PACS IHDR 12/13 Nov 2003 PACS Instrument Overview1 Instrument Design/Development Overview and System...

PACS Instrument Overview 1

PACS IHDR 12/13 Nov 2003

Instrument Design/Development Overview and

System Performance

PACS Instrument Overview

A. Poglitsch

MPE



Instrument Concept• Imaging photometry

– two bands simultaneously (60-85 or 85-130 µm and 130-210 µm) with dichroic beam splitter

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

– point source detection limit ~3 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…10 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”



Observing Modes

• Combinations of instrument modes and satellite pointing modes

• Instrument modes:– dual-band photometry– single-band photometry– line spectroscopy

• observation of individual lines

– range spectroscopy• observation of extended wavelength ranges

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



CEA

BOL/BAU

BlueBol BAU

RedBol BAU

Warm Interconnecting Harness

Instrument Overview and Subsystem Responsibilities

DPU nominal

DPU redundant

IFSI-ROME

DEC/MEC 2

MEC I/F-Module Redundant

DSP Module Redundant

RedDEC Module

Base/PSU Redundant

CSL-Liege

BOL/COOL

BOL 1 Module

BOL 2 Module

Cooler Control

CEA

FPU Cold FocalPlaneUnit

KT/MPE

BlueGe:GaArray &CRE

MPE/ASTEQ/IMEC

BlueBolArray &Read-out

CEA

RedBolArray &Read-out

CEA

RedGe:GaArray &CRE

MPE/ASTEQ/IMEC

0.3K Cooler CEA

Grating Assy CSL-Liege

Chopper Assy MPIA

2FilterWheels KT

2CalSources KT

SPU nominal

SPU redundant

IAC-Tenerife/TU-Wien

IAC-Tenerife/TU-Wien

CSL-Liege

DEC/MEC 1

MEC I/F-Module

DSP Module

BlueDEC Module

Base/PSU



FPU/Optics

FPU Cold FocalPlaneUnit

KT/MPE

BlueGe:GaArray &CRE

MPE/ASTEQ/IMEC

BlueBolArray &Read-out

CEA

RedBolArray &Read-out

CEA

RedGe:GaArray &CRE

MPE/ASTEQ/IMEC

0.3K Cooler CEA

Grating Assy CSL-Liege

Chopper Assy MPIA

2 FilterWheels KT

2 Calibrators KT

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



Design/Development Status of Technically Critical Components

• Optics• FPU/Structure• Photoconductors, CRE• Bolometers• Chopper• Grating assembly• Warm electronics



Optics

• Design of FPU optics unchanged, manufacturing of mirrors complete, filters partly delivered

• Alignment of QM optics in progress, specs fulfilled so far

• Analyses (geometrical-optical, diffraction) done; to be complemented by measurements with IL tests/ calibration

• Baffle design and manufacture for QM FPU finished; optimisation for FM in progress

• Calibration sources manufactured and tested

Details from N. Geis / D. Kampf



• Detailed design of FPU structure finished, but thermal strap interface issues open.

• Manufacture of QM structure complete, manufacture of FM started

• Cryo-vibration performed on STM– Photometer STM including cooler and Focal Plane

Assembly– Grating STM, including new launch lock (without motor)– One of two filter wheels– Both photoconductor arrays (partly dummies)– Dummy chopper

Details from J. Schubert and D. Kampf

FPU Status



9



Photoconductor Arrays

• All QM detector “sixpacks” (2 high-stress, 2 low-stress) delivered to MPE / MPIA for testing

• Tests of all low-stress modules finished at MPIA, all high-stress modules + a few low-stress modules tested at MPE after repair at ASTEQ

• QM schedule tight (critical path) – see below– Integration of modules with

housing + filters has to start• FM schedule driven by

– CREs: FM wafers (CRE v06) processed, AIT in progress

– New contact (?) problem Details from H. Richter



Responsivity of modules in Sixpack1_MPIA(left: before vibration, right: after vibration)

A/W

“Blue” Ge:Ga QM Detector Test Results

Sixpack2_MPIA

NEP ~ 5x Herschel/PACS BLIP (with QM CRE)



“Red” Ge:Ga QM Detector Test Results

• NEP (even with QM CRE) approaching advertised value• Some “weak” pixels, varying from cooldown to cooldown• Few “dead” pixels (open channels)

QM7: responsivity at T=1.9K, C=0.52pF, t=0.25s

P = 4.8e-15 W

0

100

200

300

400

500

600

0 20 40 60 80 100

bias [mV]

r [A

/W]

detector1

detector 2

detector 3

detector 4

detector 5

detector 6

detector 7

detector 8

detector 9

detector 10

detector 11

detector 12

detector 13

detector 14

detector 15

detector 16

QM7: NEP at T=1.9K, C=0.52pF, t=0.25s

P = 4.8e-15 W

1E-17

1E-16

1E-15

0 20 40 60 80 100bias [mV]

