The Mid-Infrared Instrument (MIRI)
Medium
Resolution Spectrometer for JWST
Martyn Wells
MIRI EC & UKATC
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
SPO
SMO
Collimator
Dichroic 1
IFU 1
Dichroic 2
IFU 2
Dichroic 3
IFU 3
Grating
Collimator
Grating
Collimator
Grating
Camera 1
FPA 1
Camera 2
FPA 2
IFU 4
Collimator
Grating
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
Spectrometer – l ranges, R, sampling
and fov
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
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
Diagram of the output slit
Image slicer mirror
APO output fold
Integral Field Unit Optical Layout
Pupil
images
M3
M1
Spectrometer Pre-Optics
INPUT
M4
M2
Output
slitets
Roof mirror
Re-imaging mirror array
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
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 light is dispersed by the grating.
Dispersion
direction
...and heads back to a fold mirror.
...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 camera mirror forms the final
image...
...on the Focal Plane Module (FPM),
shown here as the green cylinder.
Here comes the beam from the Channel
1 IFU, collimated and sent to one of
Channel 1’s 3 gratings...
...where it is dispersed...
...and sent via this fold mirror to share
the last two mirrors on its way to the
FPM with the spectrum from Channel 2.
Channel 2a spectra
Constant
wavelength
positions
Some manufactured components