Wikipedia : “The Sanchi oil tanker collision occurred on 6 January 2018 when the Panamanian-flagged, Iranian-owned tanker Sanchi, with a full natural-gas condensate cargo of 136,000 tonnes (960,000 barrels), sailing from Iran to South Korea, collided with the Hong Kong-flagged cargo ship CF Crystal 160 nautical miles (300 km) off Shanghai, China. The Sanchi oil spill (China) Sanchi caught fire shortly after the collision; after burning and drifting for over a week, it sank on 14 January.[1] None of the Sanchi' 32 crew members survived.[1] The crew of the CF Crystal was rescued and the ship made port in China. The financial damage of the Sanchi's sinking, based on NIOC seen by Sentinel-1 / 2 / 3 estimates, is around USD 110 million: USD 60 million for the 2D_layer_stack cargo and USD 50 million for the vessel itself.” Fig.1: Locations of the five (5) views of the “Sanchi” oil spill identified from Sentinel images. Sanchy drift path given by 6 January “Le Monde” newspaper collision dated 20 January 2018 4. Sentinel-2 MSI - 2018-01-20 02:10:09 5. Sentinel-1 C-SAR IW - 2018-01-20 09:28:53 5 14 January 115m sinking 1 2 4 1. Sentinel-3 OLCI - 2018-01-14 01:38:58 2. Sentinel-2 MSI - 2018-01-15 02:10:21 3 3 Sentinel-2 MSI - 2018-01-18 02:20:21 Fig.2: Financial Tribune: Image of Sanchi oil tanker on 14 January 2018. HYP-062-VtWeb powered by _______ Except in case of specular reflection (reflection of the Sun on the surface of the sea), it is very rare to distinguish a oil slick on the View 1 - Sentinel-3 OLCI - MR optical surface of the sea. Here we observe the intense combustion of the boat and its cargo a few hours before its sinking. • Sentinel-3 OLCI acquired on 14 January 2018 at 01:38:58 GMT Fig.3: Colour composition 10,5,1 close to natural colours. 2D_view HYP-062-VtWeb powered by _______ The drift of oil slicks is due to the combined action of ocean currents and surface winds. The wind field produced by the ECMWF applying to the January 15 at 00:00 hours shows View 2 - Sentinel-2 - HR optical relatively weak east winds (5 to 6 m/s) while the area is crossed by the powerful "Kuroshio Current" which produces a dominant eastward drift. • Sentinel-2 MSI (13 tiles) acquired on 15 January 2018 at 02:10:21 GMT The large coloured slick whose diameter approaches 46 km is probably the witness of one oil slick having drifted of about 120 km in less than 24 hours (to be confirmed). Fig.4: Colour composition 11 (SWIR), 4 (Red), 2 (Blue). 2D_view a b c HYP-062-VtWeb powered by _______ When the sky is clearer, the colour composite 4,3,2 in true colours shows the extent of this gigantic oil spill whose visible part represents 100 km of width by 200 km of height, that is a View 3 - Sentinel-2 - HR optical surface of 20,000 square km. It can be assumed that the extent is at least doubled in the eastern part because of the aspiration effect of the "Kuroshio • Sentinel-2 MSI (5 tiles) acquired on 18 January 2018 at 02:20:21 GMT Current"! Fig.5: Colour composition 4,3,2 Natural colours. 2D_view HYP-062-VtWeb powered by _______ In optical imaging, colours can also be due to absorptions of different wavelengths in the atmosphere. We note here View 4 - Sentinel-2 - HR optical variations in optical thickness of the blue certainly due to partial evaporation of the oil slick. • Sentinel-2 MSI (17 tiles) acquired on 20 January 2018 at 02:10:09 GMT Fig.6 Colour composition 11,4,2 showing the full swath (a), the 75 km slick (c) and a zoom (b). 2D_view a b c HYP-062-VtWeb powered by _______ Radar imagery is the most relevant remote sensing technic to monitor oil spills. The surface tension induced by the oil film breaks the wavelets produced by the wind. The backscattered View 5 - Sentinel-1 - Radar signal returns to the radar instrument with less intensity leading to significantly darker spots in the radar image.. Be careful, however, all black spots in the radar image are not necessarily • Sentinel-1 IW (3 scenes) acquired on 20 January 2018 at 09:28:53 GMT witnesses of oil slicks. • Sentinel-1 IW (4 scenes) acquired on 20 January 2018 at 21:33:12 GMT Six days after the sinking, the strong Kuroshio Current continues to drag oil spills along a line heading for the Japanese islands. Fig.7: Sentinel-1 on 20 January 2018 - Over GEBCO bathymetry (left) and CMEMS water velocity (right). 2018-01-20 21:33:12 6 January collision 2018-01-20 09:28:53 14 January 115m sinking Kuroshio current Fig.8: Oil spill of along the Kuroshio current towards the “Water velocity” product of CMEMS. 2D_view 63 km HYP-062-VtWeb powered by _______ .