  We present an automated system called NEORANGER that regularly computes
asteroid-Earth impact probabilities for objects on the Minor Planet Center's
(MPC) Near-Earth-Object Confirmation Page (NEOCP) and sends out alerts of
imminent impactors to registered users. In addition to potential Earth
impacting objects NEORANGER also monitors for other types of interesting
objects such as Earth's natural temporarily-captured satellites. The system
monitors the NEOCP for objects with new data and solves, for each object, the
orbital inverse problem which results in a sample of orbits that describes the,
typically highly-nonlinear, orbital-element probability-density function (PDF).
The PDF is propagated forward in time for 7 days and the impact probability is
computed as the weighted fraction of the sample orbits that impact the Earth.
The system correctly predicts the then-imminent impacts of 2008 TC3 and 2014 AA
based on the first data sets available. Using the same code and configuration
we find that the impact probabilities for objects typically on the NEOCP, based
on 8 weeks of continuous operations, are always less than 1 in 10 million
whereas simulated and real Earth-impacting asteroids always have an impact
probability greater than 10% based on the first two tracklets available.
