Informatics Publishing Limited

R. P. Singh ¹, Somya S. Sarkar ¹, Manoj Kumar ¹, Anish Saxena ¹, U. S. H. Rao ¹, Arun Bhardwaj ¹, Jalshri Desai ¹, Jitendra Sharma ¹, Amul Patel ¹, Yogesh Shinde ¹, Hemant Arora ¹, A. R. Srinivas ¹, Jaya Rathi ¹, Hitesh Patel ¹, Meenakshi Sarkar ¹, Arpita Gajaria ¹, S. Manthira Moorthi ¹, Mehul R. Pandya ¹, Ashwin Gujrati ¹, Prakash Chauhan ¹, Kuriakose A. Saji ¹, D. R. M. Samudraiah ¹, A. S. Kiran Kumar ²

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 058, IN
2 Indian Space Research Organisation, Bengaluru 560 231, IN

Abstract

Thermal Infrared Imaging Spectrometer (TIS), which operates in the infrared spectral region (7-13 μm), is one of the five instruments on-board the Mars Orbiting Mission (MOM). TIS was designed to detect emitted thermal infrared radiation from the Martian environment, which would enable the estimation of ground temperature of the surface of Mars and also map its surface composition. TIS instrument is a grating-based spectrometer which has spatial resolution of 258 m at periapsis (372 km). TIS hardware was realized with light-weight miniaturized components (total weight 3.2 kg) with power requirement of 6 W. Observations from TIS instrument were carried out during Earth-bound manoeuvres and cruise phase operations of MOM and the results were found to be in agreement with the laboratory measurements.

Keywords

Aerosol Optical Thickness, Mars Orbiter, Minerals Detection, Thermal Infrared Spectroscopy.

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Mohit Arora ¹, Nandini Ray Chaudhury ¹, Ashwin Gujrati ¹, Ramesh Chandra Patel ²

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN
2 Department of Geophysics (Applied), Kurukshetra University, Kurukshetra 136 119, IN

Abstract

Coral reefs are one of the most ancient, highly productive marine bio-diverse ecosystems on earth. They are threatened to collapse under rapid climate change. ENSO is an extreme climate change event which elevates sea-surface temperature (SST) of tropical oceans. This elevated SST increases the level of thermal stress on coral reefs. Also, coral reefs are the most sensitive among all ecosystems due to temperature change; they exhibit bleaching when SST exceeds normal summer maxima and remains high for more than 28 days. Bleaching threshold, positive SST anomaly and degree heating week (DHW) are commonly used indices for calculating thermal stress on coral reefs. The major coral reef regions in India are Andaman, Nicobar, Lakshadweep, Gulf of Mannar and Gulf of Kachchh. SST from NOAA OISST v2 highresolution daily dataset at 0.25° global grids from 1982 to the present was used for the present study. Here, we focus on the variations in SST experienced by Indian coral reef regions during known mass coral bleaching (MCB) years, viz. 1998, 2010 and 2016. The year 2010 recorded the highest thermal stress for Andaman, Nicobar and Gulf of Kachchh regions, and the year 2016 was severe for Lakshadweep and Gulf of Mannar regions. In 2010 Nicobar was observed to be the most vulnerable according to DHW index.

Keywords

Bleaching Threshold, Degree Heating Week, Mass Coral Bleaching, Sea Surface Temperature.

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R. Ratheesh ¹, Nandini Ray Chaudhury ¹, Preeti Rajput ¹, Mohit Arora ¹, Ashwin Gujrati ¹, S. V. V. Arunkumar ¹, Ateeth Shetty ², Rakesh Baral ³, Rakesh Patel ⁴, Devanshi Joshi ⁴, Harshad Patel ⁴, Bharat Pathak ⁴, K. S. Jayappa ², R. N. Samal ³, A. S. Rajawat ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN
2 Mangalore University, Mangalagangorti, Mangaluru 574 199, IN
3 Chilika Development Authority, Bhubaneswar 751 014, IN
4 Gujarat Ecological Education and Research Foundation, Gandhinagar 382 007, IN

