FM-ILT Results: MechanismsFM1 Chopper and Calibration Sources

Markus Nielbock (MPIA)

Babar Ali (IPAC)Jeroen Bouwman (MPIA)Helmut Dannerbauer (MPIA)Dario Fadda (IPAC)Helmut Feuchtgruber (MPE)Dave Frayer (IPAC)Csaba Kiss (Konkoly)Ulrich Klaas (MPIA)Jürgen Schreiber (MPIA)

MPIA

SVR III, 8th Nov 2007

Marku

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-ILT R

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CS

Chopper &

CS

Chopper Angular Calibration

angular calibration for FP1 and FP2accuracy better than 1’ (0.7” on sky)

see FM-ILT reports: PICC-MA-TR-20, 21, 23, 34, 36, 38

SVR III, 8th Nov 2007

+4°nominal

Marku

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CS

Chopper &

CS

Chopper Performancesee FM-ILT report: PICC-MA-TR-31

Req. 1: duty cycle of ≥ 80% for science observations (±4.1°) and chopping at 10 Hz

Req. 2: duty cycle of ≥ 70% for calibration observations (~8°) and chopping at 5 Hz 10 ms transition time

30 ms transition time

redundant

+8°

nominal

transition time: 19 msduty cycle: 62% (10 Hz) specifications not met for 10 Hz, but …

symmetric in positive and negative angles (DEC/MEC upgrade)

If chopping at 5 Hz: 81% duty cycle (sufficient)stable within rms = 0.03” on sky

transition time: 23 msduty cycle: 77% specifications met

stable within rms = 0.04” on sky

12 ms

nominal and redundant operation identical duty cycles

caused by filter

SVR III, 8th Nov 2007

Marku

s Nie

lbock – FM

-ILT R

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lts: PA

CS

Chopper &

CS

Implications for IST and PV1. Synchronisation with detector readout (spectrometer)

blu

e

6 rouQuestion: How do we deal with this?a) discard first 6 raw read-outs (on-board software)

b) discard whole ramp (significant loss of data)

2. PID and rest position verification and optimisationa) during IST

b) during commissioning and PV

c) verification regularly during routine phase

c) increase samples per ramp from 4 to 8

3. Degraded mode (reduced set of drive coils) not testedto be postponed to FS-ILT

First 6 read-outs are affected by chopper movement.

SVR III, 8th Nov 2007

CS2

CS1

70.6 K (80 )

76.2 K (92 )

CS1

CS2

Marku

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CS

Chopper &

CS

Calibration Sources: Performancesee FM-ILT reports: PICC-MA-TR-32, 33

Requirement 1: heat-up time to final temperature: 30 min (± 5%) (PACS-ME-RS-10)

Requirement 2: stability: 0.01% (± 7 mK @ 70 K)

CS1 faster in heat-up than CS2

nominal DEC/MEC redundant DEC/MEC

CS2 faster in heat-up than CS1

CS1 (heat-up to 70.6 K)

CS2 (heat-up to 76.2 K)

heat-up + stabilisation time: 30.7 + 12.0 min

heat-up + stabilisation time: 36.7 + 11.0 min

CS1 (heat-up to 70.6 K)

CS2 (heat-up to 76.2 K)

heat-up + stabilisation time: 29.9 + 12.3 min

heat-up + stabilisation time: 33.3 + 11.0 min

heat-up time requirement fulfilled stability requirement fulfilled SVR III, 8th Nov 2007

Marku

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lbock – FM

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lts: PA

CS

Chopper &

CS

Calibration Sources: Homogeneitysee FM-ILT report: PICC-NHSC-TR-002

sky window~ 7.5’ (sky)

calibration sources

Bolometer FOV scans:

CS emission pattern inhomogeneous

inhomogeneities consistent between measurements

blue

green

red

to be considered for flux calibration (precise detector flat field)

SVR III, 8th Nov 2007

Marku

s Nie

lbock – FM

-ILT R

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lts: PA

CS

Chopper &

CS

Calibration Sources: Positionssee FM-ILT report: PICC-NHSC-TR-002

current default positions:translated to chopper angles:

CS1: -21350 ROU CS2: +21200 ROUCS1: -21500 ROU CS2: +21885 ROU

To be confirmed in orbit

raw data

processed

field distortionnot yet included

photometerFOV

photometerFOV

SVR III, 8th Nov 2007

Marku

s Nie

lbock – FM

-ILT R

esu

lts: PA

CS

Chopper &

CS

Calibration Sources: Emissivitysee FM-ILT report: PICC-NHSC-TR-003

CQM values

stray light effects

needed to compensate for telescope background

Emissivity depends on wavelengthand ranges between 0.05 and 0.07.

CS2 (76 K)

Requirements: grey-body, 0.04 < < 0.16 within 55 m < < 210 m (PACS-ME-RS-10)

requirements fulfilled

SVR III, 8th Nov 2007

Marku

s Nie

lbock – FM

-ILT R

esu

lts: PA

CS

Chopper &

CS

CS: Implications for PV, SV1. Heat-up time constraints

a) will be faster for lower CS temperatures (e.g. ~20 min for 50 K)b) perhaps swap CS temperatures in nominal operation (CS1 is faster)

c) maybe could gain ~10 min by reducing overshoot (control parameters)

3. Emissivity and selection of CS temperaturesa) depends on telescope temperature (not very well known yet)b) can only be established with a fully cooled down telescope

2. Optimal chopper angle for CSa) CS width just matches PACS FOV of bolometersb) little flexibility in positioning the arrays on the CSc) flux calibration has to correct for CS inhomogeneitiesFlux ratio model: CS2 vs. telescope incl. stray light

SVR III, 8th Nov 2007

Marku

s Nie

lbock – FM

-ILT R

esu

lts: PA

CS

Chopper &

CS

SummaryChopper

Calibration Sources

• mostly within specifications (reduced duty cycle for 10 Hz chopping)• duty cycle of 81% at 5 Hz chopping is sufficient

• PID optimisation during IST/commissioning might improve transition• decision to be made about detector read-outs affected by chopper movement

• heat-up, stability and emissivity within specifications• spots and structures detected at CSs• photometer FOV just fits on CS

• CS temperatures to be adjusted to telescope temperature (~ 50 K ?)

• accurate angular calibration for nominal and redundant operations

SVR III, 8th Nov 2007