GR1 – Pipeline and advanced data description
3. Spectral Data Product Files
5. Primary Object Catalog - Merged FUV+NUV
Catalog (mcat file)
1. Pipeline Overview
The GALEX data pipeline converts GALEX satellite telemetry data and any necessary corollary data into calibrated images, spectra, and catalogs. The GALEX Science Operations Center (SOC) receives satellite telemetry data and ingestpipe unpacks it into time-tagged photon lists, instrument/SC housekeeping, and satellite aspect information. From these data sets, orbpipe generates images, spectra, and source catalogs.
Astrometric modules rta (for rectify, transform and aspect) and deltaphot correct the photon positions for detector and optical distortions, and determine an aspect solution using star positions from the time-tagged photon data. The astrometric refinement process is diagrammed below.
A photometric module simplemap accumulates the photons into count and intensity maps and sextra extracts sources from images. A spectroscopic module galexspac uses image source catalog inputs to extract spectra of these sources from the multiple slitless grism observations.
2. Pipeline Products
Data from
each single-orbit visit stored in a single directory in the GALEX file system.
The directory path has the following format:
<ROOT>/<proc ver>/<tile>/<obs
mode>/<product>/<image>/<try>/.
An example
path and filename is:
Path:
<root>/01-vsn/10330-AISCHV2_381_40554/d/00-visits/0002-img/03-try/
Filename: AISCHV2_381_40554_0002_sv12-xd-mcat.fits
This path
contains the pipeline processing version number, a tile identification string,
instrument observing mode (direct, grism, opaque; represented by d, g, o,
in each case preceded by the wavelength, data product type (single visit,
multiple visit), and the pipeline processing try. Additionally, a unique source
ID tag is generated by the pipeline that uniquely encodes both the path
information and the source number from merged source and spectra catalogs.
All of the
pipeline products are described in the table below.
Table 3.1– Pipeline Products Summary (the most significant files are in
bold)
|
Filename Suffix |
File type |
Description |
|
Low-level pipeline products |
|
Photon and housekeeping files |
|
-asp.rec |
Binary record |
Satellite
attitude solution. Raw S/C pointing data. |
|
-asprta.rec |
Binary record |
Refined
spacecraft attitude solution (using bright stars in the FOV). |
|
-rtastar.fits |
FITS binary
table |
Star catalog for
attitude refinement: info. on stars used for S/C
pointing solution vs. time. |
|
-scst.fits |
FITS binary
table |
Spacecraft
state file: S/C status values. |
|
Images |
|
Maps and associated files |
|
-[n or f][d
or g]-cnt.fits |
FITS image |
Count map
(J2000) in counts (photons) per pixel, corrected for image position and
dither. |
|
-[n or f][d
or g]-exp.fits |
FITS image |
Exposure map
(J2000). An image of time spent observing within the GALEX FOV (w/o response
correction). |
|
-[n or f][d or
g]-intbgsub.fits |
FITS image |
Background-subtracted
intensity map (J2000). Note: "-intbgsub"
equals "-int" minus "-skybg". |
|
-[n or f][d or g]-int.fits |
FITS image |
Intensity map (J2000). GALEX FOV image in
counts per sec. per pixel, corrected for relative response. |
|
-[n or f][d
or g]-movie.fits |
FITS image
cube |
Time-slice
count maps (J2000). Multiple images of the raw detector within selected
segments of time (not corrected for S/C motion). |
|
-[n or f][d
or g]-rr.fits |
FITS image |
Low
resolution relative response (J2000). A low resolution version of "rrhr". (Provided only for rrhr and beyond.) |
|
-[n or f][d
or g]-skybg.fits |
FITS image |
Sky
background image (J2000). |
|
-[n or f][d
or g]-wt.fits |
FITS image |
Weight/threshold
image (J2000). FOV image used by Sextractor for thresholding sources. Pixels
with values > 1 have a flux above the detection threshold. |
|
Grism-specific files |
|
