WBS 3.3 Laser Facility Jim Bell, Jason Chin, Erik Johansson, Chris Neyman, Viswa Velur Design Meeting (Team meeting #10) Sept 17 th, 2007

2 Agenda Approach to Laser Facility WBS 3.3. Phasing of these subsystem deliveries and inputs Deliverables and products from subsystems (WBS to 3.3.6) Laser Facility 3.3 internal interfaces and external interfaces. Solicit inputs from members. Laser Down Selection Criteria to assist with determining system architecture.

3 Approach Difficulty with designing without a basic architecture for the laser architecture. Laser architectures and locations affect the enclosures, safety system, and how the beam is transported to a centrally projected launch telescope and the motion control related to the laser control system. The selection of the laser is an important decision not just with design impact, but with a sizable financial impact. Similar to the AO architecture product, some emphasis is needed to provide an architecture with sufficient detail to drive the sub WBS. Team does not believe the laser decision can be made at this stage; but a product of this WBS is to generate more information to assist with the laser selection.

4 Phasing WBS System Architecture –Generation of down select criteria and using them to provide a system architecture with sufficient information to drive other WBS sub elements. –WBS (3.3.2) Generation of Laser Enclosure Requirements and Concepts –WBS (3.3.4) Generation of Laser Launch Facilities –WBS (3.3.3) Laser Requirements and comparison of laser architecture with LMCTI and SOR. –WBS (3.3.5) Generation of Safety System and Concepts –WBS (3.3.6) Laser Control System; dependency on

5 WBS Deliverables Laser System Architecture (80 hours) VV –Provide down selection criteria –Report of laser facility architecture's Layout of system architecture(s) Not expecting to point to one laser (LMCTI or SOR). Possibly points to a laser on the elevation ring and/or a laser on the nasmyth platform. Pros and Cons of the architecture(s) Determine feasibility of the architecture(s) –Provide inputs for subsequent WBS to

6 WBS Deliverables Laser Enclosure (80hrs) J. Bell –Conceptual 3D model of the enclosure completed in Solidworks showing spaces for: Laser and laser transport optics, Supports, Electronics, Environmental equipment and controls –Design report will include A first assessment of high risk items including requirement for higher reliability due to limited access. Interfaces to the enclosure including laser beam and infrastructures (power, glycol, pneumatics, etc.); Safety Concerns Estimated weight and weight distribution; effects on azimuth wrap –List of suitable vendors for proposed equipment –Preliminary cost analysis. –Inputs to the preliminary design phase WBS. –Updates and inputs to appropriate sections of FRD version 2, and System Design Manual.

7 WBS Deliverables Laser (20 hrs. after re-plan, Requesting 40 hrs.) V. Velur –A heuristic scaling law for the photon returns based on extrapolation/ past experience will be formulated. –A report summarizing the amount of laser power that will result in the necessary return will be presented for the 2 possible lasers (LMCTI vs SOR; will add fiber laser if there is time). All the effects, assumptions, and the premise for the scaling law including how the Na-return changes with spot size and laser power for each laser considered. –Update of requirements and compliance of the two lasers for FRD 2.0 (laser section). Justification for the hours: 10 hrs for scaling, 8 hrs. for laser power calculation and 22 hrs for the document and applying scaling to varying spot sizes and laser powers. And determine compliance with respect to requirements.

8 WBS Deliverables Laser Launch Facility, Laser Beam Transport, Laser Pointing and Diagnostics (200 hrs.) V. Velur –Report on the conceptual designs. To include a layout/block diagram as well as description of the interfaces within and outside of the Laser Facility. Concepts for Laser beam transport optics dependent on location of laser. Concepts to generate nine laser beacons from a single or multiple lasers; provide losses with pros and cons of the designs. Concepts for pointing and steering of laser beams on sky, includes uplink tip/tilt and maintaining asterism fixed on sky. –Launch Telescope Optical requirements. Modeling to determine feasibility as well as volume to fit into the telescope. –List of diagnostics for BTO and LLT; laser power, beam stability, spectral profile, M 2 measurements, and near and far field profiles. –Review and upgrade FRD requirements from version 1.0 to 2.0.

9 WBS Deliverables Safety System (40 hrs) J. Chin –Use as much as possible from K1 LGS AO Safety System Requirements. Changes will likely be those related to system architecture. Basic safety concerns apply. –A layout of the safety system with description of the individual subsystems. The layout will include where subsystem components will be located; dependency on the laser. –Draft on how the conceptual design will meet the possible laser architectures. –Draft of an ICD describing possible interfaces between the subsystems internal and external to 3.3. –An updated version of the FRD v2.0.

10 WBS Deliverables Laser System SW (80 hrs) Erik J. –A revised WBS dictionary definition for this task. –An overall SW architecture design covering the main laser sequencer; command, control and status interfaces to the various AO subsystems (the observing sequence, AO sequence, etc.); the motion control system; calibration and diagnostics. This design will be done in collaboration with the WBS tasks for Science operations ( , , ) The laser system (3.3.1, 3.3.2, 3.3.3, 3.3.4) The controls teams (3.2.4, 3.2.5) –A top-level block diagram showing the overall SW architecture for its main subsystems. –A top-level data-flow diagram, showing data paths, descriptions, sizes, and expected data rates. –A draft of an ICD for interfaces to laser SW; block level context diagram showing laser SW components connectivity to AO system; high-level description of the command, control, and status interfaces and functions of the laser sequencer. –A top-level description of all the laser component SW modules. –A revision of the functional requirements pertaining to the laser SW. –A report summarizing all the above items.

11 WBS Deliverables Laser System Electronics (70 hrs) Erik J. –A layout of the laser subsystems and their locations. –A block diagram of the laser control system –Block diagrams of the sub systems, to include: Laser control –Basic laser system control –Wavelength and mode control; detuning for Rayleigh background estimation Motion control –Beam transport; including beam injection. –Launch system –UTT Calibration and diagnostics Environmental system for laser and personnel Interfaces to the laser safety system –ICD Draft –Update to FRD 2.0

12 Block Diagram of External Interfaces

13 Block Diagram of Internal Interfaces

14 How to make NGAO’s multimillion dollar decision? Generation of criteria and priorities in guiding the architecture selection process –Photon return per beacon (the photon return/watt isn’t as useful) - how well it can optically pump the Na layer? –$$ price for producing a single beacon (bang for the buck) –Laser size, location (and ruggedness), BTO throughput. –Operational cost, maintenance costs (replacement diodes may be ~$1M!), failure modes (slow or catastrophic?) –Laser reliability, system complexity. –Upgradeability. –Beam quality, spot size limitation imposed by the laser. –SNR (fratricide and background may be lesser for pulsed lasers) –How well do we understand the laser format and vouch for the Na return (this is important when considering new laser formats). –How well the laser technology is adaptable to techniques (like 2 color Na pumping, Multi-color LGS to get rid of the tilt indeterminacy).

15 Previously criteria for subsystem evaluation