TU2.L09.1 - COMPACT POLARIMETRY AT THE MOON: THE MINI-RF RADARS

Compact Polarimetry at the Moon:

The Mini-RF Radars

R. Keith Raney1, Paul Spudis2, Ben Bussey1, J. Robert Jensen1, Bill Marinelli3, Priscilla McKerracher1, Ron

Schulze1, Herman Sequeira1, and Helene Winters1

1JHU/APL 2LPI/TX 3NASA/Hdqs

IGARSS, Honolulu, HI

25 - 30 July 2010

R. K. Raney IGARSS 2010, Honolulu, HI

Outline

� Mini-RF Project Overview

� Hybrid Polarimetric Architecture

� Calibration

� Results

� Conclusions



� Calibration

� Results

� Conclusions




� Calibration

� Results

� Conclusions



� Calibration

� Results

� Conclusions


Top-Level Parameters of the Mini-RF radars

Chandrayaan-1 LRO

(2008 – 2009) (2009 - )

� Polarizations Tx C; Rx L (H&V) Tx C; Rx L (H&V)

� Resolution (m) / Looks 150 / 16 Baseline 150 / 16

Zoom 15 x 30 / 8

� Wavelengths (cm) 12.6 12.6, 4.2

� Modes Strip Strip, InSAR

� Altitude (km) 100 50

� Inclination ~ Polar ~ Polar

� Mass (kg) 12 15

Chandrayaan-1 LRO

(2008 – 2009) (2009 - )

� Polarizations Tx C; Rx L (H&V) Tx C; Rx L (H&V)

� Resolution (m) / Looks 150 / 16 Baseline 150 / 16

Zoom 15 x 30 / 8

� Wavelengths (cm) 12.6 12.6, 4.2

� Modes Strip Strip, InSAR

� Altitude (km) 100 50

� Inclination ~ Polar ~ Polar

� Mass (kg) 12 15


Antenna

• Tx and Rx S/C

band signals

• Transmit CP

• Receive V&H

InterconnectModule

• Generate 90 deg.

Phase shift on

V&H Tx channels

• Isolate transmit &

receive paths

• Filter RF

Digital Receiver

• Digitize IF signals

• Perform BAQ

• Generate digital I/Q

• CCSDS packetize

QDWS• Timing & control

• Generate radar

waveforms

Transmitter

• Amplify S/C band

signals

Analog Receiver

Analog Exciter

• Provide LOs & clocks

• Up-convert: S to C

Control Processor (RAD 750)

• Digitize antenna temperatures

• Collect & report telemetry to bus electronics

• Accept commands from bus electronics

• Control & configure payload electronics

• Provide router interface from digital receiver to

bus electronics for radar data

Bus Electronics

(HK/IO)

Controls

Timing SignalsLO & Clock

Telemetry

H

V

H

V

H

V

• Down-convert

from RF to IF

• Provide gain

control

Mini-RF Radar on LRO


Conventional TWTA (40 W)

MPM (100 W)

MPM TWT

Technology Demo (LRO): Microwave Power Module


Solar panel

array (folded)

Mini-RF antenna

(~ 1 m2 area)

Mini-RF Radar on LRO During Integration and Test


85

80

Water-Ice – Relatively large CPR*

Harmon et al., 2000

Mercury’s poles:

Arecibo S-band,

delay-Doppler

processing--

enhanced “same-

sense” (SC) circular

polarization, which

is usually the

weaker return for

circular-polarization

on transmission

Mercury’s poles:

Arecibo S-band,

delay-Doppler

processing--

enhanced “same-

sense” (SC) circular

polarization, which

is usually the

weaker return for

circular-polarization

on transmission

From Ostro, 2000

*COBE: Coherent

Opposition

Backscatter Effect


Dominant Requirements on the Mini-RF Radars

� Measure circular polarization ratio (CPR)

• Consequence: radar must transmit Circular Polarization

� Maximal science with minimal flight hardware

� Measure circular polarization ratio (CPR)

