Multistatic Radar Sounding with Distributed Surface Packages for Small Body Characterization

We propose a novel radar mission architecture to characterize the internal structure, near-surface stratigraphy and gravity field of a small asteroid by multi-static radar sounding using a distributed network of miniature surface packages and orbiting radar platforms. This concept is similar to the CONSERT (COmet Nucleus Sounding Experiment by Radiowave Transmission) experiment that was part of the Philae lander on the Rosetta mission, but instead of a single unit, our system employs multiple units. By colocating transmitters and receivers on the surface, our concept eliminates free-space interface losses at the vacuum-regolith boundary. Simulations on a simplified rubble pile model (Fig. 2) show significant SNR improvements, compared to an orbiter based radar link budget.  In ground penetrating mode, direct subsurface measurements at each lander position enable high resolution radargrams. Utilizing a unique inter-satellite link (ISL) approach, descent tracking provides valuable gravitational field data. Furthermore, radar-landing dynamics and bounce behavior constrain regolith mechanical properties.In addition to the main orbiter, one or more CubeSat-class secondary orbiters are foreseen. The primary and secondary orbiters also carry radar transceivers, enabling bi-static and multi-static measurement geometries between surface packages and orbiters. Multistatic synthetic aperture measurements improve target illumination diversity, increase signal-to-noise ratio (SNR) and enable 3D tomographic reconstructions of the asteroid interior. The main scientific objectives are     1. Elucidate the internal structure (e.g. rubble pile vs. solid core, stratification, voids, compositional variations) with sub-10m resolution.     2. Resolve fine-scale stratigraphy in the upper ~10 m of regolith at each landing site to infer formation and evolutionary processes.    3. Derive gravity field information from descent trajectories to constrain mass distribution and internal density anomalies.     4. Assess regolith mechanical properties by combining radar signatures with accelerometer data from landing dynamics.     5. Measure surface temperature in situ to improve emissivity estimates and constrain thermal properties of the regolith. Up to 15 compact surface packages (1/3U CubeSat form factor; 90 × 90 × 30 mm) will be deployed by the primary orbiter. Each surface package houses a broadband radar transceiver capable of switching between: (a) high- frequency mode with up to 5.5 GHz instantaneous bandwidth for centimetre -scale resolution in the upper ~10 m; (b) lower frequencies mode (50-100 MHz) for deeper penetration.The packages are solar powered for extended operations with a pre-charged battery, sufficient for the primary objectives, even without solar power.  They include an additional sensor pack with thermometers and a MEMS based 3-axis accelerometer.  Each densely packed unit weighs about 400g and is equipped with a turnstile antenna for the low-frequency multistatic radar operation, deployed during the descent.The radar supports FMCW, gated FMCW, coherent chirp, and FSK/PSK modulation modes.  Its power consumption is