The study, published in Experimental Astronomy, develops a complete workflow for converting raw satellite signals into information about the environmental and astronomical consequences of artificial light. The researchers began with data from the SDGSAT-1 Glimmer Imager, a sensor designed to observe nighttime illumination at much finer spatial and spectral detail than widely used global night-light products. Unlike conventional satellite measurements that primarily record broadband brightness, multispectral observations can help distinguish lighting technologies. This matters because a low-pressure sodium lamp, a high-pressure sodium lamp, and a white light-emitting diode can produce very different effects in the atmosphere even when their total visible brightness appears similar. Their wavelengths determine how efficiently light is scattered and how strongly it contributes to skyglow above a protected observatory.

One of the central challenges was restoring the satellite imagery without erasing the weakest signals. Nighttime remote sensing is vulnerable to detector noise, striping, calibration errors, geometric misalignment, and variations in atmospheric conditions. In many image-processing workflows, faint pixels are treated as unwanted noise and suppressed. For dark-sky research, however, those faint signals may represent exactly the low-level stray light that travels across rural landscapes and reaches an observatory. The team therefore developed a radiance-based restoration procedure designed to preserve weak illumination while correcting artifacts. Radiance refers to the amount of light traveling from a source toward the sensor over a defined area and direction. Maintaining this physical quantity allowed the researchers to compare satellite observations with measurements made on the ground rather than relying only on visual image enhancement.

The restored SDGSAT-1 data were tested against in-situ Sky Quality Meter observations collected near the observatory regions. Sky Quality Meters estimate night-sky brightness by measuring light in a broad spectral band and typically report the result in astronomical units of magnitude per square arcsecond. The researchers found a strong log-linear relationship between satellite-derived radiance and SQM measurements, with a correlation coefficient of approximately −0.94. The negative sign reflects the astronomical magnitude scale: darker skies have numerically larger magnitudes, while brighter skies have smaller ones. A correlation this strong indicates that the satellite workflow was capable of tracking variations in sky brightness over the study areas, including subtle emissions that could have disappeared during aggressive denoising.

The multispectral classification produced the clearest evidence of a lighting transition in Antalya. Commercial and urban areas around TUG showed a growing presence of white LEDs, which accounted for approximately 9.2 percent of the classified lighting coverage. White LEDs are often promoted as efficient replacements for older lamps because they can deliver more visible illumination using less electricity. Yet their environmental impact depends strongly on their spectral power distribution, the way their emitted energy is distributed across wavelengths. Many white LEDs contain a strong blue component, and shorter wavelengths are scattered more efficiently by molecules and aerosols in the atmosphere than longer red wavelengths. That scattering can spread urban light across wide distances, creating a diffuse glow over areas that may be far beyond the city itself.

Erzurum presented a contrasting picture. More than 77 percent of its classified lighting infrastructure remained spectrally homogeneous high-pressure sodium lighting. These lamps are dominated by yellow-orange wavelengths and generally contain less short-wavelength output than many modern white LEDs. From a spectral perspective, this could make distant sources less efficient at generating broad atmospheric skyglow. But the location of the urban core created a more immediate danger for DAG. The observatory is positioned close to the main concentration of Erzurum’s artificial light, meaning that even lighting with comparatively lower scattering efficiency can produce a powerful local impact. Light emitted near an observatory does not need to travel through a long atmospheric path to contaminate the sky above the telescope.

To quantify that distinction, the researchers introduced a physically based atmospheric scattering risk model. The model accounts for factors including the radiance of individual or grouped light sources, their distance from the observatory, the wavelengths they emit, and the way atmospheric particles redirect light. Rayleigh scattering, caused by air molecules, is especially important at shorter wavelengths and increases rapidly as wavelength decreases. Aerosols, dust, and other particles can also scatter and redirect light through Mie scattering, a process that is less strongly dependent on wavelength but can become significant in hazy or polluted conditions. The model therefore treats artificial light as both a geometric and a spectral threat. A nearby source may be dangerous because of its distance and intensity, while a distant blue-rich source may remain important because its light is scattered efficiently across the atmosphere.

The resulting risk scores overturned what a simple brightness map might suggest. Erzurum recorded a total modeled risk of about 76,069, compared with approximately 56,947 for Antalya. The higher Erzurum score was driven primarily by geometric exposure: the city’s bright core lies closer to DAG. In Antalya, by contrast, the wider urban and coastal footprint generated a stronger spectral concern. White LEDs in commercial districts can send proportionally more short-wavelength light into the atmosphere, allowing distant sources to contribute to skyglow over TUG even when they are not immediately adjacent to the observatory. The result is a warning against ranking light-pollution threats by city size, total illuminated area, or satellite brightness alone. The physical pathway from a lamp to the observatory can be just as decisive as the amount of light emitted.

