  We present Herschel far-infrared and submillimeter maps of the debris disk
associated with the HR 8799 planetary system. We resolve the outer disk
emission at 70, 100, 160 and 250 um and detect the disk at 350 and 500 um. A
smooth model explains the observed disk emission well. We observe no obvious
clumps or asymmetries associated with the trapping of planetesimals that is a
potential consequence of planetary migration in the system. We estimate that
the disk eccentricity must be <0.1. As in previous work by Su et al. (2009), we
find a disk with three components: a warm inner component and two outer
components, a planetesimal belt extending from 100 - 310 AU, with some
flexibility (+/- 10 AU) on the inner edge, and the external halo which extends
to ~2000 AU. We measure the disk inclination to be 26 +/- 3 deg from face-on at
a position angle of 64 deg E of N, establishing that the disk is coplanar with
the star and planets. The SED of the disk is well fit by blackbody grains whose
semi-major axes lie within the planetesimal belt, suggesting an absence of
small grains. The wavelength at which the spectrum steepens from blackbody, 47
+/- 30 um, however, is short compared to other A star debris disks, suggesting
that there are atypically small grains likely populating the halo. The PACS
longer wavelength data yield a lower disk color temperature than do MIPS data
(24 and 70 um), implying two distinct halo dust grain populations.
