Author: Ashish Joshi, IIRS

An oil spill is one of the worst environmental disasters which affect marine ecosystems due to anthropogenic activities. Oil spills can be detected, monitored, and studied using various types of remote sensing techniques. Synthetic Aperture Radar (SAR) is widely used in oil spill detection due to its all-weather and all-time capabilities. Oil Spills have a smooth texture and thus show a low backscatter in the SAR image due to the specular reflection. Oil spills appear as dark patches in the SAR image and produce a high contrast with respect to the ocean background. Recently, Liberian container vessel MSC ELSA 3 capsized around 25 km southwest of Alappuzha on May 25, 2025, near the Kerala coast when it was sailing from Vizhinjam port in Thiruvananthapuram to Kochi. A preliminary analysis has been done to detect the Kerala oil spills using the Earth Observation Satellite-4 (EOS-4) SAR satellite.

EOS-4 is a C-band ISRO’s SAR satellite that was launched using a Polar Satellite Launch Vehicle (PSLV-C52) on 14 February 2022. EOS-4 acquired the SAR image in Medium Resolution ScanSAR mode (MRS)  of the Kerala coast on 27 May 2025. Fig 1(b) shows the dark patch in the SAR image and appears to be a possible oil spill due to the sinking of the oil containers in the ocean. Fig 1(d) shows the detected oil spill pixels in the SAR image which appear to be scattered oil spill patches. The location of the detected oil spill patches matches with the published media reports. The analysis needs to be further investigated through other methods and available ground information.

Figure 1– Oil spill detection using EOS-4 SAR data

References

https://www.mod.gov.in/sites/default/files/Oil-Slick-Detected-after-Liberian-Container.pdf

https://www.thehindu.com/news/national/kerala/mod-confirms-sinking-of-liberian-ship-off-kochi-coast-with-640-containers-including-13-with-hazardous-cargo/article69616940.ece

Joshi, Ashish, Shefali Agrawal, and R. P. Singh. 2023. “Potential of EOS-4 Imagery for SAR Interferometry.” Remote Sensing Applications: Society and Environment 32 (April): 101010. https://doi.org/10.1016/j.rsase.2023.101010