Instrument R

1
Instrument RD

• Chris Bebek
• Lawrence Berkeley National Laboratory
• 11 November 2003

2
Overview

• Requirements development
• Instrument walk through
• RD plan and goals
• RD management
• Organization
• CDR preparation
• Schedule
• Summary

3
Requirements Flowdown(as perceived to drive RD
efforts)
4
Science-Driven Requirements to Instrument Concept

• Instrument
• A large FOV (0.7 sq. deg. ).
• Observation cadence commensurate with SNe
  evolution (every 4 days).
• Allocation of time for photometry and follow up
  spectroscopy (60/40).

• Measurement Program
• Discover and follow light curves evolution of
  Type Ia SNe from z0.3 to 1.7.
• Capture spectrum near peak luminosity.
• 2000 well measured SNe

5
Science-Driven Requirements to Instrument Concept

• Photometry
• Rest frame F. U, B, V, (R)-band light curves.
• Rest frame B-band measurement to 2 at peak.
• K-correction.
• Rest frame multi-color evolution.
• Malmquist bias (early detection).
• Rise time (fused 56Ni).
• Peak-to-tail luminosity ratio (C/O ratio).

• Photometer
• Wavelength coverage from 350 nm to 1700 nm.
• Use two plate scales to cover the wavelength
  range to obtain time efficient photometry.
• 9 filters.
• Required S/N(epoch) versus magnitude achieved
  with appropriate duration and number of
  exposures.
• Zodiacal light - limited measurements.

6
Science-Driven Requirements to Instrument Concept

• Spectroscopy
• UV metalicity features strength and location.
• S and Si features
• SII 5350Å line, Dw 200Å
• SII W shape, Dw 75Å
• SiII 6150Å line, Dw 200Å
• Ejecta velocity, Dl gt15Å.
• Host galaxy z.

• Spectrograph
• Wavelength coverage from 350 nm to 1700 nm.
• S/N 20.
• Resolution 100 (l/Dl).

7
Space Ops Impacts onInstrument Concept

• Reliability
• Avoid moving parts
• No coolers passive, radiative cooling
• No filter wheel
• Allow a shutter
• Avoid multiple focal planes
• Eliminate multiple adjuster sets
• Coalesce visible, NIR, and spectrograph into one
  focal plane
• Eliminate dichroics
• Cosmic rays
• Proton rate is 4/s/cm2, after shielding.
• CCD impact is about 3 of pixels are contaminated
  per 100 s of exposure time.
• Long integrations need to be broken into a
  sequence of short exposures (say 300 s for
  photometry and 1000 s for spectroscopy).

8
Instrument Working Concept
9
Focal Plane Concept

• All instruments coalesced on one focal plane.
• Common 140K operating temperature.
• Bolted to telescope structure.
• Photometer sensors in one focal plane, example.
• 36 2k x 2k, 18 µm HgCdTe NIR sensors.
• 36 3.5k x 3.5k, 10.5 µm 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 3 x 3
  arrays.
• 6 visible bandpass filter types organized in 6 x
  6 arrays.
• Guide off the focal plane during exposures.
• 4 regions of star guider CCDs.

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Focal Plane Concept
Focus star lamps
Thermal links
Focus star projectors
Guider
Visible
NIR
Spectrograph port
Calibration lamps
Spectrograph
Calibration projectors
rin 6.0 mrad (129 mm) rout 13.0 mrad (284
mm)
11
RD Plan and Objectives
12
RD Plan and Objectives

• 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.
• Expose and documenting all interface areas with
  other subsystems.
• Produce a preliminary project cost and schedule.
• RD Major objectives
• SNAP NIR detector characterization,
  specifications, and acquisition plan.
• SNAP visible detector characterization,
  specifications, and production plan.
• Filter set and mounting concept.
• Spectrograph image slicer prototype
  characterization.
• Instrument readout electronics concept.
• Detector readout ASIC core prototypes.
• Shutter concept.
• Particle shield performance study and refined
  mass estimate.

