SNAP Systems Engineering WBS 1.3

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SNAP Systems EngineeringWBS 1.3

• David Pankow
• Space Sciences Laboratory,
• and Mechanical Engineering Department,
• University of California Berkeley
• November 2003

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SNAP Engineering Overview

• Observatory Overview
• Optical Telescope Assembly (OTA)
• Telescope (TMA-63) Packaging
• Instrument (Camera) Packaging
• Outer Stray Light Baffle
• Active Mechanism Concerns
• Spacecraft Overview
• Sub-systems Summary
• Market Survey (e.g. RSDO Catalog)
• Mission Profile - Launch Vehicle and Orbit
  Selection
• Ground Segment
• Systems Engineering
• Design and Trade Studies Status
• Documentation Configuration Control
• R D Tasks, Manpower, Schedule
• Summary

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SNAPs DESIGN EVOLUTION

• Passive Cold Biased Bus Baffle / Warm Optics
• Active Coolers are not Mature, Cryogen's are
  Short Lived
• High Earth Orbit allows Passive Cooling and
  Stable Pointing
• Build, Test, and Fly Warm Optics
• Cold Optics are a Significant Cost Schedule
  Driver (NGST)
• Compact Telescope with the Longest Light Baffle
  that can be Fit !
• Generic and Rigid Spacecraft
• One Mission Thermal Attitude ...near Sun Line
  Normal Viewing
• No Flexible Appendages and Minimal Mechanisms
• On Board Momentum Control Management
• Structural Noise Isolation at the Sources
• RSDO generic spacecraft with Identified Upgrades

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OBSERVATORY Cross Section
Secondary Mirror, Hexapod and Lampshade Light
Baffle
Primary Mirror
Spectrograph
Instrument Dewar
Focal Plane
Instrument Thermal Radiator
Spacecraft
Door Assembly
Fold-Flat Mirror
Primary Solar Array
Main Baffle Assembly
Tertiary Mirror
Optical Bench
Secondary Metering Structure
Stovepipe Baffle
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TELESCOPE OPTICS DESIGN (TMA-63)

• Annular Field Three Mirror Anastigmat (TMA)
• Folded Light Path Permits Very Compact Telescope
  Design
• 2 meter Primary in 3.3m long package with 20.66m
  Focal Length
• Allows anti-sunward Thermal Radiator for
  Instrument
• Obstructing Secondary causes Annular Field of
  View
• Single (Flat) Focal Plane Array of Detectors
• (Often called the Fully Integrated Detector
  Option (FIDO)
• 36 - CCDs
• 36 - IR Sensors
• Spectrograph (fully redundant)
• Common 140K remains Adequate
• 130K Spectrograph bias is viable

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TELESCOPE MIRROR OPTIONS

• Corning ULE Ultra-Low Expansion Glass
• Face Sheets Bonded to Water-Jetted Honeycomb Core
• 180 mm thick Core with 2.5mm Ribs Typical
• Achieves 85-90 Light weighting
• Extensive Manufacturing History
• Schott Zerodur Glass/Ceramic Material
• Solid Blank, Mass Reduced by Machining Backside
• 190 mm Pockets with 5mm Ribs Typical
• Open Back is Lowest Fabrication Risk
• Semi-Closed Back for Greater Rigidity
• Achieves 70-85 Light weighting
• Extensive Manufacturing History
• All Approaches are Viable for SNAP

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TELESCOPE STRUCTURE
COMPOSITE TELESCOPE STRUCTURE(driven by the
required 1 ppm Optics Stability)- Standard
M-55J Graphite Fibers are Adequate for
the Needed ppm / K Stability- Quasi-Isotropic
Lay Up CTE lt -0.12 ppm /? C- On Orbit
Temperature Control DT lt 2 ? C- Cyanate
Ester Matrix provides low CME
(moisture)- These are Todays Technology !
SECONDARY MIRROR SUPPORT STRUCTURE
PRIMARY OPTICAL BENCH
OPTICS COFFIN BELOW
OPTICS, THERMAL, AND GEOMETRIC DEFINITIONS ARE
COMPLETEDETAILED DESIGN AND FEM ANALYSES ARE
MATURE
with Three STIFF Metering Beams
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TELESCOPE OVERVIEW

• TMA-63 TELESCOPE DESIGN IS PROGRESSING RAPIDLY
• OPTICAL TELESCOPE (OTA) - Implementation (TMA-63
  is very mature !)
• Open Back Zerodur vs Closed Back ULE (LBL -
  Sagem-Reosc) studies complete
• No Zerodur show-stoppers Increased glass
  mass, perhaps shorter schedule
• Critical end to end Hubble (Reflex) Test
  definition results are promising
• FEM results suggest Std. 1/20th wave optics 1G
  validation appears viable
• 64 Support Fingers needed to Reduce Gravity Sag
  in Primary Mirror

