Spectral‐Resolved Light at Night: TEMPO Observations and Background Correction

Artificial Light at Night (ALAN) poses risks to public health and ecosystems. While long‐term remote sensing has tracked global nighttime light, spectrally resolved light at night (spectral light at night (SLAN)) data from geostationary orbit only became available with NASA's Tropospheric Emissions: Monitoring of Pollution (TEMPO) mission. Its Level 1 twilight radiance product enables detailed spatiotemporal analysis of ALAN's spectral characteristics. This study introduces algorithms for processing TEMPO Level 1 data into Level 2 SLAN data using two methods for solar background removal: scattering‐angle correction and spectral correction. The first method uses the relationship between scattering angle and radiance to suppress background, while the second uses the inherent spectral relations in the solar radiation in 290–390 nm range, where artificial light emissions are minimized, to estimate direct twilight contributions. Combined, these methods yield more stable correction results. The results are validated against two independent data sets: the Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) Black Marble product and astronaut photographs taken from the International Space Station (ISS) over Houston. Comparisons include (a) city light classifications from Black Marble versus both raw and corrected TEMPO data, (b) pixel‐to‐pixel radiance measurements between TEMPO and VIIRS, and (c) spectral angle analyses between ISS and TEMPO data. We also compare CONUS nighttime light maps from VIIRS DNB, TEMPO VIS, and TEMPO UV; TEMPO VIS agrees closely with VIIRS DNB, while both diverge from TEMPO UV in gas‐flaring regions, highlighting the complementary information these instruments provide.