13
Detector RD

• SNAP contemplated because low wavelength cutoff
  NIR detectors and extended red response CCDs were
  are on the horizon.
• Rockwell MBE 1.7 mm HgCdTe for WFC3
• LBNL CCDs
• A DOE review in July 2002 recommended that
• Augment the NIR group
• Development alternate sources for LBNL CCDs
• We have done this, and more

14
RD Sensors Specs
Photometer
Spectrograph
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NIR Detectors
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NIR Photometer

• Function
• Photometry from 1000 nm to 1700 nm.
• Effort
• Develop 1.7 mm cutoff detector availability
  warm telescope
• Establish facility for testing and characterizing
  NIR FPAs.
• Characterize devices
• Linkages
• Instrument mechanical engineering group
• Instrument electronics
• Filter group
• Calibration group

17
NIR Detector Plan

• Establish large format 1.7 µm cutoff detectors
• Explore detector technology options
• Establish competitive vendor environment
• We have sought to broaden both our technology and
  vendor pool.
• Rockwell MBE HgCdTe
• Raytheon LPE HgCdTe
• Sensors Unlimited/Rockwell InGaAs
• First MCT engineering parts in January / InGaAs lt
  May
• Iteration decision in summer 2004
• CDR technology and vendor(s) decision in late
  2005

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NIR Detector Roadmap
19
NIR Detectors Testing

• Characterization
• University of Michigan HgCdTe
• Electrical and optical characterization
• Pin hole projector for intra-pixel response
• Cal Tech w/ UCLA as subcontractor HgCdTe
• Electrical and optical characterization
• Long term, automated production testing
• JPL InGaAs
• Plenary talk by Greg Tarle
• Breakout presentations by Mike Schubnell and
  Roger Smith

20
Visible Detectors
21
Visible Photometer

• Function
• Photometry from 350 nm to 1000 nm.
• Effort
• Push LBNL CCD technology to conclusion
• Establish backup CCD fabrication site
• Explore alternative technologies
• Complete optical performance measurements
• Develop device packaging
• Derive a cost model.
• Linkages
• Instrument mechanical engineering group
• Instrument electronics
• Filter group
• Calibration group

22
Visible Detector Development

• Technology development
• LBNL/DALSA CCDs
• LBNL CCD technology at a traditional CCD vendor
  in negotiation
• Silicon PIN diode hybrids Rockwell (Raytheon)

SNAP v1 CCDs 3512 x 3512, 10.5 mm
RSC HyVisi 2k x 2k, 18 mm
23
Visible Detector Roadmap
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Visible Detector Testing

• Characterization
• LBNL
• General device characterization
• PSF measurements
• Radiation protons and 60Co
• Yale
• Packaging
• Radiation testing beyond protons
• Plenary talk by Natalie Roe
• Breakout presentations by Steve Holland and
  Charles Baltay

25
Filters
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Filters

• Activity
• Univ. of Indiana is working with a vendor to
  deposit filters on silicon sensors.
• Michigan will examine 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 NIR deposition.
• Linkages
• Visible group
• NIR group
• Focal plane mechanics
• Calibration group

27
Filters
4 silicon wafer with V-band filter
Discrete filter mounting
Chuck Bower breakout talk
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Spectrograph
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Spectrograph

• Function
• l/dl 100 spectroscopy from 350 to 1700 nm
• Effort
• Optics train design
• Focal plane sensor selection
• Slicer technology development
• Calibration procedures studies
• Linkages
• Focal plane mechanics
• Instrument electronics
• Calibration group

Details in Anne Ealet plenary and Eric Prieto
breakout talks.
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Spectrograph

• France supplied item
• concept design and system engineering - LAM
• calibration, simulation and ground segment - CPPM
  
• Will seek to maintain common electronics and
  readout architecture.
• Will seek to maintain common detector technology,
  but not necessarily same format.

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Electronics
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Electronics Overview

• Sensor front-end electronics
• Warm vs cold trade-offs
• Commonality across systems
• Observatory control unit
• Capture functional requirements
• Configuration
• Control/monitor
• Data flow
• Mass memory
• No data on-board data processing
• Compression studies at FNAL
• Instrument mechanisms
• Space craft interface

Details in Mike Sholl and Henrik von der Lippe
plenaries and Jean-Pierre Walder breakout talks.
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Electronics Methodology

• Top level of an essential model used to capture
  functional requirements and interoperability of
  subsystems.
• Visible and NIR sensors
• Spectrograph
• OTA mechanics
• Calibration group
• Spacecraft thermal
• Spacecraft telemetry
• Spacecraft controls

Block diagram
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OCU Functional Requirements

• CPU
• Decode ground command packets
• Decode SC discrete signals
• Send discrete signals to SC
• Transfer database set points to systems
• Execute science data observation plan
• Execute telescope focus observation plan
• Configure mass memory per exposure
• Generate data headers per exposure and insert in
  mass memory
• (Execute focal plan star guider algorithm)
• (Compress data)
• (Thermal control algorithm)
• Supervise housekeeping data collection for
  S-band transmission
• Host subsystem databases
• 1553
• Receive data packets from S-band
• Pass house keeping packets to S-band
• Pass instrument data packers to S-band, on
  occasion, eg, focus data
• Pass focal plane star guider information to ACS

