In-situ Radar for Asteroid Characterization and Altimetry

1. 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.

2. Overview • In-situ Radar for ARM • 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, ...

3. Radar LandscapePast 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

4. 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 Electromagnetic Scattering Model Iterative Dielectric Estimation Shape Measurement points Scan-line projection (anatomy) Rosetta - CONSERT MARSIS and SHARAD Dielectric inversion (physical properties) http://www.jpl.nasa.gov/news/news.php?feature=1667 Herique, Alain, and WlodekKofman. "Definition of the consert/rosetta radar performances." In EGS General Assembly Conference Abstracts, vol. 27, p. 1664. 2002. Voxelized dielectric model

5. Tomography Delay measures range Delay-Doppler Tomography • 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 spinand position 2) Space craft maneuver 1) Change in spin state (deflect thruster)

6. Rendezvous - Altimetry - Targeting Rendezvous • Rendezvous • 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 Single spacecraft impact targeting and guidance > 100k-1M km

7. System Configurations Comm. antenna Sounding 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 Scan-line sounding Tomo. Dielectric inversion On-board processing Ground processing

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

10. Rough Surface Characterization • Synthetic aperture radar (SAR) tocharacterize 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 V H RMS height qinc SAR backscatter ~ density Volume fraction scattering