The points of caution
on the FIS data
ESAC, Madrid, 18-19 September 2007
AKARI Data Reduction Workshop

Mai Shirahata (ISAS/JAXA)
Shuji Matsuura (ISAS/JAXA)
Sinʼitirou Makiuti (ISAS/JAXA)
Issei Yamamura (ISAS/JAXA)

Output Image : N60 / Wide-S
N60

Wide-S?
? ?
XX

2

3

Cross-talk
Cross-talk between the array pixels appears
only in the SW detector.
Cause: Photons diffuse into the monolithic Ge:Ga substrate.
The strength of the cross-talk is about 10%.

10% Contours

LW detector does not have the monolithic structure.
→ The cross-talk does not appear.

Output Image : Wide-L / N160
Wide-L

N160?
? ?
XX4

5GhostThe ghost image appears in all bands.
Cause: Electrical cross-talk in the MPX of the CRE.
The ghost signal appears in wide(narrow) band,
when the narrow(wide) band observes a target.
Wide-S

N60

Wide-L

N160

Ghost
SW/LW detector have two arrays.
WideNarrow~10% of the signal in the other array

The ghost signal appears
in one array when the otherarray observes a target.

6

7GhostThe ghost image appears in all bands.
Cause: Electrical cross-talk in the MPX of the CRE.

0.2
5.4

5.4
5.4

5.4

3.6

3.6
2.0

4.1

0.2

The position where the ghost appears can be calculated.
The position and strength are stable.
→ possible to remove it. (will be developing)

2.0
4.1

Point Spread Function (PSF)
The PSF of each band measured by the asteroids observations.

37”±1”

39”±1”

58”±3”

61”±4”

There are significant excesses around tails of the PSFs.
The contributions are about 30% of the total power.

8The advanced tools
ESAC, Madrid, 18-19 September 2007
AKARI Data Reduction Workshop

Mai Shirahata (ISAS/JAXA)
Shuji Matsuura (ISAS/JAXA)
Sinʼitirou Makiuti (ISAS/JAXA)
Issei Yamamura (ISAS/JAXA)

Bad Pixel Correction Tool

10

badpix_corr, in_file=‘FIS_SW_**_img.sav’,[ func=‘’, /cube_fits ]BeforeAfter

Please check the fraction of the corrected pixels !!

11Image Combining Tool

ss_mosaic_image (previously known as ss_multi_scan_map2)
make wide/deep image map with combining the multi-scan data

Time series data
FIS_SW_1_pr.sav
FIS_SW_2_pr.sav。。。

ss_coad_image

Image data
FIS_SW_1_img.sav
FIS_SW_2_img.sav。。。

ss_mosaic_image
ss_mosaic_image, targetdir, [ SIGMA=sigma, T_START=t_start, T_END=t_end,
GRID_SW(LW) = grid_sw(LW), /cube_fits, tag_name=‘ * ‘, /no_display, /aot_mix
LON_CENTER = lon_center, LAT_CENTER = lat_center,
LON_SIZE = lon_size, LAT_SIZE = lat_size,
ECLIPTIC = ecliptic, GALACTIC = galactic,

12Color Correction Factor Tool

The FIS photometric flux is defined for a flat spectrum at thedefined central wavelength of each band.
→ Color correction is necessary.

color_corr, band, factor, bb=[temp,beta] or power=[alpha], [,/check]

Relative Response( N60=0, Wide-S=1, Wide-L=2, N160=3 )
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
40

80

120

160

Wavelength [um]200Aperture Photometry

13

Images are in brightness scale units of MJy/sr.
The absolute calibration has been done by
the zodiacal light for SW and IR cirrus for LW.

Aperture photometry should give the flux of the sources in Jy.
As the flux calibrator, 19 asteroids, 20 stars and 18 galaxies were observed.
The define of the sky area
SW = 2.25-3.25 [arcmin], LW = 3.00-4.00 [arcmin]

The results of aperture photometry are …

Aperture Correction Factor Tool
From this plot, we can get the aperture correction factor.
N60

WIDE-S

WIDE-L

N160

apfactor, band, radius[arcmin], factor, factor_error

14Aperture Photometry

15

Images are in brightness scale units of MJy/sr.
The absolute calibration has been done by
the zodiacal light for SW and IR cirrus for LW.

Aperture photometry should give the flux of the sources in Jy.
As the flux calibrator, 19 asteroids, 20 stars and 18 galaxies were observed.
The define of the sky area
SW = 2.25-3.25 [arcmin], LW = 3.00-4.00 [arcmin]

The results of aperture photometry are …
This aperture correction table may depend on
the grid size of image,
AOTs such as reset interval and scan speed,
the data reduction method (the option of the ss-tool),the sky area.
Note: The table of the current version is not well checked.
This table will be replaced in the near future.

Point source - Diffuse Factor
The measured flux is compared with the expected flux.
N60

WIDE-S

There are systematic differences.
This ratio seems to be constant.
( does not depend on the source flux, the source color. )16

Point source - Diffuse Factor
The measured flux is compared with the expected flux.
N60
WIDE-L

WIDE-S
N160

There are systematic differences.
This ratio seems to be constant.
( does not depend on the source flux, the source color. )17