Changes in Apophis rotation and surface gravity during its 2029 Earth flyby
Authors: Noiset Guillaume , Tasev Elisa , Karatekin Özgür 
Published: September 2022

&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Apophis, the Asteroid 2004 MN4 is one of the Near-Earth Object (NEO) with regular and very close Earth en-&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;counters. During the next encounter in 2029, Apophis will flyby by about a distance of 36000 km above the surface&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;of Earth. During this close flyby, the orbit and dynamics of Apophis is expected to vary significantly due to gravi-&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;tational interactions with the Earth (Scheeres et al., 2006; Souchay, Lhotka, et al., 2018; Souchay, Souami, et al.,&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;2014). The surface is not expected to undergo catastrophic disruption, however it may be subject to tidal stresses&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;and localized failures resulting in debris (Scheeres et al., 2006).&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;The variations of orbital parameters, i.e.&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;spin,&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;obliquity, longitudinal and latitudinal librations am increase considerably during the closest-approach epoch which&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;will be observable in real time by groundbased radar and telescopes.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Here we present the numerical simulations using the full-two-body (F2BP), where the rotational and translational&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;dynamics are fully coupled. F2BP can fully capture the system&amp;#8217;s dynamics taking into account the objects&amp;#8217; irregular&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;shapes and the close proximity of the components . The system&amp;#8217;s dynamical evolution is especially sensitive to the&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;shapes and initial positions and orientations of each component. Here we use the open source F2BP code GUBAS&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;(Davis and Scheeres, 2020).&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;The initial position and speed come from Horizon System from the Jet Propulsion&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Laboratory, the initial orientations from Pravec et al., 2014 and the system is propagated using a LGVI integrator.&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;We use a radar based shape model for Apophis (Brozovi&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;c et al., 2018) while the Earth is modeled by an ellipsoid&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;of revolution.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Starting from when Apophis enters the sphere of influence of Earth until it leaves it, we propagate the dynamical&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;parameters. The results shows significant changes in the rotational state of Apophis already few hours before the&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;closest-approach. In addition to rotational and orbital parameters, we calculate also the changes in surface gravity&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;and dynamical slopes during the close encounter. The changes in Apophis rotation and surface changes, including&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;potential localized failures across its surface, are important parameters for planetary defense missions since they&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;provide information on otherwise inaccessible interior and mechanical properties of the asteroids.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Scheeres, D. J., et al. (2006). Dynamical configuration of binary near-earth asteroid (66391) 1999 KW4. &lt;em&gt;Science, 314&lt;/em&gt; (5803), 1280&amp;#8211;1283.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Souchay, J., Lhotka, C., et al. (2018). Changes of spin axis andrate of the asteroid (99942) Apophis during the 2029 close encounter with Earth: A constrained model. &lt;em&gt;Astronomy and Astrophysics, 617&lt;/em&gt;, 1&amp;#8211;11.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Souchay, J., Souami, D., et al. (2014). Rotational changes of the asteroid 99942 Apophis during the 2029 close encounter with Earth. &lt;em&gt;Astronomy and Astrophysics, 563&lt;/em&gt;, 1&amp;#8211;6.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Davis, A. B., &amp; Scheeres, D. J. (2020). Doubly synchronous binary asteroid mass parameter.&lt;em&gt; Icarus, 341&lt;/em&gt;.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Pravec, P., et al. (2014). The tumbling spin state of (99942) Apophis. &lt;em&gt;Icarus, 233&lt;/em&gt;, 48&amp;#8211;60.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Brozovi &amp;#769;c, M., et al. (2018). Goldstone and Arecibo radar observations of (99942) Apophis in 2012&amp;#8211;2013. &lt;em&gt;Icarus, 300&lt;/em&gt;, 115&amp;#8211;128.&lt;/span&gt;&lt;/p&gt;