  We describe digital tracking, a method for asteroid searches that greatly
increases the sensitivity of a telescope to faint unknown asteroids. It has
been previously used to detect faint Kuiper Belt objects using the Hubble Space
Telescope and large ground-based instruments, and to find a small, fast-moving
asteroid during a close approach to Earth. We complement this earlier work by
developing digital tracking methodology for detecting asteroids using
large-format CCD imagers. We demonstrate that the technique enables the
ground-based detection of large numbers of new faint asteroids. Our methodology
resolves or circumvents all major obstacles to the large-scale application of
digital tracking for finding main belt and near-Earth asteroids. We find that
for both asteroid populations, digital tracking can deliver a factor of ten
improvement over conventional searches. Digital tracking has long been standard
practice for deep Kuiper Belt surveys, but even there our methodology enables
deeper integrations than have yet been attempted. Our search for main belt
asteroids using a one-degree imager on the 0.9m WIYN telescope on Kitt Peak
validates our methodology, delivers sensitivity to asteroids in a regime
previously probed only with 4-meter and larger instruments, and leads to the
detection of 156 previously unknown asteroids and 59 known objects in a single
field. Digital tracking has the potential to revolutionize searches for faint
moving objects ranging from the Kuiper Belt through main belt and near-Earth
asteroids, and perhaps even anthropogenic space debris in low Earth orbit.
