The JWST Mid-Infrared Instrument:
MIRI
Margaret Meixner
MIRI Science Team Member
MIRI instrument support scientist
Based on Slides presented by the MIRI team as noted.
02-1
18th May 2006
STScI, Baltimore, MD
MIRI System Flight Components (Goodson & Renouf& Larson)
Optics Module
(including Thermal Strap Assembly)
FSW
FPE
ICE
Cooler
OM Stage (6K heat exchanger(s)
“Heat Sink Assy” (Recuperator,
valves)
RLDA (part of CTA)
Coldhead Environmental Shield
JT Pre-cooler Recuperator

Plus the following Harnesses that mounted to ISIM:

OM to ICE Harnesses

OM to FPE Harnesses
Cryo-cooler to FPE Harnesses

3-Stage Pulse Tube Pre-cooler
Coldhead
Precooler Compressor
JT Compressor
Relay Switch Assembly
Cooler Control Electronics
02-2
18th May 2006
STScI, Baltimore, MD
MIRI OBA Struct./Mech. Model tested (Wright/ Glasse)
02-3
18th May 2006
STScI, Baltimore, MD
MIRI OM, Cooler and ISIM (Larson)

OMS will mount at the Thermal Strap assembly interface to the OM Primary Structure lower deck component

Figure shows notional Heat Exchanger mounted to TSA thermal interface

Heat exchanger position is well inside MLI support structure and MLI

Cooler refrigerant line treated like harness

One or more standoff brackets designed to accept P-clip or similar conventional attachment (green item in
right figure below)
Refrigerant
line support
Preliminary
refrigerant line
routing
02-4
18th May 2006
OMS
Notional HSA
STScI, Baltimore, MD
Overview MIRI Cooler TRL-6 Plan (Larson)
Technology to be Demonstrated:
Operation of the 6K Cooler system in JWST environment at JWST
performance levels
TRL-6 Item Description:
Engineering grade Cooler components: Cold Head (remote), field joints,
compressor(s), and pre-cooler cold end, with DM drive electronics
Key Items to be Proved:
Performance: Base temperature under remote heat load,
leak rate, gas purity, cooling efficiency, noise, exported
vibration
Environment: Cryogenic operating temperatures, applied
heat loads, vibration, radiation
02-5
Milestones
Planned
Completion Date
• Initial remote cooling testing
1/13/06
• Cooler vendor selection
2/28/06
Current Status:
• Cold Head Assembly complete, tested
6/30/06
- Current TRL is 4 to 6 depending on component
- Technology development program has proven:
- Remote cooling capability
- Cooler compressor(s)
- Cooler vendor selection is complete and on contract
• Cooler Tower Assembly (field joints) complete and
tested (vibration, thermal cycle)
7/14/06
• Compressor Assembly complete, tested
8/25/06
• Achieve TRL-6, system test complete
12/15/06
18th May 2006
STScI, Baltimore, MD
Instrument Functions (Wright)
 Multiple Optical Configurations

Photometric Imaging over a wide field.

Coronagraphy between 10 and 27 mm.
Low Resolution (R = 100) Slit Spectrosopy of Single Sources (5 – 10 mm).
Medium Resolution (~ 100 km/sec velocity resolution) Integral Field Spectroscopy from 5 to
28.5 mm.


 Diffraction limited image quality.


To maximise the sensitivity on point sources.
To exploit JWST’s spatial resolution (resolve ~ 1 kpc at all redshifts).
 Optimised Sensitivity


02-6
The minimum noise level is bounded by the instrument environment (thermal emission from
the sky and telescope), so MIRI must
Have high Photon Conversion Efficiency (Optical Transmission x Detector QE).
Spatial and Spectral Passbands matched to the science targets.
18th May 2006
STScI, Baltimore, MD
MIRI Fields of View (Glasse)
MIRI Allocation
MIRIM FOV
Imager
4QPM
15.5µm
4QPM
11.4µm
4QPM
10.65µm
Low Resolution
Spectrometer
Lyot Mask
23mm
Medium Resolution
Spectrometer
02-7
18th May 2006
STScI, Baltimore, MD
Imager - Optical Requirements (Wright)
Requirements:
Design:
 > 2 square arcmin field of
view, with a 0.11 arcsecond
pixel scale
 Image Quality

