Glaciers and Ice Sheet Interferometric Radar April 2007 Planning Meeting Wallops Flight Facility October 10, 2006

October 10 - Agenda Meeting to Begin at 10 AM GISMO Introduction 10:00 Meeting objectives Jezek 10:10 GISMO Overview: Jezek May 2006 Experiment 10:15 May 2006 Experiment Objectives Jezek 10:30 May 2006 lessons learned for Radar: Gogineni 11:00 May 2006 lessons learned for navigation: Sonntag 11:30 Minutes data processing status: Jezek 11:45 break for lunch April 2007 Experiment 13:00 Experiment Overview – Jezek 10 min 13:10 April 2007 Radar status (150 and 440 Mhz electronics, racks, cables, antennas): Gogineni discussion of antenna mods, cable mods, rack layout, etc. 13:40 April 2007 proposed flight tracks and navigation requirements Jezek 14:10 April 2007 Wallops requirements on GISMO - eg. flight request paper work, Danish [Greenland Home Rule] approval, airworthiness approvals, costs: Krabill, Guillory, Valliant 14:50 Break 15:00 Scheduling priority issues, leading to logic diagram for selecting flight profile for a given day – Krabill 15:30 Schedule of events and milestons for April flights - Jezek Plans and Meeting Action Items Jezek 1700 Telecon with JPL and Vexcel

Meeting Objectives Review Project Goals and Status Summary of May 2006 Experiment Objectives of April 2007 Airborne Experiment Aircraft Configuration Airborne Experiment Design Navigation and location Proposed flight lines Schedule Flight Planning Guidance and Milestones Costs

GISMO Project Status K. Jezek

Objective Key Milestones TRL in =3 Approach Develop and test radars and algorithms for imaging the base of the polar ice sheets Investigate interferometric and tomographic clutter rejection and basal imaging methods -3-d topography of the glacial bed -Images of subglacial conditions Develop multiphase center P-band and VHF radars -Capable of sounding 5 km of ice -Single and repeat pass interferometric operation Assess the requirements for extension to continental scale campaigns PI: Prof. Kenneth C. Jezek, The Ohio State University Global Ice Sheet Interferometric Radar (GISIR) Use available topography data to simulate interferograms for testing the InSAR and tomographic concepts. Modify the SAR simulator to include operating characteristics of several aircraft and several radar designs Develop UHF and VHF radars and antenna systems Test methodology by collecting data over the Greenland and Antarctic ice sheets Algorithm validation and sensitivity assessment. Co-Is: E. Rodriguez, JPL; P. Gogineni, U. Kansas; J. Curlander, Vexcel Corp.; John Sonntag, EG&G; C. Allen, U. Kansas; P. Kanagaratnam, U. Kansas 1/ 06 Phase History Simulations and Algorithm Testing 5/06 First flight test in Greenland (Twin Otter 150 MHz) 9/06 Radar and Antenna Development 7/06 InSAR and tomography algorithm refinement 5/07 Greenland Field Campaign (NASA P-3) 5/08 Second Greenland Campaign (NASA P-3) 6/08 Algorithm and methodology assessment 7/08 Requirements doc. for continental scale imaging Repeat pass tomography Filtered basal inferogram InSAR Concept

Project Accomplishments Theoretical concept well defined Phase history simulations confirm theoretical predictions Radar design trade completed Scaling study completed Limited radar system deployed for May 06 test flight in Greenland Data acquired and successfully processed to SAR images and interferograms

Year 2 Project Goals Radar Development : Build sub-system and assemble the complete system. Perform laboratory tests using delay lines to document loop sensitivity,radar waveforms and impulse response. System Integration (KU, WFF, Aircraft Operator) a)Install the radar and navigational equipment on P-3 or similar aircraft and conduct flight tests over the ocean. Algorithm Development. Develop a strip IFSAR processor and compare against the results of the exact time-domain processor. Iterate the clutter removal algorithm based on experimental results (JPL). Develop software and apply software to process multiple 2-D complex SAR images coherently (Vexcel). Data acquistion and Analysis : Field experiments over the ice sheet; Finalize interferometric SAR processor and pre-processor and process data from first campaign (JPL). Extract basal topography from result.. Iterate interferometric filter design based on assessment of the results. Science and Management : Participate in field measurements; Conduct design and performance review; assess quality of results in context of science requirements.

