Instrument R

1
Instrument RD WBS 2.3

• Chris Bebek
• Lawrence Berkeley National Laboratory
• 9 July 2002

2
Overview

• Implementation concept
• Instrument walk through
• RD plan
• RD goals
• RD management
• Organization
• WBS overview
• Costs
• Summary

3
Instrument working concept
Cables/ FE elec
Cold plate
Radiator
Thermal links
Spectrograph
Guiders
Particle/ Thermal/ Light shield
Shutter
CCDs/ HgCdTe
Near electronics
Filters
Data/ Monitoring/ Command
4
Focal plane concept

• All instruments coalesced on one focal plane.
• Common 140K operating temperature.
• Bolted to telescope structure.
• Imager sensors in one focal plane.
• 36 2k x 2k HgCdTe NIR sensors.
• 36 3.5k x 3.5k CCD sensors
• Spectrograph mounted to focal plane.
• Two channel spectrograph with light access port
  in the focal plane.
• Objects dropped into spectrograph light port by
  steering the satellite.
• Fixed filter mosaic
• 3 NIR bandpass filter types organized in 3x3
  arrays.
• 6 visible bandpass filter types organized in 6x6
  arrays.
• Guide off the focal plane during exposures.
• 4 1k x 1k star guider CCDs.

Guider HgCdTe
CCDs
Spectrograph Spectr. port
rin6.0 mrad rout13.0 mrad rin129.120 mm
rout283.564 mm
5
Near Infrared ImagerWBS 2.3.3.2

• Function
• Photometry from 1000 nm to 1700 nm.
• Use HgCdTe wth 1.7 mm cutoff
• Effort
• Establish facility for testing and characterizing
  NIR FPAs.
• Characterize HgCdTe devices
• Linkages
• Instrument mechanical engineering group
• Instrument electronics
• Calibration group
• Deliverables
• Mechanical and thermal concept
• Test and qualification plan for HgCdTe devices.
• Cost and schedule.
• .

Details in Greg Tarles plenary and breakout
talks.
6
Visible ImagerWBS 2.3.3.3.1

• Function
• Photometry from 350 nm to 1000 nm.
• Use LBNL CCD
• Effort
• Complete optical performance measurements
• Develop device packaging
• Develop production method for CCDs
• Derive a cost model.
• Linkages
• Filter group
• Imager mechanics
• Calibration group
• Deliverables
• Mechanical mount concept.
• Test and qualification plan
• Cost and schedule.

Details in my following talk and Steve Hollands
breakout session talk.
7
Star guiderWBS 2.3.5

• Function
• Provide fine guiding during exposures
• Telescope/instrument IT
• Effort
• Trades and concepts by spacecraft group
• Linkages
• Instrument mechanics
• Instrument electronics
• Attitude control system
• Deliverables
• Concept or parts selection
• Cost and schedule

8
SpectrographWBS 2.3.4

• Function
• l/dl 100 spectroscopy from 350 to 1700 nm
• Effort
• Optics train design
• Focal plane sensor selection
• Slicer technology development
• Calibration procedures studies
• Software development data processing/monitoring
  
• Linkages
• Imager mechanics
• Instrument electronics
• Calibration group
• Deliverables
• Interface control requirement
• Characterized slicer demonstrator
• Cost and schedule

Details in Anne Ealets and Eric Prietos talks.
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FiltersWBS 2.3.2.3.2.3

• Activity
• Univ. of Indiana is working with a vendor to
  deposit filters on silicon sensors.
• LBNL will take a quick look at the issues for
  suspending discrete filters.
• Effort
• Concept for mechanical mounting discrete filters.
• Several cycles of direct deposition of filters on
  silicon wafers and CCDs.
• If successful, move on to HgCdTe deposition.
• Linkages
• CCD group
• HgCdTe group
• Imager mechanics
• Deliverables
• Demonstration of functioning CCDs with deposited
  filter.
• Mechanical mount conceptual design.
• Cost and schedule.

