Space Applications Centre Research Articles

Design and development of field radiometers for ground truth data collection at Antarctica

Four types of low-cost, multi-band, ground-truth radiometers have been indigenously developed at Space Applications Centre, Ahmedabad, for data collection at Antarctica. These instruments are easy to operate and portable. They are designed so as to incorporate a set of interference filters with desired spectral characteristics in the spectral region from 400 nm to 3000 nm. It is possible to tune these instruments for various types of remote sensing applications. The instruments have been calibrated in the absolute quantities of spectral radiance (w/cm2-sr-μ) and spectral irradiance (w/cm2-μ). The total radiometric calibration uncertainty including the uncertainty of standard source is of the order of ±3.5% for spectral irradiance and is of the order of ±7.5% for spectral radiance. All the instruments were tested and operated at Antarctica and voluminous radiometric ground truth data has been collected during 26th Indian Scientific Expedition to Antarctica. Measurements were carried out in terms of following parameters: a) spectral reflectance measurement of ice and fresh snow surfaces, b) terrestrial solar spectral irradiance: direct and global components. This paper gives salient features, specifications, theory of operation and description of these instruments. Some of the test results of the measured data collected at Antarctica are also presented.

Impact of Kalpana-1-Derived Water Vapor Winds on Indian Ocean Tropical Cyclone Forecasts

Abstract The water vapor winds from the operational geostationary Indian National Satellite (INSAT) Kalpana-1 have recently become operational at the Space Applications Centre (SAC). A series of experimental forecasts are attempted here to evaluate the impact of water vapor winds derived from Kalpana-1 for the track and intensity prediction of two Bay of Bengal tropical cyclones (TCs), Sidr and Nargis, using the Weather Research and Forecasting (WRF) modeling system. The assimilation of water vapor winds has made some impact in the initial position errors as well as track forecasts when compared with the corresponding control experiments for both TCs. However, no statistically significant improvement is noticed in the simulations of TC intensities [i.e., minimum sea level pressure (MSLP) and maximum surface winds forecasts when satellite winds are used for assimilation]. Moreover, the performance of Kalpana-1 winds is evaluated by repeating the same sets of experiments using Meteosat-7 winds derived at the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) and compared with observed data. The simulation of initial position errors, and track and intensity forecasts using the assimilation of water vapor winds from both satellites are comparable. Though, these results are preliminary with respect to the Kalpana-1 winds, the present study can provide some insight to the WRF model users over the Indian Ocean region.

The Moon sight by KALPANA imager

Visible and infra-red (IR) channel data of KALPANA imager received at Bopal Earth Station at Space Application Centre has captured the Moon at several times. The range of Moon surface brightness in the visible channel image is compared with that of similar size Earth scene. The increase in brightness due to a closer Moon on a particular day is also seen in the histogram of the surface brightness. The brightness temperature map from the IR channel data of the Moon is also constructed. The analysis of the Moon images has a potential for monitoring degradation of the sensor optics over time.

Advanced studies in strip pair processing of Cartosat‐1 data

AbstractWith the launch of the Indian remote sensing satellite Cartosat‐1, an along‐track stereoscopic imaging mission of the Indian Space Research Organisation (ISRO), new possibilities for operational availability of high‐resolution stereo‐imagery from space for the remote sensing and cartography user communities have emerged. The high‐resolution stereo data beamed from twin cameras on board the Cartosat‐1 mission facilitates topographic mapping up to 1:25 000 scale. The primary advantage of the Cartosat‐1 mission is seen in the generation of digital elevation models (DEMs) and the production of ortho‐images in an operational set‐up. This also facilitates 3D terrain visualisation for very large tracts of land. Stereo Strip Triangulation (SST) is a software system developed and perfected at the Space Applications Centre of ISRO for operational generation of secondary control and appropriate DEMs for subsequent use in the generation of ortho‐images. This system has been in use for almost 2 years at the National Remote Sensing Agency in Hyderabad, India, and has generated a wealth of data for use in topographic mapping. An initiative to generate a database of seamless, homogeneous DEMs and associated ortho‐image tiles at country level has been undertaken by ISRO. This data‐set has been named CartoDEM. The Cartosat‐1 data processing team has completed the design and testing of software for the generation of the CartoDEM. This software system has undergone detailed evaluation and currently is in the final stage of development of the operational procedures required to make maximum use of the capabilities of the Cartosat‐1 sensors. A data dissemination software system is currently under development. As part of the large‐scale evaluation exercises to finalise the specifications of CartoDEM, it is established that with the 2·5 m ground resolution, a base‐to‐height ratio of 0·62 and with capability to register conjugate points in the stereopair to sub‐pixel level, DEMs can be generated at 0·3 arc second intervals, with a height accuracy of 3 to 4 m, over tracts of undulating land mass up to 15 000 km2 with the use of 10 to 20 ground control points. The Cartosat‐1 data processing and evaluation team regularly monitors the radiometric quality of images. As part of the radiometric characterisation of sensors, the team computed point spread functions (PSFs) for the two cameras of Cartosat‐1. Special filters based on the PSFs then work to improve the radiometric quality of the images. Initial results from these exercises show good promise in image restoration based on PSFs for Cartosat‐1. This paper presents a summary of activities and exercises related to (i) Stereo Strip Triangulation, (ii) CartoDEM, (iii) image quality improvement using the PSF‐based image restoration and (iv) block adjustment exercises using a COTS software package. Also reported are the results of post‐launch experiments, study and evaluation of DEMs vis‐à‐vis ortho‐images from Cartosat‐1.

