The distance is going to be about half the distance between the earth and the moon, and when you come that close to the earth, the gravity of the earth is going to change your trajectory in a significant way and in order to know the trajectory after the Encounter you really need to know the position of bennu right before the encounter so that you can model how the gravity is going to perturb the motion of banner and in particular, we have to deal with the so called gravitational keyholes keyholes are narrow locations in space. At the time of 2135 encounter, if then were to pass through one of those keyholes, then the gravity of the earth would tweak the motion of bennu by just the right amount to put it on a collision trajectory at a later date in the 22nd century. So we really want to avoid those keyholes. However, there is a problem that, in order to model and predict the position of bennu in 2135, we need to account for a subcontrol gravitational perturbation called yarkovsky fat. The yokosuke effect is due to sunlight reaching the asteroid and warming up its dayside as the asteroid is rotating the night side cools down and the heat gets released and that causes a gentle push on the asteroid and thats. A very small push ill make an analogy. The yarkovsky effect acting on bennu is equivalent to the weight of three grapes. Think about that. Just three graves and thats whats really driving the motion of ben into the future, because this acceleration is persistent.

Its effect builds up over time and it becomes very significant by the time we get to 2135, so whats the problem with it. Well, the yarkovsky effect really depends on the specific properties of the asteroid. Youre working on. In particular, you need to know the asteroid size. Mass shape, rotation, state, surface and thermal properties, and those are information that are really hard to collect from the ground, its really hard to measure this kind of information from the ground and thats where desires rex comes in because the spacecraft went to bennu, it stayed in Orbit for about two years collected all the data we needed in order to quantify these physical properties, and that gave us all the ingredients we needed to compute the yarkovsky acceleration and account for that, as we modeled the future motion of bennu as the spacecraft went down To the surface and collected the sample it touched, the asteroid is that enough to perturb the motion of bennu. Well again, we spent our time computed. You know the the size of the this effect and established that that was not affecting the motion in any significant way. Whats the result of this study. Well, we have a much much better knowledge of the trajectory of bennu. Thanks to the azerus rex mission, we improved that knowledge by a factor of 20.. We have a knowledge of the position of bennu in 2035. That is better by factor 20 than what it was before and that allows us to rule out many of the possible keyholes that were out there just to quantify this.

We had about 26 keyholes greater than one kilometer. There were a possibility before designstrex mission. Now we only have two of those keyholes greater than one kilometer that we we need to consider. So this improved knowledge confirmed that ben is going to miss many of those keyholes, even though a few of them remain a possibility. The benefit is that now we have a much better knowledge of what the pathways to impact can be, and the most significant one would lead to an impact in 2182. But we should keep in mind that the impact probability overall is really small. In fact, the overall impact probability is 0.06 percent, which put another way means that there is a 99.

https://www.youtube.com/watch?v=5nMDWS8AwJY