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 – 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….closedloop 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 2 Radar Landscape Past and Current Planetary Radar Missions and Science • Goldstone Asteroid Radio Science Arecibo – Goldstone and Arecibo – NEOs, planetary science (moon, Venus, Mars satellites) • Planetary missions with radar – Atmosphere penetration Cassini (Titan) • Magellan, Cassini Magellan (Venus) – Sounding • MRO / Mars Express • Rosetta-CONCERT radar – Landing/Rendezvous • MSL, previous rovers • Apollo/Shuttle Mars Reconnaissance Orbiter (SHARAD) Mars Express (MARSIS) – Earth science remote sensing • Asteroid missions (no in-situ radar) – NEAR-Shoemaker, Dawn, Hayabusa, Osiris-Rex 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/ 9/30/2013 No in-situ radar on asteroid missions to date 3 Radar Sounding • Map the regolith – – – – – • Radar is only active modality capable of subsurface imaging – • • Internal structure Bulk dielectric properties (density) Anchoring redirect thruster Sample and boulder return Improved asteroid trajectory estimate Scan-line projection or dielectric inversion 100 MHz to 2 GHz => 20m to 1m depth 3 past/current sounder missions Reflection Measurements Shape Scan-line projection Iterative Dielectric Estimation Scan-line projection (anatomy) MARSIS and SHARAD Electromagnetic Scattering Model Measurement points Rosetta - CONSERT Dielectric inversion (physical properties) http://www.jpl.nasa.gov/news/ne ws.php?feature=1667 9/30/2013 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 4 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 • Doppler measures motion (rotation) Delay-Doppler images Shape - Spin Shape reconstruction algorithm Close-loop feed back during spacecraft maneuvers – Differential Doppler – monitor spin changes – GPS-proxy Delay measures range Delay-Doppler Tomography 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 5 Rendezvous - Altimetry - Targeting Rendezvous • Rendezvous – Apollo: X-band • Altimetry/Landing radar – Reduce orbit uncertainty using delayDoppler echoes • • Post impact assessment Targeting and guidance Landing – On-route tomography to pinpoint impact time and location Single spacecraft impact targeting and guidance > 100k-1M km 9/30/2013 6 System Configurations 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 Comm. antenna • 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) Tomo. Scan-line sounding Dielectric inversion • On-board vs. ground based processing – On-board: scan-line sounding, altimetry, targeting, tomo. – Ground-based: dielectric inversion, tomo. • End-to-end system simulation On-board processing 9/30/2013 Ground processing 7 Summary Rendezvous RFI subsections Tomography 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 ... Sounding Rendezvous Tomography GPS-proxy Altimetry Landing Impact Assessment Impact guidance 9/30/2013 4. Asteroid Capture Mission: … composition, internal structure, physical integrity … Sounding 5. Crew Systems for Asteroid Exploration: ..., prospect for resources, ... 8 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 9 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 V Complementary to LIDAR rough surface estimation H qinc RMS height SAR backscatter Volume fraction ~ density scattering 9/30/2013 10