code: def _get_header(self):
          
  
          earth_model = self.prologue['GeometricProcessing']['EarthModel']
          self.mda['offset_corrected'] = earth_model['TypeOfEarthModel'] == 2
  
          # Projection
          a, b = self.prologue_.get_earth_radii()
          self.mda['projection_parameters']['a'] = a
          self.mda['projection_parameters']['b'] = b
          ssp = self.prologue['ImageDescription'][
              'ProjectionDescription']['LongitudeOfSSP']
          self.mda['projection_parameters']['SSP_longitude'] = ssp
          self.mda['projection_parameters']['SSP_latitude'] = 0.0
  
          # Navigation
          actual_lon, actual_lat, actual_alt = self.prologue_.get_satpos()
          self.mda['navigation_parameters']['satellite_nominal_longitude'] = self.prologue['SatelliteStatus'][
              'SatelliteDefinition']['NominalLongitude']
          self.mda['navigation_parameters']['satellite_nominal_latitude'] = 0.0
          self.mda['navigation_parameters']['satellite_actual_longitude'] = actual_lon
          self.mda['navigation_parameters']['satellite_actual_latitude'] = actual_lat
          self.mda['navigation_parameters']['satellite_actual_altitude'] = actual_alt
  
          # Misc
          self.platform_id = self.prologue["SatelliteStatus"][
              "SatelliteDefinition"]["SatelliteId"]
          self.platform_name = "Meteosat-" + SATNUM[self.platform_id]
          self.mda['platform_name'] = self.platform_name
          service = self._filename_info['service']
          if service == '':
              self.mda['service'] = '0DEG'
          else:
              self.mda['service'] = service
          self.channel_name = CHANNEL_NAMES[self.mda['spectral_channel_id']]
docs: Read the header info, and fill the metadata dictionary