ins nirspec, 12 may 2005 introduction to nirspec michael regan
TRANSCRIPT
INS NIRSpec, 12 May 2005
Introduction to NIRSpec
Michael Regan
JWST Project OrganigrammeJune 2004
JWSTProject Manager
P. Jensen
NIRSpec Pr. System Engineer
G. Bagnasco
Launcher System EngineerP. Rumler
System Group
MIRI Principal System Engineer
A. Marini
Admin. AssistantA. Plitzke
Documentation & Conf. Control
D. Green
Mech. Thermal System Engineer
J-C. Salvignol
Project Control Manager
Z. El Hamel
PA ManagerJ. van Dooren
Subsystem Expert Group
Optical System Engineer
M. Te Plate
Electr. System Engineer & AIV
P. Rumler
Ops, SW & Detector System
P. Strada
Mechanism Engineer*B. Henson * leaving
Schedule ControlJ. Molleman
Project ScientistP. Jakobsen
Deputy Project ScientistT. Boeker
Science Operations Team
NN
Science SupportNN
Contracts OfficerV. D’Hoedt
Optical SupportP. Marenaci (YGT)
INS NIRSpec, 12 May 2005
JWST Architecture
Optical Telescope
Element (OTE)
Integrated Science Instrument
Module (ISIM) Element
Spacecraft Bus
Sunshield
Sun
INS NIRSpec, 12 May 2005
Telescope
INS NIRSpec, 12 May 2005
Telescope
FocalSurface
Prim
ary
M
irro
r
Secondary Mirror
Fine Steering
Mirror
Te
rtia
ry
Mirr
or
OTE ISIM
Secondary focus
(V1, V3) origin
V3
V1 V2
OTEf/#: 16.7Effective Focal Length: 116.6 mPM diameter = 7.0 m
FocalSurface
Prim
ary
M
irro
r
Secondary Mirror
Fine Steering
Mirror
Te
rtia
ry
Mirr
or
OTE ISIM
Secondary focus
(V1, V3) origin
V3
V1 V2
OTEf/#: 16.7Effective Focal Length: 116.6 mPM diameter = 7.0 m
INS NIRSpec, 12 May 2005
ISIM & Regions
INS NIRSpec, 12 May 2005
Thus Spoke ASWG
INS NIRSpec, 12 May 2005
Current Mission Requirements
(the TAC will decide anyway…)
INS NIRSpec, 12 May 2005
NIRSpec
INS NIRSpec, 12 May 2005
NIRSpec: A Pretty Picture is Not Enough
Enter NIRSpec
INS NIRSpec, 12 May 2005
NIRSpec: Thus Spoke ASWG
• 3 x 3 arcmin FOV
• 1-5 µm coverage
• R~1000, R~100 multiplexed
• >100 sources simultaneously
• Configurable slit width/length
• MEMS array preferred
INS NIRSpec, 12 May 2005
NIRSpec Procurement
• Instrument built by European industry
under ESA project leadership
• Under study since 2001
• Presently entering implementation phase
• Two NASA-provided components:• 2 x 2k x 2k HgCdTe Detector Array• 4 x 384 x 185 Micro-Shutter Array
INS NIRSpec, 12 May 2005
NIRSpec Modes
• R=100 (exploratory spectroscopy)• Single prism 0.6 - 5.0 µm
• Micro-shutter array or fixed Slits
• R=1000 (emission line diagnostics)• 3 gratings 1.0 - 5.0 µm
• Micro-shutter array or fixed slit(s)
• R=3000 (emission line kinematics)• 3 gratings 1.0 - 5.0 µm
• Fixed slit or integral field unit
INS NIRSpec, 12 May 2005
Wavelength Coverage
• R=1000 & R=3000 modes• 1.0 - 5.0 µm• Covered by three overlapping first order gratings:
• 1.0 - 1.8 µm• 1.7 - 3.0 µm• 2.9 - 5.0 µm
• R=100 mode• 0.6 - 5.0 µm (as NIRCAM)• Covered by single dual-pass prism• Coverage below 1.0 µm is not allowed to drive anything
• Resolution to be kept within factor 2 of R=100 1.0 - 5.0 µm• Resolution below 1.0 µm to follow
INS NIRSpec, 12 May 2005
You Can’t Fight Red shift
!