The study’s practical message is unusually specific. Where the primary danger is intensity and proximity, as at DAG, the most effective interventions are likely to involve strict shielding, better fixture design, reduced upward light, lower operating levels, and carefully timed curfews. Shielding prevents light from escaping above the horizontal plane, where it can enter the atmosphere and telescope lines of sight. Where the dominant danger is spectral, as in parts of Antalya, simply dimming lights may not be enough. Municipalities could instead prioritize warmer LED technologies, reduce blue emission, apply spectral filters, and restrict high-intensity commercial lighting. Such measures could lower scattering efficiency while preserving essential illumination for roads, businesses, and public safety. The researchers argue that dark-sky conservation should therefore move toward differentiated, source-specific strategies rather than a single nationwide lighting standard.

SDGSAT-1 also offers a new way to monitor these changes over time. The satellite’s detailed nighttime imagery can identify roads, commercial zones, urban expansion, and changes in lighting technology that are difficult to detect with coarse-resolution global products. The team supplemented the satellite observations with VIIRS VNP46A2 nighttime-light data and OpenStreetMap vectors to connect illuminated patterns with likely source categories. This combination can help planners determine whether a new glow comes from a highway, an industrial site, a residential district, or a coastal commercial corridor. Repeated observations could reveal whether a city’s transition to LEDs is reducing electricity demand while unintentionally increasing blue-rich emissions over protected landscapes. They could also provide a way to evaluate the success of shielding rules and lighting retrofits without depending solely on occasional ground surveys.

For astronomers, the implications are immediate. Artificial skyglow raises the background level against which faint celestial objects must be detected, reducing contrast and forcing longer exposures. It can interfere with photometry, spectroscopy, and surveys that depend on precise measurements of weak astronomical signals. For ecosystems and human communities, the consequences extend beyond observatories: artificial light at night can alter insect behavior, migration, predator-prey interactions, circadian rhythms, and landscape connectivity. The Türkiye study does not claim that satellite imagery can replace ground-based measurements or detailed lamp inventories. Instead, it demonstrates how space-based multispectral data can connect regional urban development with the physics of atmospheric light propagation. Its most striking conclusion is also its most shareable: the city that looks less threatening from space may be the one posing the greater risk on the ground, while a distant city can become a serious danger when its lighting spectrum is optimized for atmospheric scattering. Protecting the world’s observatories may ultimately depend not only on turning lights down, but on choosing the right colors, directions, and distances for every lamp.

Subject of Research: Urban light pollution, atmospheric scattering, multispectral nighttime remote sensing, and dark-sky observatory conservation in Türkiye.

Article Title: Multispectral characterization of urban lighting transitions and atmospheric scattering impacts on dark-sky preserves using SDGSAT-1 glimmer imagery

Article References: Kaba, K., Aydın, S., Türkmen, R.B. et al. “Multispectral characterization of urban lighting transitions and atmospheric scattering impacts on dark-sky preserves using SDGSAT-1 glimmer imagery.” Experimental Astronomy 62, article 13 (2026).

Image Credits: AI Generated

DOI: https://doi.org/10.1007/s10686-026-10074-8

Keywords: Light pollution; SDGSAT-1 Glimmer Imager; multispectral classification; skyglow modeling; dark-sky conservation; atmospheric scattering; astronomical observatories.

Professor Nick Dunn, a prominent figure from Lancaster University and an authority in urban design, posits that cities should not only prioritize light but also consider the intricate balance between light and darkness. He believes that achieving healthier urban ecosystems is contingent upon mitigating light pollution and creating environments conducive to both human and non-human life. Light pollution, which has escalated with technological advancements and urban sprawl, has far-reaching consequences on biodiversity, sleep patterns, mental health, and even cultural practices linked to night-time experiences. Hence, the proposal to darken cities is akin to fostering a more sustainable coexistence in the modern urban framework.

Envisioning “Dark Futures,” as articulated by Professor Dunn, is about reclaiming the valuable attributes of darkness. This includes recognizing the essential role that nighttime plays in promoting biodiversity, maintaining ecological balance, and preserving our ancestral connections to the cosmos. Historically, humans have been accustomed to a natural rhythm dictated by the day-night cycle. With the pervasive rise of artificial lighting, however, we are losing touch with these biological and cultural rhythms, which in turn affects our well-being and our relationship with other species.

