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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
s Nie
lbock – FM
-ILT R
esu
lts: PA
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
s Nie
lbock – FM
-ILT R
esu
lts: PA
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
esu
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
s Nie
lbock – FM
-ILT R
esu
lts: PA
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
s Nie
lbock – FM
-ILT R
esu
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
esu
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
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