[ ESO ]
ISAAC data reduction:
SCIENCE

CAL | HC | refs | QC
QUALITY CONTROL
    HOME
ISAAC QC
Trending & QC1
Pipeline
science recipe
Data Packages
Data Management
QC links:

SCIENCE DATA: GENERAL

On Paranal, the quick-look pipelines make an effort to automatically reduce all science data. The reduction is performed using standard calibration solutions from a local calibration database which is refreshed every few months. Generally any pipeline processing on the site is done on a best-effort basis. Its purpose is to offer a quick look to assess data quality etc.

Until the end of P87 (September 2011) science data have been processed by QC Garching with the best possible (certified) calibrations solutions. The products were ingested into the Science Archive and delivered to the PIs.

This service has been terminated with the begin of October 2011. The documentation of science pipelines and science processing is kept here for its heritage value.

SW-arm Imaging

The isaac_img_jitter recipe generates up to three products:

product name (initial tag) PRO.CATG key of product header contents
IS_SICO COADDED_IMG coadded FITS image
IS_SISO STARS_TAB sources in FITS binary table
IS_SISK SKY_TAB sky background in FITS binary table

 

[dark.gif  11K]
SW-arm imaging coadded product frame. The frame size is slightly larger as the the product has to cover a slightly larger sky area due to the jittering process.

This is an example content of a SKY_TAB product table. It shows the background counts in ADU per DIT seconds:

#
# file IS_SISK_240387_2005-02-11T03:40:13.891_SW_H.fits
# extensions 1
# --------------------------------------------
# XTENSION 1
# Number of columns 1
#
SKY_BG
4353.74
4447.24
4307.01
4341.57

This is an example content of a STARS_TAB product table:

#
# file IS_SISO_70395_2006-05-10T04:27:30.988_SW_NB_2.17.fits
# extensions 1
# --------------------------------------------
# XTENSION 1
# Number of columns 6
#
POS_X| POS_Y| ANGLE| FWHM_X| FWHM_Y| FLUX
1007.7| 96.3837| 9.76815| 4.49523| 3.71883| 9093.82
454.643| 110.846| 0| -1| -1| 1448.34
476.834| 180.978| 28.9681| 7.26331| 6.60469|4.95742e+06
489.013| 112.506| 0| -1| -1| 1001.13
401.001| 137.484| 0| -1| -1| 923.121
545.995| 139.007| 0| -1| -1| 693.24
389.979| 166.984| 0| -1| -1| 700.403
784.893| 241.222| 69.5253| 4.54863| 4.34523| 3286.78
901.184| 245.256| 134.869| 4.50522| 4.37173| 34278.9
1038.01| 262.009| 135.65| 4.82963| 4.44506| 1811.19
1137.6| 265.276| 33.8716| 4.05375| 3.76971| 2422.61
434.997| 278.061| 100.284| 6.43639| 4.22124| 732.222
452.178| 292.528| 26.8923| 6.98672| 6.08689| 7483.65
288.96| 293.053| 19.4924| 5.12456| 4.27329| 920.592
755.098| 369.108| 21.4633| 4.49043| 4.35307| 77735.9
868.97| 444.822| 4.96305| 4.49162| 4.26747| 104712
...

Th columns show the the source positions in pixels (POS_X, POS_Y), the results of fitting an elliptical shape to the source (ANGLE, FWHM_X, FWHM_Y with the meaning of major and minor elliptical axis) and the source flux inADU.

SW-arm Spectroscopy

The isaac_spc_jitter recipe generates up to two products:

product name (initial tag) PRO.CATG key of product header contents
IS_SCOM OBS_COMBINED coadded FITS image of the long slit spectrum
IS_SEXT OBS_EXTRACTED extracted spectrum in FITS binary table

[sitf.gif 14K]

SW-arm coadded spectrum product frame.For a simple observing strategy with the source being acquired on two different nodding positions A and B on the slit, the recipe generates two difference frames diff1 = A minus B and diff2 = B minus A.Both difference frames are aligned and coadded. The central bright spectrum is essentially the A plus B spectrum. The two black horizontal spectra in the left image are the negative imprint spectra of A and B respectively.

 

 

 

This is an example content of an OBS_EXTRACTED product:

#
# file IS_SEXT_266612_2001-11-08T09:54:20.456_SW_MR_SK_2.134_sl03t.fits
# extensions 1
# --------------------------------------------
# XTENSION 1
# Number of columns 3
#
X_coordinate|Extracted_spectrum_value|Sky_spectrum
20685.7| 0| 0
20686.9| 0| 0
20688.1| 2364.84| 2.98759
20689.3| 2013.1| 0.788032
20690.6| 1705.35| 1.16699
20691.8| 2119.53| 2.32681
20693| 2652.3| 1.3368
20694.2| 2815.2| 1.74892
20695.5| 2631.1| 1.90716
20696.7| 2164.52| 1.26565
20697.9| 1805.43| 1.69255
20699.1| 2093.04| 1.98858
20700.4| 2626.42| 1.81075
...

     21936.8|                  3511.1|     4.28955
21938| 3538.28| -0.375876
21939.2| 3550.47| 2.39982
21940.4| 3615.17| 2.46907
21941.7| 3673.1| 1.74935
21942.9| 3688.68| 1.6872
21944.1| 3642.75| 5.79523
21945.3| 0| 0
21946.5| 0| 0

Important:
The --wavecal=std option is an important operational change. While ISAAC products (telluric standard stars and science spectra) taken in 2005 and earlier were wavelength calibrated using the day-time arc frames, observations taken in 2006 and later are calibrated using the imprinted sky emission lines. The advantage is, that the low grating position reproducibility (= unavoidable grating offsets between night-time observations and day-time calibrations) does no longer impact the dispersion solution. The drawback is, that standard stars as bright sources with low DIT values show only faint sky lines, hence the dispersion solution might become not quite accurate. The cross-correlation value of the dispersion solution should be higher than 45%. Spectroscopic science products with higher discrete integration times and hence stronger sky emission lines are less affected by low quality dispersion solutions.
LW-arm spectra use day-time calibration arc lamp frames; no air glow sky emission atlas is available for the L and M band.

 

LW-arm Imaging

Imaging Observations in the LW-arm can be done in jitter mode or in chopping dependent on the wave band. In chopping mode there are essentially only two observation positions: the two chopping positions.

[dark.gif  11K]
LW imaging using chopping mode: The final coadded image shows the combined source in the center with two adjacent negative images of the source, each one corresponds to one of both chopping sources.

The STARS_TAB product in chopping mode is the same as for jitter mode. In chopping, no SKY_TAB product is generated. QC reports for chopping mode are the same as for jitter mode. See SW-imaging

 

LW-arm Spectroscopy

[sitf.gif 14K]

LW-arm chopping mode coadded spectrum product frame.For a simple observing strategy with the source being acquired on two different chopping positions A and B on the slit, the recipe generates two difference frames diff1 = A minus B and diff2 = B minus A.Both difference frames are aligned and coadded. The central bright spectrum is essentially A plus B spectrum. The two black horizontal spectra in the left image are the negative intensity spectra of A and B respectively.

 

 

 

Important:

As there are no air glow sky emission line atlas available for the L and M band science and telluric standard star spectra taken in these bands are wavelength calibrated using the day-time arcs frames

The SKY_TAB and STARS_TAB products are the same as for SW-arm spectroscopy.


 
[ESO][Index][Search][Help][News]