SPIRE: Herschel’s Sub-millimetre Camera and …safir.jpl.nasa.gov/BeyondSpitzerConf/proceedings/session...Feedhorns adjacent in the focal plane SPIRE Bruce Swinyard Beyond Herschel

SPIREBruce Swinyard

1Beyond Herschel and SpitzerJune 2004

SSTDRutherford Appleton Laboratory

SPIRE: Herschel’s Sub-millimetre Camera and Spectrometer

Bruce SwinyardRutherford Appleton Laboratory, Oxfordshire, UK

Matt GriffinCardiff University, Wales

On behalf of the SPIRE Consortium (Canada, Italy, France, Spain, Sweden, UK, USA)

SPIREBruce Swinyard



The SPIRE Consortium

• Caltech/Jet Propulsion Laboratory, Pasadena, USA• Cardiff University, UK• CEA Service d’Astrophysique, Saclay, France• Institut d’Astrophysique Spatiale, Orsay, France • Imperial College, London, UK• 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, Paris• UK Astronomy Technology Centre, Edinburgh, UK• Rutherford Appleton Laboratory, Oxfordshire, UK• Stockholm Observatory, Sweden• Università di Padova, Italy• University of Lethbridge, Canada

SPIREBruce Swinyard



Instrument Design Drivers

• Photometer- Deep mapping with highest efficiency and largest possible field of view

- Multi-band coverage with simultaneous observation - Point and compact source observation with high efficiency

• Spectrometer- Sensitivity optimised for point/compact source spectroscopy- Imaging spectroscopy with maximum available field of view- Wide wavelength coverage- Variable spectral resolution (few x 10 to few x 100)

• Both- Thermal background dominated by the Herschel telescope- Simplicity, affordability, reliability, ease of operation - Complementary to other Herschel instruments and other facilities

SPIREBruce Swinyard



Instrument Summary• 3-band imaging photometer

- 250, 360, 520 µm (simultaneous)- λ/∆λ ~ 3- 4 x 8 arcminute field of view- Diffraction limited beams (17, 24, 35”)

• Imaging FTS- 200 - 670 µm - 2.6 arcminute field of view- ∆σ = 0.4 cm-1 (goal 0.04 cm-1)

(λ/∆λ ~ 20 - 100 (1000) at 250 µm)

• Design features- Sensitivity limited by thermal emission

from the telescope (80 K; ε = 4%)- 3He cooled detector arrays (0.3 K)- Feedhorn-coupled spider web NTD bolometers- Minimal use of mechanisms

- Beam steering mirror, FTS mirror drive- No on-board data processing

SPIREBruce Swinyard



SPIRE Block Diagram

S1 S2

FPU Structure

SMEC

Optics

Filters, Beam dividers, Dichroics

Baffles

Warm Interconnect Harness (FSWIH)

SPIRE FPU

Optical BenchCryostat Wall

SpacecraftElectronics

RFFilter

FPU Control Unit(FCU)

Spacecraft PowerDistribution Unit

BSM

Phot. Cal. Source

FTS Cal.Source Detector Arrays (0.3 K)

Spacecraft Command andData Management System

(CDMS)

Digital Processing Unit (DPU)

JFET/RF filter Boxes

Cooler Thermometers

P1

Detector Control Unit(DCU)

P2 P3

Mirrors

SPIRE WarmElectronics on SVM

FTBp FTBs

RFFilter

RFFilter

RFFilter

RFFilter

SPIREBruce Swinyard



Focal Plane UnitSpectrometer

side

Photometerside

SPIREBruce Swinyard



Photometer Layout and Optics

3He cooler

Detector array

modules

Beam steering

sirror

SPIRE optical bench (4 K)

2-K box

M3

M4

M5 M7

M6M8

SPIREBruce Swinyard



Photometer Implementation

Herschel focal

surface

2-Kcoldstop

M3

M4

M5

M6

M7

M8

Beam steering mirror

Offner relay

Dichroics and

arrays

M9

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Photometer Alignment

SPIREBruce Swinyard



Photometer Alignment Result

SPIREBruce Swinyard



FTS Layout and Optics

SPIREBruce Swinyard



Spectrometer Implementation

SPIREBruce Swinyard



Spectrometer Alignment Results

SPIREBruce Swinyard



0

0.1

0.2

0.3

0.4

0.5

0.6

5 10 15 20 25 30 35 40 45 50 55 60 65 70Wavenumber [cm-1]

Effic

ienc

y

2RT

R^2 + T^2

2RTR2 + T2

FTS Prototype Broadband Beam Divider

SPIREBruce Swinyard



FTS Mechanism

• Double parallelogram carriage with toothless gear

• Moiré fringe position measurementsystem (0.01 µm accuracy)

• -0.3 +3.5 cm movement

• Continuous scan or step-and-integrate operation

SPIREBruce Swinyard



(Lionel’s wonderful) 3He Cooler

• Cold stage temp. < 280 mK

• Hold time > 46 hrs• Cycle time < 2 hrs• Average load on

4He tank < 3 mW• Heat lift provided to

detector arrays > 10 µW• Gas-gap heat switches

(no moving parts)