• Consequence: radar must transmit Circular Polarization

� Maximal science with minimal flight hardware


� Mini_RF Project Overview


� Calibration

� Results

� Conclusions



� Calibration

� Results

� Conclusions


Radar Result

Orthogonal Tx polsCoherent Dual Rx

One Tx Pol, Coherent Dual Rx

One polarization

Processing Nomenclature

Real image

No assumptions

Reciprocity & symmetry

4x4 scattering matrix


Symmetry assumptions

No symmetry assumptions

3x3 pseudo-scattering matrix

2x2 covariance matrix

Full polarization

Quadrature

polarization

Compact

polarization

Two Rx pols

Two Tx pols

Magnitude

2 magnitudes & co-pol phase

2 magnitudes

2 magnitudes

Like- and Cross-pol images

2 orthogonal Like-pol images

2 orthogonal Like-pol images & CPD

Dual

polarization

Mono-

polarization

Radar Result





One polarization

One polarization


Real image

No assumptions






No symmetry assumptionsNo symmetry assumptions





Full polarization

Quadrature

polarization

Compact

polarization

Two Rx polsTwo Rx pols

Two Tx polsTwo Tx pols

Magnitude Magnitude

2 magnitudes & co-pol phase2 magnitudes

& co-pol phase

2 magnitudes2 magnitudes





Dual

polarization

Mono-

polarization

Hierarchy of Polarimetric Imaging Radars


Radar Result



One polarization


Real image

No assumptions





No symmetry assumptions



Full polarization

Quadrature

polarization

Compact

polarization

Two Rx pols

Two Tx pols

Magnitude

2 magnitudes & co-pol phase

2 magnitudes

2 magnitudes




Dual

polarization

Mono-

polarization

Radar Result





One polarization

One polarization


Real image

No assumptions






No symmetry assumptionsNo symmetry assumptions





Full polarization

Quadrature

polarization

Compact

polarization

Two Rx polsTwo Rx pols

Two Tx polsTwo Tx pols

Magnitude Magnitude

2 magnitudes & co-pol phase2 magnitudes

& co-pol phase






Dual

polarization

Mono-

polarization

Mini-RF: Compact Polarimetric Radars


Hybrid-Polarity Radar Architecture*

Transmit circular; Receive orthogonal linears and relative phase

Transmitter &

waveform

Antenna

H Rx channel

V Rx channel

90o

H

V

V

H

LNA

LNA

Timing & control

L-1

L-0

L-0

L-1

Part of the Radar Processing

Facility in the ground-based

operations center

V H

V H

|H|2

|V|2

HV*H

V*XXXX

S1

S2

S3

S4

Covariance matrix => 4 Stokes

parameters => independent of

polarization basis => optimize

radar hardware => Linear pol

receiver => Hybrid Polarity

Covariance matrix => 4 Stokes

parameters => independent of

polarization basis => optimize

radar hardware => Linear pol

receiver => Hybrid Polarity

Transmits circular

polarization

* U. S. Patent # 7,746,267


Stokes Parameters

Linear basis Circular basis Poincaré basis

S1 = < |EH|2 + |EV |2 > + N0 = < |ER|2 + |EL|2 > + N0 = S1

S2 = < |EH|2 – |EV|2 > = 2 Re < EREL* > = m S1 cos 2ψ cos 2χ

S3 = 2 Re < EHEV*> = 2 Im < EREL* > = m S1 sin 2ψ cos 2χ

S4 = – 2 Im < EHEV*> = – < |ER|2 – |EL|2 > = – m S1 sin 2χ

Comments

> Assumes that LCP is transmitted (or a close approximation there to)

> Note that the radar’s additive noise N0 is included in S1 (correctly), but not

in the other Stokes parameters (also correctly)

SNR = < |EH|2 + |EV |2 > / N0

> The child parameters may be found by taking advantage of the equality of the Stokes

parameters across all bases of observation of the received EM field

> The sign of S4 is negative, consistent with the back-scattering alignment (BSA) convention


Stokes 1 Stokes 2

Stokes 3Stokes 4

Log CL

Log CLLog CL

Log CL

Log C

CLog C

C

Log C

CLog C

C

Stokes Parameters are Independent

of Receive Polarization Basis

Stokes parameters

derived from

airborne SAR data

for circularly

polarized

transmissions and

dual linear or dual

circular received

polarizations are

essentially identical

Stokes parameters

derived from

airborne SAR data

for circularly

polarized

transmissions and

dual linear or dual

circular received

polarizations are

essentially identical


Stokes Child Parameters

Degree of polarization

m = (S22 + S3

2 + S42)½ / S1

Degree of linear polarization

mL = (S22 + S3

2)½ / mS1 = cos 2χ

Degree of circular polarization

mC = – S4 / mS1 = sin 2χ

Circular polarization ratio

µC = (S1 – S4) / (S1 + S4)

Linear polarization ratio

µL = (S1 – S2) / (S1 + S2)

Degree of depolarization mD = 1 – m

Relative phase δ = arctan (– S4 / S3 )

Degree of ellipticity

mE = tan χ

Comments

> Note that the degree of linear

polarization and degree of

circular polarization include

the degree of polarization m

> The sign of S4 depends on the

handedness of the transmitted

circular polarization (and the

coordinate convention, BSA vs

FSA)

> Assumes that LCP is

transmitted (or a close

approximation there to)

> Notice the minus sign on

the S4 terms (mC , CPR, & δ)




