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1 Herschel PACS Instrument SPIE 7010-4 23 June 2008 Albrecht Poglitsch, MPE Garching Albrecht Poglitsch, MPE Garching Herschel Photodetector Array Camera & Spectrometer Herschel Photodetector Array Camera & Spectrometer Christoffel Waelkens, Katholieke Universiteit Leuven Otto H. Bauer, Max-Planck-Institut für extraterrestrische Physik Jordi Cepa, Instituto de Astrofísica de Canarias Helmut Feuchtgruber, Max-Planck-Institut für extraterrestrische Physik Thomas Henning, Max-Planck-Institut für Astronomie Chris van Hoof, Interuniversity Microelectronics Center Leuven Franz Kerschbaum, Institut für Astronomie der Universität Wien Oliver Krause, Max-Planck-Institut für Astronomie Etienne Renotte, Centre Spatial de Liège Louis Rodriguez, Commissariat a l'Energie Atomique, Saclay Paolo Saraceno, Istituto di Fisica dello Spazio Interplanetario Bart Vandenbussche, Katholieke Universiteit Leuven

Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

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Page 1: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

1Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Albrecht Poglitsch, MPE GarchingAlbrecht Poglitsch, MPE Garching

Herschel Photodetector Array Camera & SpectrometerHerschel Photodetector Array Camera & Spectrometer

Christoffel Waelkens, Katholieke Universiteit Leuven

Otto H. Bauer, Max-Planck-Institut für extraterrestrische Physik

Jordi Cepa, Instituto de Astrofísica de Canarias

Helmut Feuchtgruber, Max-Planck-Institut für extraterrestrische Physik

Thomas Henning, Max-Planck-Institut für Astronomie

Chris van Hoof, Interuniversity Microelectronics Center Leuven

Franz Kerschbaum, Institut für Astronomie der Universität Wien

Oliver Krause, Max-Planck-Institut für Astronomie

Etienne Renotte, Centre Spatial de Liège

Louis Rodriguez, Commissariat a l'Energie Atomique, Saclay

Paolo Saraceno, Istituto di Fisica dello Spazio Interplanetario

Bart Vandenbussche, Katholieke Universiteit Leuven

Page 2: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

2Herschel PACS Instrument

SPIE 7010-4 23 June 2008

FPU Mounting

9 July 2007

Page 3: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

3Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Overview

• Instrument concept– Design– Operation

• Flight Model test results– Subunits– Instrument/System level tests/verification– Ground calibration

• Predicted in-orbit performance• Observing with PACS

3

Page 4: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

4Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Instrument Concept• Imaging photometry

– two bands simultaneously (60-85 or 85-125 µm and 125-210 µm) with dichroic beam splitter

– two filled bolometer arrays (32x16 and 64x32 pixels, full beam sampling)

– point source detection limit~4 mJy (5⌠, 1h)

• Integral field line spectroscopy– range 57 - 210 µm with 5x5

pixels, image slicer, and long-slit grating spectrograph (R ~ 1500)

– two 16x25 Ge:Ga photoconductor arrays (stressed/unstressed)

– point source detection limit 3…20 x10-18 W/m2 (5⌠, 1h)

Focal Plane Footprint

32 x 16 pixels6.4” x 6.4”

64 x 32 pixels3.2” x 3.2”

Page 5: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

5Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Observing Modes Concept• Combinations of instrument modes and satellite pointing modes • Instrument modes:– photometry (dual-band) – line spectroscopy• observation of individual lines

– range spectroscopy• observation of extended wavelength ranges

• Pointing modes:– stare/raster/line scan– with/without

nodding/off-position

• Internal chopper– background subtraction– calibration

Page 6: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

6Herschel PACS Instrument

SPIE 7010-4 23 June 2008

FPU/Optics

Chopper

sGeGaDetectorRed Spectrometer

Blue Bolometer

Red Bolometer

Calibrator I and II

0.3 K Cooler

Filter Wheel I

Filter Wheel II

Grating

GeGa DetectorBlue Spectrometer

Encoder

Grating Drive

Entrance Optics

PhotometerOptics

Calibrator Optics

SlicerOptics

SpectrometerOptics

FPU

Page 7: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

7Herschel PACS Instrument

SPIE 7010-4 23 June 2008

CRE

Photoconductor Arrays (Spectrometer)• Two 25x16 pixel filled arrays• Extrinsic photoconductors (Ge:Ga, stressed/unstressed)• Integrated cryogenic

readout electronics(CRE)

• Near-background-noise limited performanceexpected

Page 8: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

8Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Detector Performance: System NEP

• System NEP of red array as expected• System NEP of blue array better than at module level

RedBlue Median detector NEP:2.1×10−17 W Hz-1/2

Median detector NEP:8.9×10−18 W Hz-1/2

Page 9: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

9Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Detector Performance: Transient Response