Evaporator (0.3 K)

Gas-gap heat switchKevlar

suspension

Sorption pump

CQM cooler

Pumping line

SPIREBruce Swinyard



Photometer Thermal Source

SPIREBruce Swinyard



SPIREBruce Swinyard



Detector Arrays (2Fλ Feedhorns)

Photometer SpectrometerPLW

43 detectorsPMW

88 detectorsPSW

139 detectorsSLW

19 detectors

45 mm

SSW37 detectors22 mm

⇒ Coincident beam centres

SPIREBruce Swinyard



NTD Ge Bolometer ArraysNTD Gethermometer

Spider-web absorbing grid

• NEP ~ 3 x 10-17 W Hz-1/2

• 120-K Si JFET readout• 1/f noise knee < 100 mHz

10-8

10-7

10-6

10-5

0.001 0.01 0.1 1 10

Low Frequency Noise Stability

Vn [

nV

Hz-1

/2 m

od 1

0N ]

Freq [Hz]

Frequency (Hz)0.01 0.1 1 10

Syst

em n

oise

vol

tage

20 nV Hz-1/2

20 nV Hz-1/2

20 nV Hz-1/2

SPIREBruce Swinyard



CQM Bolometer Array Module

2-K stage and interface to

SPIRE 2-K box

300-mK stage

Filter covering feedhorn array

Connection to 3He fridge

Kevlarsuspension

SPIREBruce Swinyard



Observing Speed vs. TelescopeBackground Power (350 µm)

0 0.5 1 1.5 2 2.5 30

0.33

0.67

1

1.33

1.67

2

2.33

2.67

3

3.33

3.67

4

4.33

4.67

5

Qdes = Qexp/2Qdes = QexpQdes = 2Qexp

350 um Qexp = 3.2 pW

Actual background/Expected background

Obs

ervi

ng sp

eed

wrt

NEP

ph a

t Qex

p

S350_half j

0.74

S350_nom j

0.74

S350_double j

0.74

Qj

3.2

Qdes GS0(pW) (pW K-1)Qexp/2 26Qexp 512Qexp 102

Actual/Expected Background

Nor

mal

ised

Obs

ervi

ng S

peed Qdes = Qexp/2

Qdes = Qexp

Qdes = 2Qexp

SPIREBruce Swinyard



Example Prototype Filtering Scheme

00.10.20.30.40.50.60.70.80.9

1

10 30 50 70 90 110 130Wavenumber [cm-1]

Tran

smis

sion

Total transmission

SPIREBruce Swinyard



Filter Out-of-Band Rejection

1.00E-25

1.00E-23

1.00E-21

1.00E-19

1.00E-17

1.00E-15

1.00E-13

1.00E-11

1.00E-09

1.00E-07

1.00E-05

1.00E-03

1.00E-01

10 100 1000 10000 100000

Wavenumber [cm-1]

Tran

smis

sion

10,000 100,000

Wavenumber cm-11,00010010

10-3

10-7

10-19

10-11

10-15

1

10-23

Tran

smis

sion

Requirement

SPIREBruce Swinyard



Test facility has an external spectrometer

SPIREBruce Swinyard



Measured CQM Response

SPIREBruce Swinyard



Measured Optical Efficiency of CQM Array

SPIREBruce Swinyard



Electronics• We need low noise amplifiers

to exploit inherent stability of detectors 10 mHz 5 Hz

Shorted inputs

Dark detectors

SPIREBruce Swinyard



Sky Sampling with Feedhorn Arrays

Full sampling of the image require scanning or “jiggling” of the telescope pointing

Beam FWHM ≈ λ/D

Beam separation ≈ 2λ/D

16 pointings needed for fully-sampled image

FWHM beams on the sky don’t overlap

Feedhorns adjacentin the focal plane

SPIREBruce Swinyard



Point Source Photometry

X

Y

Z

A

B

• Telescope pointing fixed

• Chopping in Y-directionbetween A and B (126”)

• Simultaneous observation in the three bands with twosets of co-aligned detectors

• This is OK if the pointing isaccurate enough (~ 1.5”)

SPIREBruce Swinyard



7-point Jiggle Map

θ

• Chopping 126”

• 7-point jiggle pattern

• Angular step θ ~ 4 - 6 arcseconds(> pointing or positional error)

• Total flux and position can be fitted

• Compared to single accuratelypointed observation, S/N for same total integration time is only degraded by

~ 20% at 250 µm ~ 13% at 350 µm ~ 6% at 500 µm

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

4

8

12

16

20

Pointing offset (arcsec.)

Sign

al lo

ss (

%) 250 µm

500 µm

350 µm

Signal loss for blind pointing

SPIREBruce Swinyard



Field (Jiggle) Mapping

• Telescope pointing fixed or in raster mode

• Chopping up to 4 arcminamplitude in Y direction

• 64-point “jiggle” pattern for full spatial sampling

• Available fov = 4 x 4 arcmin

X

Y

Z

± 2 arcminmaximum.

