1. Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Herschel Calibration Workshop PACS Photometer Flux Calibration: Update Markus Nielbock (MPIA Heidelberg) Thomas Müller (MPE Garching) on behalf of the PACS ICC and Calibration Working Group ESAC, 19 th January 2012

2. PACS Photometer Flux Calibration Overview Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ● current status ● non-linearity correction ● influence on PSF templates and aperture correction ● roadmap for calibration product updates ● correlation with evaporator temperature

3. PACS Photometer Flux Calibration Current status: General remarks Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ● flux calibration based on scan map observations of 5 prime fiducial stars ● model uncertainty amounts to 5% throughout ● chop-nod observations are underestimated by 4%, 4%, 6% at 70, 100, 160 µm ● aperture photometry with aperture correction (PSF template: Vesta, Mars) ● colour corrections: 1.016, 1.033, 1.074 at 70, 100, 160 µm ● all prime standards are in the linear flux regime ● secondary targets (faint stars, asteroids, planets) ● observed for consistency and extension of flux range

4. PACS Photometer Flux Calibration Current status: 70 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

5. PACS Photometer Flux Calibration Current status: 100 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

6. PACS Photometer Flux Calibration Current status: 160 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration improved data processing

7. PACS Photometer Flux Calibration Current status: Results Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ● flux calibration based on scan map observations of 5 prime fiducial stars ● scan-map: 160 µm fluxes might be underestimated by 2% ● chop-nod observations are underestimated by 4%, 4%, 6% at 70, 100, 160 µm ● fluxes of prime calibrators in PACS-P scan-map observations consistent with models within: ● 3%, 3%, 5% at 70, 100, 160 µm (weighted by calibrator, not by individual observation) ● extracted fluxes are influenced at a level of a few percent by: ● cross-talk, highpass filtering, source masking, deglitching, etc.

8. PACS Photometer Flux Calibration Non-linearity correction - Implementation Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ● established by N. Billot (CEA/IPAC/IRAM) based on pre-flight ground calibration ● non-linearity corrections of the order of 10% for signals around 60 Jy/pixel ● → small effect (0-15%) for brightest calibration sources (> 100 Jy per point source) ● flux calibrators affected: ● planets: Uranus, Neptune (5-15%) ● bright asteroids: Ceres, Pallas, Vesta (0-5%) ● independent of gain setting ● is implemented in HIPE 8

9. PACS Photometer Flux Calibration Non-linearity correction: Verification 70 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

10. PACS Photometer Flux Calibration Non-linearity correction: Verification 70 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

11. PACS Photometer Flux Calibration Non-linearity correction: Verification 70 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

12. PACS Photometer Flux Calibration Non-linearity correction: Verification 100 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

13. PACS Photometer Flux Calibration Non-linearity correction: Verification 100 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

14. PACS Photometer Flux Calibration Non-linearity correction: Verification 100 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

15. PACS Photometer Flux Calibration Non-linearity correction: Verification 160 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

16. PACS Photometer Flux Calibration Non-linearity correction: Verification 160 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

17. PACS Photometer Flux Calibration Non-linearity correction: Verification 160 µm Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e

18. PACS Photometer Flux Calibration Non-linearity correction: Results Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ● correction brings Neptune and Uranus fluxes into the ± 5% corridor ● data processing step and corresponding task is validated and available as of HIPE 8 ● should be used for all point sources above 10 Jy and bright extended regions ● noticable effects occur above 100 Jy ● Neptune models: ● truth might be between esa2 and esa3 at 70, 100 µm and close to esa3 at 160 µm ● but wait for end of this talk … ● open issues: ● PSF models are based on Vesta observations from OD 160 without NL-correction ● → 70 µm PSF model affected, aperture correction compromised OD 160 Vesta observations at 100, 160 µm are okay

19. PACS Photometer Flux Calibration Non-linearity correction: Influence on model PSFs and EEF Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ● deviations found: ● ~ 10% in peak flux, ~ 5% in total flux ● flux calibration at 70 µm affected ● aperture photometry of point sources is self-consistent and not affected ● (responsivity ↔ aperture correction) ● extended emission measured too high at 70 µm

20. PACS Photometer Flux Calibration Roadmap for flux calibration and aperture correction update Markus Nielbock (MPIA) – PACS Photometer Flux Calibration 1.re-analysis of PSF measurements with NL correction applied (Vesta, Mars) 2.evaluation of new EEF curves 3.generation of updated aperture correction calibration table (EEF values) 4.re-processing of all scan-map observations including NL correction using the new EEF 5.values for aperture correction 6.generation of updated response calibration product FM7 based on scan-map 7.observations of the five prime standards (will also correct 2% shift at 160 µm) 8.update of PhotApertureCorrectionPointSourceTask to accept new response calibration 9.validation of FM7 response calibration product on all calibrators (stars, asteroids, planets) 10.update of relevant documentation and processing scripts 11.release of new PSF models, EEF table, response calibration FM7 to be expected for HIPE 9

21. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ● PACS 3 He cooler temperature rises towards end of cooling cycle ● affects detector responsivity (this is expected) ● flux in individual observations is modified by up to ~5% ● introduces a systematic component to calibration uncertainty ● relevant for variability programmes → avoid scheduling towards the end of cooling cycle ● new scheduling scheme prevents observations at high evaporator temperatures detector debiasing -1 hour

22. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

23. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

24. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

25. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

26. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration Neptun e Uranu s

27. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

28. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

29. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

30. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

31. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration

32. PACS Photometer Flux Calibration Secondary effects: Correlation with evaporator temperature Markus Nielbock (MPIA) – PACS Photometer Flux Calibration esa3 model seems to be the best choice for all bands

33. PACS Photometer Flux Calibration Summary Markus Nielbock (MPIA) – PACS Photometer Flux Calibration ● flux calibration is in very good shape ● scan-map: 160 µm fluxes might be underestimated by 2% ● chop-nod observations are underestimated by 4%, 4%, 6% at 70, 100, 160 µm ● prime calibrator model uncertainty: 5% ● fluxes of prime calibrators in PACS-P scan-map observations consistent with models within: ● 3%, 3%, 5% at 70, 100, 160 µm (weighted by calibrator, not by individual observation) ● non-linearity correction module is verified and in place ● non-linearity significantly affects point sources above 100 Jy ● (e.g. bright asteroids, planets, but also bright extended emission) ● PSF model at 70 µm based on uncorrected observations of Vesta (OD 160) ● roadmap for PSF model, responsivity and EEF/aperture correction table update in place ● → HIPE 9 ● reponsivity affected by evaporator temperature of 3 He cooler (~ 5% integrated flux) ● after eliminating those effects: Neptune model esa3 seems most suitable for PACS-P