Abstract

This article highlights major scientific outcomes of the studies carried out using Airborne Visible/Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) airborne data over the coastal regions of Mangaluru, Gulf of Kachchh (GoK) and Chilika lagoon. Various hyperspectral remote sensing techniques involving bio-optical models and spectral classification algorithms are used to achieve different objectives related to coastal ecosystem monitoring. AVIRIS-NG airborne data are used to estimate particle size of suspended solids along the coastal waters of Mangaluru using an analytical optical model. The spatial distribution of particle size of the suspended solids in the coastal waters is brought out, while along the coastal land of Mangaluru, the beaches are classified based on uniform sediment characteristics using spectral matching algorithm. AVIRIS-NG data for Pirotan reef in GoK is analysed and species-level identification of the dominant brown macroalgae is carried out. Species-level distribution of brown macroalgae is mapped and used to study the microhabitat preference of different species. At Chilika lagoon, the AVIRIS-NG data are analysed to map the abundance of submerged seagrass using bio-optical model, which provides vital information to the coastal management community. The study asserts the importance of hyperspectral data and various advanced data analysis techniques related to the estimation of geophysical parameters of the coastal waters and monitoring the vital coastal ecosystems.

Keywords

Brown Macroalgae, Coastal Regions, Suspended Sediment Properties, Submerged Seagrass.

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S. Chander ¹, Ashwin Gujrati ¹, K. Abdul Hakeem ², Vaibhav Garg ³, Annie Maria Issac ², Pankaj R. Dhote ³, Vinay Kumar ³, Arvind Sahay ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation (ISRO), Ahmedabad 380 015, IN
2 National Remote Sensing Centre, ISRO, Hyderabad 500 037, IN
3 Indian Institute of Remote Sensing, ISRO, Dehradun 248 001, IN

Abstract

Remote sensing is a vital tool to assess water quality parameters in water bodies like rivers, lakes, estuaries and lagoons. All these fall under the category of optically complex waters (case 2), where water-leaving radiance is affected by optically active water constituents and bottom substrate. The present study estimates water quality parameters, viz. turbidity, suspended sediment concentration and chlorophyll in River Ganga in Buxar (Bihar), and Howrah (West Bengal) and Chilika lagoon (Odisha) using hyperspectral reflectance data of AVIRIS-NG. Concurrent ground-truth data of water samples were collected and simultaneous spectro-radiometer measurements were made in synchronous with the AVIRIS-NG flight over the study area. Semi-analytical simulation modelling followed by inversion and contextual image analysis-based methods were used for estimating the water quality parameters. Water turbidity maps were generated for both the study sites. Over Ganga river, water was relatively clear in Buxar (6.87–20 NTU, TSS 42–154 mg/l), while it was extremely turbid in Howrah (50–175 NTU, TSS 75–450 mg/l). In Chilika lagoon, water was more turbid in the northern sector, which may be due to the river input and resuspension from shallow bathymetry. The results suggest that the small-scale changes in turbidity due to point sources like river tributaries or sewerage discharges can be identified using hyperspectral data. The imaging spectroscopy data over water are a key source to find out potential locations of water contamination.

Keywords

Hyperspectral Data, Remote Sensing Reflectance, Semi-Analytical Algorithms, Spectroradiometer.

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R. P. Singh ¹, Shard Chander ¹, Ratheesh Ramakrishnan ¹, Ashwin Gujrati ¹, Rohit Pradhan ¹, Chirag Wadhwa ¹, A. S. Rajawat ¹, Raj Kumar ¹

Affiliations
1 Space Applications Centre, Indian Space Research Organisation, Ahmedabad 380 015, IN

Abstract

In this study we identify a region of submarine groundwater discharge (SGD) near Okha coast, Gujarat, India using thermal infrared remote sensing technique. Observations of brightness temperature (BT) in the thermal infrared spectral region (10.6–11.19 μm) from Landsat-8 satellite in the coastal region showed unique localized cooling in the Arabian Sea during winter. We observed lowering of BT in the range 0.6°– 2.3°C in the coastal region associated with SGD in comparison to sea surface temperature of the ocean during low-tide conditions. Consistent geographical pattern of thermal contrast was observed near the same location (lat. 22°26′54.43″N, long. 69°00′41.67″E) when multi date (11 datasets) thermal data were analysed between 2015 and 2019 in winter. Generally, low-tide conditions show more cooling of ocean surface at the SGD site compared to high-tide conditions, which indicates the process of SGD. Satellite-based assessment was further validated using field- and ship-based measurements.

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