How many inches will gravitational tethering move Apophis off course?
As far as I understand it, gravitational tethering is used to change the angle of the asteroid’s trajectory. Therefore to ask how many inches the asteroid is moved is not quite the right question. This is because once the angle of trajectory is changed, even by a tiny bit, eventually the asteroid will be millions of miles from where it would have been. Given enough distance and time then theoretically the asteroid will be moved an infinite distance from it’s original path. But practically it will never get infinitely far, only very very very far. The technical challenge for tethering Apophis or any other near-Earth asteroid is that you have to interfere with it’s trajectory sufficiently far from the earth in order to make a big enough change to be effective. The larger the spacecraft that is sent to tether with the asteroid and the longer it is near the asteroid the greater the angle of trajectory is changed. I hope this helps.
