def process_LST_files(self, modis_sd, lon, lat, view_zenith_angle):
        UNDEF = 0
        sds_name = {'lst':'LST_Day_1km', 'qc': 'QC_Day',
                    'view':'Day_view_time', 'angle':'Day_view_angl',
                    'lstnight': 'LST_Night_1km', 'qcnight': 'QC_Night', \
                    'viewnight':'Night_view_time',
                    'anglenight':'Night_view_angl' }

        data = dict(zip ( [var for var in sds_name.iterkeys()], \
                     [ modis_sd.select(layer).get() \
                     for layer in sds_name.itervalues ()] ))

        attributes = dict(zip ( [var for var in sds_name.iterkeys()], \
                     [ modis_sd.select(layer).get().attributes() \
                     for layer in sds_name.itervalues ()] ))

        lst = numpy.where ( numpy.logical_or ( \
                data['lst'] < attributes['lst']['valid_range'][0], \
                data['lst'] > attributes['lst']['valid_range'][1]), UNDEF,\
                data['lst']*attributes['lst']['scale_factor'] )

        lstnight = numpy.where ( numpy.logical_or ( \
                data['lstnight'] < attributes['lstnight']['valid_range'][0], \
                data['lstnight'] > attributes['lstnight']['valid_range'][1]), \
                UNDEF,\
                data['lstnight']*attributes['lstnight']['scale_factor'] )