SPIREBruce Swinyard



Scan Mapping

• Telescope in line scanningmode

• Scan rate ~ 20-30”/sec – max 60”/sec

• Map of large area is built up from overlapping parallelscans

• Most efficient mode for large-area surveys

Scan directions for instantaneous full sampling

14.036 degrees from “vertical”



SPIREBruce Swinyard



FTS Observing Modes• ∆σ = 0.04 - 2 cm-1 by adjusting scan length

• Continuous scan:- Mirror scan rate = 0.5 mm s-1

- Signal frequency range = 3 - 10 Hz- Calibrator in 2nd port nulls telescope background

• Step-and-integrate:- 2nd port calibrator is off - Mirror stepped with integration at each position- Beam Steering Mechanism chops on sky

• Point source spectroscopy/spectrophotometry- Telescope pointing fixed- Background characterised by adjacent pixels

• Imaging spectroscopy- Beam steering mirror adjusts pointing between

scans to acquire fully-sampled spectral image

SPIREBruce Swinyard



FTS Mapping simulation

SPIREBruce Swinyard



Sensitivity Estimates: PhotometerNew sensitivities taking into account increased obscuration of telescope and lower estimate of detector sensitivity

Band (µm) 250 360 520 Point source (7-point) 2.7 3.5 4.2

4’ x 4’ jiggle map 10 12 13 ∆S(5-σ; 1-hr) mJy

4’ x 8’ scan map 7.6 9.2 11

Time (days) to map 1 deg.2 to 3 mJy 1-σ

Nominal case 2.1 3.0 3.9

SPIREBruce Swinyard



Sensitivity Estimates: Spectrometer

Low-resolution spectrophotometry ∆σ = 1 cm-1 λ µm 200 - 315 315 - 500 500-670

∆S (5-σ; 1-hr) Point source 200 180 180 - 260

(mJy) Fully-sampled 2.6’ map

530 490 490 - 690

Line spectroscopy ∆σ = 0.04 cm-1 λ µm 200 - 315 315 - 500 500-670

Point source 5.9 5.5 5.5 - 7.7 ∆F (5-σ; 1-hr) W m-2 x 10-17

Fully-sampled 2.6’ map

20 18 18 - 26

SPIREBruce Swinyard



See also posters on…• First results from SPIRE CQM testing (Lim et al)• Thermal design of the SPIRE instrument (Goizel and

Griffin)• Hi-Gal survey – proposed FIR/Sub-mm survey of the

galactic plane to |l|<2.5 deg (Babar et al)• SPIRE ICC – how the data and observations will be

handled (Clements et al)

• Effects of thermal fluctuations on Planck HFI sensitivity (Fereday)

SPIREBruce Swinyard



SPIREBruce Swinyard



Some Key Programmes Involving SPIRE

• SPIRE + PACS photometry and spectroscopy of galaxies- Detailed SEDs and dust properties- Metallicity variation and evolution- AGN vs. starburst - Testing unified schemes- Templates for high-redshift

studies

IC10 (D ~ 1Mpc)

SPIREBruce Swinyard



Some Key Programmes Involving SPIRE• SPIRE + PACS extragalactic surveys (deep, medium, shallow)

- Unbiased survey of high-z dusty star-forming galaxies missed by optical and near-IR survey

- Detection of many thousands of galaxies- Test models of number counts galaxy spectra, luminosity, and SF

history out to z = 5

1

10

100

1000

10000

100000

0 - 1 1-2 2-3 3-4 4-5 > 5Redshift bin

No.

of s

ourc

es d

etec

ted

250 (Sconf = 19 mJy)360 (Sconf = 20 mJy)520 (Sconf = 15 mJy)

- Large-scale structure in the high-redshift universe

- Follow up spectroscopic observations: redshifts, physics and chemical evolution

SPIREBruce Swinyard




• SPIRE + PACS survey of nearby molecular clouds- Complete samples of protostars and pre-collapse condensations

down to Mproto ~ 0.03 M and d ~ 1 kpc- Mass function down to brown dwarf mass regime- SED coverage of spectral peak- Accurate mass, luminosity, temperature- Lifetimes of different evolutionary stages - Temperature and density profiles- Initial conditions for collapse

SPIREBruce Swinyard




MSX 6-25 µm 20” resolution

• Compete multi-band galactic plane survey to ~100 mJy rms- Census of all observable

galactic star forming regions - Wide range of masses and

evolutionary stages - Triggered star formation- Global properties of the ISM

dust and molecular clouds- Supernova remnants; PMS

star mass ejection- See poster by Ali et al.

Documents

SPIRE: Herschel’s Sub-millimetre Camera and …safir.jpl.nasa.gov/BeyondSpitzerConf/proceedings/session...Feedhorns adjacent in the focal plane SPIRE Bruce Swinyard Beyond Herschel