1. Status of the Hybrid Doppler Wind Lidar (HDWL) Transceiver ACT Project Cathy Marx (NASA/GSFC), Principal Investigator Bruce Gentry (NASA/GSFC), Michael Kavaya (NASA/LaRC), Patrick Jordan (NASA/GSFC) Co-Investigators Ed Faust (SGT), Lead Designer Space-Based Lidar Winds Working Group August 24-26, 2010 Bar Harbor, Maine

2. Outline Space-based Design Background Objectives Requirements Optical Design Mechanical Design Risks/Concerns Acknowledgements: Support for development of the HDWLT provided by the NASA ESTO ACT program.

3. Hybrid Doppler Wind Lidar Measurement Geometry: 400 km 350 km/217 mi 53 sec Along-Track Repeat “Horiz. Resolution” 586 km/363 mi

4. GWOS IDL Instrument GWOS Payload Data Telescope Modules (4) GPS Nadir Star Tracker Dimensions1.5m x 2m x 1.8m Mass567 Kg Power1,500 W Data Rate4 Mbps GWOS in Delta 2320-10 Fairing Dimensions (mm) Orbit: 400 km, circ, sun-sync, 6am – 6pm Selectively Redundant Design +/- 16 arcsec pointing knowledge (post-processed) X-band data downlink (150 Mbps); S-band TT&C Total Daily Data Volume517 Gbits Hybrid DWL Technology Solution

5. NWOS System Configurations (Courtesy M.Clark and D.Palace) Configuration 1 and 2 (Inverted GWOS) Configuration 3 (ShADOE) Return

6. Define science requirements and interfaces for7/09 the 355nm and 2um systems Complete telescope optical design12/09 Complete mechanical design of select mechanism2/10 Complete opto-mechanics of telescope mirrors8/10 Complete assembly and performance testing of3/11 select mechanism Assemble transceiver7/11 Integrate transceiver with 355nm and 2um10/11 lasers and receivers Conduct hybrid system validation1/12 Hybrid Doppler Wind Lidar (HDWL) Transceiver PI: Cathy Marx, GSFC CoIs/Partners: Bruce Gentry, GSFC; Patrick Jordan, GSFC; Michael Kavaya, LaRC Build a compact, light weight, four field-of-view (4-FOV) transceiver, including a reliable FOV select mechanism, in support of the Global Tropospheric 3D Winds mission Integrate the hybrid transceiver with ground based 355nm and 2um lasers and receivers Us e compact mechanical packaging to achieve a 4-FOV hybrid transceiver Designed for efficient operation in the UV and IR Design long life mechanisms to select operational FOV Conduct ground based tests by integrating HDWL with the Goddard Lidar Observatory for Winds (GLOW) and LaRc Validar systems Leverage prior NASA investments in coherent and direct detection lidar instrument technologies TRL in = 2 1/09 Objective Key MilestonesApproach

7. Requirements ACT Space Demo 355 nm2 um355 nm2 um Platform Altitude*12 to 20 km 400 km Telescope collecting aperture8" (0.2 m) 0.5 m Number of look angles4444 Telescope view angle 45 deg above horizon, equally spaced in azimuth Telescope magnification10 TBD Telescope configuration--unobscured telescope--unobscured telescope Throughput requirements>90% Telescope image quality 95% in 100 urad blur (TBR) diffraction limited at 2- um 95% in 100 urad blur (TBR) diffraction limited at 2- um Field of view100 uradDiffraction limited * NASA research aircraft, e.g. DC8 and WB57, are target platforms for design. ACT demonstration will be on ground.

