1. PACS Calibration Status Report
Herschel Calibration Steering Group
Meeting #28
PACS Calibration Status Report
Markus Nielbock (MPIA Heidelberg)
on behalf of the PACS Calibration Working Group
Markus Nielbock (MPIA) – PACS Calibration Status Report
ESTEC, Noordwijk, 13th April 2011

2. Outline wrap-up PACS calibration programme
implementation new PACS PHOT flux calibration
non-linearity calibration PACS PHOT
PACS SPEC SED/flux calibration
PACS PHOT/SPEC cross calibration
Markus Nielbock (MPIA) – PACS Calibration Status Report

3. Wrap-up of PACS RSP Calibration
full description and details in: PICC-MA-PL-002
up to cycle 38: 1398 AORs, h
PACS Photo
PACS Spectro
SPIRE/PACS
Parallel
Engineering
829 AORs
528 AORs
20 AORs
21 AORs
157.3 h
295.5 h
15.7 h
0.4 h
Markus Nielbock (MPIA) – PACS Calibration Status Report
anticipated calibration time needed: h

4. PACS Photometer Flux Calibration
New calibration scheme (1)
full description in: PICC-ME-TN-037
was based on point source aperture photometry of chopped observations
measured from Vesta
sky set to zero at r = 60”
combination of Vesta and Mars
sky set to zero at r = 600”
adds ~10% flux at large radii
Markus Nielbock (MPIA) – PACS Calibration Status Report
scan map now dominant observing mode (small offset in flux to chopped)

5. PACS Photometer Flux Calibration
New calibration scheme (2)
resulting correction based on the five most reliable calibrators:
will be included in the next HCSS 7.0 release
Markus Nielbock (MPIA) – PACS Calibration Status Report
together with aperture correction task
resulting absolute PACS PHOT flux calibration accuracy
(incl. model accuracy):
PACS 70 µm: %
PACS 100 µm: 2.75%
PACS 160 µm: 4.15%

6. PACS Photometer Flux Calibration
New calibration scheme (3)
Markus Nielbock (MPIA) – PACS Calibration Status Report

7. PACS Photometer Flux Calibration
New calibration scheme (4)
Markus Nielbock (MPIA) – PACS Calibration Status Report

8. PACS Photometer Flux Calibration
Colour correction tables update
full description in: PICC-ME-TN-038
calculated for standard and modified Black Bodies
tables allow for translation to neighbouring bands of other instruments (e.g. IRAS, ISO)
Markus Nielbock (MPIA) – PACS Calibration Status Report

9. PACS Photometer Flux Calibration
Non-linearity investigation
non-linearity range begins at approx. 100 Jy per point source
flux coverage in calibration programme insufficient
extension of calibrator list with bright asteroids (flux changes with time)
repeated observation at different epochs to obtain good sampling across crucial flux range
10 Hygiea
4 Vesta
1 Ceres
Markus Nielbock (MPIA) – PACS Calibration Status Report

10. PACS Spectrometer Flux Calibration
Latest progress – internal calibration block (1)
ground based total flux calibration now complemented with internal calibration block
slight improvement of total flux uncertainty
overall flux calibration uncertainty: ~20-30% 20 24 15 19 10 12 14 5 9 4
PACS-S IFU
Markus Nielbock (MPIA) – PACS Calibration Status Report
rms = 12.1%
rms = 10.9%
ground calibration + scaling from in-flight calibration
response correction from internal calibration block

11. PACS Spectrometer Flux Calibration
Latest progress – internal calibration block (2)
ground calibration + scaling from in-flight calibration
response correction from internal calibration block
good pointing
Markus Nielbock (MPIA) – PACS Calibration Status Report
bad pointing
pointing jitter is the dominating contribution to remaining uncertainty

12. PACS Spectrometer Flux Calibration
Work in progress – correction of pointing jitter induced flux uncertainty (1)
applicable to moderately bright point sources only
Basic idea:
Use reference observation of bright point source (e.g. Neptune) as proxy for flux scaling factor
to correct for missing flux in central IFU module.
Requirement:
Sufficiently large database of reference observations to determine the flux distribution for
optimal pointing performance.
Example: HD (34 observations)
Markus Nielbock (MPIA) – PACS Calibration Status Report
division by mean of all 34 observations
correction with internal calibration block
correction for pointing jitter
both corrections combined

13. PACS Spectrometer Flux Calibration
Work in progress – correction of pointing jitter induced flux uncertainty (2)
current calibration
internal calibration block + pointing jitter correction
Markus Nielbock (MPIA) – PACS Calibration Status Report
additional observations needed to complement reference observation database
25x25 rasters on Neptune at six different reference wavelengths planned for cycle 38
not applicable to extended and faint sources → CP raster pointing mode (?)

14. ground based optical/NIR
PACS Cross Calibration
SED spectroscopy (1)
well characterised Herbig Ae/Be star observed with PACS spectrometer
spectral response calibrated with background normalisation method
ground based optical/NIR
mainly SPITZER
Markus Nielbock (MPIA) – PACS Calibration Status Report
photospheric model
SPITZER
SPITZER
IRAS + AKARI
PACS

15. PACS Cross Calibration
SED spectroscopy (2)
background spectrum derived from Neptune observation
Markus Nielbock (MPIA) – PACS Calibration Status Report

16. PACS Cross Calibration
SED spectroscopy (3)
background spectrum derived from Pallas observation
additional PACS photometer observations planned for cycle 39 for cross calibration
Markus Nielbock (MPIA) – PACS Calibration Status Report

17. PACS Calibration Summary and outlook
PACS photometer calibration in good shape
non-linearity calibration to be added soon
PACS spectrometer flux calibration needs more attention
pointing performance limits calibration accuracy (RSRF, central module flux, line shape)
several data processing approaches to improve situation
implementation of new AOTs (unchopped spectroscopy)
bright line mode made available
testing of CP raster pointing mode to improve nodding performance
Markus Nielbock (MPIA) – PACS Calibration Status Report

18. PACS
Markus Nielbock (MPIA) – PACS Calibration Status Report