DISCUS – The Deep Interior Scanning CubeSat mission to a rubble pile near-Earth asteroid

Abstract

We have performed an initial stage conceptual design study for the Deep Interior Scanning CubeSat (DIS-CUS), a tandem 6U CubeSat carrying a bistatic radar as the main payload. DISCUS will be operated either as an independent mission or accompanying a larger one. It is designed to determine the internal macroporosity of a 260-600 m diameter Near Earth Asteroid (NEA) from a few kilometers distance. The main goal will be to achieve a global penetration with a low-frequency signal as well as to analyze the scattering strength for various different penetration depths and measurement positions. Moreover, the measurements will be inverted through a computed radar tomography (CRT) approach. The scientific data provided by DISCUS would bring more knowledge of the internal configuration of rubble pile asteroids and their collisional evolution in the Solar System. It would also advance the design of future asteroid deflection concepts. We aim at a single-unit (1U) radar design equipped with a half-wavelength dipole antenna. The radar will utilize a stepped-frequency modulation technique the baseline of which was developed for ESA's technology projects GINGER and PIRA. The radar measurements will be used for CRT and shape reconstruction. The CubeSat will also be equipped with an optical camera system and laser altimeter to support navigation and shape reconstruction. We provide the details of the measurement methods to be applied along with the requirements derived of the known characteristics of rubble pile asteroids. Additionally, an initial design study of the platform and targets accessible within 20 lunar distances is presented.

A Time-Domain Multigrid Solver With Higher-Order Born Approximation for Full-Wave Radar Tomography of a Complex-Shaped Target

“…Regarding the practical aspects of a space mission design, placing the transmitter in the mothership might be convenient to guarantee its power supply. Small spacecrafts could carry the additional receivers for the chosen measurement configuration [34], [35]. Therefore, in addition to the monostatic and bistatic configurations, the multistatic one can also be considered as a potential scenario for a future space mission.…”

“…The results suggest that, using the present approach, a candidate solution for the full non-linear inverse problem can be found in a sufficiently short time with improved accuracy when compared to solving a linearized inverse problem. Furthermore, it seems that maximizing the benefit of the potential future bistatic [34], [35] and multistatic measurements [36] yielding a sparse set of data might necessitate applying a higher-order BA.…”

Far-Field Inversion for the Deep Interior Scanning CubeSat

“…This paper introduced and validated a mathematical far-field model applicable in the Computed Radar Tomography (CRT) imaging [1], [2] of small solar system bodies (SSSBs). In particular, the Deep Interior Scanning CUbeSat (DISCUS) mission concept [14], [15] was examined as a potential application of this method. The numerical results obtained with the test asteroid model and the relative total noise range of -25-0 dB suggest that a sparse set of full-wave measurements can be inverted with the planned DISCUS mission specifications.…”

Bistatic Full-wave Radar Tomography Detects Deep Interior Voids, Cracks, and Boulders in a Rubble-pile Asteroid Model

“…Inheriting from the DISCUS concept (Bambach et al 2018), the radar is assumed to have a transmission power of 10 W, a 2 MHz total signal bandwidth, and a relatively low 20 MHz center frequency. In practice, ≤ 100 MHz will be necessary in order to achieve appropriate signal penetration and to minimize solar noise (Kofman 2012).…”