  Arecibo S-band (lambda=13cm) radar observations of Comet C/2001 A2 (LINEAR)
on 2001 July 7-9 showed a strong echo from large coma grains. This echo was
significantly depolarized. This is the first firm detection of depolarization
in a grain-coma radar echo and indicates that the largest grains are at least
lambda / 2 or 2 cm in radius. The grains are moving at tens of m/s with respect
to the nucleus. The non-detection of the nucleus places an upper limit of 3 km
on its diameter. The broad, asymmetric echo power spectrum suggests a fan of
grains that have a steep (differential number ~ a^-4) size distribution at
cm-scales, though the observed fragmentation of this comet complicates that
picture.
