HR: 1340h
AN: IN13B-1091 [Abstracts]
TI: A Fine-Resolution Radar for Mapping Near-Surface Isochronous Layers
AU: * Rink, T P
EM: trink@ittc.ku.edu
AF: The Center for Remote Sensing of Ice Sheets (CReSIS), 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: * Rink, T P
EM: trink@ittc.ku.edu
AF: The University of Kansas, 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Kanagaratnam, P
EM: pannir@ku.edu
AF: The Center for Remote Sensing of Ice Sheets (CReSIS), 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Kanagaratnam, P
EM: pannir@ku.edu
AF: The University of Kansas, 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Braaten, D
EM: braaten@ku.edu
AF: The Center for Remote Sensing of Ice Sheets (CReSIS), 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Braaten, D
EM: braaten@ku.edu
AF: The University of Kansas, 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Zimmerman, K
EM: kirbster@ittc.ku.edu
AF: The Center for Remote Sensing of Ice Sheets (CReSIS), 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Zimmerman, K
EM: kirbster@ittc.ku.edu
AF: The University of Kansas, 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Akins, T
EM: takins@ittc.ku.edu
AF: The Center for Remote Sensing of Ice Sheets (CReSIS), 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Akins, T
EM: takins@ittc.ku.edu
AF: The University of Kansas, 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Gogineni, S
EM: gogineni@ittc.ku.edu
AF: The Center for Remote Sensing of Ice Sheets (CReSIS), 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AU: Gogineni, S
EM: gogineni@ittc.ku.edu
AF: The University of Kansas, 2335 Irving Hill Rd., Lawrence, KS 66045
United States
AB:
Information on the spatial and temporal variation of snow accumulation is required for interpreting satellite-based radar and
laser surface elevation measurements made by CryoSAT and ICESAT altimeters. Current methods of using ice cores and analyzing
snow pit stratigraphy is time consuming and prone to errors in spatial representation due to the sparse sampling. Remote
sensing methods that can map near-surface internal layers for estimating spatial and temporal variation are required. To
accomplish this, we developed a 12-18 GHz FMCW radar to map near-surface layers with 3 cm vertical resolution to a depth of
about 10 m. We developed the system to be mobile and self-contained so that spatial variability of the accumulation over a
large area can be characterized.
The fine resolution of this radar is achieved by its wide bandwidth and by illuminating the target area with a plane-wave,
which is implemented using an offset-fed parabolic reflector. Traditional wide-beamwidth antennas are susceptible to
spherical wave scattering from off-vertical targets that can potentially mask weaker reflections from internal layers. The
radar features a fast transmit waveform synthesizer implemented using a voltage controlled oscillator (VCO) and a
phase-locked loop (PLL) using a linear chirp as the reference. The highly linear reference chirp was generated by a direct
digital synthesis (DDS) waveform generator and compared against the instantaneous output of the VCO to create a highly linear
12 to 18 GHz transmit chirp. The waveform synthesizer can be swept from 12 to 18 GHz in 500 microseconds. The antenna was
mounted on a sled and the radar system was integrated with the antenna feed. We designed and built the sled with a gimbaled
antenna mount and sensing control system to ensure that the antenna points at nadir.
The radar system was successfully tested at the Summit camp, Greenland, in July 2005. We collected a large amount of data
from various locations around Summit camp. The locations include areas adjacent to bamboo stakes measured either weekly or
monthly throughout the year to track snow accumulation. Additionally, three snow pits were dug to compare radar data with
actual stratigraphy and density. More than 200 sample traces were collected to compare with our snow pit observations. Each
sample trace uses 10 sweeps, which are coherently integrated to improve signal-to-noise ratio (SNR). The average snow density
was used to determine the dielectric constant, which enables the estimation of the propagation velocity in firn. Our initial
results show a high correlation between the snow pit stratigraphy and reflecting layers mapped with the radar. We observed
echoes from layers with the radar operated at a single spot, and with the radar traveling at a nearly constant speed along a
line over a distance in excess of 4 km.
In our presentation we will cover the design and construction of the radar, as well as provide sample results from field
experiments at Summit, Greenland. A comparison of experimental data with simulations obtained using density and stratigraphy
data will also be shown. Future plans for this system will also be discussed, including plans for measurements at the WAIS
divide deep core site in Antarctica during the 2005-2006 field season.
UR: http://tornado.rsl.ku.edu/planewave/
DE: 0726 Ice sheets
DE: 0736 Snow (1827, 1863)
DE: 0758 Remote sensing
DE: 5464 Remote sensing
DE: 8040 Remote sensing
SC: Earth and Space Science Informatics [IN]
MN: Fall Meeting 2005