PAYNE INSTITUTE COMMENTARY SERIES: COMMENTARY

By Mikhail Zhizhin and Morgan Bazilian

July 9, 2026

VIIRS DNB detected a clear nighttime-light loss in southwestern Crimea, strongest on the night of July 5–6 UTC, centered on the Sevastopol–Simferopol focus area.

Reports from July 2026 described a worsening energy crisis in Crimea after Ukrainian strikes on energy infrastructure. Reuters reported earlier outages and power curbs in Sevastopol on July 6 after strikes on the city’s power plant substation [1], and later reported that Crimea’s Russian-backed governor warned the fuel and energy situation would remain tense [2].

To check the reported blackout independently, we used VIIRS Day/Night Band imagery from Suomi-NPP, NOAA-20, and NOAA-21. VIIRS DNB is designed for low-light nighttime imaging and is widely used to monitor artificial night lights and power outages. We selected a smaller rectangle over the main affected lit area in southwestern Crimea, covering the Sevastopol–Simferopol side of the peninsula and nearby settlements. A pre-blackout example from July 2 shows the focus area under normal nighttime-light conditions, with the main urban lights still visible (Figure 1).

For comparison, we used a July 2025 VIIRS nighttime-lights baseline product [3]. Each nighttime DNB swath was reprojected to the same 15 arcsec latitude/longitude grid as the baseline, then compared pixel by pixel to calculate radiance change. Sunlit and twilight scenes were excluded. Cloudy pixels were removed using the NOAA VIIRS Level-2 Cloud Mask matched to each orbit; this 750 m swath product provides clear-sky confidence, integer cloud-mask categories, spectral-test results, and cloud-mask QA layers [4].

The detection was limited to pixels inside the focus rectangle that were covered by the orbit, cloud-free, and lit in the July 2025 baseline. We used a baseline-light threshold of 10 nW cm⁻² sr⁻¹ to separate city/settlement lights from background. A pixel was counted as strongly dimmed if its current radiance was ≤20% of the July 2025 baseline, equivalent to at least an 80% pixel-level loss. For pass-level quality control, we tracked how much of the lit focus area was actually covered by the orbit and cloud-free; low-coverage passes were treated as partial or “no decision,” not as full-area blackout evidence.

The strongest blackout signal appears in the focus rectangle on July 5, 2026, around 22:47–23:42 UTC, when multiple nighttime VIIRS passes showed high lit-area coverage and large radiance losses (Figures 2–3; see also the frame-by-frame animated movie of VIIRS overpasses [5]). In those passes, the summed radiance over cloud-free lit pixels dropped by roughly 75–83%, and the dimmed-pixel proxy also rose strongly, with roughly 60–75% of cloud-free lit pixels meeting the severe-dimming threshold. Earlier passes around July 4–5 UTC show strong dimming but lower cloud-free lit coverage, so we treat them as supporting but less definitive. The blackout signal remains visible on July 6–7, but at lower dimmed-pixel fractions, consistent with partial recovery, partial coverage, or spatially uneven restoration.

Figure 1. Pre-blackout VIIRS Day/Night Band image over Crimea from NOAA-21 on 2 July 2026, 23:43–23:46 UTC. Grayscale brightness shows nighttime DNB radiance, blue shading marks cloud-mask probability, green lines show the coastline, and the yellow rectangle marks the southwestern Crimea focus area used for the blackout analysis. Red pixels indicate locations where current DNB radiance is strongly reduced relative to the July 2025 baseline, but in this pre-blackout pass the focus area still retains its main urban light.

Figure 2. NOAA-21 VIIRS DNB quicklook on 5 July 2026, 22:47–22:49 UTC, during the blackout interval. Compared with the pre-blackout view, the focus area shows a more coherent loss of urban light, especially across the Sevastopol–southwestern Crimea corridor. Cloud cover is present nearby, but the blackout signal is strongest in the cloud-clear portion of the focus area.

Figure 3. Time series of VIIRS DNB light-loss metrics for the southwestern Crimea focus area, 1–7 July 2026. The strongest blackout signature occurs on 5 July, when both independent indicators rise together: summed radiance loss over cloud-clear lit pixels reaches about 80%, and the fraction of severely dimmed lit pixels reaches about 70–75%. Earlier high-loss points on 4 July are less reliable because lit-area cloud-clear coverage is low, while the 6–7 July observations show lower dimmed-pixel fractions, consistent with partial recovery or a less spatially complete outage. The bars show why each pass must be interpreted with coverage: some satellite overpasses only partially sample the focus area or are partly cloud-obscured.

 REFERENCES

[1] Reuters. “Drone debris damages Russia’s Ust-Luga, Vysotsk ports, other regions report attacks.” July 6, 2026. Includes reporting that Sevastopol authorities reported a power blackout due to a Ukrainian attack https://www.reuters.com/world/europe/drone-debris-damages-russias-ust-luga-vysotsk-ports-other-regions-report-attacks-2026-07-06/

[2] Reuters. “Russian-backed Crimea governor says fuel situation is likely to remain tense.” July 8, 2026 https://www.reuters.com/business/energy/russian-backed-crimea-governor-says-fuel-situation-is-likely-remain-tense-2026-07-08/

[3] Earth Observation Group, Colorado School of Mines. “VIIRS Nighttime Light.” Product documentation for the EOG VIIRS nighttime-lights annual and monthly radiance grids https://eogdata.mines.edu/products/vnl/

[4] NASA LAADS DAAC. “VIIRS/NOAA21 Cloud Mask and Spectral Test Results 6-Min Swath 750 m.” Product page for CLDMSK_L2_VIIRS_NOAA21 https://ladsweb.modaps.eosdis.nasa.gov/missions-and-measurements/products/CLDMSK_L2_VIIRS_NOAA21

[5] Frame-by-frame animated movie of VIIRS overpasses over Crimea in July 1-7, 2026 https://eogdata.mines.edu/wwwdata/public/Crimea_dimming_timeline_202607.mp4

ABOUT THE AUTHORS

Mikhail Zhizhin
Research Associate, Earth Observation Group, Payne Institute for Public Policy, Colorado School of Mines

Mikhail Zhizhin, M.Science in mathematics from the Moscow State University in 1984, Ph.D. in computational seismology and pattern recognition from the Russian Acad. Sci. in 1992. Research positions from 1987 to 2012 in geophysics, space research and nuclear physics at Russian Acad. Sci., later at NOAA and CU Boulder. Currently he is a researcher at the Earth Observation Group at Colorado School of Mines. His applied research fields evolved from high performance computing in seismology, geodynamics, terrestrial and space weather to deep learning in remote sensing. He is developing new machine learning algorithms to better understand the Nature with Big Data.

Morgan Bazilian
Director, Payne Institute and Professor of Public Policy, Colorado School of Mines

Morgan Bazilian is the Director of the Payne Institute and a Professor of public policy at the Colorado School of Mines. Previously, he wD.as lead energy specialist at the World Bank. He has over two decades of experience in the energy sector and is regarded as a leading expert in international affairs, policy and investment. He is a Member of the Council on Foreign Relations.

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