NIR MIR
!
INS NIRSpec, 12 May 2005
Micro Shutter Array
Active MSA Area
3.6’
3.4’
Mounting Frame
Detector Array
Fixed Slits and
IFU Aperture
Direction of Dispersion
4 x 384 x 185 Shutters 9 Square Arcmin of MSA
Area
Single 200 mas x 450 mas slitssurrounded by 60 mas wide bars
>100 objects simultaneously
IFU
INS NIRSpec, 12 May 2005
A Bit of MEMS History
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
• Initially both Micro Mirrors and Shutters
• Mirrors eliminated due to excessive diffraction effects
• Initially slit to be made up of several shutters
• Later transitioned to “fat MEMS”• Huge simplification of optics• Factor ~4 reduction in MSA array• Reduced slit loss • At expense of multiplexing loss
INS NIRSpec, 12 May 2005
Diffraction & Slit Loss
Telescope Exit Pupil
Spectrograph Entrance Pupil
Footprint of PSF
Diffracted OutputBeam
INS NIRSpec, 12 May 2005
MSA Close-up
Key Requirements:Contrast: >2000 (!) Open Fill factor >70%(60 mas bars on 200 mas wide slits)
INS NIRSpec, 12 May 2005
MSA Magnet Mechanism
INS NIRSpec, 12 May 2005
MSA in Action
INS NIRSpec, 12 May 2005
Integral Field Unit
Field beforeslicing
Pseudo-slit
Slicing mirror (S1)
Spectrogram
Pupil mirrors(S2)
To spectrograph
Field optics (slit mirrors S3)
From telescopeand fore-optics
INS NIRSpec, 12 May 2005
Integral Field Unit
• FOV: 3” x 3”• Sampling: 0.1”• ~30 Slicers
• Entirely passive device (no moving parts)
• Shuttered by MSA magnet mechanism
• Main use R~3000 single object• But R~1000 and R~100 too....
• Superb backup in case of MSA failure• Point and shoot operations
INS NIRSpec, 12 May 2005
Integral Field Unit
Slicer Stack(30 slices)
IFU aperturePupil mirror Line(30 elements)
Slit mirror Line(30 elements)
Relay optics
QuickTime™ and aTIFF (Uncompressed) decompressor
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INS NIRSpec, 12 May 2005
Detector Array• 2K4K FPA comprised of two 2K2K
sensor chip assemblies (SCAs)
• =0.6–5.0 µm HgCdTe detectors (Rockwell)
• FPA passively cooled to T=34–37 K
• Key Performance Parameters:• Total noise =6 electrons rms per t=1000 seconds exposure)• QE = >80%
• NIRSpec is detector background limited in nearly all
modes (!)
• Non-stop (“up the ramp”) read and telemetry• 12 s frame time, 1 frame downlink each 50 s
INS NIRSpec, 12 May 2005
Why R=1000?
INS NIRSpec, 12 May 2005
Why R=1000?
• Science requirement• Clean emission line separation
• Main challenge:• [NII] 6548.1 :1• H 6562.8 metallicity diagnostic• [NII] 6583.4 :3
• and also:• [SII] 6716.4 density diagnostic• [SII] 6730.8
R=446
R=319
R=467
[NII]
H
[NII]
INS NIRSpec, 12 May 2005
Why 200 mas Slit?
1:2 MSA aspect ratio fixed
1.4 µm - Band I2.4 µm - Band II4.0 µm - Band III
INS NIRSpec, 12 May 2005
Why 200 mas Slit?
200 mas optimal?
