GISMO Team Meeting

1
GISMO Team Meeting

• JPL
• January 31, February 1, 2007

2
GISMO Team MeetingAgenda

• January 31 Progress to date 1300  Status and
  Summary of Mid Year Review, Budget Issues - Jezek
  
• Planning for April 07 Experiment 1320  Science
  and Engineering Objectives for April 2007 (Jezek)
  1330  Radar and antenna status (Gogineni) 1400 
  Vexcel Data processing Status, Interface and
  Readiness (Refraction, Motion Compensation,
  Calibration)  (Wu) 1430 JPL Data processing
  status, Interface and Readiness (Refraction,
  Motion Compensation, Calibration) (Rodriguez)
  1500 Navigation (Sonntag) 1515  Arctic 07
  Planning Status and key milestones (Krabill)
  1530 Proposed Flight Lines (Fahnestock and
  Sonntag) and Discussion 1600  April 07
  Experiment Plan and Discussion (Jezek) (see May
  06 vu-graphs for sample experiment plan form)
  1730  Adjourn February 1
• Algorithms0830  Tomography Algorithm Status (Wu)
  0900  InSAR algorithm status (Rodriguez) 0930 
  Update on Multiaperture beam processing
  (Gogineni) 1000  Plans for reducing May 2006
  data to topography (Wu, Rodriguez, Forster)
  1030   Break 1045  Plans for investigating
  ionospheric effects and corrections (Freeman)
  1115  Data management issues, schedule for
  delivery of April 07 data, action Items (Jezek)
  1200  Adjourn

3
Objectives

• Briefly review project status
• Prepare draft experiment plan for April 07
  identify implementation issues
• Review algorithms May 06 processing
  (topography) April 07 processing issues

4
Project Status
5
Project Accomplishments

• Theoretical concept well defined
• Phase history simulations confirm theoretical
  predictions
• Radar design trade completed
• Scaling study completed
• 150 MHz radar system deployed for May 06 test
  flight in Greenland
• For the first time, SAR data acquired from
  aircraft and successfully processed to SAR images
  and interferograms of glacier bed

6
Data Processing Lessons Learned

• Time reference functions
• In range compression the ideal chirp is used for
  each receive channel. We plan to measure the
  received chirp from each receive channel and use
  them to do range compression. These actual range
  reference functions may give us some improvement
  in focus and SNR in the range compressed images.
• Motion compensation
• We are quite sure the motion data are quite
  accurate for the 150 MHz carrier frequency data.
  But in April 2007 we are going to collect data
  using 450 MHz carrier frequency. Motion data may
  become less accurate relatively. We plan to use
  the current 150 MHz data to investigate motion
  compensation methods and try to find appropriate
  approaches to improve the azimuth compression for
  the special cases of the ice sounding SAR images.
• Imaging model with ice mass refraction
• Any image formation algorithms assume that the
  electromagnetic wave which carries the radar
  waveforms is traveling in the same homogeneous
  media like the air. It is not the case for ice
  sounding radars. For the data collection in May
  2006 the ice thickness is about 2000m and the
  slant range between the radar sensors and the ice
  surface is only about 1000m long. There are two
  main differences between the ice sounding radar
  and the normal surface mapping radar. The first
  one is the refraction which happens at the
  air-ice boundary and changes the travel
  directions of the electromagnetic wave. The other
  is that the travel velocity within the ice is
  about 1.8 times slower than in the free air. We
  plan to model the ice mass with two layers and
  try to improve the azimuth compression results by
  taking into account the refraction and the
  different travel velocity.
• Tomography processing
• Try to verify tomography technique for generating
  3D volumetric images of the regions of interest
  in Greenland and/or in Antarctica using the data
  acquired in May 2006 and the data yet to be
  acquired in April 2007. The methods to be tested
  include direct convolution back-projection from
  the phase history data and the method of creating
  3D images from already-formed 2D complex images.