> 58% of light within first
dark ring of model
telescope PSF

Strehl ratio > 85 %
longward of 5.6 mm
 Coronagraphy in 4 filter
bands (see Design Doc. for
details)
 R=100 Spectroscopy
02-8
18th
May 2006
Simulated NIR JWST field (Myungshin Im 1998)
STScI, Baltimore, MD
The MIRI Imager (Glasse)

Coronagraphic masks and a slit for low resolution
spectroscopy are mounted in the telescope focal
plane.

The filter wheel includes the 10 imaging filters, 4
coronagraphic filter/pupil mask combinations and a
prism.
Focal plane
M1
M2
Filters
Cold stop
M3
M4
Detector
M5
270 mm
02-9
18th May 2006
STScI, Baltimore, MD
MIRI Filters for Direct Imaging (Meixner)
mm)
02-10
mm)
Comment
R

1.2
broad band
R
7.7
2.2
PAH, broad band
R
10
2.0
Silicate, broad band
R
11.3
0.7
PAH, broad band
R
12.8
2.4
Broad band
R
15
3.0
Broad band
R
18
3.0
Silicate, broad band
R
21
5.0
broad band
R
25.5
4.0
broad band
R
25.5
4.0
redundant filter, risk reduction
ND#
neutral dens.
Test lens
N/A
N/A
testing
Closed
blackened blank
N/A
for darks
18th May 2006
for coron. acquis.
STScI, Baltimore, MD
Implementation (Boccaletti)
monochromatic coronagraphs
M1
M2
4 masks in focal plane
M4
M3
M5
ND
Lyot diaph.
+
23 µm filter
/d = 5)
02-11
18th May 2006
4Q diaph.
+
15.5 mm filter
4Q diaph.
+
11.4 mm filter
4Q diaph.
+
10.65 mm filter
/d = 20)
/d = 20)
/d = 20)
STScI, Baltimore, MD
Low Resolution Spectrograph, LRS (Meixner)
• 5-10 mm coverage
• R~100 at 7.5 mm
•Double prism in filter wheel
LRS 5 0.6
02-12
18th May 2006
STScI, Baltimore, MD
Medium Resolution Spectrometer - Format (Wright)
REQUIREMENT - Integral Field Spectroscopy with > 3 arcsec field of view from 5 to
28.5 µm.
Each channel’s field of view is sliced,
10 arcseconds
dispersed and detected.
Channel 1
(4.9 - 7.7 mm)
Channel 2
(7.4 - 11.8 mm)
Channel 3
(11.4 - 18.2 mm)
Channel 4
(17.5 - 28.8 mm)
02-13
18th May 2006
Wavelength/Velocity
STScI, Baltimore, MD
The MRS concept (Wells)
4
Field of view along slices (arcsec)
3
2
1
IFU 1A
IFU 1B
IFU 2A
IFU 2B
0
-1
-2
Collimator
-3
Grating
-4
-4
-2
0
2
Field of view across slices (arcsec)
4
IFU 1B
SW dichroic
centre
dichroic
LW dichroic
Collimator
Grating
Collimator
Grating
18th May 2006
FPA 1
Camera 2
FPA 2
IFU 1A
IFU 2A
IFU 2B
Collimator
02-14
Camera 1
Grating
STScI, Baltimore, MD
MIRI OBA - Medium Resolution Spectrometer (Glasse)

The Spectrometer has two arms, each with its own FPM.