4 silicon wafer with B-band filter
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ElectronicsWBS 2.3.2.4

• Function
• Coordinate instrument readout
• Configure instrument electronics
• Monitor/control instrument environment
• Deliver data to spacecraft
• Effort
• Top down approach
• Capture all requirements
• Capture interconnects
• Bottoms up approach
• Identify areas where ASIC development out ways
  risk
• Analog processing of CCD signals

• Linkages
• Visible and NIR imagers
• Spectrograph
• Imager mechanics
• Calibration group
• Spacecraft thermal
• Spacecraft telemetry
• Spacecraft controls
• Deliverables
• Multiple interface control documents
• Overall architecture
• ASICs for CCD, possibly HgCdTe
• Cost and schedule

Details in Natalie Roes plenary and Jean-Pierre
Walders breakout session talks.
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ElectronicsWBS 2.3.2.4

• Electronics context.
• Boundaries to be negotiated with Spacecraft team.
• Complement of electronics components will be
  selected from architecture studied.

Top level of an essential model used to capture
functional requirements and interoperability of
subsystems,
12
Mechanics ShieldWBS 2.3.2.3.2.5

• Multifunction
• Charged particle attenuator
• Thermal vessel
• Light shield
• Backscattered light absorber
• Effort
• Concept
• Particle attenuation study
• Linkages
• OTA mechanics
• Deliverable
• Conceptual design
• Refined mass estimate
• Cost and schedule

13
Mechanics ShutterWBS 2.3.2.3.2.4

• Multifunction
• Normal exposures of well determined time
• Fast exposures for calibration on bright objects
• Flat illumination surface
• Effort
• Concept
• Drive mechanism research
• Linkages
• Calibration group
• Attitude control system
• Deliverable
• Conceptual design
• Cost and schedule

14
Mechanics Thermal/mechanical mountsWBS
2.3.2.3.1.3

• Multifunction
• Kinematic mounts
• Thermal isolation
• Effort
• Concept
• Prototype construction and characterization
• Linkages
• OTA mechanics
• Deliverable
• Conceptual design
• Cost and schedule

Small size, heritage device.
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Mechanics Thermal linksWBS 2.3.2.3.1.2

• Function
• Cooling path between radiator and focal plane
  cold plate.
• Effort
• None
• Linkages
• Instrument FPA mechanics
• Deliverable
• Vendor cost

• http//www.techapps.com/thermal.htm
• - Length 30 cm
• - Conductance 0.45 W/K
• - Weight 145 g
• - 20-fiber bundles per row, up to 3 rows
  
• - 20,000 carbon fibers per bundle
• 28.5-cm long by 5-cm wide
• An Equivalent aluminum conductor
• - Cross-section 1in2
• - Weight 1450 g

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Mechanics radiatorWBS 2.3.2.3.1.1

• Function
• Provide passive cooling for focal plane sensors
• Provide passive cooling for focal plane
  electronics
• Effort
• Concept
• Linkages
• OTA mechanics
• Deliverable
• Conceptual design
• Cost and schedule

17
RD Plan

• The RD period concentrates on
• Paper studies to eliminate or better understand
  the identified risks.
• A limited, focused hands-on RD program to
  mitigate risk.
• Producing a credible project cost and schedule.
• Exposing and documenting all interface areas with
  other subsystems.

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RD Studies and Trades

• Separate visible, NIR, and spectrograph focal
  planes.
• Small FOV NIR configurations.
• Shutterless operation.
• Filter wheel configurations and fixed filters.
• Filter placement on or off sensors
• Filter number optimization.
• Telemetry bandwidth, solid state recorder, data
  compression
• Data storage and telemetry bandwidth versus orbit
  type, orbit period, exposure time, and relative
  fraction of spectrograph time.
• Single or double channel spectrographs with
  prisms or gratings.
• Electronics development warm vs cold operation
• Precision guiding schemes using the focal plane.
• Shield charge particle attenuation efficiency
  vs mass
• Shutter concept development
• Exposure time and number of exposures to set
  limits on sensor dark current and readnoise and
  to provide sufficient dithering information.
• Thermal loads
• Calibration support hardware
• IT support hardware

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RD Hands-on Efforts

• HgCdTe operation characterization
• CCD fabrication and characterization of SNAP
  specific prototypes
• Front-end ASIC development
• Spectrograph image slicer prototype
• Filters direct deposition on sensors
• Mechanical mounts build and study thermal ball
  mounts to support shield and cold plate

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RD Major objectives

• SNAP HgCdTe characterization, specifications, and
  acquisition plan.
• SNAP preproduction CCD with full
  characterization, specifications, and production
  plan.
• CCD readout ASIC core prototype.
• Spectrograph image slicer prototype
  characterization.
• Instrument readout electronics concept.
• HgCdTe readout strategy and implementation path.
• Filter set and mounting concept.
• Particle shield performance study and refined
  mass estimate.
• Shutter concept.

