Herschel Calibration Workshop PACS Photometer Flux Calibration: Implementation Markus Nielbock (MPIA Heidelberg) on behalf of the PACS ICC and Calibration Working Group Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ESAC, 13th December 2010

General PACS Calibration Aspects Central reference documentation: PACS Calibration Document (PACS-MA-GS-001) detailed definition and description of all PACS calibration aspects PACS Commissioning Phase Plan Document (PACS-ME-PL-024) detailed implementation plan for calibration during commissioning phase PACS Performance Verification Phase Plan Document (PACS-MA-PL-001) detailed implementation plan for calibration during PV phase PACS Routine Phase Calibration Plan Document (PACS-MA-PL-002) detailed implementation plan for calibration during routine science phase http://www.herschel.be/twiki/bin/view/Pacs/PacsPhotFluxCalibrationSources database of flux calibration analysis results Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Preconditions see talk by M. Sauvage bolometers tuned to optimal bias settings for best sensitivity and optimum dynamic range (dedicated programme during CoP and PV) established detector/optical flat field two observing modes to be calibrated: - chopped/nodded point-source photometry - scan map (PACS only, SPIRE/PACS parallel) Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Related items and influences conversion from detector units to Jy (responsivity) calibration uncertainty sensitivity (non-)linearity stability / time dependence influence of source SED (colour correction, filter leakage) PSF (EEF, aperture correction, background level) point vs. extended source calibration (total power, reduction methods) relation between observing modes (chopped, scan map, parallel mode) independent checks via cross calibration with P-SPEC, SPIRE and PLANCK Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Target selection General guide lines: wide and dense flux range (from a few mJy to several hundred Jy) wide temperature range (a few hundred to several thousand K) well established model predictions across the entire spectral range (PACS, SPIRE) good database of reference measurements (ground based, IRAS, ISO, SPITZER) no (random) intrinsic variability low background confusion good visibility Flux density (chopped PS) [Jy] Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

secondary standard stars PACS Photometer Flux Calibration Target selection 4 classes: prime standard stars secondary standard stars asteroids planets α Boo, α Cet, α CMa, α Tau, β And, β Peg, (β UMi), γ Dra based on models hot source SEDs highest confidence based on archival data - ISO GBPP - Gordon MIPS calibration - IRAS converted to PACS bands extends flux range to faintest levels less confidence warm source SEDs time dependent (models) provides fine adjustment of flux grid coverage closes gap between stars and planets partly non-linear flux regime confidence varies between high and low Uranus, Neptune non-linear flux regime high confidence see talks by L. Decin, J. Blommaert see talk by T. Müller R. Moreno, G. Orton Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Programme design observed in chopped and mini scan map mode during PV: investigation of various parameter configurations (e.g. scan speed, scan angle, gain) high S/N to optimise photometric accuracy Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Programme design observed in chopped and mini scan map mode during PV: investigation of various parameter configurations (e.g. scan speed, scan angle, gain) high S/N to optimise photometric accuracy observing frequency given by visibility constraints Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Programme design observed in chopped and mini scan map mode during PV: investigation of various parameter configurations (e.g. scan speed, scan angle, gain) high S/N to optimise photometric accuracy observing frequency given by visibility constraints observation of selected SSOs synchronous with PLANCK sightings for cross calibration stability monitoring on γ Dra (always visible), once per month Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Flux extraction aperture photometry pixel size [“] aperture radius [“] aperture correction HP filter chopped scan 70 µm 1.6 1.0 10 15 0.856 0.913 100 µm 0.809 0.910 20 160 µm 3.2 2.0 14 0.801 0.897 35 Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Flux extraction aperture photometry pixel size [“] aperture radius [“] aperture correction HP filter chopped scan 70 µm 1.6 1.0 10 15 0.856 0.913 100 µm 0.809 0.910 20 160 µm 3.2 2.0 14 0.801 0.897 35 highpass filter width scaled with PSF aperture correction taken from EEF, to be updated (see PICC-ME-TN-033) Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Flux extraction aperture photometry pixel size [“] aperture radius [“] aperture correction HP filter chopped scan 70 µm 1.6 1.0 10 15 0.856 0.913 100 µm 0.809 0.910 20 160 µm 3.2 2.0 14 0.801 0.897 35 highpass filter width scaled with PSF aperture correction taken from EEF, to be updated (see PICC-ME-TN-033) colour correction 70 µm 100 µm 160 µm Stars 1.02 1.03 1.07 Asteroids 1.00 1.05 Planets 0.98 0.99 1.01 Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration PSF and Encircled Energy Fraction derived from scan map observations PSF core: (nearly) point sources Vesta and α Tau PSF wings: unsaturated areas of Mars Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration PSF and Encircled Energy Fraction derived from scan map observations PSF core: (nearly) point sources Vesta and α Tau PSF wings: unsaturated areas of Mars Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration PSF and Encircled Energy Fraction derived from scan map observations PSF core: (nearly) point sources Vesta and α Tau PSF wings: unsaturated areas of Mars WARNING! There is no single general PSF! A PSF is influenced by: fast scan PSF smearing reduction methods: highpass filtering, map pixel size, drizzling source SED straylight and ghost effects pointing quality Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration PSF and Encircled Energy Fraction measured from Vesta sky set to zero at r = 60” basis of current flux calibration combination of Vesta and Mars adds ~10% flux at large radii affects extended source calibration to be inserted into flux calibration Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Analysis (see also following talks) correlate photometry with model calculations → calibration accuracy compare different source classes → colour dependence, filter leakage? Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Analysis (see also following talks) correlate photometry with model calculations → calibration accuracy compare different source classes → colour dependence, filter leakage? Markus Nielbock (MPIA) – PACS Photometer Flux Calibration results being used to update responsivity calibration file in HCSS point source flux calibration accurate to within 5% (chopped and scan map) photometry can differ by a few percent depending on the reduction method (e.g. highpass filter width) photometry of scan maps using the consolidated set of HPF widths and apertures agrees with photometry of maps created with Scanamorphos and MadMap no significant difference between stars and asteroids → no filter leakage, colour correction okay non-linear regime begins at approx. 100 Jy (additional observations needed and planned)

PACS Photometer Flux Calibration Extended sources - Work in progress ... PACS 70 µm PACS convolved Markus Nielbock (MPIA) – PACS Photometer Flux Calibration IRIS 60 µm PACS conv.+regridded conversion between IRAS and PACS includes offset and constant factor offset depends of observed field linear relationship seems to be independent PACS maps (naïve mapper) are up to 60% brighter than IRIS maps (very preliminary)

PACS Photometer Flux Calibration Stability monitoring on γ Dra revealed long term variation of measured flux of the order of a few % appears to be correlated with main mirror temperature (affects responsivity) offers room for improvement of flux calibration accuracy Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Internal calibration – further refinery calibration block on internal gauge sources at beginning of observation currently not used analysis shows signal drifts correlated with 3He cooler temperature since last recycling also influenced by biasing of detectors at beginning of OD potential for further flux calibration improvement Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Time since last cooler recycling Time since last cooler recycling individual ODs

PACS Photometer Flux Calibration Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

PACS Photometer Flux Calibration Markus Nielbock (MPIA) – PACS Photometer Flux Calibration