  The Beyond Ultra-deep Frontier Fields and Legacy Observations (BUFFALO) is a
101 orbit + 101 parallel Cycle 25 Hubble Space Telescope Treasury program
taking data from 2018-2020. BUFFALO will expand existing coverage of the Hubble
Frontier Fields (HFF) in WFC3/IR F105W, F125W, and F160W and ACS/WFC F606W and
F814W around each of the six HFF clusters and flanking fields. This additional
area has not been observed by HST but is already covered by deep
multi-wavelength datasets, including Spitzer and Chandra. As with the original
HFF program, BUFFALO is designed to take advantage of gravitational lensing
from massive clusters to simultaneously find high-redshift galaxies which would
otherwise lie below HST detection limits and model foreground clusters to study
properties of dark matter and galaxy assembly. The expanded area will provide a
first opportunity to study both cosmic variance at high redshift and galaxy
assembly in the outskirts of the large HFF clusters. Five additional orbits are
reserved for transient followup. BUFFALO data including mosaics, value-added
catalogs and cluster mass distribution models will be released via MAST on a
regular basis, as the observations and analysis are completed for the six
individual clusters.
