class: center, middle, inverse, title-slide .title[ # Sentinel 1 ] .author[ ### Mike Hathorn ] .institute[ ### CASA, UCL ] .date[ ### 2023/01/31 (updated: 2023-03-24) ] --- # Summary: Sentinel 1 .pull-left[* Two polar-orbiting satellites * The only Sentinel mission to provide Synthetic Aperture Radar (SAR) imagery * Allows for day and night imagery regardless of weather * Focus (land) ([ESA, 2022b](#bib-esaLandMonitoringSentinel12022))`: * Forest management * Agriculture monitoring * Urban deformation mapping * Also used in marine monitoring and emergency management] <div class="figure" style="text-align: right"> <img src="images/Sentinel-1_pillars.jpg" alt="Sentinel 1P (Source: European Space Agency, 2022)" width="50%" /> <p class="caption">Sentinel 1P (Source: European Space Agency, 2022)</p> </div> --- # Summary 2: Purpose * Continuous radar mapping of Earth ([ESA, 2022b](#bib-esaSentinel1MissionObjectives2022)) * Bi-weekly coverage of world's land masses, as well as sea-ice zones and Europe's coastal zones and shipping routes (daily) * Expected mission duration: Minimum 7 years; fuel for 12 years <div class="figure" style="text-align: center"> <img src="images/Sentinel-1-Repeat-Coverage-Frequency-Geometry-2021.jpg" alt="Sentinel 1P Coverage (Source: European Space Agency, 2022)" width="70%" /> <p class="caption">Sentinel 1P Coverage (Source: European Space Agency, 2022)</p> </div> --- # Summary 3: SAR * Sentinel 1 carries a single C-band SAR instrument * Imagery produced using radio waves, not visible light - active sensor * This allows the sensor to see through clouds (operates at a different point on the electromagnetic spectrum) ## Key attributes: | **Resolution** | | | -------------- | --------------------------------------------- | | Spatial | As low as 5x5m, 400km swath | | Temporal | 6 days at equator, 3 days at higher latitudes | | Radiometric | 1 dB | | Spectral | Single C-band | --- # Applications: Maritime Monitoring * Used to detect and track objects in the oceans (ships, icebergs) * Also used for detection of oil spills, which appear darker than water in SAR imagery * Near real-time temporal resolution means that it can be used to track and persecute illegal oil spills * Also used for ice classification and iceberg data by coast guards, navies, and private shipping companies ([Tschada, 2022](#bib-tschadaUsingSentinel1SAR2022)) --- # Applications: Land monitoring * Forestry: Forest type classification, biomass estimation, disturbance detection * Mapping of fire scars * Monitoring crop conditions, soil properties, assessing land use, soil degradation ([ESA, 2022](#bib-esaLandMonitoringSentinel12022)) * Can be combined with optical data from other sources to improve the accuracy of informal settlement detection and mapping ([Matarira, Mutanga, Naidu et al., 2022](#bib-matariraObjectBasedInformalSettlement2022)) * Needs to be ground-truthed in this context * Spatial resolution not always high enough * Speckle an issue --- # Applications: Emergency management * Phase data can be used for interferometric (InSAR) analysis - used for measuring surface deformations caused by seismic events and volcanic activities <a name=cite-esaEarthquakesVolcanicEruptions2022></a>([ESA, 2022a](#bib-esaEarthquakesVolcanicEruptions2022)) * Also used to assess damage after other natural disasters * High spatial and temporal resolution combined with all-weather imagery is a huge advantage here * Unfortunately this is not possible in Google Earth Engine at the moment --- # Reflections: SAR vs Optical A short video... for fun! Here I demonstrate how an aperture works on an optical camera <div style="padding:60% 0 0 0;position:relative;"><iframe src="https://player.vimeo.com/video/811181627?h=9b1bf3d95c&badge=0&autopause=0&player_id=0&app_id=58479" frameborder="0" allow="autoplay; fullscreen; picture-in-picture" allowfullscreen style="position:absolute;top:0;left:0;width:80%;height:80%;" title="IMG_1910.mov"></iframe></div><script src="https://player.vimeo.com/api/player.js"></script> --- # Reflections: SAR vs Optical continued .pull-left[* SAR works differently - the sensor produces its own energy (radio waves) * The antenna on the satellite reads the signal that bounces back * This creates a synthetic aperture - the spatial resolution of an image is determined by the length of the antenna ([NASA, 2020](#bib-nasaWhatSyntheticAperture2020)) * This is why SAR can see through clouds - it's not reading light!] .pull-right[ A synthetic Aperture (NASA, 2020)] --- # References <a name=bib-esaEarthquakesVolcanicEruptions2022></a>[ESA](#cite-esaEarthquakesVolcanicEruptions2022) (2022a). _Earthquakes & Volcanic Eruptions - Emergency Management - Thematic Areas - Sentinel Online_. https://copernicus.eu/thematic-areas/emergency-management/earthquakes-volcanic. <a name=bib-esaLandMonitoringSentinel12022></a>[ESA](#cite-esaLandMonitoringSentinel12022) (2022). _Land Monitoring - Sentinel-1 SAR - User Guides - Sentinel Online - Sentinel Online_. https://sentinel.esa.int/web/sentinel/user-guides/sentinel-1-sar/applications/land-monitoring. <a name=bib-esaSentinel1MissionObjectives2022></a>[ESA](#cite-esaSentinel1MissionObjectives2022) (2022b). _Sentinel-1 - Mission Objectives - Sentinel Online_. https://copernicus.eu/missions/sentinel-1/mission-objectives. <a name=bib-matariraObjectBasedInformalSettlement2022></a>[Matarira, D., O. Mutanga, M. Naidu, et al.](#cite-matariraObjectBasedInformalSettlement2022) (2022). "Object-Based Informal Settlement Mapping in Google Earth Engine Using the Integration of Sentinel-1, Sentinel-2, and PlanetScope Satellite Data". In: _Land_ 12.1, p. 99. <a name=bib-nasaWhatSyntheticAperture2020></a>[NASA](#cite-nasaWhatSyntheticAperture2020) (2020). _What Is Synthetic Aperture Radar?_ https://www.earthdata.nasa.gov/learn/backgrounders/what-is-sar. Backgrounder <a name=bib-tschadaUsingSentinel1SAR2022></a>[Tschada, J.](#cite-tschadaUsingSentinel1SAR2022) (2022). _Using Sentinel-1 SAR Data for Imagery Intelligence <U+2014> Detection of Vessels_. ---