Add 6dFGS loader

specutils/io/default_loaders/sixdfgs_reader.py

@@ -0,0 +1,63 @@
+import astropy.io.fits as fits
+from astropy.table import Table
+from astropy.units import Quantity, Unit
+from specutils.io.registers import data_loader
+from specutils import Spectrum1D
+
+SIXDFGS_PRIMARY_HDU_KEYWORDS = ["OBSRA", "OBSDEC", "Z", "Z_HELIO", "QUALITY"]
+COUNTS_PER_SECOND = Unit("counts/s", parse_strict="silent")
+
+
+def identify_6dfgs_tabular_fits(origin, *args, **kwargs):
+    """
+    Identify if the current file is a 6dFGS file (stored as a table)
+    """
+    with fits.open(args[0]) as hdulist:
+        if len(hdulist) != 2:
+            return False
+        primary_hdu = hdulist[0]
+        if primary_hdu.header["NAXIS"] != 0:
+            return False
+        for keyword in SIXDFGS_PRIMARY_HDU_KEYWORDS:
+            if keyword not in primary_hdu.header:
+                return False
+        return True
+
+
+@data_loader("6dFGS-tabular",
+             identifier=identify_6dfgs_tabular_fits,dtype=Spectrum1D,
+             extensions=["fit", "fits"])
+def sixdfgs_tabular_fits_loader(filename, **kwargs):
+    """
+    Load the tabular variant of a 6dF Galaxy Survey (6dFGS) file.
+
+    6dFGS used the Six-degree Field instrument on the UK Schmidt Telescope
+    (UKST) at the Siding Spring Observatory (SSO) near Coonabarabran,
+    Australia. Further details can be found at http://www.6dfgs.net/, or
+    https://docs.datacentral.org.au/6dfgs/. Catalogues and spectra were
+    produced, with the spectra being provided as both fits tables and as fits
+    images. This loads the tabular variant of the spectra. Note that this does
+    not include uncertainties - uncertainties are only provided in the image
+    variants.
+
+    Parameters
+    ----------
+    file_name: str
+        The path to the FITS file
+
+    Returns
+    -------
+    data: Spectrum1D
+        The 6dF spectrum that is represented by the data in this table.
+    """
+    with fits.open(filename) as hdulist:
+        header = hdulist[0].header
+        table = Table.read(hdulist)
+        flux = Quantity(table["FLUX"])
+        wavelength = Quantity(table["WAVE"])
+
+        if flux.unit == COUNTS_PER_SECOND:
+            flux._unit = Unit("count/s")
+        meta = {"header": header}
+
+        return Spectrum1D(flux=flux, spectral_axis=wavelength, meta=meta)

specutils/tests/test_loaders.py

@@ -490,3 +490,11 @@ def test_subaru_pfs_loader(tmpdir):
     assert len(spec.flux) == len(spec.spectral_axis) > 10000
     assert spec.spectral_axis.unit == u.nm
     assert spec.flux.unit == u.nJy
+
+
+@remote_access([{'id': '3733958', 'filename': '1D-c0022498-344732.fits'}])
+def test_spectrum1d_6dfgs_tabular(remote_data_path):
+    spec = Spectrum1D.read(remote_data_path)
+
+    assert spec.spectral_axis.unit == u.Unit("Angstrom")
+    assert spec.flux.unit == u.Unit("count/s")