PACS PACS FM-ILT SPECTROMETER FM-ILT SPECTROMETER SPATIAL CALIBRATIONSPATIAL CALIBRATION

A. A. ContursiContursi

(H. Feuchtgruber)(H. Feuchtgruber)

PACS Science Verification Review – 8/9 November 2007PACS Science Verification Review – 8/9 November 2007MPE-GarchingMPE-Garching

TESTS EXECUTEDTESTS EXECUTED

3 27x27 rasters, ¼ pixel step, 3 chopper 3 27x27 rasters, ¼ pixel step, 3 chopper position, @ 0', +-3' (AOT), same grating position, @ 0', +-3' (AOT), same grating positionposition

3 9x9 rasters,1/4 pixel step, around 3 9x9 rasters,1/4 pixel step, around central pixel FOV, 3 grating position, central pixel FOV, 3 grating position, same chopper position @ 0'same chopper position @ 0'

TESTS EXECUTIONTESTS EXECUTION

External BB @ External BB @ 1000 1000 °°CC

Hole = 1.5 mmHole = 1.5 mm

PSFs in every modulePSFs in every module

BLUEBLUE

Telemetry drop!Telemetry drop!no time for no time for re-executionre-execution

PSFs in every modulePSFs in every module

REDRED

Cross Talks with Cross Talks with module 11. module 11. Present in all Present in all modules, all chopmodules, all choppositionposition

Module 11Module 11

FMILT 1-2-3 comparisonFMILT 1-2-3 comparison

FMILT-2FMILT-2FMILT-1FMILT-1 FMILT-3FMILT-3

COMPARISON WITH COMPARISON WITH THEORETICAL PSFTHEORETICAL PSF

Along chopper directionAlong chopper direction

BLUEBLUE

REDRED

Mod 0Mod 0 Mod 12Mod 12 Mod 24Mod 24

ObservedObserved

TheoreticalTheoretical

COMPARISON WITH COMPARISON WITH THEORETICAL PSFTHEORETICAL PSForthogonal to chopper directionorthogonal to chopper direction

BLUEBLUE

REDRED

Mod 0Mod 0 Mod 12Mod 12 Mod 24Mod 24

ObservedObserved

TheoreticalTheoretical

Spectrometer FOV fingerprintSpectrometer FOV fingerprintall spectral pixels averagedall spectral pixels averaged

Rotation array-chopper directionRotation array-chopper directionNON LINEAR!NON LINEAR!

The dependence The dependence of the rotation angle of the rotation angle from the chopperfrom the chopperposition is not linear.position is not linear.

Consistent with Consistent with photometer results photometer results obtained with more obtained with more chopper positionchopper position

Spectrometer FOV fingerprintSpectrometer FOV fingerprinteach spectral pixeleach spectral pixel

½ pixel½ pixel

Spectrometer FOV fingerprintSpectrometer FOV fingerprinteach spectral pixeleach spectral pixel

½ pixel½ pixel

Position of pixels in the skyPosition of pixels in the skychop +Lchop +L chop 0chop 0 chop -Lchop -L

Assuming XY Assuming XY stage to skystage to skyconversion:conversion:

1”= 0.18 mm1”= 0.18 mm

Assuming chopperAssuming choppercommanded units, commanded units, angle conversionangle conversion

Dependence on grating: BLUEDependence on grating: BLUE

Dependence on grating: REDDependence on grating: RED

Conservation of the fluxConservation of the flux

Full dynamical rangeFull dynamical range High cutHigh cut

BLUE homogeneous: 20% maximum variationBLUE homogeneous: 20% maximum variation

Sum of 27x27 raster in each position after havingSum of 27x27 raster in each position after having

normalized each raster to the PSF peak valuenormalized each raster to the PSF peak value

Conservation of the fluxConservation of the flux

Full dynamical rangeFull dynamical range High cutHigh cut

RED: high signal (up to a factor of 2)RED: high signal (up to a factor of 2)from module 11 cross talkfrom module 11 cross talk

Sum of 27x27 raster in each position after havingSum of 27x27 raster in each position after having

normalized each raster to the PSF peak valuenormalized each raster to the PSF peak value

RASTER MAP RECONSTRUCTIONRASTER MAP RECONSTRUCTION

!! CAUTION: not Flat Fielded !!!! CAUTION: not Flat Fielded !!

GHOST!GHOST!~< 0.1%~< 0.1%of Bright of Bright SourceSource

GHOST!GHOST!

GHOSTs in the BLUEGHOSTs in the BLUE?? 1 moving ghost or 2 fixed ghosts ???? 1 moving ghost or 2 fixed ghosts ??

RASTER MAP RECONSTRUCTIONRASTER MAP RECONSTRUCTION

!! CAUTION: not Flat Fielded !!!! CAUTION: not Flat Fielded !!

Background structuresBackground structuresworse in the REDworse in the REDresult in alignment result in alignment problems:problems:

reconstructed PSF reconstructed PSF elongatedelongated

Possible contributionPossible contributionfrom cross talk offrom cross talk ofmodule 11module 11

CONCLUSIONSCONCLUSIONS

Almost all optical misalignments Almost all optical misalignments successfully correctedsuccessfully corrected

Observed PSF widths as expectedObserved PSF widths as expected

Chopper-array rotated by ~3 degreeChopper-array rotated by ~3 degree

Cross talk module 11 in the REDCross talk module 11 in the RED

No dependency on grating positionNo dependency on grating position

Faint ghosts in the BLUE: potential Faint ghosts in the BLUE: potential concerns for weak extended sourcesconcerns for weak extended sources

OPEN ISSUEsOPEN ISSUEs

Module 11 cross talks in the DUMMY Module 11 cross talks in the DUMMY and OPEN in RED and BLUE: sometime and OPEN in RED and BLUE: sometime only in 1 supply group, sometime in all only in 1 supply group, sometime in all modules.modules.

Number of ghosts in the BLUE: 1 or 2? Number of ghosts in the BLUE: 1 or 2? Which is their origin? Inside PACS or Which is their origin? Inside PACS or external window? (may be some external window? (may be some answers in FS)answers in FS)

Spectrometer Spatial Calibration Spectrometer Spatial Calibration in PVin PV

External BB @ 1000 External BB @ 1000 °°C corresponds to:C corresponds to:

125 Jy at 77 micron125 Jy at 77 micron50 Jy at 154 micron50 Jy at 154 micron

This gives :This gives :

S/N ~ 100 in the BLUES/N ~ 100 in the BLUES/N ~ 12 in the REDS/N ~ 12 in the RED

Background levels:Background levels:

3000 Jy in the BLUE3000 Jy in the BLUE1700 Jy in the RED1700 Jy in the RED

Spectrometer Spatial Calibration Spectrometer Spatial Calibration in PVin PV

Expected Herschel background levelExpected Herschel background level

~450 Jy at 77 micron (factor 6 less)~450 Jy at 77 micron (factor 6 less)~175 Jy @ 154 micron (factor 10 less)~175 Jy @ 154 micron (factor 10 less)

Duration of 27x27 FMILT-3 raster ~2.5hDuration of 27x27 FMILT-3 raster ~2.5h

Doubled in PV due to chopping Doubled in PV due to chopping to correct to correct

for responsivity changes due to glitchesfor responsivity changes due to glitches