An old nuke report has surfaced according to the Feb 13 issue of Nature which indicates the threat of Tsunami's from small impactors is lower than thought based on more recent computer simulations. The old data seems to match more recent analysis by Jay Melosh.

The article also corrects a comment I made above. There are 2 systems in development capable of detecting smaller asteroids at a much greater rate than current systems. From the article: "The US government is funding the development of the Panoramic Survey Telescope and Rapid Response System and the Large Synoptic Survey Telescope, whose brief includes surveys of asteroids of various sizes. The latter telescope is expected to cost around $200 million." The LSST seems to have grown in cost and size by the way from 170 million 6.5 meter scope to an 8.4 meter scope at the cost above. Didn't find a cost on Pan-STARRS. Perhaps Alex would know.

Still with the threat downgraded and a capable scope at the cost of a single space mission I think the LSST would be a good deal. The dark matter angle alone makes it worth doing as pure science.

More info available at:

Pan-STARRS home
Pan-STARRS & NEOS
Pan-STARRS & tech details
other science for Pan-STARRS

LSST Overview from Bell labs
LSST as dark matter scope
LSST *.pdf info from NOAO

2003 CR20 history
2003 CR20 data