� Calibration

� Results

� Conclusions



� Calibration

� Results

� Conclusions


(

Nadir-viewing

Tx Rx PH

VHV*|H|2

|V|2

Raw signal domain

Image domain(before

calibration)

v

h

X| |2

| |2

Relative Self Calibration

PH

VHVC*

|HC|2

|VC|2

Raw signal domain

Image domain(after

calibration)

v

h

X

| |2

| |2

X

X

Cδ

1/Cδ

Cφ

Method*: <[Nadir returns]> => opposite sense of CP;

V/H magnitude imbalance; V-H phase difference =>

calibration coefficients Cδ

and Cφ

Method*: <[Nadir returns]> => opposite sense of CP;

V/H magnitude imbalance; V-H phase difference =>

calibration coefficients Cδ

and CφIf transmitted

field is not near-

perfect circular

polarization,

then external

resources are

needed

(GBT, ART)


CPR is Robust with Non-unity Transmit Axial Ratio

CPR = f(axial ratio, degree of polarization)

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

1.50

1 1.2 1.4 1.6 1.8 2

Transmit Axial Ratio

CP

R

m’ = 0.8

m’ = 0.7

m’ = 0.5

m’ = 0.6

~2.4 dB

Notes

µC

=1@m. αsin 2χ

1 + m. αsin 2χ

fffffffffffffffffffffffffffffffffff

> Smaller signal-to-noise ratio

(larger NES0) has the same effect

as smaller degree of polarization

m:

m’ = m/(1 + 1/SNR)

> α accounts for imperfect

dielectric and geometric properties

of the source backscatter, which

when evaluated from Mini-RF data

has a nominal value of about 0.19

> CPR evaluated under the

assumption of SC backscatter in

response to LC transmission, hence

- 45o ≤ χ ≤ 0




� Calibration

� Results

� Conclusions



� Calibration

� Results

� Conclusions


Radar

look

aspect

Linne Crater seen in Total Power

(S1) and Circular Polarization

Ratio (CPR)


Floor

Rim

Far-side exterior

Direct path

(rim image)

Floor-far-wall

double bounce ~ Extra

range

Image

location of

floor-wall

backscatter

Crater Floor-Wall Image Characteristic


The decomposition colorization scheme is:

S1 = R2 + G2 + B2

R = [S1m (1 + sin δ)/2]1/2

G = [S1 (1 – m)]1/2

B = [S1m (1 - sin δδδδ)/2]1/2

S1 first Stokes parameter (total power)

m degree of polarization

δ relative H/V phase (e.g., ellipticity)

R (Red) double bounce backscatter (e.g., dihedral, volume ice)

G (Green) randomly polarized (e.g., volume scattering)

B (Blue) odd bounce backscatter (e.g., Bragg scattering)

CL-Pol Decomposition: m-δ color code


Example of m-delta DecompositionAnomalous odd-bounce and even-bounce (or

COBE?) floor-wall signatures from the same crater

Radar look

aspect


Rozhdestvensky(177 kilometers in diameter)

North polar mosaic

(S-band Zoom

mode) CPR

rendition

(Late June 2010)

Processing, Courtesy of

Catherine Neish, APL

CPRSC


Interesting crater in

the floor of

Rozhdestvensky…

SC


Permanent sun shadow

Not

permanent sun shadow

Calculate the CPR histograms of

shadowed vs non-shadowed

backscatter

SC background for reference

SC


Permanent sun shadow

Not

permanent sun shadow

CPR Signature is Consistent

with Water-Ice Deposition

Inside the Crater

CPR Signature is Consistent

with Water-Ice Deposition

Inside the Crater




� Calibration

� Results

� Conclusions



� Calibration

� Results

� Conclusions


Conclusions

� The Mini-RF radars are the first polarimetric imagers

outside of Earth orbit

� Hybrid-Polarity (Tx Circular, Rx dual coherent linear

polarizations) is an ideal compact polarimeter for lunar or

planetary exploration: maximum science and minimal hdw

� In the lunar application, CPR interpretations are robust

in response to imperfect circular transmit polarization

� Calibration techniques unique to and pioneered by the

Mini-RF radars have proven to be effective

� Lunar imagery and interpreted products are as expected

� The Mini-RF radars are the first polarimetric imagers

outside of Earth orbit

� Hybrid-Polarity (Tx Circular, Rx dual coherent linear

polarizations) is an ideal compact polarimeter for lunar or

planetary exploration: maximum science and minimal hdw

� In the lunar application, CPR interpretations are robust

in response to imperfect circular transmit polarization

� Calibration techniques unique to and pioneered by the

Mini-RF radars have proven to be effective

� Lunar imagery and interpreted products are as expected

TU2.L09.1 - COMPACT POLARIMETRY AT THE MOON: THE MINI-RF RADARS

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Transcript of TU2.L09.1 - COMPACT POLARIMETRY AT THE MOON: THE MINI-RF RADARS