CASCA 2001 Page 1 of 12

SPIRE:The Spectral and Photometric

Imaging Receiver

Presentation to CASCA 2001The SPIRE Team

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The Herschel Space Observatory

THE HERSCHEL MISSION:• Herschel is a general purpose astronomical observatory to

carry out photometry and spectroscopy over the spectral range 80 – 670 m

• Cornerstone ESA mission

UNIQUE FEATURES:• Large (3.5m), cold (80K), low-emissivity (4%) telescope• Access to poorly-explored spectral range with no atmospheric

interference• Large amount of high-quality observing time

VITAL STATISTICS:• Launch: April 2007 on Ariane 5; Lifetime: 4.25 years• Orbit: around Sun-Earth L2 point• Payload cooling: to 4K using onboard LHe (ISO cryostat

technology)

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The Herschel Spacecraft

PAYLOAD INSTRUMENTS:

• Heterodyne Instrument for FIRST (HIFI)

High-resolution spectroscopy over selected spectral bands

• Photoconductor Array Camera and Spectrometer (PACS)

Imaging photometry and low-resolution spectroscopy, 80-210 m

• Spectral and Photometric Imaging Receiver (SPIRE)

Imaging photometry and low-resolution spectroscopy, 200-670 m

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SPIRE Science ObjectivesPRIMARY OBJECTIVES:

• The main scientific goals of SPIRE are the investigation of the statistics and physics of galaxy and structure formation at high redshift and the study of the earliest stages of star formation, while the protostar is still coupled to the interstellar medium

• These studies require the capability to carry out large-area deep photometric imaging surveys at far-infrared and submillimetre wavelengths

• Survey observations will be followed up with spectroscopy of selected sources

• SPIRE will exploit the unique advantages of Herschel and will have unmatched sensitivity

SECONDARY OBJECTIVES:• SPIRE will also be a powerful tool for many other

astrophysical studies: giant planets, comets, the galactic interstellar medium, nearby galaxies, ultraluminous infrared galaxies and active galactic nuclei

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Galaxies and Protostars

Log L

(L )

1000 100 10 1 0.1

12

7

9

11

8

10

1312 13 14 15 16

Log (rest) (Hz)

rest (m)

Sanders & MirabelAnn. Rev. Astron.Astrophys. 34, 749,1996

GALAXIES:

• emit primarily in the far infrared due to reprocessing of stellar UV by interstellar dust; redshifted into submm for z~1-5

• determination of bolometric luminosity (star formation rate) requires that submm SED be known

PROTOSTARS:

• cold cloud cores emit primarily in the far infrared and submm

• bolometric luminosity and temperature can be determined from measurement of the thermal continuum including the peak

PACS

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Instrument Summary

In order to carry out large-scale photometric surveys and follow-up spectroscopy, SPIRE consists of two separate parts.

3-BAND IMAGING PHOTOMETER: = 250, 350, 500 m; / ~ 3• 4 x 8 arcmin field of view; diffraction-limited beams

IMAGING FOURIER TRANSFORM SPECTROMETER: = 200-670 m; / = 20-1000 (variable)• 2.6 arcmin field of view• Mach-Zehnder configuration with novel broadband

beamsplitters

DESIGN FEATURES:• feedhorn-coupled spider web bolometer detector arrays• detector arrays cooled to 0.3 K by 3He fridge• minimal use of mechanisms• sensitivity limited by thermal emission from low-emissivity

telescope at 80 K

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SPIRE Photometer

FIRST focal

surface

M3

M4

M5

M6

M7

M8

Beam steering mirror

Offner relay

Dichroics and

arrays

M9

2-K coldstop

Detector array

modules

3He coolerShutter

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SPIRE Spectrometer

Telescope input port

Calibrator input port

Output port

Output port

Intensity beam

dividers

Fore-optics shared with photometer

Detector array

modulesMirror

mechanism

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Mach-Zehnder FTS

FEATURES: Access to two input ports, complementary output ports Optical amplification of 4 Novel beamsplitters: high and uniform efficiency over broad

spectral range FTS of similar design is being built for use at the JCMT

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The SPIRE Consortium

PI: Matt Griffin, QMW, London

COUNTRIES: Canada, France, Italy, Spain, Sweden, UK, USA

CONSORTIUM INSTITUTES: Caltech/Jet Propulsion Laboratory, Pasadena, USA CEA Service d’Astrophysique, Saclay, France Imperial College, London, UK Institut d’Astrophysique Spatiale, Orsay, France Instituto de Astrofisica de Canarias, Tenerife, Spain Istituto di Fisica dello Spazio Interplanetario, Rome, Italy Laboratoire d’Astronomie Spatiale, Marseille, France Mullard Space Science Laboratory, Surrey, UK NASA Goddard Space Flight Center, Maryland, USA Observatoire de Paris, Meudon, France Queen Mary and Westfield College, London, UK Rutherford Appleton Laboratory, Oxfordshire, UK UK Astronomy Technology Centre, Edinburgh, UK Stockholm Observatory, Sweden Università di Padova, Italy University of Saskatchewan, Canada

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Canadian Participation in SPIRE

AGREED WORK PACKAGES:

• shutter subsystem, ICC manpower

• other possibilities are under investigation

CANADIAN SPIRE TEAM:

• Principal Investigator: G.R. Davis, University of Saskatchewan

• Co-Investigators: P.A. Feldman, HIA M. Halpern, UBC D.A. Naylor, University of Lethbridge D. Scott, UBC C.D. Wilson, McMaster University

• Project Manager: D.G. Peterson, CSA

• Instrumentation Scientist: J.K. Taylor, University of Saskatchewan

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Actuator

PositionSensor

Heater Thermometry

Thermometer

Shutter Subsystem

DESCRIPTION:• vane will cover SPIRE

entrance aperture to block flux from cryostat

• surface facing detectors will be coated with high-emissivity material

• vane temperature will be controllable between 5 and 20K to provide known flux to detectors (heater and temperature monitor)

• 4-K actuator and position sensor

• Industrial partner: COM DEV

(Courtesy COM DEV)