We describe the HST ACS Coma cluster Treasury survey , a deep two-passband imaging survey of one of the nearest rich clusters of galaxies , the Coma cluster ( Abell 1656 ) .

The survey was designed to cover an area of 740 arcmin ^ { 2 } in regions of different density of both galaxies and intergalactic medium within the cluster .
The ACS failure of January 27th 2007 leaves the survey 28 % complete , with 21 ACS pointings ( 230 arcmin ^ { 2 } ) complete , and partial data for a further 4 pointings ( 44 arcmin ^ { 2 } ) .

Predicted survey depth for 10 \sigma detections for optimal photometry of point sources is g ^ { \prime } = 27.6 in the F475W filter , and I _ { C } =26.8 mag in F814 ( AB magnitudes ) .
Initial simulations with artificially injected point sources show 90 % recovered at magnitude limits of g ^ { \prime } = 27.55 and I _ { C } = 26.65 .
For extended sources , the predicted 10 \sigma limits for a 1 arcsecond ^ { 2 } region are g ^ { \prime } = 25.8 mag arcsec ^ { -2 } and I _ { C } = 25.0 mag arcsec ^ { -2 } .

We highlight several motivating science goals of the survey , including study of the faint end of the cluster galaxy luminosity function , structural parameters of dwarf galaxies , stellar populations and their effect on colors and color gradients , evolution of morphological components in a dense environment , the nature of ultra compact dwarf galaxies , and globular cluster populations of cluster galaxies of a range of luminosities and types .
This survey will also provide a local rich cluster benchmark for various well known global scaling relations and explore new relations pertaining to the nuclear properties of galaxies .