code: def get_geostationary_mask(area):
      
      # Compute projection coordinates at the earth's limb
      h = area.proj_dict['h']
      xmax, ymax = get_geostationary_angle_extent(area)
      xmax *= h
      ymax *= h
  
      # Compute projection coordinates at the centre of each pixel
      x, y = area.get_proj_coords_dask()
  
      # Compute mask of the earth's elliptical shape
      return ((x / xmax) ** 2 + (y / ymax) ** 2) <= 1
docs: Compute a mask of the earth's shape as seen by a geostationary satellite
  
      Args:
          area (pyresample.geometry.AreaDefinition) : Corresponding area
                                                      definition
  
      Returns:
          Boolean mask, True inside the earth's shape, False outside.