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INSTRUMENT and THERMAL
PASSIVE GIGA-CAM 140K DEWAR THERMAL BUDGET 45
w Radiating Capacity from 2m2 unobstructed 130K
Radiator to Space lt 4wgt Radiator Thermal
Isolation Mounts MLI behind RADIANT COUPLING
LOSSES lt 6wgt CONICAL Cosmic Ray Shield - MLI
outside (e 1) lt17wgt Open End CONE Blackbody
Loss to warm Coffin Cavity CONDUCTIVE COUPLING
LOSSES lt 1wgt Giga-Cam Thermal Isolation Mounts lt
2wgt Dewar Thermal Isolation Mounts and Cold Plate
Gaskets lt 1wgt Electrical Flex-Print (TBD
traces) lt 8wgt Average Electrical Power for
HgCdTe CCDs 6w CURRENT MARGIN 10C
Gradient allocated for Cold Plate, Radiator, and
Flex-Links
NOTE Thermal and Contamination Close Outs NOT
SHOWN for Clarity
130K PASSIVE RADIATOR
FOCAL PLANE
Spectrograph
SHUTTERS
DEWAR
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INSTRUMENT THERMAL NOTES
RECENT SSL MISSION EXPERIENCE
HESSI DETECTORS Extensive Thermal Isolation Only
3W of Active Cooling
HESSI COLD PLATE ASSEMBLY Supports Germanium
Detector Assembly under Vacuum
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STRAY LIGHT BAFFLE DESIGN

• FUNDAMENTAL BAFFLE DESIGN CONSIDERATIONS
• Top Cut Angle Chosen to Block Sunlight in All
  Science Attitudes
• Earth-Lit Region must be Well Baffled
• BaffleLamp ShadeStove Pipe diffraction line
  dictates the Hat Size
• Trades Indicate an Ordinary Aluminum Shell
  Construction is Adequate !
• Detailed ASAP (software) Stray Light analysis are
  now underway !

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TELESCOPE THERMAL

• OPTICS Build,Test, Fly Warm

• High Earth orbit (HEO) to minimize Earth-glow
  Loading
• GaAs - OSR Striping of the (warm) Solar Array
  Panels
• Front surface heat rejection Only
• Optical Solar Reflectors are back silvered
  Quartz tiles (a 8, e 80)
• Low emissivity Silvered Mirrors
• Thermal Isolation mounting and Extensive MLI
  blanketing
• Cool Light Baffle and
• Actively Heated Telescope

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SNAP OBSERVATORY STRUCTURES

• PRIMARY STRUCTURES
• Total, or Integrated Observatory Design Finite
  Element Model (FEM) is done
• Baffle, Door, Telescope, Optics Design Studies
  Posted - Stout Bus defined
• 17 Hz -1st Mode exceeds 10 Hz Delta IV reqmt,
  with 20 Launch Mass Margin

GFRP Composite Telescope Structure
Telescope Light Baffle Structure
17 Hz First Mode
Coffee Table Spacecraft Bus
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ACTIVE MECHANISM CONCERNS
Our Guess at Reviewers Likely First Reactions !
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SNAPs ELECTRICAL DIAGRAM OVERVIEW
INSTRUMENT FUNCTIONS
HIGH SPEED DATA PORTS
MIL-STD 1553 BUS Interfaces
SPACECRAFT FUNCTIONS
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SNAP SPACECRAFT OVERVIEW

• MOSTLY GENERIC SUBSYSYEMS
• EPS (electrical), CDH (command data handling),
  TCS (bus thermal)
• MISSION UNIQUE SUBSYSTEMS
• ACS (attitude control), SMS (structure
  mechanisms), RF (Communications)
• THE CLEAN INTERFACE EXCEPTIONS
• Telescope mounts to the Spacecraft Coffee
  Table, or ANY FLAT SURFACE
• Load Path expands from (66) PAF to 2.5m Baffle
  Telescope Bipod Ring
• Stiffness Strength Requirements must be imposed
  on Primary Structure
• Star Trackers, Gyro (IRU), and Solar Arrays mount
  on the Instrument
• Observatory Control Unit Memory mount on the
  Spacecraft
• IMDCs (GSFC) Risk Assessment New Technologies
  Comments
• Risk on spacecraft bus is generally low, with
  well-understood technologies and readily
  available components
• No significant technology development required
  for bus

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SNAP Mission Profile

• Delta IV M (4240) Launch from KSC
• 2.6 x 25 Re Injection to Final 28? Inclination
  Orbit
• Phased for near Ecliptic Plane Orbit
• Our Plus The perigee is Stable Over Berkeley !
• Commissioning Phase - several overlapping weeks
• Spacecraft Turn On Activities
• Structured Cool Down of the Telescope
• Slow Roll, or Auxiliary (rear) Solar Arrays
• Degassing Dry Out Period
• Optics Turn On Open Cover, Focus, Cal., etc.
• Mission / Science Operations (Routine Survey)
• Alternate near N/S Ecliptic Pole Observing
• Observing is Suspended below 9 Re (radiation
  issues)
• Onboard Storage and High Speed Data Down-Link