NE

P [

W /

Hz]

detector1

detector 2

detector 3

detector 4

detector 5

detector 6

detector 7

detector 8

detector 9

detector 10

detector 11

detector 12

detector 13

detector 14

detector 15

detector 16

BLIPHerschel/PACS

FM14, FM12, FM11QM12, QM11, QM8

FM11, QM7, QM9, QM3QM12, QM11, QM8

Details from U. Grözinger



Cryogenic Read-Out Electronics

• CQM run (v05)– Integrated in QM modules + test modules– Tested extensively – current noise too high (at least for

low-stress array – by factor ~5)– CQM not suitable for FS, but useful for QM ILT

• FM run (v06)– Significant design modifications (3 variations

implemented)– Wafers processed– First tests very promising in terms of noise

performance– Delivery starting Nov/Dec ’03

• FS run my become necessary to reach all specs– should come in time to allow allow detector swapping

Details from P. Merken



QM CRE (v05) Performance

• Linearity : <3% non-linearity over >2V

• Cross talk between channels: <1% full range

• Linearity, cross talkmeet requirements– with blind channel

subtraction

• Noise too high by factor ~514

Raw ramp

Blind channel subtracted



Bolometer/Readout Development

• QM blue focal plane array mounted at LETI

• The working arrays showed a very large responsivity (good!)

• The working arrays show very large noise and very slow response of the clocks, due to high contact resistance (~MΩ) at the 2K Buffer Unit level (known error in QM buffer run causing poor indium bumps hybridization)

• A new blue focal plane is being mounted with FM Buffer Unit to be used in the CQM

More from L. Rodriguez et al.

Blue Focal Plane



Bolometer/Readout DevelopmentRed Focal Plane• A red focal plane with two sub arrays has been assembled• No tests because of known Buffer Unit problems. Decision to

replace the BU right away• This detector is now completed and under test• The measured noise levels are good everywhere except for a few

pixels on each array• Spectral response measured with FTS; absorption ~80% in band50 100 150 200 250 300 350 400 450 500 550 600

0

2

4

6

8

10

12

14

16

Wavelength in microns

ReferenceRed array

50 100 150 200 250 300 350 400 450 500 550 6000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Wavelength in microns

Ab

sorp

tion

measured

calculated

PACS band



Bolometer Performance Tests

• Detector bandwidth measured ~4 - 5 Hz

• “1/f” noise “knee”/ stability measurement: no significantincrease downto 0.05 Hz

requirement

goal requirement

= 10-16 W/√Hz (requirement)^



3He Sorption Cooler Development

0

1 10-5

2 10-5

3 10-5

4 10-5

5 10-5

6 10-5

0 50 100 150 200 250

y = 4,11371e-06 + 2,09004e-07x R= 1

1/ti

me

(s

-1)

Applied load (µW)

CQM SPIRE - Autonomy tests Nominal conditions - L0 = 1.7 K / L1 = 4 K

Theoretical curve

0 5 10-5 0,0001 0,00015 0,0002 0,00025

y = 5,3392e-06 + 0,22163x R= 0,99898

Applied load (µW)

Theoretical curve

CQM PACS - Autonomy tests Nominal conditions - L0 = 1.7 K / L1 = 4 K

First test with 10 µWapplied load:

35 hours @ 291 mK

250

300

350

0 20 40 60 80 100

HCR#1 - horizontalHCR#1 - right side upHCR#1 - upside downHCR#2 - horizontalHCR#2 - right side upHCR#2 - upside downHCR#3 - horizontalHCR#3 - right side upHCR#3 - upside down

Tem

pe

ratu

re (

mK

)

Cooling power (µW)

CQM PACS - Thermal tests June - August 2003 Comparison HCR #1 HCR#2 and HCR#3Level 1 (titanium frame) : 2 KLevel 0 (cryostat cold plate) : Å 1.6 K

Note : HCR#3/upside downLevel 0 at1.66 K

• extra load of 8-10 µW identified (potential heat switch problem)• 10% undercharged Details from L. Duband



Chopper

• QM delivered for integration in FPU

• Performance demonstrated• Scratches on mirror

– t.b. avoided with FM

• Tests of chopper control with DECMEC and LM concluded

• Adjustment of control parameters for QM only during IL tests

Details from R. Hofferbert

19



Grating Assembly

• Grating Mechanism/Drive– STM including new launch-lock (without actuator) passed

cryo-vibration test• STM mechanism shows better dynamic characteristics than

before vibration. The apparent "friction" torque is roughly reduced by a factor 2 to 3.

