first prototype API implementation

models.py

@@ -75,6 +75,9 @@ class GaiaSource(models.Model):
 
     healpix_nested_index = models.BigIntegerField(null=True, blank=True)
 
+    #healpix_nside = models.IntegerField(null=True, blank=True)
+    #additional field storing nside value
+
 
 
 

serializers.py

@@ -4,4 +4,4 @@ from .models import GaiaSource
 class GaiaSourceSerializer(serializers.ModelSerializer):
     class Meta:
         model = GaiaSource
-        fields = '__all__'
+        fields = ['uuid', 'ra', 'dec']

views.py

@@ -1,14 +1,58 @@
 from rest_framework.views import APIView
 from rest_framework.response import Response
 from rest_framework import status
+
 from .models import GaiaSource
 from .serializers import GaiaSourceSerializer
 
+import numpy as np
+import healpy as hp
+from astropy.coordinates import SkyCoord
+from astropy import units as u
+
+
 class ConeSearchView(APIView):
+
     def get(self, request, ra, dec, radius):
         radius = float(radius)
-        ra = radians(float(ra))
+        ra = float(ra)
-        dec = radians(float(dec))
+        dec = float(dec)
-        objects = GaiaSource.objects.all()
+        nside = 2048
-        result = []
+
+        center = SkyCoord(ra=ra*u.deg, dec=dec*u.deg, frame='icrs')
+
+        #fetch healpix indices in the specified disc
+        healpix_indices = get_healpix_indices(ra, dec, radius, nside)
+        #fetch all objects from those healpixes
+        objects = GaiaSource.objects.filter(healpix_ring_index__in=healpix_indices)
+
+        results = []
+
+        for obj in objects:
+            
+            source_coordinates = SkyCoord(
+                ra=obj.ra*u.deg, 
+                dec=obj.dec*u.deg, 
+                frame='icrs'
+            )
+            
+            separation = center.separation(source_coordinates)
+
+            if separation <= radius:
+
+                results.append(obj)           
+
+        serializer = GaiaSourceSerializer(results, many=True)
+
+        return Response(serializer.data, status=status.HTTP_200_OK)
+
+    def get_healpix_indices(ra, dec, radius, nside):
+        # Convert the input coordinates to a SkyCoord object
+        center = SkyCoord(ra=ra*u.deg, dec=dec*u.deg, frame='icrs')
+        # Convert the center coordinates to HEALPix vector
+        vec = hp.ang2vec(center.ra.deg, center.dec.deg, lonlat=True)        
+        # Find the pixels within the given radius
+        indices = hp.query_disc(nside, vec, np.radians(radius))        
+        return indices
+