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Probing The Interior Of 99942 Apophis In 2029 With The 2 Cubesats Of The Droid Mission

Presentation #405.12 in the session Asteroids: Planetary Defense (Poster + Lightning Talk)

Published onOct 23, 2023
Probing The Interior Of 99942 Apophis In 2029 With The 2 Cubesats Of The Droid Mission

The DROID (Distributed Radar Observations of Interior Distributions) mission is proposed to rendezvous Apophis before closed approach offering a unique opportunity to survey this PHA. The DROID mothership will arrive months prior to Earth closest approach (ECA) proving crucial optical observations before and after closest approach to monitor any induced response. After ECA, the mothership will release two CubeSats which will orbit Apophis for several weeks. These two CubeSats will offer a unique opportunity to directly observe Apophis internal structure with a Bistatic Low Frequency Radar associated to the gravity field from the Inter Satellite Link (ISL). The mission concept has been developed in collaboration between NASA/JPL and CNES. In the frame of the JPL/CNES collaboration, the mothercraft and its payload is proposed to be developed and operated by JPL while the two CubeSats are proposed to be developed and operated by CNES, including the radar and the ISL.

Knowledge of Apophis’ internal structure is crucial to better understand its accretion and dynamical evolution, to improve our ability to study its stability conditions and to model its response to the gravitational constraints induced by Earth close approach. This is also crucial to plan any interaction of a spacecraft with Apophis especially for Planetary Defense purposes. Radar observation of Apophis from a spacecraft is one of the most mature technique capable of achieving these objectives, by providing a direct measurement of its interior. The proposed radar will be a modified version of JuRa developed for the Hera/ESA mission allowing it to operate in both monostatic and bistatic modes with a carrier frequency of 60MHz and 20MHz bandwidth. Multipass processing allows us to build a 3D tomographic image of the interior to identify internal structure like layers, voids and sub-aggregates, to bring out the aggregate structure and to characterize its constituent blocks in terms of size distribution and heterogeneity at different scales from submeter to global. Accurate knowledge of the CubeSats orbit from ISL is also an opportunity for radio science to retrieve the first orders of the gravity field which are related to the larger scales of the interior heterogeneity.

The presentation will focus on the radar and the ISL, the science objectives and the operations strategy.

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