2017.A.3.4. What is a rubble pile asteroid? A CubeSat Mission to find out


Patrick Bambach (1)
Jakob Deller (1)
Sampsa Pursiainen (2)
Hans Braun (3)
Mika Takala (2)

  1. Max-Planck-Institute for Solar System Research, Germany
  2. Tampere University of Technology, Finland
  3. RST Radar Systemtechnik, Germany




Swarm, Asteroid, radar, navigation


While most smaller asteroids in the size range of around 130 m to 100 km in diameter are not monolithic bodies, but rather rubble pile aggregates, little is known about the exact configuration of their internal structure. The internal configuration of rubble pile asteroids is fundamental to understand the collisional evolution of the solar system, and also it is of high importance for the design of future asteroid deflection concepts.

A conceptual design was performed for a tandem (bistatic) 6U CubeSat mission to reconstruct the interior of a rubble pile asteroid. An off-theshelf electric propulsion system would offer a dv of more than 2.4 km s−1 for the mission. Together with one of the many proposed launcher platforms going into a lunar transfer orbit reaching NEAs with a dv of up to 4 km/s is possible. Various NEAs approaching closer than 20 LD  are reachable with this dv budget. In order to image the interior of an asteroid,. Using a configuration of two identical satellites enables the measurement through the asteroid.

The full wave information can be inverted through an advanced computed radar tomography (CRT) approach originating from medical imaging applications. Full-wave inversion is a computationally intensive imaging technique which allows for robust volumetric reconstruction of targets that are penetrable by a waveform signal. In CRT, the 3D relative permittivity distribution of the interior can be recovered. The resulting data will therefore be able to answer the question of the interior structure of rubble pile asteroids.

The radar itself will be a one-cube element carrying a 2×3.75 m dipole antenna. It uses a stepped frequency modulation with programmable number of frequency lines between 256 and 2048 providing a bandwidth of about 2 MHz in order to keep the data rate at an acceptable limit.


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