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CLP Measurement Technologies Passive Microwave

CLP Measurement Technologies Passive Microwave. Passive Microwave Team at NASA Goddard Space Flight Center. Outline. Developed study strategy Determined key driving parameters Chose candidate orbit Developed science performance metrics Prioritizing study areas

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CLP Measurement Technologies Passive Microwave

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  1. CLP Measurement Technologies Passive Microwave Passive Microwave Team at NASA Goddard Space Flight Center CLP Measurement – Passive Microwave

  2. Outline • Developed study strategy • Determined key driving parameters • Chose candidate orbit • Developed science performance metrics • Prioritizing study areas • Preliminary identification of technology drivers CLP Measurement – Passive Microwave

  3. Cold Land Passive MW Concepts • Real aperture • Dual frequency, dual polarization, conical scanning • 6-m deployable reflector, multiple feedhorns • Reflector emissivity and spin rate are concern • 1-D STAR • Dual frequency, dual (or single) polarization • 6-m deployable cylindrical reflector • Nearly constant 50o incidence angle • 2-D STAR • Single frequency, single polarization • Three 3-m deployable arms each with 250 elements • Multiple incidence angles (nadir to >50 degrees) CLP Measurement – Passive Microwave

  4. preliminary Red = catchments with <100 pixels at indicated spatial resolution 5x5 km 25x25 km CLP Measurement – Passive Microwave

  5. Study Approach- Key Parameters • Three strawman passive concepts were chosen by the CLPWG at the Ann Arbor Meeting (Nov 2002) • Each is paired with a driving remote sensing science parameter, which directs our investigation CLP Measurement – Passive Microwave

  6. Technology Development Issues for Real Aperture Concept • Issues • Balance and Power Transfer Assembly (BAPTA) • Active system would be de-spun ( e.g. inside BAPTA) • Momentum compensation • Deployment / alignment , thermal stability • Notes • “conventional“ concept • Largest rotating reflector system ever flown for MW instrument • Lifetime issues with mechanism, will drive spacecraft design CLP Measurement – Passive Microwave

  7. Technology Development Issues for 1D-STAR Concept 65 elements/channel to get a reasonable NEDT (<1K) • Issues • Stow and deploy fixed mesh reflector system • Material selection of mesh/coatings • Surface control of mesh backing structure • Reduce power required for multi-channel, multi-pol receivers • Lots of cabling & interconnects • Calibration • Notes • Need deployment mechanism, but no spinning mechanism • Graceful degradation if/as receivers die • No technology heritage at high frequencies, spaceborne LRR might demonstrate STAR at 19, 37. CLP Measurement – Passive Microwave

  8. Technology Development Issues for 2D STAR Concept ~700 elements/channel gives 1.5K NEDT • Issues • Stow and deploy boom structure • 2D STAR receivers at 19 and 37 GHz will need to be packaged densely to minimize image aliasing • Current technology: rcvrs~0.5W/chan; 0.5-1.0 mW/correlation • Reduce Power required for multi-channel, multi-pol receivers • Interconnects and signal distribution • Calibration • Notes • Single stage deployment, no moving parts after deployment • Power will be large, and interconnects are complex tallest pole CLP Measurement – Passive Microwave

  9. Spatial resolution Aperture diameter Surface figure Mass Brightness temperature uncertainty Emissivity Surface figure NEDT Thermal stability Swath width/coverage Antenna geometry Beamwidth of STAR elements STAR bandwidth Compatibility with SAR Interface characteristics ACS Power Thermal Summary & Next Tasks TBD TBD CLP Measurement – Passive Microwave

  10. Technology Assessment • Concentrate on 1-D STAR and real aperture • Most promising for fusion with SAR • Electrically the simplest vs. 2D, • Mechanically more complex vs. 2D • Questions identified • How to integrate with SAR • Engineering issues: thermal, deployment/ packaging-in-shroud, power, mass, cabling/ inter-connects, reflector (solid, mesh, etc), metrology • Answers lead to technology needs CLP Measurement – Passive Microwave

  11. 1D-STAR concept deployment (show animation) CLP Measurement – Passive Microwave

  12. Some Technologies Already Identified • Mesh for reflector (1D-STAR and Real Aperture) • 14 / 19 / 37 GHz operation • Surface figure: ~200 um rms • BAPTA for Real Aperture concept • Keep SAR feed static at focal point • Rotate radiometers with reflector CLP Measurement – Passive Microwave

  13. Next tasks • Examine SAR integration with 1D-STAR • Continue detailed study of Real Aperture • Assess state-of-the-art TRL • Tie technologies to science metrics • Determine break points in metrics where technology development is needed • Make roadmaps CLP Measurement – Passive Microwave

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