Speaker
Description
The close flyby of asteroid (99942) Apophis on April 13, 2029 presents a unique
opportunity to achieve scientific and planetary defense goals. A multi-spacecraft
mission concept to exploit this opportunity has been developed in a collaboration
between Caltech, JPL and CNES. The Caltech-led mission is being pursued as a
privately funded venture with commercial partners. Its architecture employs a high
delta-V Mothership and two 12U CubeSats that would rendezvous with Apophis prior
to Earth closest approach and escort it through the encounter. Its measurements can
determine: the body’s shape and density; the size, distribution, and arrangement of
blocks and voids in the interior; surface movements or reshaping during the Earth
flyby; as well as spin state changes. Its goals are to understand the interior structure
of a (presumed) rubble pile asteroid and implications for its formation, evolution and
response to deflection, and to understand how close planetary encounters affect
asteroids. The Caltech mission would provide unique high fidelity in situ data to
complement and enhance Earth-based optical and radar observations of Apophis, as
well as data from NASA’s OSIRIS-APEX mission. Low-frequency (≤60 MHz) bistatic
radar observations are performed to probe Apophis’s interior, revealing the
distribution of monolithic objects and voids within. These data would complement
low-frequency monostatic radar data from ESA’s RAMSES mission should it fly a
radar. The Mothership would carry the CubeSats to Apophis, achieve the
rendezvous cruise trajectory, perform high resolution imaging, and act as a Direct-to-
Earth node for the constellation. A narrow-angle multi-band camera on the
Mothership performs imaging for shape, morphology and geology. After deployment,
the CubeSats insert themselves into coordinated low orbits to perform monostatic
and bistatic radar observations to probe internal structure. Radar data products
include 3D volumetric backscatter via monostatic/bistatic tomographic SAR, and
average dielectric constant along interior bistatic ray paths to assess internal
heterogeneity. Inter-Spacecraft Link S-band transponders on all spacecraft perform
intra-constellation data transfer, synchronize the CubeSat clocks for accurate bistatic
radar measurements, and aid in recovering Apophis’s gravity field. The mission is
currently in Phase A, with partnerships and funding to be finalized early next year.
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Acknowledgement: A portion of this work was carried out at the Jet Propulsion
Laboratory, California Institute of Technology, under a contract with the National
Aeronautics and Space Administration (80NM0018D0004).