In-situ Radar for Asteroid Characterization and Altimetry NASA Asteroid Initiative Idea Synthesis Workshop Lunar and Planetary Institute, Houston, TX Sept 30 – Oct 2, 2013 In-situ Radar for Asteroid Characterization and Altimetry Mark Haynes Radar Science and Engineering (334c) Jet Propulsion Laboratory, California Institute of Technology Mark.S.Haynes@jpl.nasa.gov CL#13-4243 This document has been reviewed and determined not to contain export controlled technical data. (c) 2013 California Institute of Technology. Government sponsorship acknowledged.

Overview In-situ Radar for ARM Radar features Integrated sensing system Avionics tool Secondary science Radar features Self-illumination, shadow/dust independent Fast, near or far range Range, Doppler, physical scattering RFI subsections 2. Asteroid Redirect Mission: b) Integrated sensing system … rendezvous, proximity operations … characterize size, shape, mass and inertia properties, spin state, surface properties, and composition….closed-loop control. 3. Asteroid Deflection Demonstration: c) ... sub-surface penetrating imaging... 4. Asteroid Capture Mission: d) Asteroid composition, internal structure, and physical integrity will likely be unknown until after rendezvous and capture. 5. Crew Systems for Asteroid Exploration: ..., prospect for resources, ... 9/30/2013

Radar Landscape Past and Current Planetary Radar Missions and Science Goldstone Arecibo Asteroid Radio Science Goldstone and Arecibo NEOs, planetary science (moon, Venus, Mars satellites) Planetary missions with radar Atmosphere penetration Magellan, Cassini Sounding MRO / Mars Express Rosetta-CONCERT radar Landing/Rendezvous MSL, previous rovers Apollo/Shuttle Earth science remote sensing Asteroid missions (no in-situ radar) NEAR-Shoemaker, Dawn, Hayabusa, Osiris-Rex Cassini (Titan) Magellan (Venus) Mars Reconnaissance Orbiter (SHARAD) Mars Express (MARSIS) Rosetta (CONCERT) http://gssr.jpl.nasa.gov/dss-14.jpg http://www.naic.edu/public/about/photos/ http://saturn.jpl.nasa.gov/multimedia/images/newsevents/images/ http://science1.nasa.gov/media/medialibrary/ http://mars.jpl.nasa.gov/mro/mission/instruments/sharad/ http://mars.jpl.nasa.gov/express/gallery/ http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2002/11/ No in-situ radar on asteroid missions to date 9/30/2013

Radar Sounding Map the regolith Internal structure Bulk dielectric properties (density) Anchoring redirect thruster Sample and boulder return Improved asteroid trajectory estimate Radar is only active modality capable of sub-surface imaging Scan-line projection or dielectric inversion 100 MHz to 2 GHz => 20m to 1m depth 3 past/current sounder missions Scan-line projection Reflection Measurements Shape Iterative Dielectric Estimation Electromagnetic Scattering Model Scan-line projection (anatomy) Measurement points Rosetta - CONSERT MARSIS and SHARAD Dielectric inversion (physical properties) http://www.jpl.nasa.gov/news/news.php?feature=1667 Herique, Alain, and Wlodek Kofman. "Definition of the consert/rosetta radar performances." In EGS General Assembly Conference Abstracts, vol. 27, p. 1664. 2002. Voxelized dielectric model 9/30/2013

Shape reconstruction algorithm Tomography Delay-Doppler Tomography Delay measures range In-situ delay-Doppler asteroid tomography “Goldstone analog” Asteroid size, shape, spin, range to target, relative motion Frequency: 1 to 35 GHz => 1 to 0.1 m resolution Coarse antenna pointing Close-loop feed back during spacecraft maneuvers Differential Doppler – monitor spin changes GPS-proxy Doppler measures motion (rotation) Delay-Doppler images Shape - Spin Shape reconstruction algorithm Busch, Michael W., et al. "Physical properties of near-Earth Asteroid (33342) 1998 WT24." Icarus 195.2 (2008): 614-621. GPS-proxy New-delay Doppler Table lookup: determine spin and position 2) Space craft maneuver 1) Change in spin state (deflect thruster) 9/30/2013

Rendezvous - Altimetry - Targeting Apollo: X-band Altimetry/Landing radar Reduce orbit uncertainty using delay-Doppler echoes Post impact assessment Targeting and guidance On-route tomography to pinpoint impact time and location Landing General purpose rendezvous radar Try to repurpose the imaging radar for this. Impact: Same can be done optically possibly, LIDAR is out Single spacecraft impact targeting and guidance > 100k-1M km 9/30/2013

System Configurations Sounding antenna Comm. antenna System configurations Single antenna: tomography and sounding Sounding: separate UHF, VHF, or L-band antenna Use DSN comm. dish: S, X, Ka-band Power vs. range Earth observation radars: Satellite (800 km) ~ 1 kW (peak) Airborne (10 km) ~ 1-20 W (peak) Close range (100 m) ~ 1-10 mW (peak) On-board vs. ground based processing On-board: scan-line sounding, altimetry, targeting, tomo. Ground-based: dielectric inversion, tomo. End-to-end system simulation Tomo. Scan-line sounding Dielectric inversion On-board processing Ground processing 9/30/2013

Summary RFI subsections 2. Asteroid Redirect Mission: … integrated sensing system … … rendezvous, proximity operations … … characterize size, shape, mass and inertia properties, spin state, surface properties, and composition … …. closed-loop control … 3. Asteroid Deflection Demonstration: ... sub-surface penetrating imaging ... 4. Asteroid Capture Mission: … composition, internal structure, physical integrity … 5. Crew Systems for Asteroid Exploration: ..., prospect for resources, ... Rendezvous Tomography Sounding Rendezvous Tomography GPS-proxy Altimetry Landing Impact Assessment Impact guidance Sounding 9/30/2013

Thank you Questions Mark Haynes Radar Science and Engineering (334c) Jet Propulsion Laboratory, California Institute of Technology Mark.S.Haynes@jpl.nasa.gov 9/30/2013

Rough Surface Characterization Synthetic aperture radar (SAR) to characterize rough surface properties Correlation length, rms height, near-surface volume scattering (density estimation) Rough surface parameters used for thermal inertial modeling Volume fraction potentially used to estimate b (momentum multiplication factor for impact redirection) SAR requires Fully polarimetric radar (HH, VV, HV) Shape and attitude knowledge Complementary to LIDAR rough surface estimation qinc RMS height H V SAR backscatter Volume fraction scattering ~ density 9/30/2013