  The first experimental data from single-particle scattering experiments from
free electron lasers (FELs) are now becoming available. The first such
experiments are being performed on relatively large objects such as viruses,
which produce relatively low-resolution, low-noise diffraction patterns in
so-called "diffract-and-destroy" experiments. We describe a very simple test on
the angular correlations of measured diffraction data to determine if the
scattering is from an icosahedral particle. If this is confirmed, the efficient
algorithm proposed can then combine diffraction data from multiple shots of
particles in random unknown orientations to generate a full 3D image of the
icosahedral particle. We demonstrate this with a simulation for the satellite
tobacco necrosis virus (STNV), the atomic coordinates of whose asymmetric unit
is given in Protein Data Bank entry 2BUK.
