Add get_zeropoint and more flexible metadata querying to SVO FPS

CHANGES.rst

@@ -94,6 +94,7 @@ svo_fps
 ^^^^^^^
 
 - Add ``get_filter_metadata`` to allow retrieval of filter metadata. [#3528]
+- Add ``get_zeropoint`` to allow retrieval of filter zeropoints and allow kwarg passing to ``get_filter_metadata``. [#3545]
 
 heasarc
 ^^^^^^^

astroquery/svo_fps/core.py

@@ -108,7 +108,7 @@ 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):
+    def get_filter_metadata(self, filter_id, *, cache=True, timeout=None, **kwargs):
         """Get metadata/parameters for the requested Filter ID from SVO
 
         Parameters
@@ -122,13 +122,26 @@ def get_filter_metadata(self, filter_id, *, cache=True, timeout=None):
             See :ref:`caching documentation <astroquery_cache>`.
         timeout : int
             Timeout in seconds. If not specified, defaults to ``conf.timeout``.
+        kwargs : dict
+            Appended to the ``query`` dictionary sent to SVO.
 
         Returns
         -------
         params : dict
             Dictionary of VOTable PARAM names and values.
         """
         query = {'ID': filter_id, 'VERB': 0}
+        query.update(kwargs)
+
+        bad_params = [param for param in query if param not in QUERY_PARAMETERS]
+        if bad_params:
+            raise InvalidQueryError(
+                f"parameter{'s' if len(bad_params) > 1 else ''} "
+                f"{', '.join(bad_params)} {'are' if len(bad_params) > 1 else 'is'} "
+                f"invalid. For a description of valid query parameters see "
+                "https://svo2.cab.inta-csic.es/theory/fps/index.php?mode=voservice"
+            )
+
         response = self._request("GET", self.SVO_MAIN_URL, params=query,
                                  timeout=timeout or self.TIMEOUT,
                                  cache=cache)
@@ -143,6 +156,53 @@ def get_filter_metadata(self, filter_id, *, cache=True, timeout=None):
                 params[param.name] = param.value
         return params
 
+    def get_zeropoint(self, filter_id, mag_system='Vega', **kwargs):
+        """
+        Get the zero point for a specififed filter in a specified system.
+
+        This is a highly-specific downselection of the metadata returned by
+        `get_filter_metadata`; the full metadata includes the zero point with
+        ``Vega`` as the default system.
+
+        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.
+        mag_system : str
+            The magnitude system for which to return the zero point.
+        kwargs : dict
+            Appended to the ``query`` dictionary sent to SVO.
+
+        Examples
+        --------
+        >>> from astroquery.svo_fps import SvoFps  # doctest: +REMOTE_DATA
+        >>> SvoFps.get_zeropoint(filter_id='2MASS/2MASS.J', mag_system='AB')  # doctest: +REMOTE_DATA
+        {'MagSys': 'AB',
+         'ZeroPoint': <Quantity 3631. Jy>,
+         'ZeroPointUnit': 'Jy',
+         'ZeroPointType': 'Pogson'}
+        >>> SvoFps.get_filter_metadata(filter_id='2MASS/2MASS.J', PhotCalID='2MASS/2MASS.J/AB')  # doctest: +REMOTE_DATA
+        {'FilterProfileService': 'ivo://svo/fps',
+         'filterID': '2MASS/2MASS.J',
+         ...
+         'PhotCalID': '2MASS/2MASS.J/AB',
+         'MagSys': 'AB',
+         'ZeroPoint': <Quantity 3631. Jy>,
+         'ZeroPointUnit': 'Jy',
+         'ZeroPointType': 'Pogson'}
+
+        """
+        metadata = self.get_filter_metadata(filter_id=filter_id,
+                                            PhotCalID=f'{filter_id}/{mag_system}', **kwargs)
+
+        zeropoint_keys = ['MagSys', 'ZeroPoint', 'ZeroPointUnit', 'ZeroPointType']
+
+        zp = {key: metadata[key] for key in zeropoint_keys if key in metadata}
+
+        return zp
+
     def get_transmission_data(self, filter_id, **kwargs):
         """Get transmission data for the requested Filter ID from SVO
 

