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  • The effort is a collaboration between the Biospherics Sciences branch and the Microwave instruments branch.The science drivers for the DBSAR measurements include biomass, soil moisture, ocean roughness, ice dynamics and surface topography.

    1. 1. DigitalBeamformingSynthetic ApertureRadar<br />For Biomass Estimation<br />Rafael F. Rincon, Guoqing Sun, TemilolaFatoyinbo, Jon Ranson and Paul Montesano <br />NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA<br /><br />Phone: (301) 614-5725. Fax: (301) 286-1810 <br />July 26, 2010<br />
    2. 2. Outline<br /><ul><li>Motivation and Science Objectives
    3. 3. The DBSAR Concept
    4. 4. System Architecture
    5. 5. Operational Modes
    6. 6. Biomass Retrieval Efforts
    7. 7. Concluding Remarks</li></li></ul><li>Motivation and Science Objectives<br /><ul><li>Climate change constitutes one of the greatest environmental problems of this century. Quantifying the carbon cycle is one of the most important elements in understanding climate change and its consequences.
    8. 8. The amount of carbon in above ground vegetation, especially forests, is poorly understood because of the difficulty in acquiring sufficient on-ground measurements of biomass across the diversity of vegetated ecosystems. 
    9. 9. Improved remote sensing measurement methodologies are required to understand the relationships between the biosphere and atmosphere with respect to greenhouse gases and close the current deficiencies in modeling the Earth’s carbon budget.</li></li></ul><li>The DBSAR Concept<br /><ul><li>DBSAR is an L-band airborne imaging radar system developed at the NASA Goddard Space Flight Center (GSFC) in order to formulate, implement and test new radar techniques in support of Earth Science and planetary applications.
    10. 10. DBSAR combines digital beamforming, reconfigurable waveform generation, and real-time processing in order to enable multi-mode radar techniques not possible with conventional SARs.
    11. 11. DBSAR's highly innovative architecture provide the means to implement and demonstrate advanced SAR techniques that can provide the needed data for biomass studies.
    12. 12. Work is currently underway at GSFC to implement robust SAR image formation algorithms for the processing of the DBSAR data in order to retrieve key biomass parameters</li></li></ul><li>System Architecture<br /><ul><li> 8 channels enable cross-track scanning over a wide range of angles
    13. 13. Transmit modules feature digital phase steering and amplitude taper
    14. 14. Phased array antenna has 64 active microstrip patch elements
    15. 15. DBSAR was designed for operation on board of the NASA P3 aircraft </li></ul>Waveform Generator / Digital Beamformer<br />Processor<br />A/D<br />A/D<br />A/D<br />A/D<br />A/D<br />A/D<br />A/D<br />A/D<br />REU<br />T/R<br />T/R <br />T/R<br />T/R<br />T/R<br />T/R<br />T/R<br />T/R<br />Antenna<br />
    16. 16. System Architecture<br />The Real-time Processor<br /><ul><li> Fully Reconfigurable
    17. 17. Custom design
    18. 18. Three Stratix II FPGAs
    19. 19. Eight A/D converters
    20. 20. Six SRAMs
    21. 21. ARM microcontroller
    22. 22. 1-Gb Ethernet interface
    23. 23. Size (cm): 17 x 24 x 4
    24. 24. Power: 94 W max</li></ul>Mixed signal board<br />Digital signal board<br />
    25. 25. System Architecture<br />Main Parameters <br />R<br />A<br />D<br />A<br />R<br />A<br />N<br />T<br />E<br />N<br />N<br />A<br />M<br /> I<br />S<br />C<br />DBSAR Calibration in Anechoic Chamber<br />
    26. 26. System Architecture <br />Main Features Summary<br />Performs 1-Dimensional scanning (across track in nominal configuration).<br />Capable of sequential polarimetricoperation (HH,VV,VH). (New)<br />Employs software defined radar functions: waveform, T/R taper, digital In-phase and quadrature (I&Q) generation, digital filtering, etc…<br />Implements real-time onboard processing.<br />Supports In-phase and quadrature (I&Q) high data rate acquisition mode.<br />Capable of adjustable transmitter illumination from narrow-beamwidth(high-gain) beam steering to wide-beamwidthillumination.<br />Capable of in-flight reconfigurable waveform generation <br />Employs noise source and closed loop calibration schemes <br />Uses real-time data monitoring through a customized graphical interface unit. <br />
