diff --git a/CAL/CalibrationCommon/lib/datacontainers/holography_dataset.py b/CAL/CalibrationCommon/lib/datacontainers/holography_dataset.py
index d5466f8d4ffd0e8f8c9b8fd56b04f4be0ea96ef0..f2af02ac5253b6fb722bf9dba87dcc6c756de6ee 100644
--- a/CAL/CalibrationCommon/lib/datacontainers/holography_dataset.py
+++ b/CAL/CalibrationCommon/lib/datacontainers/holography_dataset.py
@@ -10,12 +10,23 @@ logger = logging.getLogger(__name__)
 
 class HolographyDataset():
     def __init__(self):
-        self.version = HOLOGRAPHY_DATA_SET_VERSION  # float, HDS version
-        self.rcu_list = list()  # list of ints
-        self.mode = None  # integer
-        self.sas_ids = list()  # list of strings
-        self.target_station_name = None  # string
-        self.target_station_position = None  # list of 3 floats
+        # float, HDS version
+        self.version = HOLOGRAPHY_DATA_SET_VERSION
+
+        # list of ints
+        self.rcu_list = list()
+
+        # integer
+        self.mode = None
+
+        # list of strings
+        self.sas_ids = list()
+
+        # string
+        self.target_station_name = None
+
+        # list of 3 floats
+        self.target_station_position = None
         self.source_name = None  # string
         self.source_position = None  # list of 3 floats
         self.start_time = None  # date time when the observation started in MJD in seconds (float)
@@ -23,17 +34,18 @@ class HolographyDataset():
         self.rotation_matrix = None  # array(3,3), translation matrix for
         # (RA, DEC) <-> (l, m) conversion
 
-        self.beamlets = None # list of beamlet numbers
-        self.antenna_field_position = []  # coordinates of the antenna position in the target
+        self.beamlets = list() # list of beamlet numbers
+        # coordinates of the antenna position in the target
+        self.antenna_field_position = []
         # station
         self.reference_stations = list()  # list of reference station names
         self.frequencies = list()  # list of frequencies
-        self.ra_dec = None # array(Nfrequency, Nbeamlets) contains the ra_dec of which a beam
+        self.ra_dec = dict() # array(Nfrequency, Nbeamlets) contains the ra_dec of which a beam
         # points at given a frequency and a beamlet number
         # numpy.dtype([('RA', numpy.float64),
         #              ('DEC',numpy.float64),
         #              ('EPOCH', 'S10')]) 
-        self.data = None # array(NreferenceStations, Nfrequencies, Nbeamlets) that contains the
+        self.data = dict() # array(NreferenceStations, Nfrequencies, Nbeamlets) that contains the
         # 4 polarization crosscorrelation for the 4 polarizations, the l and m coordinates, and
         # the timestamp in mjd of the sample, and whether or not the data has been flagged
         # numpy.dtype([('XX', numpy.float),