How to intercept an incoming NEO
Joachim Köppen Kiel/Strasbourg/Illkirch February 2002
The NEOscan Applet extends the NEOintercept Applet by the option to make a systematic search for all true interceptions of the incoming NEO, and to inspect and compare the condistions and the requirements of these mission. For the explanations for most features, we refer to its Help Page .
The Scan Page looks like this
Zoom in a bit on the left diagram, and start the Simple Scan
The green dots show where the interception is too late, while the red dots where an interception is too early.
Because in the region chosen in the left plot, there are both kinds of dots, we can start the Full Scan to automatically find all optimal interceptions, as a function of the initial speed. This takes some time, and whenever the optimum was found for a given speed, this trajectory is marked on the right hand plot, and a red dot is placed on the left hand one. You may always break off this scan by clicking on the Stop button. Eventually, all calculations have been done
And now we can inspect on the right hand side all kinds of quantities as they depend on the initial speed, such as the energy required for a deflection:
Evidently, a fast approach requires less energy to make the same deflection than a slow approach....
The Simple Scan makes a systematic survey of the shown parameter space on an evenly spaced grid, as you can see.
The Full Scan searches on each value of the parameter on the horizontal axis where the borderline between red and green dots is. This is done by the bisection method: we start with two guesses, one above and one below, and we try out the parameter in the middle. Depending on the outcome, we then select for further search that pair of parameter guesses which give a late and an early interception. This procedure is repeated until a given small tolerance is reached.
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