8. Functional Block Diagram

9. Optics

10. Telescope Design Key parameters –4 identical telescopes –8” collecting aperture –Demagnification of 10 –Afocal system –Primary and secondary are both off-axis parabolas Iterated packaging to continue to make compact Added the window up front to ensure compatibility with aircraft version. Outgoing laser Incoming return Primary Secondary Window 4 Primaries Outgoing laser Incoming return

11. Telescope Packaging Window Top View Side View

12. Telescope Mirrors Primary mirror specifications: –Clear Aperture: 200 mm –Off-axis distance: 150mm –Focal Length: 500mm –Surface accuracy: 1/10 wave PV at 633nm –Surface Quality: 40-20 –Fiducials indicating off-axis distance, direction to parent vertex, clocking Secondary mirror specifications: –Clear Aperture: 18 mm –Off-axis distance: 13.5mm –Focal Length: 45mm –Surface accuracy: 1/10 wave PV at 633nm –Surface Quality: 40-20 –Fiducials indicating off-axis distance, direction to parent vertex, clocking Current baseline is to use light-weighted, low CTE mirrors –Requested quotes from several vendors.

13. Lightweight Zerodur substrates reduce the mass of each 8 in mirror in half (From 8.5 lbs To 4.25 lbs). Fabrication Process: -Grind & polish solid blank using conventional techniques -Lightweight using machining per drawing -Cut 4 mirrors from single blank Light Weight Mirrors Option

14. Multi-layer Dielectric Mirror Coating Design Current design is two multi-layer designs. Coating optimized for 2.054um on substrate. Coating optimized for 355 nm on top. 7 pairs optimized for performance at 354.7 nm and 7 pairs optimized for performance at 2 um. Predicted reflectivity of greater than 98% at 355 nm and 98% at 2 μm. <1.5% difference in Rs and Rp at 355 nm. <0.4% difference in Rs and Rp at 2054 nm. Test windows have been ordered. Preparing to test coatings with high powered lasers.

15. Error Budget tip/tilt of secondary1arcmin clocking of secondary15arcmin decenter of secondary25microns focus of secondary5microns tip/tilt of primary20arcsec clocking of primary2arcmin decenter of primary25microns focus of primary5microns Optical performance driven by requirement for diffraction limited performance at 2um. Alignment and fabrication requirements are tight. Flats and beamsplitters cause beam displacement. Also causes wavefront error if, when tracing transmit beam, the beam is not parallel to the telescope optical axis. Using alignment plan to aid in error allocations. Using this analysis to help determine adjustment range and step size.

16. Mechanical

17. Mechanical Design - Design of Telescope Light Weight Structure (Material Selection) Light Weight 8 in Mirrors Design Select Mechanism Release Optic ICD drawings (In Process) Interface with optics designs (In Process) Analysis (In Process) - Assembly Assy Plan Location GSE - Package Lasers / Receiver and interface with telescope

18. Design of Telescope Structure Latest layout of ACT Structural Design

19. Ray Trace Layout Risely optics Primary mirror Secondary mirror Folding Mirror Indexing mirror Indexing mechanism

20. Telescope Volume 27.66 inches 19.30 inches 18.48 inches Top View

21. Composite Structure One Piece Frame Design

22. Select Mechanism Reqts Purpose: Sends outgoing laser light to correct telescope Requirements (derived from GWOS study for demo mission): Four position mechanism where each position is separated by 90 deg Make as redundant as possible No preferred state if mechanism fails (because if it fails the mission is over….) Duty Cycle is 9*10 6 moves for 3-year mission 1 move every 11 seconds (10 sec for stare, 1 sec for move) Will always move in same direction First move is 90 deg, next move is 180 deg, next move is 270 deg and last move is 180 deg Operation speed is 1 sec for movement and stabilization Working with Pure Precision for a Precision Rotary Table that will meet our requirements.

23. Technical Risks/Concerns Precision of optics required for coherent system. Maintaining precision when thermal environment is changing. Laser damage of mirror coatings. Maintaining manpower due to other commitments.

24. Summary Telescope optical design and alignment tolerancing complete Primary and secondary mirrors ordered (20 wk delivery) COTS Select Mechanism identified Mechanical design ~85% complete. –Working on mirror mounting details – Iterating design with GSFC composites group to optimize fabrication/cost