Abstract
Abstract. The GEOstationary Coastal and Air Pollution Events (GEO-CAPE) Airborne Simulator (GCAS) was developed in support of NASA's decadal survey GEO-CAPE geostationary satellite mission. GCAS is an airborne push-broom remote-sensing instrument, consisting of two channels which make hyperspectral measurements in the ultraviolet/visible (optimized for air quality observations) and the visible–near infrared (optimized for ocean color observations). The GCAS instrument participated in its first intensive field campaign during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) campaign in Texas in September 2013. During this campaign, the instrument flew on a King Air B-200 aircraft during 21 flights on 11 days to make air quality observations over Houston, Texas. We present GCAS trace gas retrievals of nitrogen dioxide (NO2) and formaldehyde (CH2O), and compare these results with trace gas columns derived from coincident in situ profile measurements of NO2 and CH2O made by instruments on a P-3B aircraft, and with NO2 observations from ground-based Pandora spectrometers operating in direct-sun and scattered light modes. GCAS tropospheric column measurements correlate well spatially and temporally with columns estimated from the P-3B measurements for both NO2 (r2=0.89) and CH2O (r2=0.54) and with Pandora direct-sun (r2=0.85) and scattered light (r2=0.94) observed NO2 columns. Coincident GCAS columns agree in magnitude with NO2 and CH2O P-3B-observed columns to within 10 % but are larger than scattered light Pandora tropospheric NO2 columns by 33 % and direct-sun Pandora NO2 columns by 50 %.
Highlights
The GEOstationary Coastal and Air Pollution Events (GEOCAPE) Airborne Simulator (GCAS) is an airborne hyperspectral remote-sensing instrument that was developed in support of future Earth-observing geostationary satellite missions
We present GCAS trace gas retrievals of nitrogen dioxide (NO2) and formaldehyde (CH2O), and compare these results with trace gas columns derived from coincident in situ profile measurements of NO2 and CH2O made by instruments on a P-3B aircraft, and with NO2 observations from ground-based Pandora spectrometers operating in direct-sun and scattered light modes
We have presented trace gas retrievals of NO2 and CH2O from the GCAS instrument during the DISCOVER-AQ Texas 2013 campaign
Summary
The GEOstationary Coastal and Air Pollution Events (GEOCAPE) Airborne Simulator (GCAS) is an airborne hyperspectral remote-sensing instrument that was developed in support of future Earth-observing geostationary satellite missions. As a satellite airborne simulator, GCAS provides an algorithm development test bed for GEO-CAPE and TEMPO, serves as a satellite analogue during field campaigns, and will eventually act as a validation instrument when geostationary satellite instruments are on orbit. The first spectrometer operates in the UV–Vis region of the spectrum, where observations can be made of several atmospheric constituents of interest to air quality. NO2 and CH2O have spectral absorption signatures in the UV–Vis channel and are two core operational data products of future geostationary air quality instruments.
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