

In the present study, agroforestry was mapped in nine districts from Western Himalayan Region. The agroforestry area in these nine selected districts was estimated to be 332127.55 ha (12.4%). Salix alba, an important agroforestry species, accounted for about 12% of total agroforestry area in three districts of Kashmir valley

Keywords

Agroclimatic Zone, Agroforestry Mapping, Object-Oriented Classification, Remote Sensing, Tree Species.

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