How many forced sources?

For DP0.2, the DiaObject table has 41 million objects, DiaSource has 162 million and ForcedSourceOnDiaObject 17 billion. Therefore each DiaObject has on average 4 DiaSources and 400 ForcedSourceOnDiaObject. The forced sources go back 4 years, so it comes to 100 per year per object.

When the real alerts start, brokers are expecting 10 million per night. If a year of forced sources is included for each alert, that 100 per alert, meaning a billion forced sources per night. Is that correct?

Can we just have the most recent forced sources? Those are the most useful.

Hi @roy, I agree that a twelve month history for any location in the sky covered with the wide-fast-deep strategy would include on average ~80 visits (over all filters). With the estimate of 10 million alerts per night, that would be 800 millions forced sources transmitted, so yes about a billion seems accurate to me too.

The option to remove histories from the alert packets was considered in Section 2 of Data Management Tech Note DMTN-248 (Options for Alert Packets), but was not recommended. The motivation for including historical records in alert packets is to enable brokers to assess the full time-domain event in order to make a robust classification (or prioritization) for follow-up, without the additional layer of complication and potential delay in having to query the Prompt Products Database for the history.

Hi @roy, I hope Melissa’s response addressed your question. But let us know if you have any follow-up questions. This is probably just different perspective, but I tend not to think of it as a billion forced sources per night, but rather that the light curve history (for a year) of each alert will be available in each alert packet. As Melissa mentioned, this is helpful for brokers to try to classify the object based on its past variability.