thor VS oorb

Hi, I work on N-body orbit determination software for asteroid detection and planetary defense (for example, https://github.com/moeyensj/thor). Ask me anything.

You're right that orbit determination is unstable over long runs, and very sensitive to initial conditions. But the good news is that the solar system is big. Most trajectories do not intersect with the earth's location. So perturbing an orbit that we think has a small chance of hitting us tends to be safe.

Also, of course, after deflection, any object is going to be monitored really closely for a long time.

Imagine my surprise to see OpenOrb, the standard open source software package for orbit determination and minor planet propagation, on the front page of HackerNews. Its interesting software with a beautiful theoretical basis in Bayesian statistics, and a gnarly Fortran codebase - I can’t wait to see the discussion!

Oh.

It’s one thing to land near a name in use. It is quite another to take it directly!

https://github.com/oorb/oorb

Mostly Python and Fortran. See for example https://github.com/oorb/oorb.

The hardest problems are always the social ones. How do you get uptake of a new method, how do you get funding, how do you politely tell a collaboration they are doing the wrong thing, etc.

But if you mean pure technical stuff - the hardest problem I had to solve was rethinking some of the inner loops of the THOR algorithm. The problem was essentially to speed up a Hough transform in 6D space. Lots of time spent profiling CPU cache timings to get that fast.