The APERO Data Reduction Software (DRS) for SPIRou data processing
Last update: April 22, 2024.

SPIRou science data are partially processed during the night by a specific version of the APERO Data Reduction Software (the "trigger") tailored to quickly extract the spectra for quantitave Quality Control during the night. After the morning calibrations, the full night (afternoon + morning calibrations + observations) is reprocessed with APERO to provide "quicklook" data (reduced data but not optimal, i.e. templates are not updated) within the next 12h after the end of the night. The raw files (labeled *o.fits for observation and *r.fits for ramp) are automatically archived at CADC. Products from the "quicklook" reduction are not, and PI are invited to download them from their Kealahou page The most relevant APERO DRS outputs are blended into packages (or products) *e.fits, *s.fits, *p.fits, *t.fits and *v.fits, and this last step also adds the QSO grades and comments given by the remote observer (RO) and the validation status of each odometer given by the queue coordinator (QC).

When a program is completed, or/and at the end of a semester, data are reprocessed to recalculate the templates (including all data since 18B) and provide the PI with the best possible telluric-corrected data and Radial Velocity. Those final reduced data appears in the Distribution section of Kealahou as well, and are also sent to CADC. SPIRou data are also re-processed and sent again to CADC after a new version of the APERO DRS is released by Montréal. The current DRS is v0.6.132 for the quicklook and 0.7.288 for the reduced data sent to CADC.

This page summarizes the steps of the processing and the content and format of the products.

SPIRou spectra are composed of 3 channels: two channels on science fibers labelled A and B and combined into an AB channel, and one channel on a reference fiber labelled C. The science fibers go from the Cassegrain Unit under the telescope to the SPIRou vessel in the Coude room. The reference fiber goes from the Calibration Unit in the slit room to the SPIRou vessel in the Coude room (both at the 3rd floor in the dome building). In addition, there is a calibration fiber going from the Calibration Unit to the Cassegrain Unit to inject calibration lamps (flat-field, Fabry-Perot) to the science channels for calibration purposes.

Darks and bad pixels from images of the non-illuminated spectrograph, the pipeline generates a master dark 2D image and a bad-pixel map
Order localization from flatfield images, the pipeline identifies the precise position of all 49 orders and stores it into "loco" files
Blaze function from flatfield images, the pipeline computes the blaze function of each order and stores it into "blaze" files
Instrumental Profile from Fabry-Perot images, the pipeline modelizes the instrumental profiles, or "shape" of the pseudo-slit, at all locations in the spectrum and stores it into "tilt" and "shape" files
Wavelength Calibration from Fabry-Perot and Hollow-Cathod images, the pipeline produces a wavelength map "wave" for each fiber
Science Observations (Detailes information in Data Products: File Structure )
e files 2D extracted spectra that use the instrument profile and order localization and performs optimal extraction.
s files FITS table containing the 1D extracted and rebinned spectra, for each channel (AB, A, B, C).
p files Polarimetric products are data packages only processed in polarimetric mode, from the combination of 4 consecutive exposures.
t files 2D spectra in the same format than e spectra, after the correction of telluric lines has been applied.
v files FITS table containing the radial velocity of the star extracted from the CCF.
Some keywords explained (in main or in extension headers)
DPRTYPE Type of exposure configuration (OBJ_FP or OBJ_DARK means there is a star on channels A and B and a Fabry-Perot or Dark on channel C)
TRG_TYPE Type of science exposure: object or sky
EXTNAME Name of the extension (A, B, AB or C)
CRVAL1 Value of the first wavelength bin in nm for s files
CDELT1 Bin size in nm for the s files (typically 0.005nm)
NAXIS1 Number of data points in the s files, per extension
WAVEFILE Name of the relevant wavelength solution file for e, t, and p files
OBJECT Target name
DATE-OBS UT date of the exposure, in the format yyyy-mm-dd
UTC-OBS UT hour corresponding to the start of the exposure in
MJD-OBS Modified Julian Date at start of observation
EXPTIME Exposure time in seconds
SPOZPMED Median of zero point absorption from SkyProbe during the exposure (optical band, in magnitude)
SGCSEE Seeing measured during acquisition (not always) (")
SGSSEE Seeing estimated on guide images with star in the hole (")
SBRHB1_P Rhomb position in drawer 1
SBRHB2_P Rhomb position in drawer 2
EXTSN034 S/N per pixel in DRS order 34 (1.65mic) (the keyword in DRS 0.5 or older versions was SNR34)
SPEMSNR S/N at 1.65mic measured by the exposuremeter at the end of the exposure
SGCMAGN Magnitude estimated on the guide images with star in the hole
BJD Barycentric Julian Date (in processed files)
BERV Barycentric Earth Radial Velocity (km/s)
CCFRV Raw Stellar Radial Velocity in channel AB (km/s)
WFPDRIFT Drift of the input Fabry-Perot with respect to the FP mask (computed by cal_WAVE) (km/s)
RVDRIFT Drift between the wavelength solution and the stellar spectrum (computed by cal_CCF) (km/s)
CCFRVC Stellar Radial Velocity on channel AB, corrected from the instrumental drift (km/s)
CCFFWHM Full width half maximum of stellar cross correlation function on channel AB (km/s)
CCFCONT Contrast of stellar cross correlation function on channel AB
CCFLINE Number of lines used in the cross correlation with the stellar mask (for AB fibers) or the FP mask (for C fiber)
DVRMS RV photon noise uncertainty on the stellar spectrum (for AB fibers) or the FP spectrum (for C fiber) (computed by cal_CCF)