Development of Chlorophyll-$a$ Algorithm for Ocean Colour Monitor Onboard OCEANSAT-2 Satellite

An empirical chlorophyll algorithm has been developed using the coincident in situ chlorophyll-a and remote sensing reflectance Rrs measurements from global ocean waters. The basic data set used for developing the algorithm was obtained by merging the bio-optical data from the global NASA bio-Optical Marine Algorithm Data (NOMAD) (~2438 spectra from ~3000 stations) and from the waters of the northern Arabian Sea (~159 spectra) collected by the Space Applications Centre, Ahmedabad, India. The chlorophyll-a concentration ranged from 0.01 to 50.0 mg ldr m-3 for the data set used. Regression analysis between chlorophyll-a concentration and remote sensing reflectance in different bands and a combination of band ratios was performed. Algorithms using modified cubic polynomial (MCP) regression of Rrs ratios with chlorophyll-a concentration showed good estimates of chlorophyll-a in full range of 0.01 to 50.0 mg ldr m-3 of the merged data set. However, the best results were obtained by using MCP regression between maximum band ratio (MBR) of Rrs (443, 490, 510 nm)/Rrs 555 nm with chlorophyll-a concentration having an r2 of 0.96 and rms error of 0.12 for log-transformed data. The developed MBR-based algorithm named Ocean Colour Monitor (OCM)-2 chlorophyll algorithm was compared with the OC4v4 algorithm routinely used the for Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data processing. For the used data set, OC4v4 algorithm overestimated chlorophyll-a concentration for > 5.0 mg ldr m-3 and yielded an r2 of 0.90 with rms error of 0.23, when compared to the newly developed OCM-2 chlorophyll algorithm. It is proposed to use this OCM-2 chlorophyll algorithm with OCEANSAT-2 OCM data to be launched in the third quarter of the year 2008 by the Indian Space Research Organisation.

Vibration Damping on Graphite and KEVLAR(R)Composites Using Piezoceramic Powder Coatings: A Review

