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
2Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
3Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
4Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
5Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
6Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Focal Plane UnitSpectrometer
side
Photometerside
SPIREBruce Swinyard
7Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
8Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Photometer Implementation
Herschel focal
surface
2-Kcoldstop
M3
M4
M5
M6
M7
M8
Beam steering mirror
Offner relay
Dichroics and
arrays
M9
SPIREBruce Swinyard
9Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Photometer Alignment
SPIREBruce Swinyard
10Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Photometer Alignment Result
SPIREBruce Swinyard
11Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
FTS Layout and Optics
SPIREBruce Swinyard
12Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Spectrometer Implementation
SPIREBruce Swinyard
13Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Spectrometer Alignment Results
SPIREBruce Swinyard
14Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
15Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
16Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
(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
17Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Photometer Thermal Source
SPIREBruce Swinyard
18Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
SPIREBruce Swinyard
19Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Detector Arrays (2Fλ Feedhorns)
Photometer SpectrometerPLW
43 detectorsPMW
88 detectorsPSW
139 detectorsSLW
19 detectors
45 mm
SSW37 detectors22 mm
⇒ Coincident beam centres
SPIREBruce Swinyard
20Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
21Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
22Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
23Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
24Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
25Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Test facility has an external spectrometer
SPIREBruce Swinyard
26Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Measured CQM Response
SPIREBruce Swinyard
27Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Measured Optical Efficiency of CQM Array
SPIREBruce Swinyard
28Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Electronics• We need low noise amplifiers
to exploit inherent stability of detectors 10 mHz 5 Hz
Shorted inputs
Dark detectors
SPIREBruce Swinyard
29Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
30Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
31Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
32Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
33Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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”
50.194 degrees from “vertical”
74.0546 degrees from “vertical”
SPIREBruce Swinyard
34Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
35Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
FTS Mapping simulation
SPIREBruce Swinyard
36Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
37Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
38Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
39Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
SPIREBruce Swinyard
40Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
41Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
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
42Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Some Key Programmes Involving SPIRE
• 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
43Beyond Herschel and SpitzerJune 2004
SSTDRutherford Appleton Laboratory
Some Key Programmes Involving SPIRE
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.
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