Satellite remote sensing of soil related content for hydrological purposes have been considerably studied and developed over past three decades. This soil estimation by means of remote sensing depends upon the measurements of electromagnetic energy that has either been reflected or emitted from the soil surface and are accessible to remote sensing through measurements at the thermal infrared and microwave wavelengths. Recent advances in remote sensing, in the last few years, have shown that microwave techniques have the ability to measure soil moisture/wetness monitoring under a variety of topographic and vegetation cover conditions quantitatively. This is due to the all-weather and all-time capability of these data, as well as to their high sensitivity to water content in the soil.
This study utilize the approach to investigate the soil wetness variation over the Jammu and Kashmir(J&K), which experienced one of the worst floods in the past 60 years, during first week of September 2014, due to unprecedented and intense rains. The Soil Wetness Estimation (SWE) has been computed from the data acquired by real time direct broadcast (DB) receiving system installed at three places of India Meteorological Department (IMD) using microwave radiometer AMSU (Advanced Microwave Sounding Unit), flying aboard NOAA (National Oceanic and Atmospheric Administration) polar satellites. A multi-temporal analysis of AMSU channel 15 (at 89 GHz) and channel 1 (at 23 GHz) have been used to find the variation of SWE. In the present analysis, the proposed SWE indicator has been very well brought out the soil wetness changes specifically for the flood event which could give some indication of early 'signals' of an anomalous value of soil water content. In order to improve the forecast capabilities over the tropics, SWE approach is found to be promising for operational use.
Radiometric performances of earth observation satellite/sensors vary from ground pre-launch calibration campaign to post launch period extended to lifetime of the satellite due to launching vibrations. Therefore calibration is carried out worldwide through various methods throughout satellite lifetime. In India Indian Space Research Organization (ISRO) calibrates the sensor of Resourcesat-2 satellite by vicarious method. One of these vicarious calibration methods is the reflectance-based approach that is applied in this study for radiometric calibration of sensors on-board Resouresat-2 satellite. The results of ground-based measurement of atmospheric conditions and surface reflectance are made at Bap, Rajasthan Calibration/Validation (Cal/Val) site. Cal/Val observations at site were carried out with hyper-spectral Spectroradiometer covering spectral range of 350nm- 2500nm for radiometric characterization of the site. The Sunphotometer/Ozonometer for measuring the atmospheric parameters has also been used. The calibrated radiance is converted to absolute at-sensor spectral reflectance and Top-Of-Atmosphere (TOA) radiance. TOA radiance was computed using radiative transfer model ‘Second simulation of the satellite signal in the solar spectrum’ (6S), which can accurately simulate the problems introduced by the presence of the atmosphere along the path from Sun to target (surface) to Sensor. The methodology for band averaged reflectance retrieval and spectral reflectance fitting process are described. Then the spectral reflectance and atmospheric parameters are put into 6S code to predict TOA radiance which compare with Resourcesat-2 radiance. Spectral signature and its reflectance ratio indicate the uniformity of the site. Thus the study proves that the selected site is suitable for vicarious calibration of sensor of Resourcesat-2. Further the study demonstrates the procedure for similar exercise for site selection for Cal/Val analysis of other satellite over India region.
Lunar measurements are part of the calibration strategy for the instruments in Earth Observing System and satellites. The purpose of using moon as an absolute radiometric standard for calibration it is used solely as a diffuse reflector whose surface remains unchanged. INSAT-3D is India’s meteorological geostationary satellite an exclusive next-generation mission designed for enhanced meteorological observations having 6 channel imager and 18 channel sounder. INSAT-3D Spacecraft was dedicated to Nation at National Satellite Meteorological Center (NSMC) indigenously designed developed INSAT-3D Meteorological Data Processing System (IMDPS), commissioned at India Meteorological Department (IMD) New Delhi on January 15, 2014. The Moon is being observed from INSAT-3D regularly in the of full-disk operational image of earth with rectangular field of regard in IMDPS New Delhi. INSAT-3D measurements of lunar surface observed in Visible (0.55 - 0.75μm), Short Wave Infrared 1.55 - 1.70μm, Mid Wave Infrared (3.80 - 4.00μm), Water Vapor (WV) 6.50 - 7.10μm, Thermal Infrared (TIR) 1 & 2, 10.3 - 11.3μm & 11.5 - 12.5μm wavelength regions. The visible and infrared wavelengths region provide a new and intriguing methodology of distinguish in sensitivities of Earth observing radiometers.
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