Radar satellite imagery (SAR) offers great opportunities for assisting humanitarian operations during war, offering support to displaced people in their own and in hosting countries, like the current situation in Ukraine. It helps relief organizations to closely follow the number of people in need and their locations, by monitoring the areas affected by the war.
Satellites are the silent eyewitnesses of the atrocities of war. Through their eyes the government causing this all this destruction cannot deny their actions or escape their liabilities.
It had been demonstrated in numerous studies that Earth observation can deliver important information for things like the management of crises, the organisation of refugee camps, and the mapping of damage to cities and the environment. Radar sensors have characteristics which make them highly suitable for humanitarian response, most notably through their potential to capture images through cloud cover and at night.
Change Detection With SAR Radar Satellites
Change detection is a technology to determine damage that occurred during extreme events in a area, such as a war. This change detection is a process that analyses multi-temporal remote sensing images acquired in the same geographical area at different moments in time, to identify changes that occurred between these acquisition dates.
Above example of the L’Aquila earthquake (that we wrote about earlier) used Very High-Resolution SAR images in an multitemporal dataset, using two spotlight (COSMO SkyMed) images acquired before (5 April 2009) and after (12 September 2009) the earthquake in the town of L’Aquila in Italy, that occurred on 6 April 2009.
Using change detection technology, it can be determined which buildings collapsed during the earthquake. When combined with population data, the estimate number of people affected by the catastrophe can be quantified.
SAR to Detect War Damage
The biggest value of VHR SAR data for humanitarian relief organisations lies in the spatial and temporal resolution of SAR data, which makes it very useful for monitoring small areas, in short response times, with more transparency – as it is weather agnostic – and with high quality information.
The images above show the change in backscattering of three SAR images before and after attacks that happened in the Syrian city of Aleppo during the Syrian civil war. The change detection images indicate structures affected by airstrikes and barrel bombs.
SAR Satellites and Ukraine
On 24 February 2022, Russia invaded Ukraine in a major escalation of the Russo-Ukrainian War that began in 2014. The invasion caused Europe’s fastest-growing refugee crisis, with more than 7.7 million Ukrainians fleeing their country and a third of the population displaced. The invasion also caused global food shortages.
SAR satellites can extract information about destruction of the cities affected by the war in Ukraine, with several government and commercial SAR satellite operators working in this area.
Companies like Capella Space and Maxar Technologies are using SAR Earth observation data to monitor the war in Ukraine. These companies help determine damage to infrastructure and buildings, movements of troops, location of refugee camps, etc. The ability of SAR satellites to deliver clear imagery, despite bad weather and cloud coverage over Ukraine, has been a game-changer.
Satellite imagery has been used to track every phase of the war. In the days leading up to the February 24 invasion, satellite imagery gave some of the first indications that the Kremlin had decided to proceed with an attack. As the deadly conflict has dragged on, key elements of Russia’s narrative have been debunked by commercial satellite imagery. A recent article on the ValueWalk blog even states that Russia’s war in Ukraine will turbocharge the commercial space industry.
The following images are referred a two Sentinel-1 images dated between 11 January 6 June 2022 applying a change detection using an RGB multitemporal composition where we can see increase and decrease of the backscattering performed automatically in the zone of Mariupol city in Ukraine, show us the change occurred during the war.
In conclusion we can say that SAR remote sensing offers great advantages over other Earth observation methods when it comes to around-the-clock monitoring of war situations, due to its all-weather sensing capabilities. By using change detection techniques SAR data analysis shows changes to structures with great precision, showing things like damage to buildings, new construction, and even vehicle displacements.
SAR is therefore a very valuable tool for both military and humanitarian operations. Collaboration between scientists, SAR analysts and relief workers is therefore critically important, and transfer of knowledge and experience to assist humanitarian work in countries affected by the war should be encouraged.
Read more about SAR satellite applications
In this series about SAR satellite applications by our SAR specialist author Gabriela Quintana we have published:
The author wants to thank Remco Timmermans for editing this text.
The TerraSAR X image was taken from the thesis of A. Braun: “Radar satellite imagery for humanitarian response. Bridging the gap between technology and application” Universität Tübingen, 2019
Featured image: “Pushing Sentinel-1B towards the ‘high bay’ for testing in 2016”, credit: ESA