Infrared Atmospheric Sounding Interferometer (IASI) Level 3 Daily 3x3 Global Grids

Infrared Atmospheric Sounding Interferometer (IASI), is a hyperspectral infrared sounder residing on the European Space Agency's (ESA) MetOp series of polar orbiting satellites. The main goal is to provide atmospheric emission spectra to derive temperature and humidity profiles with high vertical resolution and accuracy. It is a Michelson interferometer with spectral coverage between 3.6 and 15.5 micrometers. At nadir, the instrument samples data at intervals of 25 km along and a cross track, each sample having a maximum diameter of about 12 km. The 3x3 product is on a 3x3 degree global grid.
The product is created daily and consists of (1) 8461 channels of IASI Level 1C radiances, (2) 6 channels of AVHRR Level 1B radiances averaged on to the IASI fields of view, (3) all associated navigational and temporal information for the observations, and (4) quality flags. These data are collocated to points on a 3° X 3° global grid. On a scan line, the IASI fields of view are clustered into 2 X 2 matrices. These clusters of fields of view are referred to as fields of regard. It is actually this field of regard that is collocated and stored for each grid point. A daily gridded data set consists of two files, one for the ascending orbits and the other for the descending. Because the product requires an entire day's data it is produced one day behind real time. For both the ascending and descending daily files NOAA/NESDIS/STAR will generate one associated xml format metadata file.