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 1
IFU Image
Slicer
Channel 3
Channel 2
Channel 4
Dichroic/grating wheel
02-15
18th May 2006
Focal Plane Module
STScI, Baltimore, MD
Spectrometer Eng. Qualification Hardware (Glasse)
 A dichroic wheel
 An image slicing mirror
02-16
18th May 2006
STScI, Baltimore, MD
MIRI MRS - Spectral Coverage (Glasse)
 The MRS covers the 5 to 28 micron range in 12 sub-spectra
Spectral Resolving Power
4000
3500
Requirement
Channel 1A
3000
Channel 1B
Channel 1C
2500
Channel 2A
Channel 2B
2000
Channel 2C
Channel 3A
Channel 3B
Channel 3C
Channel 4A
1500
Channel 4B
Channel 4C
1000
500
How the spectra will
appear on the MRS’s
two detectors
02-17
18th May 2006
4
6
8
10
12
14
16
18
20
22
24
26
28
30
FRD
2.5.1.2
Wavelength [mm]
STScI, Baltimore, MD
Pretty Hardware Pictures – Ressler
“Front” side of FPM showing
installed detector assembly.
02-18
18th May 2006
“Back” side showing connector and
thermal strap attachment point.
STScI, Baltimore, MD
QE, Ressler
Predicted QE With AR-Coatings
1.00
0.90
Predicted Response / Photon
0.80
0.70
0.60
0.50
0.40
FPM-IC
0.30
FPM-LW
FPM-SW
0.20
Required
TSA Raw
0.10
0.00
0.0
5.0
10.0
15.0
Wavelength (µm)
20.0
25.0
30.0
QE exceeds requirement at all wavelengths < 23 microns. MIRI Science
Team has accepted this performance with the understanding that there will
be a reduced sensitivity margin in the 25.5 micron filter.
02-19
18th May 2006
STScI, Baltimore, MD
Nearing TRL 6 Completion
 “System/subsystem model or prototype demonstration in a relevant
environment (ground or space)”
 MIRI Sensor Chip Assemblies (SCAs) or representative models must be
proven to be at TRL 6
 6 key measurements:
02-20

QE

Dark Current

Read Noise

Radiation Immunity

Vibration Levels

Thermal Cycling
18th May 2006
STScI, Baltimore, MD
Detector Readout Scheme (Ressler)
02-21
18th May 2006
STScI, Baltimore, MD
Detector Readout Scheme (Meixner)
02-22
18th May 2006
STScI, Baltimore, MD
Sensitivity Requirements (Ressler)
 Ultimately bounded by the flux of background radiation from the sky and telescope.
[photon s-1 mm-1 arcsec-2]
JWST Background
106
OTA
105
Sunshield
104
Zodiacal Dust
103
5
02-23
18th May 2006
10
15
20
25
Wavelength [micron]
STScI, Baltimore, MD
MIRI Team (Meixner)



02-24
MIRI Science Team: George Rieke (U of Az/lead)

US: George Rieke (U of Az/lead), Michael Ressler (JPL/Proj. Sci), Margaret Meixner
(STScI), Tom Greene (NASA/Ames)

Europe (members rotate): Gillian Wright (UK ATC/co-lead), Torsten Boeker (ESA), Ewine van
Dishoeck (Leiden/Netherlands), Christoffel Waelkens (Leuven/Belgium)
MIRI Engineering Leads:

US: Graham Bothwell (JPL/Project Manager); Greg Goodson (JPL/Systems Engineer), Phil
Driggers (Goddard/Instrument Manager)

Europe/ESA: Andrea Marini (ESA/PM), John Thatcher (PM/Astrium), Ian Renouf (Systems
Engineer)
MIRI Team at STScI:

Margaret Meixner & Scott Friedman MIRI Instrument Scientists

Jerry Kriss: JWST/ISIM lead

Vicki Balzano & Michael Robinson: MIRI operations and flight software support
18th May 2006
STScI, Baltimore, MD
MIRI Milestones (Meixner)
 MIRI PDR: March 17&18 2005; passed
 Detector TRL 6, June 2006
 MIRI CDR: September 2006
 Cooler TRL 6, January 2007
 JWST launch: >2013
02-25
18th May 2006
Fomalhaut
MIRI
Spitzer
STScI, Baltimore, MD