• Bearings qualified: no movement noise or hard point over the useful stroke

– Transformer for Inductosyn position readout shows excellent cold performance. Dissipation measured 1.5 mW

– CQM delivered to CSL• Few minor NCRs, one major (connectors swapped)• Functional/performance tests performed • FUB QM transformers integrated in QM ILT• Launch-lock actuator will be integrated• Loose spring washer, shaft-to-bearing coupling part has moved

in cryo-vibration test



• Diffraction grating– QM grating fully

characterised– Test of grating

constantand grating periodicity: all parameters inor near spec(acceptedby optics SE)

Grating Assembly


PACS IHDR 12/13 Nov 2003Warm Electronics: AVM Instrument Level

Tests



Status of AVM Tests (1)

• CDMS simulator upgrade to V2.4– Has solved some counter overrun problem and the time

bug (now we have correct TAI)– Burst mode for PACS implemented

• DPU OBSW: several updates– Mainly for 1355 link loss investigation– But solving only the other known problems (EEPROM,

jump to application software)– Bug found in DPU ISR routine (by comparison with

DECMEC)– New problem with 1553 interface discovered. HW? SW?

DPU problems not solved in >1 year – start of ILT at risk!

• DECMEC OBSW is pretty stable



Status of AVM Tests (2)

• AVM SPU– Identified HW problem fixed – A small problem related to the SPU-DMC 1355 link initial

self-test has been found, but apparently this is inherent to the SMCS chip. Either the SPU_SUSW and/or the user manual need to be updated.

• SPU HLSW upgraded to version 6.0– It contains some performance improvements both with

respect to CPU work load and compression ratio– Parallel mode will require small update– Goal for CQM is to develop, in parallel, an improved

strategy (noise estimate from averaged ramp per pixel) and test it

• Down-link of “near-raw” data to allow ramp modeling / glitch removal on ground

• CPU load down presently still too high, optimisation in progress



SPU Ground Simulator

Ground simulation of SPU code useful for several reasons:

• Use PACS “raw data” transmission mode to redo, on ground, the same operations as performed by the on-board S/W

• Dispose of a test bed to try out new compression algorithms before they are up-linked and used by on-board S/W

• Subject PACS simulator data to same artifacts, i.e. compression and reduction, as on-board obtaineddata

• New version of on-board SPU has been “grounded” in less than five minutes work



Instrument Performance

• Instrument Requirements– Photometer– Spectrometer

• Instrument Model– Optical performance– Sensitivity budget

• optical transmission• background• detector performance



Photometer Performance Requirements

• Image quality– blur: telescope limited– distortion: ±1 pixel; alignment: <1/3 pixel

• Sensitivity (point source detection)– requirement: 5 mJy (5), 1h of integration– goal: 3 mJy (5), 1h of integration

• Dynamic range– detection from 3 mJy to >1000 Jy (goal: 3000 Jy) – contrast of up to 1:500 in one field

• Post-detection bandwidth– requirement: 0.5 - 5 Hz– goal: 0.05 - 5 Hz



Spectrometer Performance Requirements

• Image quality– blur: telescope limited– distortion: ±1 pixel; alignment: <1/4 pixel

• Sensitivity (point source detection)– requirement: 3x10-18 W/Hz1/2 (5), 1h of integration– goal: 2x10-18 W/Hz1/2 (5), 1h of integration

• Dynamic range– detection from ~1x10-18 W to >10-13 W– contrast of up to 1:100 in one field

• Post-detection bandwidth– requirement: 5 Hz– goal: 10 Hz



Optical Performance

• Optical design / implementation fulfills requirements regarding– field of view– spatial sampling– distortion– geometrical spot sizes (Strehl ratio)– alignment– internal calibration capability– chopping– spectral coverage and resolution– transmission / diffraction losses

Details from N. Geis / D. Kampf



(a) Values for the photometry modes from 60-85 or 85-130 µm / 130-210 µm, respectively.

(b) The formal transmission of >1 takes into account the acceptance solid angle of the photoconductor light cones / bolometer baffles which differs from the beam solid angle.

Parameters of PACS Instrument Model(Present estimate, partly based on

measurements)



Grating diffraction order efficiency

Resolving power

Telescope efficiency(main beam)

Main beam / pixel coupling

Spectrometer Performance



Detective quantum efficiency

Background power [W] BLIP NEP [W/Hz1/2]

on-array chopping

off-positionchopping

Sensitivity [W/m2](5, 1 hour)

Spectrometer Performance

Requirement



Photometer Sensitivity

• Assumed detector QE: 80% (based on FTS measurements)

• Assumed detector NEP: 10-16 W/Hz1/2 (based on electrical noise and responsivity measurements)

• Margin for requirement, goal likely to be metWavelength [µm]

Poin

t so

urc

e d

ete

ctio

n lim

it(5

, 1

h)

[mJy

]

goal

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