NEO trajectory math.
Posted 11 January 2013 - 10:39 AM
The degree of accuracy must be, for a lack of a better term, Astronomical.
As an example, what kind of accuracy was required to determine that Shoemaker Levy 9 was going to hit Jupiter on it's next pass?
Also, How much of the computations involve gravitational influences of the sun and planets and moons?
I am thinking it is roughly equivalent to shooting a BB at a beach ball from across the ocean. (just a guess)
Posted 11 January 2013 - 10:50 AM
The trick is you need to know precisely where an object is and its exact mass -and that is not the easiest thing to find. A tiny error at the start can amplify into millions of miles after several orbits.
That's why you hear, 'A NEO object has the potential to to Hit Earth in the year 2075' or something to that effect. They project out the orbit and the farther they go the more the error brackets enlarge. What they are saying is that at some point in their margin of error the Earth could coincide in orbit with the NEO.
Pesse (It's a great headline but if the error brackets extend from Venus to Mars...?) Mist
Posted 11 January 2013 - 11:20 AM
For objects that are far apart (like the planets from each other), you can calculate their orbits out a long way very accurately. This is because gravity works by the inverse square of the distance - when you objects are far apart, the change in gravity is small per unit distance, so even if your estimate of position is off a bit, it doesn't change the prediction much.
Close passes are a different matter - when something is passing close to a massive object, small changes in location turn into big changes in gravity and velocity. So predicting orbits after one of those either requires that you get really precise measurements ahead of time, or wait until after the close pass and see what happens.
Posted 11 January 2013 - 02:17 PM
Fortunately, the trajectory of encounters such Shoemaker-Levy-9 involve relatively few bodies and short time scales, so the numerical methods available can make quick work of its path.
Posted 11 January 2013 - 05:09 PM