As cities become increasingly illuminated, there is growing concern about the adverse effects of artificial light on nocturnal wildlife, disrupting their foraging, mating, and migratory behaviors. For instance, moths are drawn towards artificial light sources, which can lead to their demise as they become easier prey for predators. Likewise, migratory birds are known to become disoriented by artificial lighting, leading them to fly off course or collide with structures. Therefore, a radical shift in how we perceive darkness could not only safeguard ecological networks but also stimulate a paradigm shift towards regenerative urban landscapes.

In his book “Dark Futures: When the Lights Go Down,” Professor Dunn outlines an ambitious vision that challenges the entrenched dichotomy of light versus dark. He suggests that embracing darkness allows cities to emerge as dynamic ecosystems that honor and encourage biodiversity. This would require urban architects and planners to innovate spaces that adapt to natural light cycles, utilizing materials and designs that minimize reliance on excessive artificial illumination while enhancing the nighttime experience for urban dwellers.

Moreover, the societal implications of a darker urban environment deserve attention. As we navigate through an era marked by rising anxiety and stress levels, creating more tranquil spaces devoid of overwhelming artificial light can foster mental well-being. Exposure to darkness is linked to improved sleep, a critical component of physical and psychological health. In urban contexts, where the fast pace of life leads to chronic sleep deprivation, adjusting our environmental settings to reflect a more balanced light-dark ratio could yield substantial health benefits.

The narrative around the urban nightscape isn’t merely about limiting artificial light; it’s also about reimagining urban aesthetics and functionalities. Consider night markets, starlight events, and environmentally responsible lighting technology that respects local wildlife and encourages community bonding in darkened settings. Cities can thrive by becoming places where people gather to experience the night, engaging in activities that celebrate the natural world while allowing for contemplative solitude.

Another critical dimension of this discourse is climate change, which poses an existential threat to all life on Earth. By re-evaluating our relationship with light and darkness, we can embrace sustainable design practices that illuminate ecological futures rather than exacerbate environmental degradation. Urban areas often consume unnecessary energy for lighting, contributing to carbon emissions and resource depletion. Adopting a philosophy that values darkness can inspire innovations in energy-efficient design, spatial planning, and sustainable urban development.

To further emphasize the urgency of this conversation, Dunn suggests incorporating dark design principles into educational curricula. Equipping future architects, urban planners, and environmental scientists with the knowledge of how darkness can be beneficial might catalyze a shift in design philosophies that align with resilience, sustainability, and connectivity with the broader ecosystem. A comprehensive approach to urban design will undoubtedly necessitate collaboration across various disciplines, from engineering to the arts, fostering a multi-faceted understanding of how light and darkness can coexist harmoniously.

Additionally, the implications of reclaiming darkness could extend beyond human health and ecological preservation. This initiative may also provide profound insights into cultural and spiritual aspects of life, as many societies have historically associated darkness with meditation, reflection, and a deeper understanding of one’s place in the universe. Redefining urban nocturnal experiences could encourage cultural revival and connectivity to tradition, enhancing community ties as shared experiences under starlit skies become more prevalent.

While the objective of darkening urban environments may seem ambitious, it serves to ignite dialogues that propel society toward rethinking its values. The intertwined relationships of light, darkness, and life should not be underestimated; they form the very fabric of our existence on this planet. By envisioning dark futures, we place emphasis on returning to a state of balance, which not only enriches our lives but also fortifies the biodiversity that sustains us.

In conclusion, the paradigm of urban living must shift towards a harmonious blending of light and dark, recognizing the inherent value and necessity of both elements. “Dark Futures: When the Lights Go Down” is not just a book; it represents a call to action that urges us to reassess the impact of urban design on ourselves, the planet, and all its inhabitants. Engaging with darkness in our urban centers may very well be the key to ensuring healthier cities and ecosystems as we continue to grow in an ever-changing world.

Subject of Research: The impact of reducing light pollution and embracing darkness in urban environments for improved biodiversity and human health.
Article Title: Rethinking Urban Design: The Case for Darkening Cities
News Publication Date: October 10, 2023
Web References: Lancaster University
References: Dunn, Nick. "Dark Futures: When the Lights Go Down."
Image Credits: Credit: Lancaster University UK

Keywords: Urban design, light pollution, biodiversity, human health, sustainability, darkness, ecology, urban living, environmental design.