WBS 3.3 Laser Facility

1
WBS 3.3 Laser Facility

• Jim Bell, Jason Chin, Erik Johansson, Chris
  Neyman, Viswa Velur
• Design Meeting (Team meeting 10)
• Sept 17th, 2007

2
Agenda

• Approach to Laser Facility WBS 3.3.
• Phasing of these subsystem deliveries and inputs
• Deliverables and products from subsystems (WBS
  3.3.1 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 3.3.1 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
  3.3.4.

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WBS 3.3.1 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 3.3.2 to 3.3.6.

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WBS 3.3.2 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.

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WBS 3.3.3 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.

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WBS 3.3.4 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, M2
  measurements, and near and far field profiles.
• Review and upgrade FRD requirements from version
  1.0 to 2.0.

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WBS 3.3.5 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.

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WBS 3.3.6.2 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 (3.4.1.2, 3.4.2.1, 3.4.2.2)
• 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.

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WBS 3.3.6.2 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

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Block Diagram of External Interfaces
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Block Diagram of Internal Interfaces
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How to make NGAOs multimillion dollar decision?

• Generation of criteria and priorities in guiding
  the architecture selection process
• Photon return per beacon (the photon return/watt
  isnt 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).

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Previously criteria for subsystem evaluation