A Direct Observation of the Asteroid's Structure from Deep Interior to Regolith: Two Radars on the AIM Mission Alain Herique V Ciarletti, D Plettemeier, J Grygorczuk & radars team

Internal structure Which internal structure ?  No direct observation …  Aggregate ?  Covering regolith ? Fathom asteroid : Science  To validate and to improve our understanding of the asteroid’s evolution from accretion to now  To better model low gravity mechanics Spacecraft interactions with asteroids  Planetary defense, Exploration, Sample return Alain Herique

Internal structure : Deep interior Discriminate Agregate / Monolith Characterization of the size of building blocks  Binary formation scenarios  Collisional history  Modeling the response to impacts o Dynamical model including accretion o Condition of stability o Risk mitigation Understanding heterogeneities of composition & porosity  Individual blocks => Parent bodies o Metamorphism o Relation between meteorites and asteroids Alain Herique

Internal structure : shallow subsurface Diversity between different NEAs  Depth, Texture, size of elements  Spatial distribution Formation and evolution  Gravitational accretion  Thermal fragmentation  Mass redistribution main / moon  Reconnection surface / deep interior Thermal properties  Yarkovsky acceleration DART Impact modeling  Mass redistribution Alain Herique 10m

Internal structure : How ? The radar is the only instrument to characterize the interior from metric scale to global scale Deep Interior Radar : LFR / AIM A Low Frequency Radar to perform the tomography of the deep interior (structure, size of block and compositional heterogeneity) o Bistatic radar (Consert like) with Mascot 2 on Didymoon Shallow Subsurface Radar : HFR / AIM A Higher Frequency Radar channel to fathom the regolith (depth and structure) Alain Herique

LFR : concept Alain Herique

30 min of soundings Propagation delay Power (dB) ESA/Rosetta/Consert/Philae/IPAG, LATMOS, MPS, CNES, DLR Orbiter’s angular location LFR : Consert

LFR : Transponder Transponder :  Clock stability:  f/f ~10 -8 Alain Herique

LFR : antenna Mascot 2 2 short antennas (from separation to final location)  large BW / low gain -10 dB (TBC) 2 long antennas for science  Heritage : TRL 7  1.5 m long CBK design Alain Herique

LFR : antenna AIM 4 booms  Circular polarization  1.5 m long Alain Herique

LFR : Budgets and performances Alain Herique Mass (g)AIMMASCOT-2 Electronics920 Antenna Total wo marging Power max / mean 50 W / 10 W Data (Gbit) 10.3 LFR carrier 60 MHz signal BPSK BW 20 MHz nominal 30 MHz extended Resolution 10 – 15 m (1D) Polarization Circular (AIM) Linear (Mascot) Tx power 12 W Total dynamics 180 dB

LFR : moon structure Discrimination : aggregate / monolith  1 measurement sequence (moon revolution)  Texture of the signal : scattering, multipath ….  Averaged permittivity Detail Internal structure  7 measurement sequences from -25° to +25° latitude  Spatial variation of the signal texture - propagation delay  Replayed after DART Signal reflected by surface during descent  Map of the surface permittivity close to landing point Alain Herique

LFR : main surface Grazing incidence angle sounding  Near surface layering of the main (~50 m TBC) Signal reflected by the main surface  Permittivity estimation of the first 10 meters  Requires coherent processing (clock ) Feasibility depends in the final landing site Alain Herique

LFR : dynamical state & gravity field S/C - Lander Ranging during descent & relocation  Good SNR => resolution better than 3 m  Gravity field  Operational purpose => lander localization S/C - Lander ranging during visibility  Dynamical state  Added value to be evaluated Very prospective : LOFAR  Ground based radiotelescope  Ranging Earth / DidyMoon (mascot)  Long term monitoring  Mascot Automatic mode  SW issue only Alain Herique

HFR : concept Monostatic (orbiter only) radar inheriting from Wisdom / Exomars  Step frequency  Nominal bandwidth from 300 MHz to 800 MHz  Extended up to 3 GHz  Tx 20 W  Circular polarization Alain Herique

HFR antenna 2 Vivaldi antennas  Inheriting from Wisdom  Enlarged (optimized for MHz)  Large beam (> 60°)  TUD / Dresden Alain Herique

HFR : Budgets and performances Alain Herique Mass (g)AIM Electronics830 Antenna1 560 Total wo marging2 390 Power max / mean 137 W / 90 W Data 300 Gbit HFR carrier 300 – 800 MHz => 3 GHz signal Step frequency Resolution 1 m (3D) Polarization Tx : 1 Circular Rx : OC and SC Tx power 20 W NEσ dB.m 2 /m 2

HFR : Tomographic SAR Synthetic Aperture Radar with 3D tomography First tens meters / metric resolution Performances given by the acquisition geometry.  range measurement (1 st dim.)  moon / main motion (2 nd dim.)  S/C motion : multipasses acquisition (3 rd dim.) Alain Herique

HFR : moon / main regolith 1 pass  2D mapping  including surface and subsurface  2 Polarizations ~20 passes  3D tomography  Resolution ~1 m  Sensitivity -40 dB.m 2 /m 2  Dynamic range -20 dB Before / after DART interferometry  Coherence losses  Crater shape  Shape deformation (10 cm) Alain Herique Chandrayan MiniSAR S Band (2.3GHz)

HFR : moon / main regolith 1 pass  2D mapping  including surface and subsurface  2 Polarizations ~20 passes  3D tomography  Resolution ~1 m  Sensitivity -40 dB.m 2 /m 2  Dynamic range -20 dB Before / after DART interferometry  Coherence losses  Crater shape  Shape deformation (10 cm) Alain Herique

HFR : moon / main regolith 1 pass  2D mapping  including surface and subsurface  2 Polarizations ~20 passes  3D tomography  Resolution ~1 m  Sensitivity -40 dB.m 2 /m 2  Dynamic range -20 dB Before / after DART interferometry  Coherence losses  Crater shape  Shape deformation (10 cm) Alain Herique

HFR : secondary objectives Dynamical state  Altimetry : Distance S/C - moon & S/C – main (closest point)  300 – 800 MHz o 30 cm resolution  Full bandwidth resolution o better than 5 cm  Orbit reconstruction o Support LFR operations? Arecibo mode  2.3 – 2.4 GHz  2D mapping with resolution o Cross interpretation of Arecibo o Joint measurement ? Alain Herique