clp measurement technologies passive microwave
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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CLP Measurement Technologies Passive Microwave
Passive Microwave Team at NASA Goddard Space Flight Center
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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Outline
• Developed study strategy• Determined key driving parameters• Chose candidate orbit• Developed science performance metrics• Prioritizing study areas• Preliminary identification of technology drivers
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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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)
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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25x25 km 5x5 km
Red = catchments with <100 pixelsat indicated spatial resolution
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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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
Concept Key RS science parameter
Key technology parameter
Real aperture Spatial resolution Aperture diameter
1D-STAR Spatial resolution Array size
2D-STAR NEDT Thinning/power
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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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
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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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.
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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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
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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Summary & Next Tasks
• 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
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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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
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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(show animation)
1D-STAR concept deployment
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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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
May 28, 2003 CLP Measurement – Passive Microwave
Goddard SpaceFlight Center
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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