Some researchers have studied passive vibration damping using thin hybrid layer(s) of magnetostrictive powder coatings on a wide gamut of composite laminates. Although these magnetostrictive materials can be used for damping of thin flexible structural systems, in practice their use is limited in the domain of microwave spacecraft antenna applications because of electromagnetic interference (EMI) and electromagnetic coupling (EMC) issues at higher transmit and receive radio frequencies (RFs). Ultra-lightweight, high-frequency satellite reflectors made of high specific stiffness/high specific strength graphite and KEVLARcomposites, with stringent precision design requirements with respect to (w.r.t.) the root mean square surface error; pick up post-launch microvibrations in the deployed condition because of the movement of the three-axis gyros of the spacecraft or because of altitude correction exercises along with steep thermal gradients in the space domain. These vibrations at elevated temperatures need to be damped out, particularly in the passive domain, without affecting the overall stability of the spacecraft. Therefore, it is proposed to use particularly non-magnetic, thin hybrid piezoceramic powder coating(s) on one side of the graphite and KEVLAR® composites to cater for the microvibration suppression issue of the spacecraft reflectors. Moreover, at elevated temperatures, the adhesion of thin layers of piezoceramic materials on graphite and KEVLAR® composites also becomes an important issue, which needs to be addressed separately and has been reviewed at length. Therefore, in this paper, an attempt has been made to thoroughly review and investigate experimentally the use of the surface activation technique of RF plasma corona on composites along with coatings of thin hybrid layer(s) of high-sensitivity ferroelectrically soft, non-magnetic piezoelectric ceramic material for achieving passive vibration damping benefits on KEVLAR® and graphite composites with embedded KEVLAR® flexcore at varying temperatures. The surface activation has been performed using the plasma-etching approach to obtain improved adhesion of the piezoceramic material with composites at elevated temperatures. KEVLAR® and graphite composites were treated with RF plasma to modify the surface properties such that they contribute to the adhesion enhancement between plasma-treated polymer surfaces and the piezoceramic material coatings. We have referred to American Society for Testing and Materials (ASTM) standards for the finalization of test specimen sizes for the experimental work. Strain-dependent material damping in the thin piezoceramic passive layers on KEVLAR® and graphite composites leads to a typical nonlinear behavior at varying temperatures. Therefore, an Oberst vibrating beam technique has been chosen for experimentation on a cantilever specimen made of graphite and KEVLAR® in order to estimate the composite loss factor at elevated temperatures. The thin hybrid layer(s) of non-magnetic piezoceramic materials when coated on KEVLAR® and graphite substrates (on one side only) have given improved results w.r.t. passive structural damping at elevated temperatures with almost negligible weight penalty; this is with practically no EMI/EMC issues when tested separately for Ku-band frequencies at the Space Applications Centre, Indian Space Research Organization, Ahmedabad. The encouraging results, w.r.t. the enhanced passive damping at resonant frequencies for piezoceramic powder coated high specific stiffness/high specific strength graphite and KEVLAR® composites at elevated temperatures, may make the present investigation and review on piezocoated composites a possible candidate for high-frequency applications in future w.r.t. the microvibrations experienced in orbit by the reflectors of today's sophisticated Earth observation satellites, which are designed for stringent pointing accuracies and resolutions.

The Fe-Line Feature in the X-Ray Spectrum of Solar Flares: First Results from the SOXS Mission

We present the first results from the low-energy detector payload of the solar X-ray spectrometer (SOXS) mission, which was launched onboard the GSAT-2 Indian spacecraft on May 08, 2003 by the GSLV-D2 rocket to study solar flares. The SOXS low-energy detector (SLD) payload was designed, developed, and fabricated by the Physical Research Laboratory (PRL) in collaboration with the Space Application Centre (SAC), Ahmedabad and the Indian Space Research Organization (ISRO) Satellite Centre (ISAC), Bangalore. The SLD payload employs state-of-the-art, solid-state detectors, viz., Si PIN and Cadmium-Zinc-Telluride (CZT) devices that operate at near room temperature (−20 °C). The energy ranges of the Si PIN and CZT detectors are 4 – 25 and 4 – 56 keV, respectively. The Si PIN provides sub-keV energy resolution, while the CZT provides ~1.7 keV energy resolution throughout the energy range. The high sensitivity and sub-keV energy resolution of the Si PIN detector allows measuring the intensity, peak energy, and the equivalent width of the Fe-line complex at approximately 6.7 keV, as a function of time in all ten M-class flares studied in this investigation. The peak energy (Ep) of the Fe-line feature varies between 6.4 and 6.7 keV with increase in temperature from 9 to 58 MK. We found that the equivalent width (w) of the Fe-line feature increases exponentially with temperature up to 30 MK and then increases very slowly up to 40 MK. It remains between 3.5 and 4 keV in the temperature range of 30 – 45 MK. We compare our measurements of w with calculations made earlier by various investigators and propose that these measurements may improve theoretical models. We interpret the variation of both Ep and w with temperature as being to the changes in the ionization and recombination conditions in the plasma during the flare, and as a consequence, the contribution from different ionic emission lines also varies.

Validations of suspended sediment concentration (ssc) derived using ocean colour monitor (ocm) data off Chennai coast, India

Indian Remote Sensing Satellite (IRS) — P4 Ocean Colour Monitor (OCM) data were used to estimate Suspended Sediment Concentration (SSC) in the coastal waters off Chennai and to study the distribution along the coast. Surface water samples were collected during May and October 2000 synchronized with satellite overpass, and quantitative estimates of Suspended Sediment Concentration (SSC) were done. OCM — Data Analysis System (DAS) software developed by the Space Applications Centre, Ahmedabad was used for OCM data processing and analysis. The field data and OCM derived SSC showed a correlation of r = 0.85 and r = 0.95 for the months of May and October respectively.