21
Instrument Management

• Management
• All instrument subsystem requirements will be
  generated at the instrument level in
  collaboration with the subsystems.
• All ICD and IT plans are negotiated at the
  system level with the subsystems and system
  engineering.
• The above two are to maintain the system
  coherency we have achieved in the working
  concept.
• This summer, we will institute a monthly joint
  tele/video-conference with the subsystem groups.
• Issues
• CDR preparation
• Coordinating and documenting internal linkages
• Coordinating and documenting external linkages

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CDR preparation

• Convert working concept to a conceptual design
• Interface Control Documents - drafts
• Discover and document interfaces amongst
  instrument systems.
• Discover and document interfaces with other
  systems.
• Iterate instrument conceptual design as required.
• Integration and test planning - drafts
• IT plan development for instrument.
• IT plan development with telescope and
  spacecraft.
• Iterate instrument conceptual design as required.
• Project cost and schedule
• Cost and schedule conventional components.
• RD results will define cost and schedule of
  custom items.
• Identify long lead items.

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Examples of internal linkages

• Cross linkages between the Spectrograph and other
  instrument systems.
• From NIR team
• First performance results (Sept 03)
• Read-out electronic choice (Sept 03)
• From CCD Team
• First performance results (Sept 03)
• Read-out electronic choice and performances
  (Sept 03)
• Detector format adaptation possibilities (i.e.
  pixel size, number of pixels)
• Chip procurement possibility for a evaluation
  (Sept 03)
• Chip for evaluation procurement (March 04)
• From calibration group
• Preliminary evaluation of work for the
  spectrograph (Dec 02)
• Calibration statement of work for spectrograph
  (July 03)
• From Instrument team
• Draft of interface document (Dec 02)

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Examples of interfaces to other systems
Optical Telescope Assembly Optical
parameters Mechanical mount ICD IT plan
Atitude Control System Star guider ICD IT plan
Calibration group Shutter Filters Readout RFD
Bus power ICD IT plan
Simulation Provide sensor characteristics data
Telemetry Command Monitoring Science
data ICDs IT plan
ICD Interface Control Documents
IT Integration and Test Plans RFD Requirements
flow down
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RD cross links index
To
From
This is a work in progress to document the
interactions during RD, and eventually during
construction, of the instrument subsystems among
themselves and of the instrument with other SNAP
systems.
26
RD Organization WBS 2.3
Project Management C. Bebek N. Roe WBS 2.3
Mech Thermal J. Bercovitz SNAP SE WBS 2.3.2.3
CCD sensors C. Bebek WBS 2.3.3.3.1
Spectrograph E. Prieto WBS 2.3.4
NIR sensors G. Tarle WBS 2.3.3.3.2
Electronics H. Von der Lippe WBS 2.3.2.4
Guider M. Lampton WBS 2.3.5
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WBS 2.3 Instrument Package
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Instrument Schedule
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Instrument Milestones
These are early start dates relative to project
dates since instrument conceptual design will
impact all other systems.
30
Summary

• We have a working concept of an instrument and
  its operation.
• The concept is a total package that has evolved
  from an optimization of SNe science requirements,
  anticipated sensors performance, and operational
  constraints. This has been iteratively arrived at
  with the spacecraft and telescope systems. (see
  my breakout session talk)
• We have identified technology risks in the areas
  of CCDs, HgCdTe, and custom integrated circuits,
  and require development in the areas of
  spectrograph image slicer, filters, shielding,
  and shutter.
• A few limited scope RD plans target the
  realization of the anticipated sensors
  performance.

• Plenary talks
• IR Detectors G. Tarle
• Spectrograph A. Ealet
• Electronics N. Roe

• Breakout session
• Instrumentation C. Bebek
• CCD development S. Holland
• IR Detectors G. Tarle
• Spectrograph E. Prieto
• ASIC development J-P Walder