Sentinel-2 nighttime imagery: applications, limits & future potential

Kurzfassung

Optical nighttime remote sensing enables the monitoring of human settlements, anthropogenic disasters, as well as wildfires and heavy industry. However, no dedicated optical nighttime satellite mission exists. Existing sensors capable of nighttime imaging face significant trade-offs: instruments like VIIRS are characterized by a coarse spatial resolution, while higher-resolution platforms such as SDGSAT-1 lack global coverage capabilities. In this context, nighttime imagery from the Copernicus Sentinel-2 (S2) mission offers a unique opportunity. Although designed for daytime imaging, two nighttime imaging campaigns in 2025 and 2026 captured well over 400 datatakes, allowing for a systematic assessment of S2A’s nighttime capabilities. This study conducts a review of S2’s nighttime potential, in both the visible/near-infrared (VNIR) and short-wave infrared (SWIR) ranges. Detection limits are established, and observations are compared against EnMAP data. Additionally, an automated workflow capable of classifying lighting types and estimating temperatures across entire S2 datatakes is implemented. Results suggest that S2A’s VNIR detection limit lies at approximately 0.4 W/m²/µm/sr. While higher than VIIRS Day/Night Band, this means that S2A can still successfully detect bright objects, such as large buildings and bright fishing vessels. In the SWIR range, a lower threshold of around 0.1 W/m²/µm/sr enables the detection of gas flaring and wildfires. Compared to VIIRS, a more accurate location of high thermal events, such as individual blocks within a power station, is thus possible. Additionally, the proposed classification approach successfully categorizes scene-wide emissions into "modern" lighting (VIS peak), "legacy" lighting (VIS and NIR peak), and thermal sources (SWIR peak). While challenges remain regarding inaccurate co-registration, low signal-to-noise ratios, and a lack of validation data, S2’s high spatial and temporal resolution can provide a valuable contribution to the nighttime data record. These findings can inform the role of nighttime observations in future satellite missions, including Sentinel-2 Next Generation.