Delta IV fairing
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SNAP GROUND DATA SYSTEM
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SNAP GROUND DATA SYSTEM

• SSLs Berkeley Ground Station (BGS) - 11m S-Band
  Dish
• 3rd Year of mostly Automated Operation
• MOC SOC Infrastructure for FAST / RHESSI /
  CHIPS
• BGS dish is SX-Band Capable (but not Ka-Band)

NRAOs ALMA project - 12m Ka Band VERTEX RSI
dish (Jan 03 1st Light)
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SNAP S.E. Resources Allocation
MASS ALLOCATION (21 margin) 2020 kg Direct to
Orbit Launch Capacity
MISSION REQUIREMENTS Complete Document is Posted
at snap.lbl.gov
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SNAP S.E. Resources Allocation

• ELECTRICAL POWER REQUIREMENTS

MISSION REQUIREMENTS Complete Document is Posted
at snap.lbl.gov
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SYSTEMS ENGINEERING DOCUMENTS

• TOP LEVEL SNAP PLANNING DOCUMENTS
• Mission Definition and Requirements Document
  (MDRD) Describes our Negotiated Level 1 Science
  Requirements version 1d is posted.
• Integrated Requirements Databaseis the evolving
  Flow Down of Requirements to the Level 2, 3 4
  Requirements and is posted.
• Work Breakdown Structure (WBS) is in Place and
  Being Used for all SNAP Planning and Budgeting
  Efforts.
• Draft Observatory IT Plan is under Active Review
  and Discussion
• Solid Works and PDM is Networked, and the
  Maturing SNAP Solid Model is under Configuration
  Control (15th release now posted).
• IGES export issues to structural and thermal
  models are being examined
• Instrument, Telescope Spacecraft ICDs will be
  developed as designs mature

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SYSTEMS ENGINEERING DOCUMENTS

• SNAPs EVOLVING CONTROLLED DOCUMENTS DATABASE

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SYSTEMS ENGINEERING STUDIES

• STRUCTURES 1st Generation NASTRAN Model
  Complete
• Baffle Trades, Telescope Trades, Optical Element
  Trades, Bus defined
• End to end 1G Optics verification plan is
  progressing
• THERMAL DESIGN
• Excel Matlab Lumped Node Telescope Camera
  Models allow cross checks
• TELESCOPE OPTICS
• Optics Tolerancing Submitted, and detailed Stray
  Light Studies are underway
• Draft Telescope Primary Mirror Specification
  Documents under Review
• ATTITUDE CONTROL SYSTEM
• Image Jitter based Modeling and Simulation
  Studies are Show Promise
• Parallel Physical and State Models allow
  interactive cross checking
• COMMAND DATA HANDLING
• Industry std. fully redundant cross strapped
  1553 avionics bus defined
• High speed selectively redundant Instrument
  data bus architecture defined

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SYSTEMS ENGINEERING REVIEWS

• SNAP MISSION LEVEL REVIEWS
• 01 IMDC ISAL Mission and Instrument Design
  Reviews at GSFC
• Extremely useful for Refining the Mission
  Concepts
• 02 Independent Lehman RD Review
• SNAP team received many complements for a
  thorough presentation
• 02 Team X Mission Design Review at JPL
• Mission Implementation refined, No New Mission
  concerns raised
• NASAs BEYOND EINSTEIN Announcement of
  Opportunity
• Type 1 Type 2 proposal outcomes are not yet
  fully known
• ISSUES CONCERNS
• Critical Path (Optics) Procurement Options are
  being pursued

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SYSTEMS ENGINEERING STATUS

• TELESCOPE packaging options and requirements are
  well defined
• Several Light-weighting Options are Actively
  being Considered
• Our teams desire is to maintain technology and
  vendor flexibility
• OPTICS PROCUREMENT IS OUR CRITICAL PATH ITEM
• INSTRUMENT needs and viable approaches are known
  actively pursued
• Sensor Packaging Electrical Packaging Trades
  are In Progress
• Thermal management calls for continuing
  vigilance
• SPACECRAFT can be a generic ( interagency) RSDO
  procurement
• Instrument - ACS interactions calls for studies
  tracking
• LAUNCH VEHICLE Track the Options and New
  Development Maturity

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Systems RD Schedule
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SUMMARY COMMENTS

• Build, Test, Fly Warm is both Proven and Cost
  Effective
• Passive Thermal Approach Remains Viable for the
  Instrument
• SNAP has Several Lightweight, Low CTE Mirror
  Options
• Composite Telescope Structures Are Well
  Understood, and this Technology Continues to
  Mature
• Spacecraft Bus has several concerns, but No New
  Technology
• Healthy Competition in the Heavy Lifter Launch
  Business
• Delta IV (3 for 3) EUTELSAT, DSCS-A3, DSCS-B6
• Atlas V (3 for 3) Hotbird 6, Hellas-Sat,
  Rainbow 1 (or Atlas IIIB)
• Sea-Launch (9 for 10) but International
  Partnership is a concern