Merge pull request astropy#3528 from cgobat/main

ENH: SVO FPS - add method to easily retrieve filter metadata

Author: bsipocz

CHANGES.rst

@@ -41,6 +41,11 @@ mast
 Service fixes and enhancements
 ------------------------------
 
+svo_fps
+^^^^^^^
+
+- Add ``get_filter_metadata`` to allow retrieval of filter metadata. [#3528]
+
 heasarc
 ^^^^^^^
 - Add ``query_constraints`` to allow querying of different catalog columns. [#3403]

astroquery/svo_fps/core.py

@@ -108,6 +108,41 @@ def get_filter_index(self, wavelength_eff_min, wavelength_eff_max, **kwargs):
                 "succeed. Try increasing the timeout limit if a large range is needed."
             )
 
+    def get_filter_metadata(self, filter_id, *, cache=True, timeout=None):
+        """Get metadata/parameters for the requested Filter ID from SVO
+
+        Parameters
+        ----------
+        filter_id : str
+            Filter ID in the format SVO specifies it: 'facilty/instrument.filter'.
+            This is returned by `get_filter_list` and `get_filter_index` as the
+            ``filterID`` column.
+        cache : bool
+            Defaults to True. If set overrides global caching behavior.
+            See :ref:`caching documentation <astroquery_cache>`.
+        timeout : int
+            Timeout in seconds. If not specified, defaults to ``conf.timeout``.
+
+        Returns
+        -------
+        params : dict
+            Dictionary of VOTable PARAM names and values.
+        """
+        query = {'ID': filter_id, 'VERB': 0}
+        response = self._request("GET", self.SVO_MAIN_URL, params=query,
+                                 timeout=timeout or self.TIMEOUT,
+                                 cache=cache)
+        response.raise_for_status()
+        response_content = io.BytesIO(response.content)
+        votable = parse_single_table(response_content)
+        params = {}
+        for param in votable.iter_fields_and_params():
+            if param.unit is not None:
+                params[param.name] = param.value*param.unit
+            else:
+                params[param.name] = param.value
+        return params
+
     def get_transmission_data(self, filter_id, **kwargs):
         """Get transmission data for the requested Filter ID from SVO
 

astroquery/svo_fps/tests/test_svo_fps_remote.py

@@ -23,6 +23,16 @@ def test_get_transmission_data(self, test_filter_id):
         # Check if data is downloaded properly, with > 0 rows
         assert len(table) > 0
 
+    @pytest.mark.parametrize('test_filter_id',
+                             ['NewHorizons/MVIC.Blue', 'Palomar/ZTF.r'])
+    def test_get_filter_metadata(self, test_filter_id):
+        params = SvoFps.get_filter_metadata(test_filter_id)
+        # Check if expected keys are present
+        assert "WavelengthEff" in params
+        assert "ZeroPoint" in params
+        # Check existence and value of what should be a constant
+        assert params.get("FilterProfileService") == "ivo://svo/fps"
+
     @pytest.mark.parametrize('test_facility, test_instrument',
                              [('HST', 'WFPC2'), ('Keck', None)])
     def test_get_filter_list(self, test_facility, test_instrument):

docs/svo_fps/svo_fps.rst

@@ -173,6 +173,22 @@ These are the data needed to plot the transmission curve for filter:
 
    The 2MASS H-band transmission curve
 
+Get metadata for a specific filter
+----------------------------------
+
+Given a ``filterID``, a dictionary of metadata associated with that filter can be retrieved
+from the FPS using `~astroquery.svo_fps.SvoFpsClass.get_filter_metadata`:
+
+.. doctest-remote-data::
+
+    >>> info = SvoFps.get_filter_metadata('PAN-STARRS/PS1.r')
+    >>> print(info['WavelengthEff'])
+    6155.4659814728 Angstrom
+    >>> print(info['FWHM'])
+    1397.7332085088 Angstrom
+    >>> print(info['components'])
+    Filter + Instrument + Atmosphere
+
 
 Troubleshooting
 ===============