2 pixels across slit
INS NIRSpec, 12 May 2005
Optical Schematic
MIcro-shutterArray Collimator
Prism/Grating CameraDetector
Array
Telescope Focus
Foreoptics FilterWheel
200 mas per 79.5 µm wide shutter
2.52 “/mm, f/12.5
100 mas per 18 µm pixel
5.56 “/mm, f/5.671.58 “/mm, f/20
INS NIRSpec, 12 May 2005
Optical Layout
Buzzwords: • TMA’s• Scheimflug
INS NIRSpec, 12 May 2005
Focal Plane Layout & Scheimflug
NIRCam NIRSpec
INS NIRSpec, 12 May 2005
Physical Layout
INS NIRSpec, 12 May 2005
Physical Layout
INS NIRSpec, 12 May 2005
SiCThe wonder of modern ceramics
INS NIRSpec, 12 May 2005
WFE at MSA
• Requirement:• Diffraction-limited at 2.4 µm• WFE = 180 nm rms or better• 131 nm rms OTE input specified
• Fore optics challenging
• Relaxation requires degrading sensitivity• Increased slit losses• Reduced photometric accuracy
INS NIRSpec, 12 May 2005
WFE at FPA
• Requirement:• Diffraction-limited at 3.0 µm• WFE = 225 nm rms or better
• Camera optics challenging• Relaxation requires degrading
sensitivity• Larger resolution element• Decreased sensitivity• Jeopardize spectral resolution [NII]
H
[NII]
INS NIRSpec, 12 May 2005
NIRSpec Image Quality
PSF at MSA
PSF at FPA
FPA 100 mas pixels
PSF at MSA
FPA with Cross-talk
INS NIRSpec, 12 May 2005
Grating Wheel8 Positions:
1. R=100 Prism 2. Band I R=1000 Grating 3. Band II R=1000 Grating 4. Band III R=1000 Grating 5. Band I R=3000 Grating 6. Band II R=3000 Grating 7. Band III R=3000 Grating 8. Provision for imaging mode
INS NIRSpec, 12 May 2005
Filter Wheel
8 Positions:
1. Clear Aperture 2. Closed 3. Band I Long Pass >1.0 µm4. Band II Long Pass >1.7 µm5. Band III Long Pass >2.9 µm6. Narrow Band TA =1.1 µm7. Broad Band TA 0.9 < 1.1 µm8. Broad Prism 0.9 < 5 µm
Current Issue: Filters in pupil – should they second as pupil stops?
INS NIRSpec, 12 May 2005
Why Long Pass?One Object per Row
INS NIRSpec, 12 May 2005
Calibration Unit
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Carries both continuum and (FP-filtered) line sources
INS NIRSpec, 12 May 2005
NIRSpec Sensitivity
Formal Level I Specs
INS NIRSpec, 12 May 2005
Mission Requirements
INS NIRSpec, 12 May 2005
Mission Requirements
INS NIRSpec, 12 May 2005
Target Acquisition
Partially documented in gory detail… • NIRSpec Operations Concept• Two dedicated tech notes (more to come)
Accuracy Goal: 12.5 mas (1)
INS NIRSpec, 12 May 2005
Image Mode Simulation
2.2 µm
Centroid shift!
INS NIRSpec, 12 May 2005
Target Acquisition will be interesting
INS NIRSpec, 12 May 2005
STScI is currently working on several NIRSpec related studies
• MSA planning tool (J. Valenti)• NIRSpec Target Acquisition Alternatives
(M. Regan)• What’s in phase 1 and phase 2 with
JWST (J. Valenti)
INS NIRSpec, 12 May 2005
STScI plays a crucial role in NIRSpec
• MSA planning tool (J. Valenti)• NIRSpec Target Acquisition Alternatives (M.
Regan)• What’s in phase 1 and phase 2 with JWST (J.
Valenti)• NIRSpec Calibration Plan ( T. Keyes)• Guide Star Availability and planning (J. Valenti)• Do we use Observing templates? (J. Valenti)
INS NIRSpec, 12 May 2005