An Initial Assessment of the GeoXO ACX Measurements Conditions and Scan Coverage

NOAA’s next generation Geostationary Extended Observations (GeoXO) satellite system will advance Earth observations from geostationary orbit. GeoXO will supply vital information supporting the U.S. weather, ocean, and climate operations. The recommended three-satellite constellation includes spacecraft at GOES-Central position, that will carry an Atmospheric Composition Instrument (ACX) among its payloads; the requirement on the ACX is to scan its region of interest in one hour. An initial assessment of ACX observational conditions is presented, based on view geometry and solar angle range over the year. Example scan pattern is applied to demonstrate the conditions at each pixel at each revisit. The availability for observations of each pixel is estimated per day of the year, as function of the geometric air mass factor (AMF), which can be related to signal to noise ratio using a model of the ACX instrument performance, and ultimately to expected column error for specific atmospheric species. In addition, cloud climatology – based on statistics derived from three years of GOES-16 ABI cloud data – is considered to determine typical fractions of cloud-free ACX observations, typical cloud optical depths and cloud top heights, for each pixel as function of time of day and season. The results of such assessments can be used to prepare for GeoXO ACX data and further the understanding and development of the future instrument operations.