May 2006 Experiment Summary

May 2006 Experiment Summary and Objectives Flight of opportunity to acquire early GISMO data Data acquired using KU 140 MHz radar and WFF navigation equipment Single pass and repeat pass data acquired Objectives in priority order: –investigate whether data of suitable signal strength and with suitable knowledge of aircraft navigation parameters could be acquired for successful InSAR processing for measurements of basal topography and reflectivity; –evaluate phase filtering clutter rejection concept; –evaluate tomographic imaging concept for clutter rejection –Evaluate clutter rejection using multiple antenna elements

May 06 Experiment Twin otter flight from Thule: Camp Century; interior 150 MHz Radar 5 transmit and 5 receive elements (1 m spacing) ~ 2 m baseline outbound (achieved 7 m) Return flight offset 25 m to the south for larger baseline Maximum comfortable altitude (achieved 3000 m) Range window setting procedure

May 06 flight route

May 06 Data Processing Status

Range and Azimuth Compressed Slant Range Images (log scale) Left WingRight Wing Base Internal Layers Surface

140 MHz Interferogram Base surface layers noise

May 06 Data Processing Lessons Learned 1) Single pass, across track SAR imaging from aircraft is possible even in areas where the base of the ice sheet appears to be relatively smooth. We will analyze the rest of the May 23 data set to investigate the range of relative backscatter values observable along this flight path. 2) Across track interferometry is possible in the area where backscatter is relatively weak. This is consistent with theory. We will investigate whether the fringe rates we observe are reasonable for the short (7 m) baseline we achieved on the Twin Otter aircraft. 3) Given the measured fringe rate patterns, we will investigate whether we can retrieve across track measurements of basal topography. 4) Data processed so far steer the beam 20 degrees off nadir. Depending on the product of the beam pattern with the backscatter falloff, this may or may not be optimum. We will analyze the data with different degrees of beam steering. 5) We did not observe fringes from the ice sheet surface in the most recently processed data. Yet we can clearly see internal layers, which should have a much lower backscatter value than the surface return. We will investigate how beam steering angle influences the measured backscatter from the ice sheet surface. Are there blanking signals or AGC cirucuits that reduce the surface return? 6) We observe detailed internal layers in the range and azimuth compressed data. We also observed the frequently described internal layer free zone near the base of the ice sheet. Are the returns solely from nadir or are we imaging the layer surface? 7) 140 MHz backscatter strength is sufficient to yield a measurable signal. We will test and compare 140 MHz and 440 MHz systems. 8) The May 23 data collected observations along the same in and out bound track. We will investigate how longer baselines derived from repeat pass data effect data quality. 9) We observed a systematic noise pattern in the amplitude and interferometric data. The noise artifacts in the InSAR data will be an additional complication for interferogram filtering. The noise source is not always on and we will attempt to identify the origin of the noise source.

GISMO Flights Plans and Objectives

Technical Objectives for April ’07 Experiment 1) Acquire data over the May 2006 flight line to compare high and low altitude observations and to compare interferometry acquired with different baselines. Are results consistent with theory? 2) Acquire data at 140 MHz and 440 MHz along every flight line and compare backscatter and interferometric frequency response? Are the results consistent with theory? 3) Acquire data over areas where we expect to find subglacial water. Is water detectable either from backscatter maps or from topography? 4) Acquire data over regions of increasing surface roughness. This may require observations over heavily crevassed shear margins such as those found around Jacobshavn Glacier. Can we successfully implement interferogram phase filtering? 5) Acquire data for tomographic analysis 6) Investigate repeat pass interferometry over repeat periods of days. 7) Verify volume clutter is weak (all snow zones) 8) Collect data over thick and thin ice to test for absorption effects