Solar x-ray spectrometer (SOXS) mission – Low energy payload – First results

We present the first results from the ‘Low Energy Detector’ pay-load of ‘Solar X-ray Spectrometer (SOXS)’ mission, which was launched onboard GSAT-2 Indian spacecraft on 08 May 2003 by GSLV-D2 rocket to study the solar flares. The SOXS Low Energy Detector (SLD) payload was designed, developed and fabricated by Physical Research Laboratory (PRL) in collaboration with Space Application Centre (SAC), Ahmedabad and ISRO Satellite Centre (ISAC), Bangalore of the Indian Space Research Organization (ISRO). The SLD payload employs the state-of-the-art solid state detectors viz., Si PIN and Cadmium-Zinc-Telluride (CZT) devices that operate at near room temperature (-20°C). The dynamic energy range of Si PIN and CZT detectors are 4–25 keV and 4–56 keV respectively. The Si PIN provides sub-keV energy resolution while CZT reveals ∼1.7keV energy resolution throughout the dynamic range. The high sensitivity and sub-keV energy resolution of Si PIN detector allows the measuring of the intensity, peak energy and equivalent width of the Fe-line complex at approximately 6.7 keV as a function of time in all 8 M-class flares studied in this investigation. The peak energy (E p) of Fe-line feature varies between 6.4 and 6.8 keV with increase in temperature from 9 to 34 MK. We found that the equivalent width (ω) of Fe-line feature increases exponentially with temperature up to 20 MK but later it increases very slowly up to 28 MK and then it remains uniform around 1.55 keV up to 34 MK. We compare our measurements ofw with calculations made earlier by various investigators and propose that these measurements may improve theoretical models. We interpret the variation of both Epand ω with temperature as the changes in the ionization and recombination conditions in the plasma during the flare interval and as a consequence the contribution from different ionic emission lines also varies.

Surface Heat Fluxes over Global Oceans Exclusively from Satellite Observations

AbstractA new approach is introduced for determining surface latent heat flux (LHF) and sensible heat flux (SHF) over the global oceans exclusively from satellite observations. Measurements of wind speed (U), sea surface temperature (SST), near surface specific humidity (Qa), and air–sea temperature difference (ΔT = SST − Ta) are required for computing these fluxes by bulk formulas. To compute the heat fluxes exclusively from satellite data, U is obtained from Special Sensor Microwave Imager (SSM/I), SST is obtained from Advanced Very High Resolution Radiometer (AVHRR), empirical algorithm proposed earlier is used to compute ΔT, and a new one is developed to estimate Qa. The developed empirical equation for Qa estimations is an extension of the authors’ previous method. Compared to the Comprehensive Ocean–Atmosphere Data Set (COADS), the Qa retrieved by the previous approach had a negative bias of the order of more than 2 g kg−1 over the Gulf Stream and Kuroshio during winter but had a positive bias of more than 2 g kg−1 over the Arabian Sea and the Bay of Bengal during summertime. The new empirical equation takes into account these seasonal biases over the Gulf Stream, Kuroshio, and the Arabian Sea. Compared to COADS observations, the Qa retrieved from the developed empirical equation has global mean root mean square error (rmse), bias, and correlation of the order of 0.55, −0.007, and 0.98 g kg−1, respectively.Compared to COADS, the satellite-derived monthly mean LHF has global mean rmse, bias, and correlation of the order of 20, 6, and 0.97 W m−2, respectively. Likewise, satellite-derived monthly mean SHF has global mean rmse, bias, and correlations of the order of 6, 0.4, and 0.98 W m−2, respectively. The monthly fields show that the spatial patterns and seasonal variability of satellite-derived latent and sensible heat fluxes are generally good in agreement with those of the COADS and earlier satellite-derived fluxes.Sixteen-year (January 1988–December 2003) datasets of surface heat fluxes and basic input parameters over the global oceans have been constructed using SSM/I and AVHRR data. This dataset has a spatial resolution of 1° × 1° latitude–longitude and temporal resolution of one month. This unique dataset is constructed exclusively from satellite observations, and it can be obtained from the Meteorology and Oceanography Group Space Applications Centre.

