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Doppler Lidar Scanning Telescope Technology

Doppler Lidar Scanning Telescope Technology. Geary Schwemmer Meeting of the Working Group on Space-based Lidar Winds Welches, Oregon June 28- July 1, 2005. Topics. Requirements Constraints Approaches Comparisons Roadmaps. Requirements. Narrow field of view Large collecting area

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Doppler Lidar Scanning Telescope Technology

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  1. Doppler Lidar Scanning Telescope Technology Geary Schwemmer Meeting of the Working Group on Space-based Lidar Winds Welches, Oregon June 28- July 1, 2005

  2. Topics • Requirements • Constraints • Approaches • Comparisons • Roadmaps

  3. Requirements • Narrow field of view • Large collecting area • Large off-nadir scan angles (~30-50°) • Step-stare preferred over continuous scanning • Rapid slew • 2 ~orthogonal looks into each sample volume • Laser bore-sighting

  4. Constraints • Volume • Mass • Power • Vibration • Torque • Momentum compensation • Space environment

  5. Approaches • Conventional telescope w/ rotating mount • Multiple telescopes • Scanning flat mirror • Rotating wedge prism • Rotating Fresnel prism • Rotating HOE • Multiplexed HOE / SHADOE

  6. Comparisons Mass and Power comparisons. (Source - GSFC Doppler Lidar Technology assessment, 2001.)

  7. IR UV Holographic Optics

  8. Hybrid SHADOE Roadmap TRL3 TRL4 TRL5

  9. Key Remaining Issues • Space qualification • 2-micron performance (diffraction limited) • SHADOE demonstration • System trades: • laser • # of FOVs & dwell time / spatial resolution • hybrid configuration • Scaling to  1 meter

  10. Conclusions • Conventional scanning telescope too heavy • 2-micron & 355 nm requirements very different (size & image quality), perhaps equally difficult • HOE technologies offer significant weight and power savings for large apertures • Perhaps the lowest TRL of UV Doppler components • No show stoppers, but significant risk & development

  11. Baseline Scan Configuration 3 tracks, 6 lines of sight 237 km 30° YA= 324 km YB= 87 km 150° Satellite nadir ground track 324 km 90° YC= 237 km 0 12 78 90 33 57 seconds timing Z = 400 km,  = 40°, A = 75°, B = 15°, C = 45°

  12. Optical Layout(single HOE)

  13. UV-A exposure effects

  14. Wavefront Error Correction Wave-front distortion caused by HOE materials Wave-front corrective prescription applied to cover glass

  15. Hybrid R-T Combination SHADOE Receiver(One FOV shown) UV Focal Plane UV Reflection SHADOE IR Transmission SHADOE IR Focal Plane

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