Source Association

DIA object association

DiaSources are associated with known solar system objects and stationary objects using an association radius of 1 arcsecond.

Solar System objects are stored in the SSObject catalog and stationary objects are stored in the DiaObject catalog. DiaSources not associated with either will create new DiaObjects.

Variability characterization

A small set of light curve characterization parameters (timeseries features) are calculated for all DiaObjects.

Alert Production Database

The live results of association are held in a Cassandra database known as the Alert Production Database (APDB).

Daily exports of the APDB contents will be make available to Data Rights holders for query in the Prompt Products Database (PPDB).

Duplication

Because is run in real time, if two consecutive images of the same sky area are processed simultaneously, it is possible for two new DiaObjects to be created at the same position. These duplicates will be cleaned up in morning processing. Similarly, alerts may not include the DiaSources from images taken immediately prior to the current image. Such DiaSources will appear in future alerts to that DiaObject, however. This situation is most common for deep drilling fields but can also occur in field overlaps.