Multi-Crop separability study of Rabi Crops using Multi-Temporal satellite data

Space Applications Centre, Indian Space Research Organisation, Ahmedabad - 380 015, India "Indian Institute of Remote Sensing, Dehra Dun-248001, India @Corresponding author : spvyas@sac.isro.org Pre-harvest estimation of crop acreage and yield are very important for crop production forecasting. A number of studies have been carried out under the Remote Sensing Applications Mission (RSAM) programme to operationalise the methodology for crop-acreage estimation using remote sensing (RS) data and sampling approaches. Procedures for use of RS data in crop acreage and production forecasting have been developed in India since 1983 (Dadhwal

Remote sensing of spectral signatures of tropospheric aerosols

With the launch of the German Aerospace Agency's (DLR) Modular Opto-electronic Scanner (MOS) sensor on board the Indian Remote Sensing satellite (IRS-P3) launched by the Indian Space Research Organization (ISRO) in March 1996, 13 channel multi-spectral data in the range of 408 to 1010 nm at high radiometric resolution, precision, and with narrow spectral bands have been available for a variety of land, atmospheric and oceanic studies. We found that these data are best for validation of radiative transfer model and the corresponding code developed by one of the authors at Space Applications Centre, and called ATMRAD (abbreviated for ATMospheric RADiation). Once this model/code is validated, it can be used for retrieving information on tropospheric aerosols over ocean or land. This paper deals with two clear objectives, viz., 1 Validation of ATMRAD model/code using MOS data and synchronously measured atmospheric data, and if found performing well, then to 2 derive relationship between MOS radiances and Aerosol Optical Thickness (AOT). The data validation procedure essentially involves •near-synchronous measurements of columnar aerosol optical thickness and altitude profiles of aerosol concentration using ground-based multi-filter solar radiometers and Argon-ion Lidar, respectively and •computation of the top-of-the-atmosphere (TOA) radiances from a low reflecting target (near clear water reservoir in the present study) using the ATMRAD model. The results show that the model performance is satisfactory and a relationship between the spectral parameters of MOS radiances and aerosol optical thickness can be established. In this communication, we present the details of the experiments conducted, database, validation of the ATMRAD model and development of the relationship between AOT and MOS radiance.

Quantitative study on chlorophyll using IRS-P4 OCM data of Tuticorin coastal waters

Quantification of Chlorophyll using IRS-P4 OCM data was attempted. OCM-DAS software developed by Space Applications Centre, Ahmedabad was used in data analysis. The results showed considerable variations in nearshore (case 2) waters due to interference from yellow substance and suspended sediments. However, in offshore areas (case 1) the measurements showed good correlations. The r values are 0.663 for nearshore waters and 0.892 for offshore waters.

Field based spectral reflectance studies to develop NDSI method for snow cover monitoring

Snow is highly reflective in the visible region of the electromagnetic spectrum making it possible to easily distinguish on a satellite image. However, cloud cover and mountain shadows pose a serious problem in the identification of snow in a mountainous region. Therefore, to identify snow in such an environment, a Normalized Difference Snow Index (NDSI) has been applied. The NDSI is based on the high reflectance of snow in the visible region and its low reflectance in the SWIR region, whereas, reflectance of cloud remains high compared to snow in the SWIR region. Efforts have been made to carry out field observations on reflectance of various land features near Manali in Himachal Pradesh (HP) to develop NDSI values for identifying snow. Field data have been collected using three field radiometers, viz., Multi-band Ground Truth Radiometer (GTR) operating in the 12 spectral bands ranging from visible to near-infrared wavelengths, Near-Infrared Ground Truth Radiometer (NIGTR) operating in the SWIR range, and Ratio-Radiometer (RR) operating in two spectral bands, one in the visible range, and another band in the SWIR range. All these three field radiometers have been designed and developed indigenously at the Space Applications Centre (ISRO), Ahmedabad. NDSI values for all types of snow, such as, fresh, clear, patchy and wet, have been found to be in the range 0.9 to 0.96. In addition, the NDSI value for snow under mountain shadow is found to be more than 0.9. This suggests the use of NDSI method for snow cover monitoring under mountain shadow. NDSI values for other land features such as soil, vegetation, and rock were substantially different than snow. However, water bodies have NDSI values close to snow and they need to be masked during snow cover delineation using NIR band.

