TEMPO at Night

The NASA Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument is hosted on a geostationary commercial communications satellite. TEMPO is an imaging spectrometer with primary mission to measure trace-gas concentrations from the observed spectra of reflected sunlight over the Continental United States and parts of Canada, Mexico, and the Caribbean. TEMPO produces an ultraviolet (UV, 293–494 nm) and a visible (538–741 nm) spectrum for each spatial pixel. TEMPO saw first light in August 2023. At night, TEMPO can observe city lights, gas flaring, maritime lights from fishing and offshore oil platforms, clouds and snow in the moonlight, lightning, aurorae, and nightglow without interfering with its primary daytime air quality/chemistry mission. This paper describes the capabilities of TEMPO to make nighttime observations and surveys of some early results. Repetitive coverage of North America enables production of clearest-sky composites that are similar to VIIRS Day-Night Band (DNB) “Black Marble” products. Spectra of urban areas contain spectral signatures of artificial lighting of various types that allow the radiance from each class of lighting to be estimated. Moonlight imaging of clouds provides a useful capability for discriminating clouds and fog. Lightning illuminating cloud tops from below is seen with distinct spectral features. Gas flares, associated with oil production, are observed and flare temperatures can be estimated from their spectra. Known auroral and nightglow spectral lines of atomic oxygen and molecular nitrogen are seen in the UV and visible spectra. The sodium d-layer is also observed.