• Fast modulation is possible at expected background with small penalty in terms of sensitivity

• But detailed calibration required9

Response of blue detectorto transient signal of 1/3of typical background flux

Page 10: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

10Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Detector Performance: Transient Response

• Flux-step dependent photometric correction necessary

RedBlue

Page 11: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

11Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Detector Operation/Performance under p+ Irradiation

11

• Responsivity Jumps: – Must be filtered out – Different for LS & HS – Force short chopper plateaus

Page 12: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

12Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Bolometer Arrays (Photometer)

• Two filled arrays: 64x32 pixels (blue) and 32x16 pixels (red)• Bolometers and multiplexing readout electronics operating at 0.3K• Detector/readout noise comparable to background-noise (FM)• Cooler hold time ~48h

Bluefocal plane

Photometer unitwith blue + red

focal planesand 3He cooler

Pixel

Page 13: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

13Herschel PACS Instrument

SPIE 7010-4 23 June 2008

13

FM Bolometer Performance

• Pixel yield ~98%• NEP ~1.7...5 x BLIP

– Trade-off NEP <--> speed– 1/f noise– Narrow frequency window for

signal modulation (scanning, chopping

Page 14: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

14Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Bolometer Bandwidth <--> NEP Optimization

• Simulations show acceptable PSF at close-to-minimum NEP

• Re-optimization for actual background in orbit necessary14

Page 15: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

15Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Mechanisms: Dynamics and Precision

• Chopper reaches duty-cycle >90% for 1/4s plateaus• Grating achieves required 30ms settling time for small steps

(normal scanning)15

Page 16: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

16Herschel PACS Instrument

SPIE 7010-4 23 June 2008

16

Filter Performance

Spectrometer filter bands (grating order sorters)

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17Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Photometer PSF

• Source: ~ diffraction PSF size hole mask in front of external blackbody, contrast ~1%of background

• Slightly wider core / excess at 1-3 gaussian sigmasNo indication for unexpected large scale wings

• Slight astigmatism

gain up

Page 18: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

18Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Photometer Focal Plane Geometry/Distortions

• Positions/distortions determined with ~1/20 pixel accuracy

• All these precise results refer to the test optics (XY stage)!

• Ongoing modeling to transfer to sky 18

Page 19: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

19

along slice direction

Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Spectrometer PSF

• No significant deviations from predicted performance

19

across slice direction

Page 20: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

20Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Spectrometer Focal Plane Geometry/Distortions

• Some displacement between slices in IFU• Chopper-angle dependent field rotation (as in

photometer)• No dependency on grating position 20

Spatial pixel positions red/blue(spectral pixels averaged)

Spatial positions of allspectral pixels (blue)

Center positions red/bluevs. chopper angle

Page 21: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

21Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Spectrometer Resolution

• Spectral line profiles determined with FIR gas laser

• Derived spectral resolution in good agreement with calculated values

Page 22: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

22Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Spectrometer Spectral Calibration

• FIR laser, H20 + CO (absorption cell)• Requirement “peak position to within

10-20% of a spectral resolution element” fulfilled (Littrow + pixel correction terms)

C=1pF

C=0.1pF

C=0.2pF

n=3, 2’ n=1n=2

Leak models

Page 23: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

23Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Predicted Spectrometer Sensitivity

• Proposal sensitivity partly achieved

Spectral linesensitivity [W/m2](5⌠, 1 hour)

Continuumsensitivity [Jy](5⌠, 1 hour)

Spectrometervelocity resolution

...but cosmic rays!

Page 24: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

24Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Predicted Photometer Sensitivity

• Point source sensitivity equivalent to mapping speed of ~10’ x 10’ in 1 day

24

Page 25: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

25Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Spectrometer Observing Modes

• Line Spectroscopy: observation of individual line(s)

– Chop/nod or wavelength switching– Staring or mapping– R ~ 1500

• Range Spectroscopy: observationof extended range(s)

– Chop/nod or off position– Staring or mapping– SED mode

Page 26: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

26Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Spectrometer Line Scan Schemes

“BrightLine”Mode

“FaintLine”Mode

Page 27: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

Herschel PACS Instrument

SPIE 7010-4 23 June 2008

Photometer Observing Modes

Dual Band: 70+160 μmor 100+160 μm

Page 28: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

Herschel PACS Instrument

SPIE 7010-4 23 June 2008

βουστροφηδόν

Remarks on Scan Map

Page 29: Herschel Photodetector Array Camera & Spectrometer SPIE …herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_talk.pdf · Herschel Photodetector Array Camera & Spectrometer Christoffel

Herschel PACS Instrument

SPIE 7010-4 23 June 2008

1.4°x1.4° XMM COSMOS (Hasinger et al.)

Simulated deep PACS sub-field survey

~100 Mpc spatial scale~1014 Msun mass scale

~200h for full 2sq.deg field to 11mJy

Sneak preview (SPIE 2010) …