• Monitor lamp power
• Control lamp shutter
• Focal plane star guider
• Guide star database
• Load guide star(s) coordinates into centroid
  hardware
• Set centroid hardware parameters
• Configure sensors readout
• Receive data streams
• Power supplies
• Control power supplies
• Monitor power supplies
• Control power routing to sub-systems
• Visible
• Operation modes database
• Load/read DACs
• Load/read timing parameters
• Load/read operating mode
• Execute read mode (synchronous across devices)
• Monitor sensor temperature

• Load/read operating mode
• Execute read mode
• Shutter (if present)
• Visible
• NIR
• Monitor sensor temperature
• Visible
• NIR
• Monitor remote generated voltages
• Visible
• NIR
• Receive data streams
• Visible
• NIR
• Command actuators
• Command internal calibration lamps (if any)
• Data compression
• Load/read compression parameters
• Monitor compression performance per sensor

35
Detector Front-end Electronics

• Goal to mount electronics, cold at the focal
  plane
• Photons to bits on serial cable per detector.

• Required development
• Rockwell SIDECAR for NIR
• SNAP CDSADC for CCD
• CCD clocking-bias system
• DC-DC power supplies

36
Detector Front-end Electronics
37
Focal Plane Guider

• Function
• Provide fine guiding during exposures
• Telescope/instrument IT
• Effort
• Trades and concepts by spacecraft group
• Star catalog survey for candidate stars
• Detector area vs magnitude vs ACS update rate
• Linkages
• Instrument mechanics
• Instrument electronics
• Attitude control system

38
Shutter and Calibration
39
Shutter

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

40
Calibration Support Hardware

• Function
• OTA IT support
• On-orbit focusing
• Detector stability
• Filter monitoring
• Absolute ? calibration for spectrograph
• Effort
• Capture calibration group needs
• Explore lamp technology

Lamp
Lens
Fiber optic
Shack-Hartman light sources
41
Mechanical/Thermal
42
Thermal/Mechanical Mounts

• Multifunction
• Kinematic mounts
• Thermal isolation
• Effort
• Concept
• Prototype construction and characterization
• Linkages
• OTA mechanics

43
Radiator

• Function
• Provide passive cooling for focal plane sensors
• Provide passive cooling for spectrograph sensors
• Provide passive cooling for focal plane
  electronics
• Provide passive cooling for thermal shield
• Effort
• Concept
• Linkages
• OTA mechanics

E.g., thermal links
44
Shield

• Multifunction
• Charged particle attenuator
• Thermal vessel
• Light shield
• Back-scattered light absorber
• Contamination control
• Effort
• Concept
• Particle attenuation study at FNAL
• Linkages
• OTA mechanics
• Additional shielding studies for spectrograph and
  backside of focal plane, in general.

45
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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Project Management
47
Instrument Management

• Management activities
• Oversee RD technical activities
• Receive Level 2 science requirement.
• Generate instrument concept specifications
• Derive instrument component requirements
• Assemble component specifications into instrument
  level specifications
• Validate against Level 2 science requirements.
• CDR planning and execution

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Institutional RD Responsibilities
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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.
• Integration and test planning - drafts
• IT plan development for instrument.
• IT plan development with telescope and
  spacecraft.
• Project preliminary cost and schedule
• Cost and schedule conventional components.
• RD results will define cost and schedule of
  custom items.
• Identify long lead procurement items.

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Examples of Interfacesto 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.
52
RD Schedule Milestones
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Summary

• We have a limited scope RD program to mitigate
  technology risks in
• visible and NIR detectors
• spectrograph image slicer
• custom integrated circuits
• Other activities center on concept development
  for CDR preparation
• More details in

• Plenary talks
• Visible detectors N. Roe
• NIR detectors G. Tarle
• Spectrograph A. Ealet
• Electronics H. von der Lippe

• Breakout session
• Filters C. Bower
• CCD development S. Holland/C. Baltay
• NIR detectors M. Schubnell/R. Smith
• Spectrograph E. Prieto
• ASIC development J-P Walder

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Backup material
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RD Schedule Milestones
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RD Schedule Milestones
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RD Schedule Milestones
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RD Schedule Milestones