7
Multi-Aperture Lessons Learned

• Using multi-aperture arrays and spatial
  filtering, measured for the first time the ice
  thickness across Jacobshavn Glacier and to the
  calving front
• Analyses indicate that increasing the number of
  antenna elements from 4 to 10-15 at 450 MHz
  improves spatial filtering sufficiently to
  develop an automatic clutter rejection algorithm

8
Navigation Lessons Learned from May 2006

• 2006 GISMO flight used Soxmap / Twin Otter
  combination
• Configuration more suitable for outlet glacier
  work
• Steering within /-50m, could be better
• 2007 GISMO flights will use CDI with P-3
• Better repeatability for straight flight lines
• Soxmap backup
• More info atm.wff.nasa.gov click Aircraft
  Navigation

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May 06 Experiment SummaryLessons 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.
  
• 2) Across track interferometry is possible in
  the area where backscatter is relatively weak.
  This is consistent with theory. 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
  expect to 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.
• 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.
• 7) 150 MHz backscatter strength is sufficient to
  yield a measurable signal. We will test and
  compare 150 MHz and 450 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.
• 10) We must measure the time reference functions
  prior to the experiment.

10
Project Tasks(green complete orange in
progress)

• Year 1
• Science and Management (OSU) Convene Science
  Team conduct initial design review refine
  project plan compile information on ice
  dielectric properties and ice sheet physical
  properties such as surface roughness and slope.
  Prepare reports as required by NASA
• Radar Development (University of Kansas a)
  Design of new set of optimized antennas We will
  build a model structure and measure its
  electrical performance. We will identify and work
  with a contractor to build the antenna
  installation mounted under the wings and flight
  test it in collaboration with engineers at NASA
  Wallops. b) End-to-end simulation of the system
  including antennas. (work completed for Twin
  Otter flight testing in progress for P-3)
• Algorithm Development Develop a motion
  compensation processor and a time-domain
  (back-propagation) IFSAR processor. Use legacy
  code from the GeoSAR and MOSS IIP projects. (JPL
  planned for April 07) b) Prototype first
  version of the interferogram filtering code
  (JPL) c) Modify simulation software and
  generate simulated IFSAR returns from basal and
  surface layers (Vexcel) and evaluate the filter
  performance on the simulated data.

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Project Tasks

• Year 2
• Radar Development Build sub-system and assemble
  the complete system.(150 MHz complete, 450 MHz in
  progress) 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. (Planned for April 07)
• 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)(awaits Arctic 07 data). 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. (Completed for Twin Otter
  In progress for P-3)

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Project Tasks

• Year 3
• Data Acquisition and analysis Conduct second
  airborne campaign Reduce and analyze data.
  Develop software and apply software to process
  multiple raw data acquisitions tomographically.
  Apply linear beam forming techniques
  (Demonstrated with twin otter). Extract basal
  topography from result. (Vexcel)
• Mission Design Spaceborne mission design based
  on the experimental results.
• Science and Management Participate in final
  field experiment convene final review develop
  mission concept in terms of science requirements
  and experimental results prepare final reports.

13
Additional Issues

• After discussion with ESTO, JPL and Vexcel, 50k
  will be transferred from the OSU budget to Vexcel
  for additional effort as specified in a
  workstatement provided in Year 2. 50k will be
  deducted from the JPL budget in Year 3 and added
  to the OSU budget. A short proposal to ESTO will
  be required during the annual resubmit.
• The Year 3 airborne experiment will occur near
  the end of the project. Given current spending
  projections, a no-cost extension is anticipated
  to allow for analyzing data from the experiment.
• OSU will provide budgetary details on all project
  expenditures. However, this is complicated by
  the fact that monies are transferred directly
  from ESTO to Wallops (aircraft support Year 2)
  and to JPL (processor development). It is
  proving challenging for OSU to get this
  information through formal channels. That said,
  OSU is aware of under-spending at JPL. OSU
  closely works with Wallops on flight costs for
  Arctic 07 and will monitor expenditures.
• An issue is whether to again transfer aircraft
  costs directly from ESTO to Wallops or whether
  there can be more exact accounting if monies are
  sent directly to OSU as originally planned.

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Cummulative Spending ESTO Requirement to Update
for All Projects Expenditures