CFHT, Instruments, Spectroscopy, ESPaDOnS

Upena, CFHT's reduction pipeline for
ESPaDOnS: an Echelle SpectroPolarimetric Device
for the Observation of Stars at CFHT

This page gives information relevant for the March 2008 run only. The first version of Upena, v0.1, was used in March. After March, Upena 1.0 is used, and is a little bit different than v0.1.

Upena v0.1 provides reduced data in FITS format only; a Linux tool (upena_LE_table) was developed to extract from the FITS file the ASCII table usually provided with Libre-ESpRIT, and take as input one FITS file at a time. All data for the March run has already been converted to the *.s format. Each FITS processed data is associated with 2 *.s files, with the same odometer number. One file has a 'n' in its name, for the reduction with the continuum normalized to 1; the other file has a 'u' in its name for the reduction done without any continuum normalization.

For example, the file 987123i.fits was converted to produce 987123in.s and 987123iu.s, and the file 912345p.fits produces 912345pn.s and 912345pu.s.

FITS format of reduced spectra [Back to Top]

To increase the legacy value of the reduced spectra produced by Libre-ESpRIT, FITS keywords are added to the file than contains the reduced data. The FITS keywords from the original raw FITS files are copied over. The reduced spectra with its continuum normalized to 1 follows; a few FITS keywords report on the reduction (see an example), and the table follows. The file ends with the reduced spectra with its continuum not normalized, again with FITS keywords and data.

The following Linux tool upena_read_table can be used to browse through a file, for example, by typing
upena_read_table 978123p.fits | more

Standard Libre-ESpRIT *.s file are also provided to PIs.

Data reduction for PIs [Back to Top]

The final reduction component re-reduces all the data with additional flats taken in the morning (if available), and performs the polarimetric calculations if appropriate. All data are reduced, whether the exposures were validated or not (except for the first 5 nights of the first run where the 4th exposure of a polarimetric sequence is useless); if Libre-ESpRIT can reduce an exposure, regardless of Image Quality or extinction by clouds, the exposures are reduced. All data are reduced with the continuum normalized to 1, and also not normalized; PIs do not need to make a special request regarding continuum normalization. In QSO mode, the only option available to PIs is to not use the telluric lines to correct the wavelengths (the w option); in that case, an additional set of reduced data will be provided to PIs. For Stokes U measurements, the sign of the Stokes parameter (column 3) needs to be flipped (inverted). A comment in the FITS header indicates this.

The naming scheme for the reduced files is the following: regardless of the Observing Mode used, each single FITS raw file (o.fits) produces one reduced FITS file named i.fits using the same odometer number as the original raw file. Both spectra, with the continuum normalized and not normalized, are found within that FITS file. If the Observing Mode is the polarimetric one, an additional FITS file is produced, named p.fits, with the odometer number used the number of the first polarimetric file of the sequence of 4.

The w option [Back to Top]

For PIs who have requested the w option, the additional set of spectra will be called j.fits (for spectroscopy) and r.fits (for polarimetry).

Files distributed and their content
FilenameRaw/ProcessedFile typeNote
x.fitsRawFocusNot needed by PIs
i.fitsProcessedIntensityContinuum normalised (first table) and not normalized (second table)
in.sProcessedIntensityLibre-ESpRIT format, continuum normalised to 1
iu.sProcessedIntensityLibre-ESpRIT format, continuum not (un) normalised
p.fitsProcessedPolarizationContinuum normalised (first table) and not normalized (second table)
pn.sProcessedPolarizationLibre-ESpRIT format, continuum normalised to 1
pu.sProcessedPolarizationLibre-ESpRIT format, continuum not (un) normalised
j.fitsProcessedIntensity with w optionContinuum normalised (first table) and not normalized (second table)
jn.sProcessedIntensity with w optionLibre-ESpRIT format, continuum normalised to 1
ju.sProcessedIntensity with w optionLibre-ESpRIT format, continuum not (un) normalised
r.fitsProcessedPolarization with w optionContinuum normalised (first table) and not normalized (second table)
rn.sProcessedPolarization with w optionLibre-ESpRIT format, continuum normalised to 1
ru.sProcessedPolarization with w optionLibre-ESpRIT format, continuum not (un) normalised
i/p/j/r.outoutput file from the Libre-ESpRIT reductionContains useful information on S/N ratios, radial velocity corrections, etc.
ffProcessedAverage flat field
th*.sProcessedComparison exposure (1D), not calibrated in wavelength
th*.wsProcessedComparison exposure (1D), calibrated in wavelength
geom*datgeometric calibration data
geom*outgeometric calibrations output file
wcal*datwavelength calibration data
wcal*outwavelength calibrations output file
This CFHT Web page is maintained by Nadine Manset (manset -=AT=-