Global Ice Sheet Mapping Observatory (GISMO) Ohio State Univ., JPL, Univ. Kansas, VEXCEL Corp., E.G&G Corp., Wallops Flight Facility

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

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

Data Collections May 2006 (twin otter platform & KU’s ice sounding radar) – 150 MHz (VHF) with 20 MHz bandwidth, in western Greenland September 2007 (P3 platform & KU’s ice sounding radar) – 150 MHz data with 20 MHz bandwidth – 450 MHz data with 30 MHz bandwidth

P-3 Radar Installation

Radar Power Amplifiers (upper left); Radar control unit, receivers, and test equipment (right)

GISMO Navigation Performance and Motion Files for September 2007

Ice Stream

Swiss Camp Racetrack

SAR image of May 2006 Flight,150 MHz Western Greenland Ice Sheet 5.8 km in the air 25 km surface internal layers base

May 2006 GISMO Interferogram 5.8 km 25 km 150 MHz 3.9 m baseline

Left-Right separation: Phase Gradient S1S1 S2S2 r1r1 r 2, right r1r1 r 2, left P Q H x h(x) B Cross terms neglected but these could be important

Left/right side interferogram separation Left side interferogram Right side interferogram

High elevation Approximation for Thickness sin  1 = n·sin  2   r1r1 r2r2 B 

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 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

September 2007 GISMO flight with 450 MHz 5.8 km in the air 19 km surface base

450 MHz GISMO interferogram 1 km in air 19 km 1.3 m baseline

Depth Sounder mode data: Filtered Interferogram largely one-sided September MHz GISMO Data Collection

Topography from 450 MHz Depth Sounder Mode Data Data gaps

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

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.