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PACS FM-ILT SPECTROMETER SPATIAL CALIBRATION. A. Contursi (H. Feuchtgruber). PACS Science Verification Review – 8/9 November 2007 MPE-Garching. TESTS EXECUTED. 3 27x27 rasters, ¼ pixel step, 3 chopper position, @ 0', +-3' (AOT), same grating position.

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PACS

FM-ILT SPECTROMETER

SPATIAL CALIBRATION

A. Contursi

(H. Feuchtgruber)

PACS Science Verification Review – 8/9 November 2007

MPE-Garching


TESTS EXECUTED

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

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


TESTS EXECUTION

External BB @ 1000 °C

Hole = 1.5 mm


PSFs in every module

Telemetry drop!

no time for

re-execution

BLUE


PSFs in every module

Cross Talks with

module 11.

Present in all

modules, all chop

position

Module 11

RED


FMILT 1-2-3 comparison

FMILT-1

FMILT-2

FMILT-3


COMPARISON WITH

THEORETICAL PSF

Along chopper direction

Observed

BLUE

Theoretical

RED

Mod 0

Mod 12

Mod 24


COMPARISON WITH

THEORETICAL PSF

orthogonal to chopper direction

Observed

BLUE

Theoretical

RED

Mod 12

Mod 0

Mod 24


Spectrometer FOV fingerprint

all spectral pixels averaged


Rotation array-chopper direction

NON LINEAR!

The dependence

of the rotation angle

from the chopper

position is not linear.

Consistent with

photometer results

obtained with more

chopper position


Spectrometer FOV fingerprint

each spectral pixel

½ pixel


Spectrometer FOV fingerprint

each spectral pixel

½ pixel


Position of pixels in the sky

chop +L

chop 0

chop -L

Assuming chopper

commanded units,

angle conversion

Assuming XY stage to sky

conversion:

1”= 0.18 mm




Conservation of the flux

Sum of 27x27 raster in each position after having

normalized each raster to the PSF peak value

Full dynamical range

High cut

BLUE homogeneous: 20% maximum variation


Conservation of the flux

Sum of 27x27 raster in each position after having

normalized each raster to the PSF peak value

Full dynamical range

High cut

RED: high signal (up to a factor of 2)

from module 11 cross talk


RASTER MAP RECONSTRUCTION

!! CAUTION: not Flat Fielded !!

GHOST!

GHOST!

~< 0.1%

of Bright

Source


GHOSTs in the BLUE

?? 1 moving ghost or 2 fixed ghosts ??


RASTER MAP RECONSTRUCTION

!! CAUTION: not Flat Fielded !!

Background structures

worse in the RED

result in alignment

problems:

reconstructed PSF

elongated

Possible contribution

from cross talk of

module 11


CONCLUSIONS

Almost all optical misalignments

successfully corrected

Observed PSF widths as expected

Chopper-array rotated by ~3 degree

No dependency on grating position

Cross talk module 11 in the RED

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


OPEN ISSUEs

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

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


Spectrometer Spatial Calibration

in PV

External BB @ 1000 °C corresponds to:

125 Jy at 77 micron

50 Jy at 154 micron

This gives :

S/N ~ 100 in the BLUE

S/N ~ 12 in the RED

Background levels:

3000 Jy in the BLUE

1700 Jy in the RED


Spectrometer Spatial Calibration

in PV

Expected Herschel background level

~450 Jy at 77 micron (factor 6 less)

~175 Jy @ 154 micron (factor 10 less)

Duration of 27x27 FMILT-3 raster ~2.5h

Doubled in PV due to chopping

to correct

for responsivity changes due to glitches


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