April 07 Experiment P-3 flights from Thule and Kangerdlussuaq 150 MHz and 440 MHz Radars Define antenna spacing Define outbound baseline Return flight offset 25 m to the south for larger baseline Maximum altitude allowable Range window setting procedure

Update to May 06 Experiment Plan ParameterValue Frequency150 Mhz, 440 MHz Band width20 MHz, 50 MHz Range window Start 4 us to 44 us with pulse 1 (lo-gain) Then 15 us to 55 us pulse 2 (hi-gain) ?? Pulse width3 us ?? PRF10 KHz (5 Khz for each pulse) ?? Baseline offsetReturn flight 25 m south of outbound flight CalibrationRough ocean observations at these specs Aircraft elevation above ellipsoid (geoid)~ ft (install additional external attunuators into the receiver Antennas configured for two frequencies At least one flight with multiple repeats for tomography High elevation flights on any flights of opportunity26,000 ft At end of project, switch to 2 transmit element and 6 receive elements ???? r r r b b t b b b r r r which means about a 7 m baseline (r=receiver, b= blank, t= transmit) r r r b t t b r r r (ping pong) ???? Early evaluation of Greenland dataVECO assisted DVD or electronic file transfer to KU after first GISMO flight: Process to depth sounder mode; Process to SAR image

Aircraft Configuration

P-3 Modifications Multiple conductors to antenna array (one conductor used in past experiments) Additional antenna elements beneath wings Additional element in the tail GPS and Inertial navigation information on aircraft position and attitude

Cable Spec’s SMA (2x) on BPE240, bundled With polyolefin jacket

Airborne Experiment Design

Single Pass Interferometry Maximize altitude Maximize antenna array separation 6 km swath

Multi-Pass SAR Imaging Synthetic Elevation Aperture Ground Reference Point Synthetic Aperture

Constraints on Flight Operations Fly at maximum allowable altitude Limit flight duration to allow for daily data Q/A and experiment modifications (about 6 hours assuming 150 Gb/hour and 3, 300 Gb disks) Allow enough field time to repeat flight lines Fly over high and low clutter areas Fly over areas where some information on basal properties is known VHF and UHF radars cannot operate simultaneously – P-band outbound; VHF inbound along same track to within 30 m Schedule 2 to 4 repeat flights at 30 m horizontal offsets for tomography

Aircraft Navigation Expected Performance 20 m ground track repeatability 0.02 degree post flight knowledge on aircraft roll and pitch 1 degree post flight knowledge on yaw

Proposed Flight Lines

Flight Description Inbound flight displaced 25 m from outbound flight Each flight flown twice: 150 and 440 MHz Flight 1 is highest priority at 440 Mhz Each flight is between 2000 and 2500 km (roundtrip) Flights 1 and 2 include segments over the ocean Flight 3 should include a segment down the Sondrestrom Fjord

Flight 1 and 2

Flight 3

Preliminary list of actions 2007 Flight Planning - Actions F113-Sep-06purchase cables F213-Sep-06complete antenna design COMPLETE F313-Sep-06confirm cabling and antenna plans with WFF F413-Sep-06Install test cables F501-Sep-06Install and test antennas F613-Sep-06Airworthiness certifcation on antennas F713-Sep-06Continengency plan if Antennas cannot be modified F813-Sep-06Install and test radar system F913-Jan-00Begin construction of in flight InSAR processor F1013-Sep-06Test inflight SAR processor with May 06 data F1113-Sep-06Interface check between radar and navigation data acquisition systems and inflight processor F1213-Sep-06Installation of inflight processor F1313-Sep-06Lessons learned document from May 06 experiment COMPLETE F1413-Sep-06Flight lines for 2007 experiment F1513-Sep-06List of team members for deployment F1613-Sep-06 Danish approval for experiment and team member deployment

IPY Flight Request CampaignAircraftBase LocationTotal Experime nt Flight Hours Individual Flight Duration Elevation (ft) Equipment May 2007NASA P-3Kangerlussuaq/ Thule Greenland hours~26, MHz 450 MHz U. Kansas Radar May 2008NASA P-3Kangerlussuaq/ Thule Greenland hours~26, MHz 450 MHz U. Kansas Radar