The Mid-Infrared Instrument (MIRI)

Medium Resolution Spectrometer for JWST

Martyn WellsMIRI EC & UKATC

Carbon Fibre Hexapod (Denmark)

Spectrometer Main OpticsNetherlands

Imager (France)

Input Optics and Calibration Unit

(Belgium)

Deck (Leicester)

Spectrometer Focal Plane

Module (USA)

Spectrometer Pre Optics

UKATC

Summary description

Spectrometer block diagram

IFU 1

IFU 2

IFU 3

IFU 4

Collimator

Collimator

Collimator

Collimator

Camera 1

Camera 2

FPA 1

FPA 2

Grating

Grating

Grating

Grating

Dichroic 1

Dichroic 2

Dichroic 3

SPO SMO

Spectrometer fov

-4

-3

-2

-1

0

1

2

3

4

-4 -2 0 2 4Field of view across slices (arcsec)

Fie

ld o

f vie

w a

lon

g s

lices (

arc

sec)

IFU 1

IFU 2

IFU 3

IFU 4

Dichroic passbands

1

1. 2

1. 4

0 5

10 15 20 25 30

Channel 1A Channel 1B Channel 1C

Channel 2A Channel 2B Channel 2C

Channel 3A Channel 3B Channel 3C

Channel 4A Channel 4B Channel 4C

Exposure A

Exposure B

Exposure C

Spectrometer – ranges, R, sampling and fov

WHEEL A

WHEEL B

CHANNEL 1 APO

CHANNEL 2 APO

INPUT MIRROR

Blocking filter

Light trap

Fold mirror

Adjustable fold mirror

CHANNEL 3 exit port

D1

D2

D3

Light trap

Ray-trace diagram of the Channel 1 IFU

David Lee 17 February 2004

Image Slicer MirrorRe-imaging mirrors

Output slits

Location of input Pupil

IFU input fold mirror

Location of output Pupils

~150 (length varies with slice position)Slice #1 151.60 mm z offset = 2.32 mmSlice #11 149.28 mm z offset = 0.00 mm

10 31.1

22.1

41.3

Channel 1 - IFU APO exit fold mirror

Diagram of the output slit

Integral Field Unit Optical Layout

M1

M2M4

M3APO output fold

Image slicer mirror

Roof mirror

Re-imaging mirror array

Outputslitets

Pupilimages

INPUT Spectrometer Pre-Optics

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 wavelengthpositions

Some manufactured components