Transcript 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
[email protected]
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, ...
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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/
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No in-situ radar on
asteroid missions
to date
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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
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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
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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)
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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
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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
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Ground processing
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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
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4. Asteroid Capture Mission:
… composition, internal structure, physical integrity …
Sounding
5. Crew Systems for Asteroid Exploration:
..., prospect for resources, ...
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Thank you
Questions
Mark Haynes
Radar Science and Engineering (334c)
Jet Propulsion Laboratory, California Institute of Technology
[email protected]
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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
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