# Presentation: 213779

## The MIRI medium resolution spectrometer for the James Webb Space Telescope

**David Lee (UKATC)**
**On behalf of the MIRI spectrometer team**
**SPIE 6265-38, 26 May 2006**

## MIRI System Overview

**MIRI System Overview**

**MIRI has four functions:  **
-   Mid-Infrared Imaging from 5 to 27μm, 0.11” pixels, 1.3’ x 1.7’ field of view
-   Coronagraphic Imaging  (at 10.65, 11.4, 15.5, 23 μm)
-   Low Resolution Slit Spectroscopy R ~100 from 5 to 10 μm
-   Medium Resolution Integral Field Spectroscopy, R ~ 3000, from 5 to 28.3μm

## MIRI Optical Module –  Key Design Features

- Lightweighted, all aluminium,  modular optical system
- Supported by thermally isolating carbon fibre hexapod which attaches to ISIM structure.
- Cooled to ~7K by a dedicated cryo-cooler
- Three 1kx1k SiAs detectors.
- 4 Mechanisms – 3 wheels based on ISO design (filters,dichroics, gratings) and a contamination control cover
- Light enters from the telescope via the pick-off mirror
- The fields of view of the Imager and the Medium Resolution Integral Field Spectrometer are defined and separated in an “Input optics/calibration module”
- Imager optics on one side of primary structure, spectrometer on the other

## MIRI spectrometer scientific requirements

**Wavelength range 5 – 28 microns**
**Field of view not less than 3.5 x 3.5 arc-seconds squared**
**Spatial sampling to match FWHM of JWST PSF**
**Spectral resolving power **
- 5μm <  < 10m R > 2400
- 10μm <  < 15m R > 1600
- 15μm <  < 28m R > 800
**Image quality: 80% EED @ 8********m < 1.1 x 80% EED of an unaberrated JWST**** – translated to an RMS wavefront error specification for the sub-systems**
**Detector format: Two 1024 x 1024 SiAs arrays with 25********m pixels**

## Optical path through MIRI spectrometer

## Spectrometer pre-optics (SPO) layout

**Spectrometer pre-optics (SPO) layout**

**Key**
**1 input baffle tube**
**2 Dichroic wheel A**
**3 Dichroic wheel B**
**4 Fold mirror**
**5 APO**

- Calibration system

- Exit port to SMO collimator

- Input/output port to SMO collimator/camera/grating

## SPO – layout of dichroic level

## SPO – dichroic wheel assembly EQM

- CdTe filter

- Diamond machined aluminium wheel

## SPO – verification model chassis hardware

**SPO – verification model chassis hardware**

- Black anodized baffle structure

- Mirror mounting pads

## SPO – Anamorphic Pre-Optics (APO)

**SPO – Anamorphic Pre-Optics (APO)**

- Input aperture

- Output fold mirror

- Toroidal mirror

- Aluminium mirror substrate

## APO verification model hardware

**APO verification model hardware**

- Toroidal mirror

- Output fold mirror

- Input aperture

## SPO – Integral Field Unit

**SPO – Integral Field Unit**

- Image slicer mirror

- Output slit mask

- Main body of IFU

- Re-imaging mirror arrays

**For more details on the mirror arrays, manufactured at Cranfield University, see****talk 6273-74, Mon 14:00**

## IFU assembly

**Assembly carried out in class 100 clean room**

## SMO – opto-mechanical layout

- Focal plane module

- Grating assembly

- Input from IFU

- Collimator mirror

- Camera optics

## SMO – optical layout of camera optics

## SMO – grating wheel mechanical hardware

## SMO – mechanical structure

- Short wavelength spectrometer (Channel 1 + 2)

- Long wavelength spectrometer (Channel 3 + 4)

- Grating assembly

## SMO – qualification model assembly

**QM is**
- • Manufactured
- • Assembled
- • Verified regarded alignment
- • Vibration tested
- • Verified regarding alignment

## SMO – QM Alignment inspection

## SMO – QM vibration test

**Vibration Test**

## Modelled performance for channel 2 at 8 m

- Full end to end optical system analysis done using physical optics propagation tool in zemax

- Specsim - MIRI spectrometer simulator described in Lorente et al. 6274-55

- Central slice

- Reconstructed image meets specifications on FWHM and EED

## Summary and status

**Opto-mechanical design complete. Both SPO and SMO have completed CDR**
**Verification model hardware **
- SPO components have been received
- SMO CMs are ready
- SMO M1-1, M1-2 and M3 are ready to be gold-coated
- SMO VM Gratings on track for a June 2006 delivery
**Most of sub-system testing now complete**
**Assembly of Verification Model in progress**
**Delivery of spectrometer sub-systems to Rutherford Appleton Laboratory for integration and test into MIRI VM will be later this year**

## MIRI draws on the expertise of the following organizations: 

**Ames Research Center, USA; Astron, Netherlands Foundation for Research in Astronomy; CEA Service d'Astrophysique, Saclay, France; Centre Spatial de Liége, Belgium; Consejo Superior de Investigacones Científicas, Spain; Danish Space Research Institute; Dublin Institute for Advanced Studies, Ireland; EADS Astrium, Ltd.U.K, European Space Agency, Netherlands;  Institute d'Astrophysique Spatiale, France; Instituto Nacional de Técnica Aerospacial, Spain; Institute of Astronomy, Zurich, Switzerland; Jet Propulsion Laboratory, USA; Laboratoire d'Astrophysique de Marseille (LAM), France; Lockheed Advanced Technology Center, USA;  Max-Planck-Insitut für Astronomie (MPIA), Heidelberg, Germany; Observatoire de Paris, France; Observatory of Geneva, Switzerland; Paul Scherrer Institut, Switzerland; Physikalishes Institut, Bern, Switzerland; Raytheon Vision Systems, USA; Rutherford Appleton Lavoratory (RAL), UK; Space Telescope Science Institute, USA; Toegepast-Natuurwetenschappelijk Ondeszoek (TNO-TPD), Netherlands; U.K.  Astronomy Technology Centre (UK-ATC); University College, London, UK; Univ. of Amsterdam, Netherlands; Univ. of Arizona, USA; Univ. of Cardiff, UK; Univ. of Cologne, Germany; Univ. of Groningen, Netherlands; Univ. of  Leicester, UK; Univ. of Leiden, Netherlands; Univ. of Leuven, Belgium; Univ. of Stockholm, Sweden, Utah State Univ. USA**

## SPO – VM dichroic wheel assemblies