Quality Governance for Developing High Reliable Satellite Systems

Click to increase image sizeClick to decrease image size Additional informationNotes on contributorsP L KulkarniP L Kulkarni born on 4th September 1949, obtained ME (Electronics & Telecommunication) from Univeristy of Pune and joined ISRO in September 1973.At present, he is designated as Deputy Project Director-Product Assurance (Pay-loads) for all INSAT-3 series of satellites and also the Head of the Quality Assurance Electronics Division (QAED), of Systems Reliability Group in Space Applications Centre, ISRO, Ahmedabad. He started his career in the field of Test & Evaluation in 1977, and since then he has significantly contributed in the areas of Quality Assurance and Test & Evaluation of Indigenously developed payloads for operational Remote Sensing satellites of IRS-series and Goestationary satellites of INSAT-series. Significant and effective contribution is made in the design and implementation of environmental tests levels for complex communication payloads of INSAT series. He ensured the successful completion of Reliabiltiy Engineering related activities including Reliability assessment, Derating Analysis, FMECA, FTA, etc at the early stage of the projects.He was fully involved in the generation & successful execution of Product Assurance plans for the space hardware developed for INSATs. His contribution was noted significantly in the technical evaluation of Non-standard RF& Microwave parts and subsystems to be used in the operational satellite payloads having long mission life, procured from US and European vendors. Test & Evaluation is one of the prime atributes to the payloads Quality Assurance, wherein his contribution was during testing and performance evaluation & analysis including the Finalization retest philosophy, etc.He has been actively involved in the indigenisation activities of various electronic components, RF subsystems, etc. He has guided the Indian industries to come up to the mark to deliver space-qualified products and maintain a fabrication line for such hi-rel products.

Satellite data in monsoon researchSatellite data in monsoon research

The Space Applications Centre of the Indian Space Research Organization is engaged in exploring and demonstrating the application of satellite observation in various disciplines. In this review paper the utilization of satellite data in monsoon research, in progress at SAC and ISRO Headquarters is described: Most of the studies use satellite data in combination with insitu data.

Urban land use mapping and zoning of Bombay Metropolitan Region using remote sensing data

Bombay Metropolitan Region covering an area of about 4,360 sq. km. was selected for urban land use studies and for urban land use zoning. Urban land use mapping was carried out using SPOT multispectral linear array imagery on 1∶25,000 scale employing visual analysis tehcniques. Fifteen maps were prepared depicting the spatial distribution of various urban classes in the Greater Bombay and New Bombay regions. Sixteen urban land use maps were also prepared using Landsat TM data showing the distribution of land use pattern on 1∶50,000 scale for the entire metropolitan region. Urban land use zoning was carried out based upon suitability index on 1∶250,000 scale. This map provides information on the areas to be used for construction and areas to be kept under green belt in the metropolitan region. This study is a joint venture of Space Applications Centre with Bombay Metropolitan Development authority.

Synchronization of Pseudo Noise Spread Spectrum Signals

Importance of synchronization and different synchronization methods in spread spectrum systems are indicated. Serial search for code acquisition and non-coherent Delay Lock Loop (DLL) for code tracking are explained in detail alongwith the various design considerations, implementation problems etc. The performance of a code synchronizer at 2 Mbps developed for Spread Spectrum Multiple Access (SSMA) experiment via APPLE satellite has been described. An improved code synchronizer at 20 Mbps being developed for use in a Large Channel Capacity Spread Spectrum system currently under development at Space Applications Centre (SAC), ISRO, Ahmedabad has also been presented.

Experimental Results of Spread Spectrum Multiple Access Communication System

The development of Pseudo Noise (PN) type Spread Spectrum Multiple Access (SSMA) Communication system at Space Applications Centre, ISRO, Ahmedabad, is described. The spread spectrum voice communication experiments conducted at ISRO's Earth Stations at Ahmedabad and Delhi through APPLE, the First Indian Experimental Communication Satellite have been described and test results obtained have been presented.

Application of digitally processed and enhanced LANDSAT imagery for geological mapping and mineral targeting in the Singhbhum Precambrian mineralized belt, Bihar-Orissa

Abstract Standard methods of digital processing and enhancement techniques have been followed to generate linearly stretched band products, band-to-band ratio images and normal and ratio colour composites from LANDSAT multispectral data on computer compatible tapes for nine test areas in the Singhbhum Precambrian mineralized belt. The software has been developed at the Space Applications Centre Laboratory, Ahmedabad, The data products have been subjected to general assessment and geological evaluation by visual interpretation methods. The study has resulted in a number of significant conclusions regarding utility and optimization of data products, stratigraphic lithologic and structural interpretations, identifying guides for mineralization and spectral characterization of major rock types.