ground-based fmcw radar measurements: a summary of the nasa clpx data h.p. marshall institute of...

Ground-Based FMCW radar measurements: a summary of the NASA CLPX data

H.P. Marshall Institute of Arctic and Alpine Research, Univ. of ColoradoGary Koh, Cold Regions Research and Engineering Lab, New HampshireRick Forster, Department of Geography, University of Utah

Brief FMCW Theory I

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Brief FMCW Theory II

• Linear frequency chirp transmitted (T)

• Received signal (R) “mixed” with transmitted wave before signal acquisition

• Recorded signal contains the sum and difference frequencies from T + R

• Frequency differences from reflectors linearly related to the distance to target

cd

vd

BT

dFTsw

plw

222

Windowed FFT, zero-padded, normalized by DC-coupling, power from

surface calibration

Filter instrumentation-related signals

• Locations where mean of signal > 5x mean deviation found

• Mean trace at these depths subtracted from scan

Depth Calibration

• Metal reflectors placed at known depths

• Accurate depth scale, will also be used to calculate attenuation

Michigan Ridge, North Park, Feb 21,2003

Berthud Pass, February 22, 2003

Relationship of FMCW signal manual measurements

Density profile vs radar

In-situ Dielectric Properties

In-situ Dielectric Properties II

LSOS Feb 19, 2002, C-Band: 2-6 GHz

DRY SNOWPACK

LSOS Feb 19, 2002, X-Band: 8-12 GHz

DRY SNOWPACK

LSOS Feb 19, 2002, Ku-Band: 14-18 GHz

DRY SNOWPACK

LSOS March 26, 2002, C-Band: 2-6 GHz

WET SNOWPACK

LSOS March 26, 2002, X-Band: 8-12 GHz

WET SNOWPACK

LSOS March 26, 2002, Ku-Band: 14-18 GHz

WET SNOWPACK

Effect of incidence angle

oc

rc

r

c

oeff P

PRR

4

Effect of incidence angle II

Conclusions • FMCW signal strongly related to

in-situ dielectric measurements• Resolution highest at Ku-Band,

but little penetration if wet• Incidence angle measurements

indicate surface scattering dominates below ~15 deg and volume scattering above 30

• Preliminary comparison with FMCW measurements at more narrow bandwidths encouraging

Acknowledgements

NASA Earth System Science Fellowship

CRREL

Kelly Elder, Don Cline

Nate Mullheren