The Mid-Infrared Instrument (MIRI)
MIRI Image Slicers
(or how the MIRI spectrometer comes together)
Gillian Wright
JWST MIRI European PI
with thanks to
Martyn Wells, David Lee, Alistair Glasse, Jan-Willem Pel, Ad Oudenhuysen, Gabby De Groes
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
To spectrograph
f/ratio
convertor
Pupil mirrors
Field optics
(slit mirrors S3)
Pseudo-slit
Spectrogram
Slicing mirror (S1)
UIST
image
slicer
concept
(basis
for MIRI
concept)
Pupil mirrors
(S2)
Field before
slicing
From telescope
and fore-optics
Basic Image Slicing, from J. Allington-Smith
Spectrometer
Main Optics
Netherlands
Spectrometer
Pre Optics
UKATC
Deck (Leicester)
Spectrometer
Focal Plane
Module (USA)
Carbon Fibre Hexapod
(Denmark)
Imager (France)
Input Optics and
Calibration Unit
(Belgium)
Summary description
Spectrometer block diagram
SMO LW-Arm
Camera 3 & 4
FPA 22
FPA
Collimator
Collimator
Collimator
FPM 2
IFU 33
IFU
IFU 4
SPO
Grating 3c
Grating 4c
Grating 4b
Grating 4a
IOC
8 x 8 arcsec
FOV
8 x 8 arcsec FOV
relayed
relayed from
OTE from
OTE
D1a,b,c
Grating 3b
Grating 3a
D2a,b,c
Grating 1c
Grating 2c
Grating 1b
Grating 1a
DGA-A
D3a,b,c
Grating 2b
Grating 2a
IFU 1
IFU 2
Collimator
Collimator
DGA-B
FPM 1
Camera 1 & 2
SMO SW-arm
FPA
FPA 11
IOC: MRS path
The 8 x 8 arcsec FOV
Relayed to the MRS-SPO
with a magnification of ~2
Pupil is imaged at the
Cold Stop at the SPO input
SPO: Layout of Dichoics and IFUs
LIGHT
TRAP
BLOCKING
FILTER
CHANNEL #1
CHANNEL #2
ENTRANCE
PUPIL
CHANNEL #3
CHANNEL #4
CHANNEL 1 APO
INPUT MIRROR
Blocking filter
Light trap
WHEEL A
Adjustable fold mirror
D1
D2
CHANNEL 2 APO
D3
Light trap
Fold mirror
WHEEL B
CHANNEL 3 exit port
The Spectrometer Pre-Optics
Zero Order Light Dumps
MECHANISMS
(WITH GRATING WHEELS SHOWN)
CH 3 & 4
IFU /APO
DUMMY ASSEMBLIES
Calibration Source
APO
IFU
SCU
IOC
BAFFLE TUBE
Spectrometer fov
4
Field of view along slices (arcsec)
3
2
1
IFU 1
IFU 2
IFU 3
IFU 4
0
-1
-2
-3
-4
-4
-2
0
2
Field of view across slices (arcsec)
4
Dichroic passbands
1. 4
Exposure C
Exposure B
1. 2
Exposure A
Channel 1A
Channel 1B
Channel 1C
Channel 2A
Channel 2B
Channel 2C
Channel 3A
Channel 3B
Channel 3C
Channel 4A
Channel 4B
Channel 4C
30
25
20
15
10
5
0
1
Ray-trace diagram of the Channel 1 IFU
APO exit fold mirror
Channel 1 - IFU
Location of output Pupils
Output slits
Image Slicer Mirror
Re-imaging mirrors
Location of input Pupil
41.3
IFU input fold mirror
22.1
~150 (length varies with slice position)
Slice #1
151.60 mm z offset = 2.32 mm
Slice #11 149.28 mm z offset = 0.00 mm
David Lee 17 February 2004
10
31.1
Image slicer mirror
APO output fold
Integral Field Unit Optical Layout
Pupil
images
INPUT
M4
M3
M1
Spectrometer Pre-Optics
M2
Output
slitets
Roof mirror
Re-imaging mirror array
Detail of image slicer output
Pupil
images
Roof
mirror
Reimaging
mirrors
Output Dekker
mask
Diagram of the output slit
Here are the flattened envelopes of the
sliced and stacked sky images, heading off
to the spectrometer collimator mirrors in
the Spectrometer Main Optics (SMO)
The position of the Channel 2
collimator mirror
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
Here, the beam from the Channel 2
collimator is shown, heading back to one of
Channel 2’s three diffraction gratings.
The position of a Channel 2
grating.
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
The light is dispersed by the grating.
Dispersion
direction
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
...and heads back to a fold mirror.
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
...which sends it to the final, camera
mirror, which is a common optical element
for Channels 1 and 2 (as is the fold mirror)
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
The camera mirror forms the final image...
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
...on the Focal Plane Module (FPM), shown
here as the green cylinder.
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
Here comes the beam from the Channel 1
IFU, collimated and sent to one of Channel
1’s 3 gratings...
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
...where it is dispersed...
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
...and sent via this fold mirror to share the
last two mirrors on its way to the FPM with
the spectrum from Channel 2.
The presented document is Proprietary information of the MIRI European Consortium. This document shall be used and disclosed by
the receiving Party and its related entities (e.g. contractors and subcontractors) only for the purposes of fulfilling the receiving Party's
responsibilities under the JWST Project and that the identified and marked technical data shall not be disclosed or retransferred to
any other entity without prior written permission of the document preparer.
The Medium Resolution Spectrometer



The Spectrometer has two arms, each with its own Focal Plane Module.
Each spectrometer arm is further divided into 2 channels.
Two mechanisms present gratings and dichroics which cover the full 5 to 28 micron
wavelength range by rotation between three positions.
Channel 2
IFU Image
Slicer
Channel 4
Channel 3
Dichroic/grating
wheel
SPO
Long Wavelength
Focal Plane Module
MRS: Channels 1 & 2 - Cold stop to FPA optical layout
IFU 2
Grating 2
FPA
Collimator 1
Dichroic 2
Dichroic 1
M3
Grating 1
SPO input
(cold stop)
IFU 1
Collimator 2
Channels 1a and 2a Spectra on FPA 1
~5.77 microns
~8.85 microns
Constant
wavelength
positions
~5.35 microns
~4.89 microns
~8.15 microns
~7.43 microns
Example of MRS image analysis
Some manufactured components