    27. 27. DBSAR Operational Modes<br /><ul><li> Current operational modes include scatterometry over multiple antenna beams, several modes of SyntehticApeture Radar (SAR), and Altimetry.</li></ul>Altimetry<br />Scatterometry up to 32 beams<br />SAR Wide swath<br />Two sides of the track <br />SAR single swath / Narrow beam <br />ScanSAR<br />
    28. 28. DBSAR First Airborne Campaign 2008<br /><ul><li> 7 Flights where conducted on the NASA P3 aircraft during October 2008 over areas of the Delmarva Peninsula, Eastern Shore, USA.</li></ul>Wallops Flight Facility<br />DBSAR and NASA P3 Aircraft Wallops Island, VA<br />Atlantic Ocean<br />Delmarva Peninsula, Eastern USA<br />DBSAR Integrated to P3 aircraft<br />
    29. 29. DBSAR Operational ModesTx wide beam Recv multiple narrow beams <br /><ul><li>A broad beam is generated by energizing a small section of the antenna
    30. 30. The beam illuminates entire field of view</li></li></ul><li>DBSAR Operational ModesTx wide beam Recv multiple narrow beams <br /><ul><li>A broad beam is generated by energizing a small section of the antenna
    31. 31. The beam illuminates entire field of view
    32. 32. Signal returns are collected with the full aperture
    33. 33. Several beams are synthesized simultaneously
    34. 34. SAR processing is performed on each beam</li></li></ul><li>DBSAR Operational ModesTx wide beam Recv multiple narrow beams <br />FLIGHT TRACK<br />Aircraft Altitude = 4 km<br />Aircraft Speed = 150 m/s<br />Image resampled and multi-looked to 10 m x 10 m pixels.<br />Range Res. = 7.5 mAzim Res. = 0.5 m (single look)<br />NESZ ≤ -28 dB (single look)<br />
    35. 35. DBSAR Operational ModesTx narrow (focused) beam Recv narrow beam <br /><ul><li> A single beam is generated by electronic steering
    36. 36. The beam illuminates a single swath
    37. 37. Signal returns are collected with the full aperture
    38. 38. Selected beam is synthesized on receive
    39. 39. SAR processing is performed on selected beam</li></li></ul><li>DBSARStrip Mode<br />Range Res. = 7.5 mAzim Res. = 0.5 m (single look)<br />NESZ ≤ -35 dB (single look)<br />Image resampled and multi-looked to 10 m x 10 m pixels.<br />Cosine taper on TX and Rcv<br />Aircraft Altitude = 4 km<br />Aircraft Speed = 150 m/s<br />
    40. 40. Biomass Retrieval Efforts<br />Evaluation of DBSAR and PALSAR Images over the Delmarva Peninsula.<br />Biomass Field measurements over DBSAR mapped areas. <br />Correlation between DBSAR backscatter and ground truth biomass.<br />
    41. 41. Biomass Retrieval Efforts<br />Image calibration and evaluation using PALSAR<br />PALSAR<br />DBSAR<br />
    42. 42. Biomass Retrieval Efforts<br />Wallops Biomass Field Campaign<br />
    43. 43. Biomass Retrieval Efforts<br />Wallops Biomass Field Campaign<br />Coastal plain mixed forest (loblolly pine, hardwood spp.)<br />Mature forest<br />Understory varied:<br />shrub <br />regeneration<br />open<br />10 m circular plots<br />dGPS location of plot center<br />Trees > 10cm DBH: DBH, species collected <br />
    44. 44. Biomass Retrieval Efforts<br />Wallops Biomass Field Campaign<br />
    45. 45. Concluding Remarks<br /><ul><li> The biomass retrievals currently underway at GSFC using DBSAR data will seek to generate required data to better understand radar backscatter from forests.
    46. 46. Results from the DBBSAR first campaign indicated a successful performance of the radar system and its potential benefits for biomass studies.
    47. 47. DBSAR was recently upgraded with polarimetric operation (HH,VV,VH) which enhances the science capability of the system.
    48. 48. DBSAR’s next flight campaign is schedule in the summer 2011 when the system will be used to map forests over the US east coast.
    49. 49. New techniques to be explored with DBSAR for Biomass include interferomery.</li></li></ul><li>Backup Slides<br />
    50. 50. System Architecture<br />Waveform Generator<br /><ul><li> Waveform generator is fully reconfigurable .
    51. 51. Transmit channels include programmable attenuators and phase shifter.
    52. 52. Receive channels amplify and condition and signal returns .
    53. 53. Performs internal calibration by sampling 1) the transmit signal and 2) the signal from a noise source.</li></ul>Single Channel<br />
    54. 54. End of Presentation<br />LIS in Anechoic Chamber<br />DBSAR Processor<br />Graphical User Interface<br />Chirp Spectrum<br />Reconfigurable Algorithms<br />Chirp Signal Generator<br />Rack mount Host computer<br />
    55. 55. Derived from Jenkins et al. 2003<br />