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 were 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.

For some instruments, science-grade data products are created by QC Garching, using certified pipelines. Currently these are 1D spectral data products from UVES (Echelle mode), XSHOOTER (Echelle mode), and GIRAFFE (Medusa MOS modes). See the QC pages for those instruments for more information.

The isaac_img_jitter recipe generates up to three products:

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:

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.

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.

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 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.