Full-Field Exposure Map (exp3.fits)
The full-field exposure map file consists of a single FITS format file for each observation and science energy band that results from catalog processing. A full-field instrument map is generated at the equivalent monochromatic energy for each science energy band, and a set of exposure maps—ACIS observations are blocked by 1 and HRC observations are blocked by 2 in SKY coordinates—are computed by applying the aspect histogram sampled at 0.5 arcsec resolution.
The exp3.fits exposure maps are created as shown in the CIAO thread "Multiple Chip ACIS Exposure Map."
ACIS Exposure Map
The full-field exposure map FITS file is named: 〈i〉〈s〉〈obs〉_〈obi〉N〈v〉[_〈c〉]_〈b〉_exp3.fits
where 〈i〉 is the instrument designation, 〈s〉 is the data source, 〈obs〉 is the observation identification, 〈obi〉 is the observation interval identification, 〈v〉 is the data product version number, 〈c〉 is the cycle, and 〈b〉 is the energy band designation. The optional discriminator identified in square brackets is included only for ACIS alternating exposure (interleaved) mode observations.