NOPR Collection:

Emission and scattering behaviour of bare and vegetative soil surfaces of different moist states by microwave remote sensing

2013-02-01T00:00:00Z

Title: Emission and scattering behaviour of bare and vegetative soil surfaces of different moist states by microwave remote sensing Authors: Gupta, V K; Sharma, Neeta; Jangid, R A Abstract: Dielectric constant (ε′) and dielectric loss (ε′′) of artificially moistened soil of Alwar have been determined at microwave frequency 9.78 GHz and at temperature 32.5°C using wave guide cell method. In view of the active and passive microwave remote sensing, the horizontal-horizontal radar backscattering coefficient () for bare and vegetative soil surface have been estimated by Integral Equation Model (IEM) and Water Cloud Model (WCM), respectively using ε′ and ε′′ of soil and view angle as input parameters. The horizontal component of microwave emissivity (e_h) for bare soil surfaces have been determined by emissivity model. The e_hfor vegetative soil surfaces determined by radiative transfer equation using suitable vegetation dependent parameters, like single way vegetation transmissivity and single scattering albedo (ω) for agricultural vegetation, respectively. The present study reveals that the for bare and vegetative soil surface exhibit a positive correlation with soil moisture content (SMC). Vegetative soil surface is lower than that of bare soil surface for the same values of SMC and view angle. Further, e_h for bare and vegetative soil surfaces decreases with an increase in SMC. Vegetative soil surface emissivity is higher than that of bare surface for the same values of SMC and observation angle. Further, backscattering coefficient and emissivity for bare and vegetative soil surfaces decrease as the angle of observation increases due to contribution of diminished coherent component. Page(s): 42-51

Ionospheric electron and ion temperatures response to seismic activity

2013-02-01T00:00:00Z

Title: Ionospheric electron and ion temperatures response to seismic activity Authors: Sharma, D K; Bardhan, A; Rai, Jagdish Abstract: A connection between earthquake and ionosphere has been proposed in the last few decades. A number of hypotheses have been suggested as the earthquake precursory to reduce the hazard of life and property but could not succeed. In the present study, effort has been made to correlate the ionospheric temperature anomalies to seismic activities. The ionospheric electron and ion temperatures were measured with the help of Retarding Potential Analyzer (RPA) payload aboard the Indian SROSS-C2 satellite. The data is used for the period 1995-1998 in the altitude range 430-630 km over the Indian region. The details of seismic events during this period were downloaded from the United State Geological Survey (USGS) website. The normal day ion and electron temperatures have been compared to the temperatures recorded during the seismic event. It has been observed that there is significant enhancement in the electron and ion temperatures. The electron temperature was enhanced by 1.2 - 1.5 times compared to the average normal day electron temperature. However, the ion temperature was 1.1 - 1.3 times over the average normal day ion temperature. The satellite data was analysed for corresponding seismic event duration in such way that the other possible effects are eliminated. Page(s): 18-26

Ionospheric TEC variations during the ascending solar activity phase at an equatorial station, Uganda

2013-02-01T00:00:00Z

Title: Ionospheric TEC variations during the ascending solar activity phase at an equatorial station, Uganda Authors: Oron, S; D’ujanga, F M; Ssenyonga, T J Abstract: The total electron content (TEC) is a vital and most dominant ionospheric parameter that can cause Global Positioning System (GPS) signal delays, signal degradation and in extreme cases loss of lock. This results into inefficient operations of ground and space based Global Navigation Satellite System (GNSS) applications. The study of TEC variability is, therefore, useful for GNSS users in order to minimize errors where high levels of accuracy in measurements are required. This paper presents the diurnal, seasonal and solar activity dependence of TEC at the GPS-SCINDA (SCIntillation Network Decision Aid) station in Kampala, Uganda (geographic coordinates: latitude 0.3°N, longitude 32.6°S; and geomagnetic coordinates: latitude -9.3°, longitude 104.2°) for the years 2010 and 2011. The results obtained show that the diurnal variability in TEC at this station has a pre-dawn minimum followed by an early morning steady increase, an afternoon maximum and then a post sunset gradual reduction in TEC, with the equinoctial months depicting nighttime enhancements more prominently at around 2000 hrs UT (2300 hrs LT). Scintillation occurrence, a consequence of TEC fluctuations, was observed from about 1800 hrs UT (2100 hrs LT) to local midnight giving S₄ index values above 0.4, with the equinox months recording higher occurrences than other seasons. TEC variations were also seen to exhibit solar activity dependence. The sunspot numbers and the F10.7 solar flux exhibited a good correlation with TEC recorded over the two years. Page(s): 7-17

Oil spill detection using SSM/I satellite data over Bombay High location in Arabian Sea

2013-02-01T00:00:00Z

Title: Oil spill detection using SSM/I satellite data over Bombay High location in Arabian Sea Authors: Calla, O P N; Dadhich, Harendra Kumar; Singhal, Shruti Abstract: Oil spill pollution is a severe environmental problem, which persists in marine environment or in inland water across the world. It has grown to an alarming magnitude with increased levels of oil production and transport. Thus, it is important to study and analyze this environmental pollution. The study and detection of oil spills can only be accomplished by satellite microwave remote sensing techniques. As microwaves have unique all weather penetration capability and can be used both in day and night, it does not require illumination of target from the sun. Two types of microwave sensors [Ulaby F T et al. Microwave remote sensing – Active and passive, Vol 1 and 3, 1981] exist: one is passive sensor and other active sensor. Passive microwave sensor is radiometer that operates in the microwave region and detects microwave radiation emitted by the earth surface in addition to passively sensing emissions coming from objects on Earth. Active microwave sensor emits microwaves toward the earth's surface. These microwaves are reflected back from earth's surface and return back to the sensor. In this paper, for the detection of oil spills, data of passive microwave sensors onboard Special Sensor Microwave/Imager (SSM/I) [Hollinger J et al. Special Sensor Microwave/Imager user’s guide, 1987, 120] satellite at 19.3 GHz frequency is used and analyzed. The analyses shows sudden decrease of brightness temperature values in both horizontal and vertical polarization over the oil spill area (Bombay High Area, Arabian Sea) when compared to the brightness temperature values over oil free area in the Arabian sea. Page(s): 52-59