7.2 Properties of the input data

7.2.1 Gaia MDB data model

Author(s): Alex Hutton

The final step in a DPAC data reduction cycle is the execution of the MDB Integrator. The MDB Integrator takes a starting catalogue, represented by the CompleteSource table in the MDB data model, and updates it with the outputs of the DPAC cyclic processes such as AGIS, PhotPipe etc. which have previously been added to the MDB. For Gaia DR1, the starting catalogue will be the CompleteSource derived from the IGSL (see Section 2.2.3). The output from the MDB Integrator is a new version of the CompleteSource table, and this is used both as input for the next data reduction cycle and for Gaia DR1.

The tables in the Gaia MDB data model used as input by the MDB Integrator are listed in table 7.1.

Table 7.1: The input tables from Gaia MDB data model.
Table Description
Integrated CompleteSource The CompleteSource table generated from the IGSL catalogue ( 2.2.3 ).
IDU Match The match table from IDU (Section  2.4.2 )
IDU NewSource The new sources generated by IDU (Section  2.4.2 )
IDU Track Track records generated by IDU (Section  2.4.2 )
AGIS Source Source records holding the output from AGIS (Section  3 )
PhotPipe CalPhotSource Output from PhotPipe: This table collects all the photometric output for each source. Mean calibrated G, BP, RP photometry and colour are provided ( 5 ).
PhotPipe CalSpecSource Output from PhotPipe: Continuous representation of the internally calibrated mean spectra computed by CU5 ( 5 ).
CU7 SourceResult Output from CU7: It contains information about the variability, periodicity and classification ( 6 ).

7.2.2 Input data description from all DPCs

Author(s): Alex Hutton

For further information on the scientific properties of the input data tables taken from the MDB and used as input by the MDB Integrator, see the referenced sections in table 7.1. In this section the properties of the input data are limited to statistics on the number of records and data volume of the supplied data.

Table 7.2: MDB Integrator Input Records.
MDB Table No. of records input Size of input data (bytes)
Integrated CompleteSource 1,222,598,530 128,371,713,914
IDU Match 23,753,436,962 285,092,430,102
IDU NewSource 2,062,191,820 68,436,583,022
IDU Track 2,062,191,820 7,576,832,810
AGIS Source 2,578,806,414 646,918,489,170
PhotPipe CalPhotSource 1,368,438,497 115,684,489,620
PhotPipe CalSpecSource 1,736,618,434 3,958,676,941,868
CU7 SourceResult TBD TBD

Note that in this data reduction cycle 01, the NewSource records from IDU completely replace all NewSource records generated by IDT for the OBMT intervals which define segments (00) and (01). In the future, it is expected that new sources generated by IDT will also be used as input by the MDB Integrator.

Also note that the input CompleteSource table used by the MDB Integrator corresponds to the initial IGSL catalogue and does not correspond to the CompleteSource catalogue generated at the end of data reduction cycle 00. In future data reduction cycles it is expected that the input to the MDB Integrator will be the CompleteSource generated in the previous cycle.

The two previous changes from the nominal operations plan are intended to reduce the number of new sources generated from spurious detections.