FM-ILT Results: Mechanisms FM1 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, 8 th Nov 2007

Markus Nielbock – FM-ILT Results: PACS Chopper & CS Chopper Angular Calibration angular calibration for FP1 and FP2 accuracy better than 1’ (0.7” on sky) see FM-ILT reports: PICC-MA-TR-20, 21, 23, 34, 36, 38 SVR III, 8 th Nov 2007

+4° nominal Markus Nielbock – FM-ILT Results: PACS Chopper & CS Chopper Performance see 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, 8 th Nov 2007

Markus Nielbock – FM-ILT Results: PACS Chopper & CS Implications for IST and PV 1. Synchronisation with detector readout (spectrometer) blue 6 rou Question: 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 optimisation a) 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 tested to be postponed to FS-ILT First 6 read-outs are affected by chopper movement. SVR III, 8 th Nov 2007

CS2 CS K (80  ) 76.2 K (92  ) CS1 CS2 Markus Nielbock – FM-ILT Results: PACS Chopper & CS Calibration Sources: Performance see 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 70 K) CS1 faster in heat-up than CS2 nominal DEC/MECredundant 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: min heat-up + stabilisation time: min CS1 (heat-up to 70.6 K) CS2 (heat-up to 76.2 K) heat-up + stabilisation time: min heat-up + stabilisation time: min  heat-up time requirement fulfilled  stability requirement fulfilled SVR III, 8 th Nov 2007

Markus Nielbock – FM-ILT Results: PACS Chopper & CS Calibration Sources: Homogeneity see 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, 8 th Nov 2007

Markus Nielbock – FM-ILT Results: PACS Chopper & CS Calibration Sources: Positions see FM-ILT report: PICC-NHSC-TR-002 current default positions: translated to chopper angles: CS1: ROUCS2: ROU CS1: ROUCS2: ROU To be confirmed in orbit raw data processed field distortion not yet included photometer FOV photometer FOV SVR III, 8 th Nov 2007

Markus Nielbock – FM-ILT Results: PACS Chopper & CS Calibration Sources: Emissivity see 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 CS2 (76 K) Requirements: grey-body, 0.04 <  < 0.16 within 55  m < < 210  m (PACS-ME-RS-10)  requirements fulfilled SVR III, 8 th Nov 2007

Markus Nielbock – FM-ILT Results: PACS Chopper & CS CS: Implications for PV, SV 1. 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 temperatures a) 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 CS a) CS width just matches PACS FOV of bolometers b) little flexibility in positioning the arrays on the CS c) flux calibration has to correct for CS inhomogeneities Flux ratio model: CS2 vs. telescope incl. stray light SVR III, 8 th Nov 2007

Markus Nielbock – FM-ILT Results: PACS Chopper & CS Summary Chopper 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, 8 th Nov 2007