SSObject association algorithm

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#1

Hello,

As far as I understand (LSE-163, latest Revision: 2023-07-10), the Solar System Processing pipeline will make the association between DIA sources and SSOject, and if successful, it will populate the SSObject, leaving the DIAObject null. This is somehow different from what brokers were used to with e.g. ZTF, where a set of alert fields were provided in the packet, and based on the values of those fields each broker would make the association (or not). In LSE-163, footnote 22, one can read:

LSE-163 (footnote 22)
The association algorithm will guarantee that a DIASource is associated with not more than one existing DIAObject or SSObject. The algorithm will take into account the parallax and proper (or Keplerian) motions, as well as the errors in estimated positions of DIAObject, SSObject, and DIASource, to find the maximally likely match. Multiple DIASources in the same visit will not be matched to the same DIAObject

Is there somewhere one could find a more detailed explanation on the criteria (or a link to the code if publicly available)? And what about crowded fields, with stars nearby? Thanks!

#2

Hi @JulienPeloton, the association algorithm described in the DPDD is not yet fully implemented (in particular, parallax and proper motions are not available yet as we don’t have sufficient data, and we are not using positional uncertainties). You can find the code here and in the function calls therein.

#3

Thanks for the pointer – so according to SolarSystemAssociationTask, for all system objects that should be within the footprint, it currently searches around a radius of 1 arcsecond centered on each source, and makes the association if a single DIASource is found (i.e. no association if many DIASources are within, or none).

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