astroquery/svo_fps/tests/data/svo_fps_PhotCalID=2MASS.2MASS.H.Vega.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0"?>
+<VOTABLE version="1.1" xsi:schemaLocation="http://www.ivoa.net/xml/VOTable/v1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <INFO name="QUERY_STATUS" value="OK"/>
+  <RESOURCE type="results">
+    <TABLE utype="photdm:PhotometryFilter.transmissionCurve.spectrum">
+    <PARAM name="FilterProfileService" value="ivo://svo/fps" ucd="meta.ref.ivorn" utype="PhotometryFilter.fpsIdentifier" datatype="char" arraysize="*"/>
+    <PARAM name="filterID" value="2MASS/2MASS.H" ucd="meta.id" utype="photdm:PhotometryFilter.identifier" datatype="char" arraysize="*"/>
+    <PARAM name="WavelengthUnit" value="Angstrom" ucd="meta.unit" utype="PhotometryFilter.SpectralAxis.unit" datatype="char" arraysize="*"/>
+    <PARAM name="Description" value="2MASS H" ucd="meta.note" utype="photdm:PhotometryFilter.description" datatype="char" arraysize="*"/>
+    <PARAM name="WavelengthEff" value="16620" unit="Angstrom" ucd="em.wl.effective" datatype="float" >
+       <DESCRIPTION>Manually specified. See reference</DESCRIPTION>
+    </PARAM>
+    <PARAM name="ZeroPoint" value="1024" unit="Jy" ucd="phot.flux.density" utype="photdm:PhotCal.ZeroPoint.Flux.value" datatype="float" />
+    <PARAM name="PhotCalID" value="2MASS/2MASS.H/Vega" ucd="meta.id" utype="photdm:PhotCal.identifier" datatype="char" arraysize="*"/>
+    <PARAM name="MagSys" value="Vega" ucd="meta.code" utype="photdm:PhotCal.MagnitudeSystem.type" datatype="char" arraysize="*"/>
+    <PARAM name="ZeroPointUnit" value="Jy" ucd="meta.unit" utype="photdm:PhotCal.ZeroPoint.Flux.unit" datatype="char" arraysize="*"/>
+    <PARAM name="ZeroPointType" value="Pogson" ucd="meta.code" utype="photdm:PhotCal.ZeroPoint.type" datatype="char" arraysize="*"/>
+      <DATA>
+        <TABLEDATA>
+        </TABLEDATA>
+      </DATA>
+    </TABLE>
+  </RESOURCE>
+</VOTABLE>

astroquery/svo_fps/tests/test_svo_fps.py

@@ -9,12 +9,14 @@
 
 DATA_FILES = {'filter_index': 'svo_fps_WavelengthEff_min=12000_WavelengthEff_max=12100.xml',
               'transmission_data': 'svo_fps_ID=2MASS.2MASS.H.xml',
-              'filter_list': 'svo_fps_Facility=Keck_Instrument=NIRC2.xml'
+              'filter_list': 'svo_fps_Facility=Keck_Instrument=NIRC2.xml',
+              'zeropoint': 'svo_fps_PhotCalID=2MASS.2MASS.H.Vega.xml',
               }
 TEST_LAMBDA = 12000
 TEST_FILTER_ID = '2MASS/2MASS.H'
 TEST_FACILITY = 'Keck'
 TEST_INSTRUMENT = 'NIRC2'
+TEST_MAG_SYSTEM = 'Vega'
 
 
 def data_path(filename):
@@ -35,6 +37,10 @@ def get_mockreturn(method, url, params=None, timeout=10, cache=None, **kwargs):
         and (params['WavelengthEff_min'] == TEST_LAMBDA
              and params['WavelengthEff_max'] == TEST_LAMBDA+100)):
         filename = data_path(DATA_FILES['filter_index'])
+    elif ('PhotCalID' in params
+          and params.get('ID') == TEST_FILTER_ID
+          and params['PhotCalID'] == f'{TEST_FILTER_ID}/{TEST_MAG_SYSTEM}'):
+        filename = data_path(DATA_FILES['zeropoint'])
     elif 'ID' in params and params['ID'] == TEST_FILTER_ID:
         filename = data_path(DATA_FILES['filter_index'])
     elif 'Facility' in params and (params['Facility'] == TEST_FACILITY
@@ -84,6 +90,17 @@ def test_get_filter_list(patch_get):
     assert 'filterID' in table.colnames
 
 
+def test_get_zeropoint(patch_get):
+    zp = SvoFps.get_zeropoint(TEST_FILTER_ID, mag_system=TEST_MAG_SYSTEM)
+    assert 'ZeroPoint' in zp
+    assert 'MagSys' in zp
+    assert zp['MagSys'] == TEST_MAG_SYSTEM
+    assert 'ZeroPointType' in zp
+    assert zp['ZeroPointType'] == 'Pogson'
+    assert 'ZeroPointUnit' in zp
+    assert zp['ZeroPoint'].unit == u.Jy
+
+
 def test_invalid_query(patch_get):
     msg = r"^parameter bad_param is invalid\. For a description of valid query "
     with pytest.raises(InvalidQueryError, match=msg):

astroquery/svo_fps/tests/test_svo_fps_remote.py

@@ -40,6 +40,23 @@ def test_get_filter_list(self, test_facility, test_instrument):
         # Check if column for Filter ID (named 'filterID') exists in table
         assert 'filterID' in table.colnames
 
+    @pytest.mark.parametrize('test_filter_id, mag_system, expected_zp_jy', [
+        ('2MASS/2MASS.J', 'Vega', 1594.0),
+        ('2MASS/2MASS.J', 'AB', 3631.0),
+    ])
+    def test_get_zeropoint(self, test_filter_id, mag_system, expected_zp_jy):
+        zp = SvoFps.get_zeropoint(test_filter_id, mag_system=mag_system)
+        # Check all expected keys are present
+        assert 'ZeroPoint' in zp
+        assert 'MagSys' in zp
+        assert 'ZeroPointType' in zp
+        assert 'ZeroPointUnit' in zp
+        # Check the magnitude system matches what was requested
+        assert zp['MagSys'] == mag_system
+        # Check zero point has the right unit and an approximately correct value
+        assert zp['ZeroPoint'].unit == u.Jy
+        assert abs(zp['ZeroPoint'].value - expected_zp_jy) < 10.0
+
     def test_query_parameter_names(self):
         # Checks if `QUERY_PARAMETERS` is up to date.
         query = {"FORMAT": "metadata"}