The European satellite that keeps watching when others go dark

On April 7, 2026, the investigative journalism organization Bellingcat released an updated version of the Iran Conflict Damage Proxy Map, a public tool that uses data from the European satellite Sentinel-1 to flag areas in Iran and the Persian Gulf where the ground surface has changed in a statistically anomalous way since the start of hostilities. The map, available online and open to anyone, is updated once or twice a week, in step with the satellite’s passes.

Figure 1 — Screenshot from Bellingcat’s Iran Conflict Damage Proxy Map showing an area west of Tehran, around the Fath Highway corridor (the Tehransar and Shahrak Esteqlal districts). The colored pixels mark areas where the Sentinel-1 radar signal has changed in a statistically anomalous way relative to the period before March 1, 2026: yellow corresponds to the lowest damage probabilities, purple to the highest. A dense cluster of flags is visible over an industrial complex south of the highway. As Bellingcat itself notes, changes in reflectivity can be associated with damage but also with construction sites, industrial activity, or vegetation growth: every flag requires independent verification. Source: Bellingcat / Ollie Ballinger — Sentinel-1 © Copernicus / ESA.

The tool was built to answer a concrete problem. For several weeks now, at the request of the United States government, the leading commercial operators of high-resolution optical satellites have halted or restricted the distribution of recent imagery over Iran. A significant share of the photographs we see in the press when military sites, airports, or government buildings are hit comes precisely from these private operators: Maxar, Planet, Airbus. The moment they choose, or are compelled, not to publish, the flow of information to media outlets, researchers, and humanitarian organizations narrows.

Bellingcat therefore built a tool that does not depend on optical imagery and instead relies on a different class of satellites: synthetic aperture radar, known by the acronym SAR. SAR satellites beam microwave pulses at the Earth and measure the echo that bounces back. They work at night, because they do not depend on sunlight, and they see through clouds and rain because microwaves are not blocked by the atmosphere. Above all, the Sentinel-1 program is part of Copernicus, the European Union’s and the European Space Agency’s public Earth observation infrastructure: the data is free, open, and its distribution cannot be suspended at the request of a single government.

The method the Bellingcat map uses to identify “suspect” areas is called the Pixel-Wise T-Test, developed by geographer Ollie Ballinger. The idea is simple in principle. For every pixel in the study area, a year’s worth of radar observations preceding the start of the conflict is collected. From these, a “normal” behavior is calculated — that is, the expected average and variability of the radar signal at that point. Then, each time a new Sentinel-1 image arrives, the pixel’s current value is compared against its historical baseline. If the new value falls outside the range within which 99 percent of observations would fall under ordinary conditions, the pixel is flagged. This does not mean damage is proven, only that something outside the norm has happened there: a collapsed building, a torn-up road, a sudden construction site, a fire. It is then up to the journalist or researcher to take that red flag and verify it.

Bellingcat tested the accuracy of the approach on a large sample: more than two million buildings mapped by the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) across some thirty cities in Gaza, Ukraine, Sudan, Syria, and Iraq. In contexts with heavy cloud cover, without useful nighttime windows, or where private operators did not consider it profitable to cover the area, the public radar kept producing data. This is the case of Sudan, for instance, where the civil war of recent years has received little coverage from commercial imagery because there was no market for it, and where Sentinel-1 has become one of the go-to tools for anyone trying to reconstruct the conflict’s impact.

The difference from commercial optical satellites is not just technical: it is also political. Maxar and Planet operate under licenses issued by the United States government; their terms of use allow the American administration to request restrictions on distribution in cases of national security concern. This is the so-called shutter control — the power to “close the shutter” over sensitive areas. Copernicus was designed the opposite way: the Sentinels are European Space Agency missions, funded with the European Union’s public money, and the principle of open data is written into European regulation. There is no political switch a single government can use to turn them off.

This architecture is not perfect. Sentinel-1 has a resolution of about twenty meters, useful for spotting changed areas but not for making out individual details, and revisit times of several days rather than a few hours. But it is precisely in the combination of open data, service continuity, and the ability of anyone to build tools like Bellingcat’s on top of it that the value of the infrastructure lies.

In the end, the lesson is not just about Iran or the Gulf. It is about the fact that the ability to see a conflict from above, and to document it independently, is not a natural function of satellites: it is a choice. It depends on who owns them, who pays for them, and what terms of use govern their output. Having at least one public, European infrastructure that cannot be switched off on request means having an accountability tool that stays on even when someone would rather dim the lights. And it is one of the reasons, perhaps rarely told, why Copernicus is one of the highest-impact civilian scientific programs the European Union has built in the last twenty years.