The JWST Mid-Infrared Instrument: MIRI

STScI, Baltimore, MD02-1 18th May 2006

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.


MIRI System Flight Components (Goodson & Renouf& Larson)

Plus the following Harnesses that mounted to ISIM:

OM to ICE Harnesses OM to FPE Harnesses Cryo-cooler to FPE Harnesses

Optics Module(including Thermal Strap

Assembly) FSWFPE

ICE

Precooler Compressor

JT Compressor

Cooler Control Electronics

Relay Switch Assembly

“Heat Sink Assy” (Recuperator, valves)

Coldhead Environmental Shield

JT Pre-cooler Recuperator

3-Stage Pulse Tube Pre-cooler Coldhead

RLDA (part of CTA)

OM Stage (6K heat exchanger(s)

Cooler


MIRI OBA Struct./Mech. Model tested (Wright/ Glasse)


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)

OMS

Refrigerant line support

Notional HSA

Preliminary refrigerant line routing


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 vibrationEnvironment: Cryogenic operating temperatures, applied heat loads, vibration, radiation

Current Status:- 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

MilestonesPlanned

Completion Date

• Initial remote cooling testing 1/13/06

• Cooler vendor selection 2/28/06

• Cold Head Assembly complete, tested 6/30/06

• 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


Instrument Functions (Wright)

Multiple Optical Configurations Photometric Imaging over a wide field. Coronagraphy between 10 and 27 m. Low Resolution (R = 100) Slit Spectrosopy of Single Sources (5 – 10

m). Medium Resolution (~ 100 km/sec velocity resolution) Integral Field

Spectroscopy from 5 to 28.5 m.

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

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.


Medium Resolution Spectrometer

MIRI Allocation

MIRIM FOV

Imager

4QPM15.5µm

4QPM11.4µm

4QPM10.65µm

Lyot Mask23mLow Resolution

Spectrometer

MIRI Fields of View (Glasse)


Imager - Optical Requirements (Wright)

Requirements:

> 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 m

Coronagraphy in 4 filter bands (see Design Doc. for details)

R=100 Spectroscopy

Simulated NIR JWST field (Myungshin Im 1998)

1.3 arcmin

1.7 arcminDesign:


The MIRI Imager (Glasse)

Focal plane M1

M2

M3

M4

M5

Detector

Cold stop

Filters

270 mm

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.


MIRI Filters for Direct Imaging (Meixner)

m) m) 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. for coron. acquis.

Test lens N/A N/A testing

Closed blackened blank

N/A for darks


Implementation (Boccaletti)

4 masks in focal plane

monochromatic coronagraphs

ND Lyot diaph.+

23 µm filter

/ = 5)

4Q diaph.+

10.65 m filter

/ = 20)

4Q diaph.+

15.5 m filter

/ = 20)

4Q diaph.+

11.4 m filter

/ = 20)


Low Resolution Spectrograph, LRS (Meixner)

LRS 5 0.6

• 5-10 m coverage

• R~100 at 7.5 m

•Double prism in filter wheel


Medium Resolution Spectrometer - Format (Wright)

10 arcseconds

Channel 1(4.9 - 7.7 m)

Channel 2(7.4 - 11.8 m)

Channel 3(11.4 - 18.2 m)

Channel 4(17.5 - 28.8 m) Wavelength/Velocity

Each channel’s field of view is sliced, dispersed and detected.

REQUIREMENT - Integral Field Spectroscopy with > 3 arcsec field of view from 5 to 28.5 µm.


The MRS concept (Wells)

-4

-3

-2

-1

0

1

2

3

4

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

IFU 1A

IFU 1B

IFU 2A

IFU 2B

IFU 1B

IFU 1A

IFU 2A

IFU 2B

Collimator

Collimator

Collimator

Collimator

Camera 1

Camera 2

FPA 1

FPA 2

Grating

Grating

Grating

Grating

LW dichroic

centredichroic

SW dichroic


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 3

Channel 4

Channel 1

Channel 2

Focal Plane ModuleDichroic/grating wheel

IFU Image Slicer


Spectrometer Eng. Qualification Hardware (Glasse)

A dichroic wheel

An image slicing mirror


500

1000

1500

2000

2500

3000

3500

4000

4 6 8 10 12 14 16 18 20 22 24 26 28 30

Requirement

Channel 1A

Channel 1B

Channel 1C

Channel 2A

Channel 2B

Channel 2C

Channel 3A

Channel 3B

Channel 3C

Channel 4A

Channel 4B

Channel 4C

MIRI MRS - Spectral Coverage (Glasse)

Wavelength [m]

Sp

ectr

al R

eso

lvin

g P

ow

er

The MRS covers the 5 to 28 micron range in 12 sub-spectra

FRD 2.5.1.

2How the spectra will appear on the MRS’s

two detectors


Pretty Hardware Pictures – Ressler

“Front” side of FPM showing

installed detector assembly.

“Back” side showing connector and

thermal strap attachment point.


QE, Ressler

Predicted QE With AR-Coatings

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0.0 5.0 10.0 15.0 20.0 25.0 30.0Wavelength (µm)

Predicted Response / Photon

FPM-IC

FPM-LW

FPM-SW

Required

TSA Raw

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.


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:

QE Dark Current Read Noise Radiation Immunity Vibration Levels Thermal Cycling


Detector Readout Scheme (Ressler)


Detector Readout Scheme (Meixner)


Sensitivity Requirements (Ressler)

Ultimately bounded by the flux of background radiation from the sky and telescope.

[photon s-1 m-1 arcsec-2] JWST Background

Wavelength [micron]5 10 15 20 25

106

105

104

103

Zodiacal Dust

Sunshield

OTA


MIRI Team (Meixner)

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


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 FomalhautMIRI Spitzer

The JWST Mid-Infrared Instrument: MIRI

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