The TEMPO instrument is a grating spectrometer, sensitive to visible and ultraviolet wavelengths of light, which will be attached to the Earth-facing side of a commercial telecommunications satellite (to be selected) in geostationary orbit. This allows TEMPO to maintain a constant view of North America so that the instrument's light-collecting mirror can make a complete East to West scan of the "Field of Regard" each and every hour of the day. By measuring sunlight reflected and scattered from the Earth's surface and atmosphere back to the instrument's detectors, TEMPO's ultraviolet and visible light sensors will provide spectra of ozone, nitrogen dioxide, and other elements of daily atmospheric chemistry cycles.
Schematic of TEMPO Spectrometer
The instrument's optical system resolves a few square miles per pixel, so that pollution can be tracked at sub-urban scales. TEMPO's dataset showing daily (and hourly) variations in the concentrations of these pollutants will enable researchers, air quality managers, policy makers, and public citizens to better monitor the changing "chemical weather" locally, regionally, and across the continent.
TEMPO will be able to resolve pollution at sub-urban scales. Each orange rectangle represents the footprint of a single pixel
© OpenStreetMap contributors/SAO.
The key instrument characteristics and capabilities are:
- Spectral range: 290–740 nm (UV, VIS); spectral sampling: 0.2 nm; spectral resolution: 0.6 nm. Two 2D detectors (2 k x 1 k pixels) images the full spectral range except for a gap from 490–540 nm for each geospatial scene.
- Spatial resolution: 2 km/pixel in the north-south direction, 4.5 km /pixel in the east-west direction at the center of the FOR (Field of Regard) which is desired to be 36.5° N, 100° W. Co-add/cloud clear as needed for specific data products.
- Hourly measurements stepping east to west of the entire FOR (2.5 x 106 spectra/hour).
- Standard data products and sampling rates:
- NO2, O3, aerosol, and cloud products sampled hourly, including eXceL O3 for selected target areas
- H2CO, C2H2O2, SO2 sampled 3 times/day (hourly samples averaged to get S/N)
- Product spatial resolution ≤ 8 km N/S x 4.5 km E/W at center of domain
- Signal/noise requirements met at SZA (Solar Zenith Angles) less than 50° for all products—and at angles up to 70° for NO2, clouds, and aerosols.
- Ozone profile products include 0–2 km O3, free tropospheric O3, and the stratospheric O3 column.