Spectral 1-D arrays or 2-D images |
|
-[n or f]g-gsax.fits |
FITS binary table |
Spectral extraction
parameter information for each source |
|
-[n or f]g-pri.fits |
FITS binary table |
Image strips for each
source from a single visit |
|
-[n or f]g-prc.fits |
FITS binary table |
Image strips (combined) for
each source from multiple visits |
|
-[n or f]g-prm.fits |
FITS binary table |
Image strips (median) for
each source from multiple visits |
|
-[n or f]g-gsp.fits |
FITS binary table |
Spectral data for each
extracted source vs. wavelength |
|
-xg-gsp.fits |
FITS binary table |
Spectral data for each
extracted source vs. wavelength (both bands) |
|
Quality assurance (QA) |
|
QA file description |
|
-x[d or g]-int_2color*.jpg |
FITS binary table |
JPEG images of the field. |
|
*.ps |
postscript text |
Various postscript plots. |
|
-[n or f]d-dphcent.txt |
ASCII text |
Aspect refinement QA data . |
|
-[n or f]d-gauss*.txt |
ASCII text |
Gaussian filter used by
Sextractor. |
|
-[n or f]d-sexcols.txt |
ASCII text |
Sextractor catalog columns. |
|
-[n or f]d-sexparams.txt |
ASCII text |
Parameter file used by
Sextractor. |
|
-[n or f]d-sexnnw.txt |
ASCII text |
Neural network parameter
file used by Sextractor. |
|
*stats.txt |
ASCII text |
Various QA statistics. |
|
-[n or f]d-cat.ds9reg |
ASCII text |
ds9 region file: ellipses of sources listed in the -[n
or f] d-c at.fits file. [Note: a ds9 region file is
a file of ellipse parameters used by the image viewing program "DS9". These parameters include the RA, Dec, major and
minor axes and position angle of the major axis.] |
|
-fd-ncat.ds9reg |
ASCII text |
ds9 region file: ellipses of sources listed in the -fd-ncat. fit s file. |
|
-nd-fcat.ds9reg |
ASCII text |
ds9 region file: ellipses of sources listed in the -nd-fcat. fit s file. |
|
_getmask-[n
or f]d-cat.ds9reg |
ASCII text |
ds9 region file: Objects ignored in estimating
background flux. |
|
rtastar.ds9reg |
ASCII text |
ds9 region file: ellipses of bright stars from rtastar.fit s file used in the attitude solution (aspect
correction). |
|
Catalogs |
|
FUV, NUV and merged catalogs |
|
-[n or f]d-cat.fits |
FITS binary table |
Sextractor catalogs for
images. Table of objects extracted by GALEX reduction pipeline. The table
contains positions, flux, magnitude, and major/minor axes. |
|
-[n or f]d-[f or n]cat.fits |
FITS binary table |
NUV (FUV) extractions using
FUV (NUV) positions; the latter are taken from the FUV (NUV) source catalog
"fd |
|
-xd-mcat.fits |
FITS binary table |
Merged source catalog. Band-merged table
of extracted objects. Contains all objects contained in "[n or f]d-cat.fits" matched to the
best candidate. The table contains positions, flux, magnitude, and
major/minor axes. By definition, it contains all data from the two
single-band catalogs. |
|
Flags |
|
Artifact flag information |
|
-[n or f][d or g]-flags.fits
|
FITS image |
Artifact Flag image (J2000). Identifies
predetermined regions which may introduce systematic errors in data
extraction. These artifact regions are caused mainly by reflections of nearby
bright stars. |
|
-[n or f]d-flagstar.fits
|
FITS binary table |
Star catalog for flagging. List of known
bright stars used to determine artifact regions. |
3. Spectral Data Product Files
The
spectral data product files are stored in binary FITS format, but they are
GALEX-specific. The formats of these files are described below:
-pri.fits
This file contains the image strips for individual exposures for each spectral-extracted source. The photon data, response, and masking images are recorded for each source. Masking for the image strip is stored in the response image (neighbor masking) and the photon data image (other masking) as negative numbers. Spectral response variations with position (column) are stored in the response image in the final row. These images contain the total accumulated photon dat