  We present photometric and morphological analysis of the behavior of
sungrazing comet C/2012 S1 ISON in SOHO and STEREO images around its perihelion
on 2013 November 28.779 UT. ISON brightened gradually November 20-26 with a
superimposed outburst on November 21.3-23.5. The slope of brightening changed
about November 26.7 and was significantly steeper in SOHO's orange and clear
filter images until November 27.9 when it began to flatten out, reaching a peak
about November 28.1 ($r_H{\sim}17 R_\odot$), then fading before brightening
again from November 28.6 ($r_H{\sim}5 R_\odot$) until disappearing behind the
occulting disc. ISON brightened continuously as it approached perihelion while
visible in all other telescopes/filters. The central condensation disappeared
about November 28.5 and the leading edge became progressively more elongated
until perihelion. These photometric and morphological behaviors are reminiscent
of the tens of meter sized Kreutz comets regularly observed by SOHO and STEREO
and strongly suggest that the nucleus of ISON was destroyed prior to
perihelion. This is much too small to support published gas production rates
and implies significant mass loss and/or disruption in the days and weeks
leading up to perihelion. No central condensation was seen post-perihelion. The
post-perihelion lightcurve was nearly identical in all telescopes/filters and
fell slightly steeper than $r_H^{-2}$. This implies that the brightness was
dominated by reflected solar continuum off of remnant dust in the coma/tail and
that any remaining active nucleus was <10 m in radius.
