Global Ice Sheet Mapping Observatory (GISMO)

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Global Ice Sheet Mapping Observatory (GISMO)

• Ohio State Univ., JPL, Univ. Kansas, VEXCEL
  Corp., E.GG Corp., Wallops Flight Facility

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GISMO Create new 3-D mosaics of Greenland and
Antarctica stripped of their icy cover
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Objectives

• Develop and test radar systems and algorithms for
  imaging the base of the polar ice sheets
• Investigate interferometric, multiaperture
  array, and tomographic clutter rejection methods
  for basal imaging
• Develop multiphase center P-band and VHF radars
  capable of sounding kilometer thick ice and
  interferometric operations
• Assess the requirements for extension to
  continental scale campaigns

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Data Collections

• May 2006 (twin otter platform KUs ice sounding
  radar)
• 150 MHz (VHF) with 20 MHz bandwidth, in western
  Greenland
• September 2007 (P3 platform KUs ice sounding
  radar)
• 150 MHz data with 20 MHz bandwidth
• 450 MHz data with 30 MHz bandwidth

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P-3 Radar Installation
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Radar Power Amplifiers (upper left) Radar
control unit, receivers, and test equipment
(right)
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• GISMO Navigation Performance and Motion Files for
  September 2007

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070910 Ice Stream
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070914 Swiss Camp Racetrack
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SAR image of May 2006 Flight,150 MHz
Western Greenland Ice Sheet
base
25 km
surface
internal layers
5.8 km in the air
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May 2006 GISMO Interferogram
5.8 km
25 km
150 MHz 3.9 m baseline
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Left-Right separation Phase Gradient
S1
S2
x
B
r1
r1
r2, right
H
r2, left
P
Q
h(x)
Cross terms neglected but these could be important
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Left/right side interferogram separation
Left side interferogram
Right side interferogram
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High elevation Approximation for Thickness
B
?
?
r2
r1
sin?1 nsin?2
?
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May 2006 GISMO Flight, 150 MHz, InSAR Swath
Measurements of Topography Beneath the Greenland
Ice Sheet
Basal topography measured along a 25 km flight
line and across a 3 km swath over the western
Greenland Ice Sheet in May 2006. Thickness was
measured using an airborne 150 MHz Synthetic
Aperture Radar. The data were processed to
simultaneously image the left and right sides of
the aircraft. Thickness was subtracted from
ICEsat surface elevation data to compute basal
topography.
left
right
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September 2007 GISMO flight with 450 MHz
5.8 km in the air
19 km
base
surface
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450 MHz GISMO interferogram
19 km
1.3 m baseline
1 km in air
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Depth Sounder mode data Filtered Interferogram
largely one-sided September 2007 450 MHz
GISMO Data Collection
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Topography from 450 MHz Depth Sounder Mode Data
Data gaps
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GISMO Short Term Plans

• Conduct a third experiment in May, 2008
• Develop better multi-look processing schemes
• Re-assess technical requirements on radar
  performance and platform

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GISMO Long Term Plans

• 3-Year IIP activity demonstrated capability to
  collect 2-d images of the bed and construct 3-d
  basal topography from aircraft.
• Opportunity for further technical development
  includes increased bandwidth and increased power.
  ESTO has encouraged a new IIP proposal which
  would continue the NASA/NSF collaboration.
• The next science step is to acquire regional,
  glaciological data during the IPY, for example,
  reflectivity and topography maps of the base of
  the North East Ice Stream.
• Next decade to develop operational instrument
  and processing capability to construct image and
  topography mosaics of Greenland and Antarctica
  stripped of the overlying ice.