1. 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
CL#
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 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, ...
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3. 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)
No in-situ radar on asteroid missions to date
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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
Shape
Iterative Dielectric Estimation
Electromagnetic Scattering Model
Scan-line projection
(anatomy)
Measurement points
Rosetta - CONSERT
MARSIS and SHARAD
Dielectric inversion
(physical properties)
Herique, Alain, and Wlodek Kofman. "Definition of the consert/rosetta radar performances." In EGS General Assembly Conference Abstracts, vol. 27, p
Voxelized dielectric model
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5. 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 (2008):
GPS-proxy
New-delay Doppler
Table lookup: determine spin and position
2) Space craft maneuver
1) Change in spin state (deflect thruster)
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6. 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
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7. 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) ~ 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
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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
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9. Thank you Questions Mark Haynes Radar Science and Engineering (334c)
Jet Propulsion Laboratory, California Institute of Technology
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10. 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
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