The Center for Atmospheric Sciences | » Alok K. Shrestha

    • MSc, Electrical Engineering, South Dakota State University, 2010

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      alok.k.shrestha@nasa.gov

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      Recent News:

      May 8, 2015 : APS Gradstudent Aids Nepal Earthquake Relief

      Alok Shrestha, an APS Graduate Student, is offering his expertise in satellite-based remote-sensing to guide the relief efforts following the disastrous earthquake in Nepal on April 25th, 2015. Alok and his wife are from Nepal — their family members are okay, but have been living outdoors due to the frequent aftershocks. Alok was interviewed on […]


  • Alok K. Shrestha

    Alok is a part-time Phd student since 2011 at the department of Atmospheric and Planetary Science, Hampton University, USA. He received his Bachelor degree in Electronics Engineering in 2003 from Tribhuvan University, Nepal and Master of Science degree in Electrical Engineering in 2010 from South Dakota State University (SDSU), USA.  He has a year of experience working as a lecturer in an engineering college and several years of experience working as a Sr. system engineer for telecommunication projects. He developed his interest in the remote sensing area while having his Master Degree at SDSU. He worked there as a graduate research assistant and imaging engineer, developing algorithms to perform absolute and cross-calibration of various satellite sensors to evaluate their performance, including radiometric characterization. His familiarization with satellite instruments includes broadband, multi-spectral, as well as hyper spectral sensors, including pushbroom and whiskbroom instruments.

    Further, he is currently working as a Research Scientist at SSAI, contractor for NASA Langley Research Center. He is involved in reprocessing the climate & radiation datasets provided by ERBE (Earth Radiation Budget Experiment) instruments, particularly ERBE scanner and non scanner, including their calibrations. These instruments primarily measured the solar radiation reflected from the Earth including terrestrial radiation emitted by the Earth since 1984 to 1999 which assists in developing the Earth radiation budget. The study and accurate estimate of these radiation budgets are important to understand radiative forcing causing the global climate change for the Earth.  The primary objective of this reprocessing effort is to improve the accuracy of climate and radiation data provided by ERBE instruments and develop a consistent longterm data records, comparable to that provided by more recent CERES instruments since 1999. The consistent longterm data record of the Earth’s radiation budget will assist in better understanding of its effect to climate change and improve the prediction models.

    Project: Unfiltering Earth Radiation Budget Experiment (ERBE) Scanner Radiances Using the CERES Algorithm and Its Evaluation with Nonscanner Observations

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    The NOAA-9 Earth Radiation Budget Experiment (ERBE) scanner measured broadband shortwave, longwave, and total radiances from February 1985 through January 1987. These scanner radiances are reprocessed using the more recent Clouds and the Earth’s Radiant Energy System (CERES) unfiltering algorithm. The scene information, including cloud properties, required for reprocessing is derived using Advanced Very High […]

    Project: Relative Gain Characterization and Correction of Pushbroom Sensors Based on Lifetime Image Statistics and Wavelet Filtering

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    Developed a tool that is able to reduce stripes from imagery acquired by pushbroom sensors caused by detector-to-detector non-uniform response. This tool concentrates on two methods for the minimization of stripes. The first method estimates the best set of relative gains by identifying the best type of image based on histogram equalization from the lifetime […]

    Project: Dome Degradation Characterization of Wide-Field-of-View Nonscanner aboard ERBE and its Reprocessing

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    Earth Radiation Budget Experiment (ERBE) wide-field-of-view (WFOV) nonscanners aboard ERBS and NOAA-9/NOAA-10 provided broadband shortwave and longwave irradiances from 1985 to 1999. The previous analysis showed dome degradation in the shortwave nonscanner instruments. The correction was performed with a constant spectral (gray assumption) degradation. We suspect that the gray assumption affected daytime longwave irradiance and […]

    Project: Assessment of Spectral, Misregistration, and Spatial Uncertainties Inherent in the Cross-Calibration Study

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    Cross-calibration of satellite sensors permits the quantitative comparison of measurements obtained from different Earth Observing (EO) systems. Cross-calibration studies usually use simultaneous or near-simultaneous observations from several spaceborne sensors to develop band-by-band relationships through regression analysis. The investigation described in this paper focuses on evaluation of the uncertainties inherent in the cross-calibration process, including contributions […]