Could someone use Julia to predict what location on Earth would be affected if 2006QV89 impacts Earth? I imagine it would depend on the Earth’s daily rotation at the time.
Please let me know if somebody can predict what the rotation of the Earth would be at the time and location of the area where an impact is possible, would be interesting if Julia could be used for that.
You could use BF, too, I’m sure. It just takes work. Asking others to do that work for you is neither feasible nor kind.
You might find better success asking what tools are currently available and how to use them or doing a bit more legwork yourself in determining what predictions are currently available.
Hi @chakravala,
Yes, you can do this in Julia for sure. The real problem is that the accuracy would be very, very bad (not because of Julia, but the system itself).
You will have to use a package to get the position of the planets, compute the force each one applies to the asteroid, possibly consider things like relativistic effects, create an ODE to be solved by a high order, very accurate solver, and solve the system using a measured state vector for the initial condition. Then, you will have propagated the asteroid orbit. Now, you need to check for close approaches to the Earth. All of this can be done using available toolboxes in Julia (DifferentialEquations.jl, JPLEphemeris.jl, SatelliteToolbox.jl, etc.).
Let’s suppose your algorithm shows a possible collision. In the simulated world, it is easy to predict where the asteroid will fall. However, this system can even be chaotic sometimes. A very small change in the initial state would lead to huge differences in the outcome. The asteroid initial state (position and velocity) measurement you have now are not that accurate. Thus, the result you obtain today would be likely very different one week from now.
This is why the margins we consider to declare risk are very high. This particular asteroid, according to ESA, will pass 2,655,140 km away from Earth on December 19, 2023. This is more than 7x the distance between Earth and Moon. Yet, this object is in the risk list.
What it is possible to do in Julia (and will be very nice) is to construct a system that accounts for the impact probability given the measurement and modeling uncertainties. ESA is using something like that on that website you linked.
Thus, TL;DR: yes, you can do this in Julia using existing packages with some glue code, but the accuracy will be very bad given the characteristics of the system.
Regarding computing the possible collision of the asteroid with the Earth, as @Ronis_BR described above, this is possible and not easy. Accuracy is important, not only due to the intrinsic complicated ODE system (which does require including relativistic corrections and other non-gravitational interactions), the errors introduced by your numerical integrator, but also because initial conditions and other parameters involve uncertainties. In JuliaCon 2017 we presented something related for Apophis using TaylorIntegration.jl; you can find the presentation here. Apophis’ close approach is about ~1/10 the Earth-Moon distance; the important date is April 13th, 2029.
cc @PerezHz
This is awesome! I completely missed this presentation. I am looking forward to watch it. Thanks for posting it here 
At the JuliaCon 2019 I will present Grassmann.jl, which together with Leibniz.jl will be able to do multivariate Taylor number computation with relativistic space-time geometry using conformal algebra.
Right now, I just committed an entire suite of hyperbolic / trigonometric functions for use with arbitrary conformal space-time algebras, which will also work with the Taylor numbers when ready.
Perhaps these kind of problems will be easier to solve when the geometry of space-time is built into the algebra used for the automatic differentiation, since CGA is a natural language for it. This is not the kind of problem I am specifically working on, but it would be one of the possible applications perhaps.
This year I will be unable to attend JuliaCon, which I am regretting. So please ping me when your presentation is online, though i will try to follow it as others have done previously. I am certainly interested in the subject and I would like to know more about your work.
I would like to simply note that the ODE system referred above uses post-newtonian corrections among other (non-sphericity of some major bodies), and what is more important, non-gravitational corrections which in some cases are dissipative. I do not expect that the ODE system is invariant under Lorentz transformations, but I maybe wrong. It is certainly a fair possibility worth investigating.
When you have determined whether and where the asteroid enters Earth’s atmosphere the fun only begins. The interactions between a body and the atmosphere are highly complex and depend on a lot of factors, e.g. shape and composition of the asteroid which will influence the breakup behaviour and the aerodynamic characteristics.
I had an interesting conversation with one of ESA’s space debris analysts about the reentry of Tiangong-1 last year. While it is, of course, a different problem it nicely illustrates the difficulties of predicting an impact location on Earth even for an object with a closely monitored orbit.
IMHO Julia would still be a prime choice for doing this kind of modelling, though 
The point about interactions with the atmosphere is interesting.
In the context of 50 years since Apollo, at that time NASA Seemed to be able to predict the landing area of the capsule to within a few miles. I guess a regularly shaped capsule is easier to model than an irregular asteroid which may be splitting up.
Also the work on Apollo capsules would have followed on from nuclear weapons targeting, as the capsule shape is the same. And indeed the Mercury/Gemini capsules were coupled to ICBMs.
2006 QV89 might be regarded as an example of how observational uncertainties add another challenge when predicting impact probabilites of asteroids with Earth. For example, as this tweet shows, an amateur astronomer who provided observations of 2006 QV89 back when it was discovered, re-measured his observations wrt the Gaia stellar catalog and re-submitted them to the Minor Planet Center; this happened as recently as May 2019. In turn, his updated observations prompted impact risk monitors to update their orbital solution for 2006 QV89. JPL’s latest solution for this asteroid (labeled as solution #20) was produced on May 30th, 2019, and their impact risk monitoring system, Sentry, reports an impact probability of 1.1e-4 on September 2019 for this object. 2006 QV89 should be observable from July/August onwards; new observations should further reduce the impact probability.
That is exactly the point 
. The aerodynamic properties of a reentry vehicle are very well understood and then you can make highly accurate predictions.
The accuracy of the landing site prediction is still quite low compared to the level of accuracy we can achieve in space where the forces are much easier to model, e.g. sub-meter (if you track long enough and the spacecraft participates) vs. several kilometers.