Every day, observations and orbit solutions for Near-Earth Asteroids (NEAs) are received from the Minor Planet Center (MPC) in Cambridge, Massachusetts. Once classified as an NEA, the asteroid is thereafter given automatic orbit updates within our Sentry system. A new orbit solution for an NEA is computed whenever new optical or radar observations for that object become available. Some high-priority objects are observed daily, while other objects go unobserved for days or weeks, even though they may still be bright enough to be seen. Optical observations cease when an object recedes from the Earth (becoming too faint to be seen even with moderate-size telescopes), or when the object moves into the daytime sky. Similarly, radar observations are possible only when the object is near enough to the Earth for the echo of a radar bounce to be detected. Once all the observations for an object have been collected, an orbit determination process is used to find the orbit that best fits all the observations.

It is important to understand that an object’s orbit is never known perfectly. Although the nominal orbit solution fits the observations best, slightly different orbits may still fit the observations to within their expected accuracies. There is in fact a whole set of orbits around the nominal that will fit the observations acceptably well: these all lie within what we call the uncertainty region about the nominal orbit. The ‘true’ orbit is expected to lie somewhere within this region. As new observations of the object are made, the uncertainty region becomes more tightly constrained and the range of possible values for the orbital elements narrows. As a result, objects that have been observed for decades will have highly constrained, well-known orbits, while newly discovered objects tracked for only a few days or weeks, will have relatively poorly constrained, uncertain orbits.

Once the nominal orbit and its associated uncertainty region have been determined, the object’s motion is numerically propagated forward in time for at least 100 years in order to determine its close approaches to the Earth. These nominal orbit close approach predictions are tabulated in our Earth Close Approach Tables along with other uncertainty-related information such as the minimum possible close approach distance, and the impact probability. The uncertainty-related parameters in the close approach tables are computed by propagating the uncertainty region from the epoch to the respective close approach times via so-called linearized techniques. Since these techniques lose accuracy when the uncertainties become large, we include only reasonably certain predictions in our Close Approach Tables. As a result, close approaches may be tabulated decades into the future for objects with well-known orbits, but only a few months or years into the future for objects with poorly known orbits. On the other hand, Sentry assesses the long-term possibilities of an Earth impact for all objects whose orbits can bring them close to the Earth, even those with poorly known orbits. To perform this risk analysis Sentry uses more sophisticated nonlinear methods.

I don't know if there's an API or feeds or what, I haven't looked that closely into it yet.

The official website for a transhumanist-themed RPG which is light on the rules but heavy on the "Wow, my character can do that?!" factor.

An interesting article discussing a hierarchy of potential eschatological events.

A well thought out and carefully written paper discussing existential risks to the human race.

A website that discusses apocalypse/X-threat scenarios with a tongue-in-cheek sense of humor.

Anders Sandberg's transhuman warning signs.