How to evaluate multiplets

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Message 1886947 - Posted: 30 Aug 2017, 21:34:30 UTC

Want to help us find ET? One way is to look at multiplets, and find ones that suggest problems or bugs in our algorithms or data. Lists of of multiplets are linked to from here. Look at the lists under "Top scores (adjusted). Pick a signal type. Eric, Jeff and I are looking at the top 30 of each type, so you might want to start after that.

A multiplet page lists its signals. Some red flags:

    Signal times too close together. They should be from separate observations (telescope pointings) which means at least 1-2 minute separation. Currently there's a bug, and some multiplets have pixels only a few seconds apart.

    Excessive signal power. The reporting threshold is 24, and most signals should be in the 24-40 range. We're seeing spikes with powers like 130,000 and 32,000. These suggest a problem with the data.

Next, look at the waterfall plots for the individual signals. The signal will be in the box in the middle of the window. Check whether it's part of RFI, which roughly speaking means that it's part of a line of signals. This means we need to improve our RFI algorithms.

As an example, this Gaussian seems to part of drifting RFI that shows up in spikes. We need to change our algorithm so that other signal types are removed from areas marked as spike RFI.

When you find problems like this, please create a "bookmark". This makes it easy for us to check our changes to RFI removal.

As you evaluate multiplets, keep notes. When done, post them to this thread, and also send them to me and Eric in email (davea, korpela at ssl . berkeley . edu).

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Message boards : Nebula : How to evaluate multiplets

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